Talphera (TLPH) 10-K 17 Mar 14 2013 FY Annual report Financial data

Document_and_Entity_Informatio

Document and Entity Information (USD $)	12 Months Ended
	Dec. 31, 2013	Feb. 25, 2014	Jun. 28, 2013
Document And Entity Information [Abstract]	'	'	'
Document Type	'10-K	'	'
Amendment Flag	'false	'	'
Document Period End Date	31-Dec-13	'	'
Document Fiscal Year Focus	'2013	'	'
Document Fiscal Period Focus	'FY	'	'
Trading Symbol	'ACRX	'	'
Entity Registrant Name	'ACELRX PHARMACEUTICALS INC	'	'
Entity Central Index Key	'0001427925	'	'
Current Fiscal Year End Date	'--12-31	'	'
Entity Well-known Seasoned Issuer	'No	'	'
Entity Current Reporting Status	'Yes	'	'
Entity Voluntary Filers	'No	'	'
Entity Filer Category	'Accelerated Filer	'	'
Entity Common Stock, Shares Outstanding	'	43,181,363	'
Entity Public Float	'	'	$180,565,000

Balance_Sheets

Balance Sheets (USD $)	Dec. 31, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified
Current Assets:	'	'
Cash and cash equivalents	$88,401	$47,932
Short-term investments	15,262	11,831
Prepaid expenses and other current assets	897	2,003
Total current assets	104,560	61,766
Property and equipment, net	5,179	2,485
Restricted cash	250	205
Other assets	42	64
Total Assets	110,031	64,520
Current Liabilities:	'	'
Accounts payable	2,341	2,235
Accrued liabilities	3,904	4,653
Deferred revenue, current portion	623	'
Long-term debt, current portion	'	7,443
Total current liabilities	6,868	14,331
Deferred rent	188	312
Long-term debt, net of current portion	14,364	8,530
Deferred revenue	2,007	'
Contingent put option liability	334	82
Warrant liability	13,111	7,418
Total liabilities	36,872	30,673
Stockholders' Equity:	'	'
Common stock, $0.001 par value-100,000,000 shares authorized as of December 31, 2013 and 2012; 43,050,580 and 37,055,027 shares issued and outstanding as of December 31, 2013 and 2012	43	37
Additional paid-in capital	218,568	155,836
Accumulated deficit	-145,453	-122,027
Accumulated other comprehensive income	1	1
Total stockholders' equity	73,159	33,847
Total Liabilities and Stockholders' Equity	$110,031	$64,520

Balance_Sheets_Parenthetical

Balance Sheets (Parenthetical) (USD $)	Dec. 31, 2013	Dec. 31, 2012
Statement Of Financial Position [Abstract]	'	'
Common stock, par value	$0.00	$0.00
Common stock, shares authorized	100,000,000	100,000,000
Common stock, shares issued	43,050,580	37,055,027
Common stock, shares outstanding	43,050,580	37,055,027

Statements_of_Comprehensive_Lo

Statements of Comprehensive Loss (USD $)	12 Months Ended
In Thousands, except Share data, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Revenue:	'	'	'
Collaboration agreement	$27,370	'	'
Research grant	2,132	2,394	1,072
Total revenue	29,502	2,394	1,072
Operating expenses:	'	'	'
Research and development	26,292	24,908	13,624
General and administrative	9,877	7,199	6,800
Total operating expenses	36,169	32,107	20,424
Loss from operations	-6,667	-29,713	-19,352
Interest expense	-1,518	-2,283	-2,309
Interest income and other income (expense), net	-15,241	-1,367	1,560
Net loss	-23,426	-33,363	-20,101
Other comprehensive loss:	'	'	'
Unrealized gains on available for sale securities	'	1	'
Comprehensive loss	($23,426)	($33,362)	($20,101)
Net loss per share of common stock, basic and diluted	($0.59)	($1.51)	($1.16)
Shares used in computing net loss per share of common stock, basic and diluted	39,746,678	22,124,637	17,344,727

Statements_of_Convertible_Pref

Statements of Convertible Preferred Stock and Stockholders' Equity (Deficit) (USD $)	Total	Convertible Preferred Stock	Common Stock	Additional Paid-in Capital	Accumulated Deficit	Other Comprehensive Income (loss)
In Thousands, except Share data
Beginning balance at Dec. 31, 2010	($65,892)	$55,941	$3	$2,668	($68,563)	'
Beginning balance (in shares) at Dec. 31, 2010	'	7,151,802	674,353	'	'	'
Conversion of convertible preferred stock to common stock (in shares)	'	-7,151,802	8,555,713	'	'	'
Conversion of convertible preferred stock to common stock	55,941	-55,941	8	55,933	'	'
Conversion of Bridge Note and warrants to common stock	9,824	'	2	9,579	'	'
Conversion of Bridge Note and warrants to common stock (in shares)	'	'	2,141,684	'	'	'
Issuance of Warrants	967	'	'	967	'	'
Issuance of Warrants (in shares)	'	'	'	'	'	'
Stock-based compensation	1,833	'	'	1,833	'	'
Issuance of common stock upon exercise of stock options and in connection with restricted stock units	61	'	1	60	'	'
Issuance of common stock upon exercise of stock options and in connection with restricted stock units (in shares)	'	'	147,792	'	'	'
Issuance of common stock upon ESPP purchase (in shares)	'	'	48,236	'	'	'
Issuance of common stock upon ESPP purchase	139	'	'	139	'	'
Issuance of common stock upon IPO	34,939	'	8	34,931	'	'
Issuance of common stock upon IPO (in shares)	'	'	8,000,000	'	'	'
Change in unrealized gains and losses on investments, net of taxes	'	'	'	'	'	'
Net loss	-20,101	'	'	'	-20,101	'
Ending balance at Dec. 31, 2011	17,468	'	22	106,110	-88,664	'
Ending balance (in shares) at Dec. 31, 2011	'	'	19,567,778	'	'	'
Issuance of Warrants	'	'	'	'	'	'
Issuance of Warrants (in shares)	'	'	'	'	'	'
Stock-based compensation	2,150	'	'	2,150	'	'
Issuance of common stock upon exercise of stock options and in connection with restricted stock units	80	'	'	80	'	'
Issuance of common stock upon exercise of stock options and in connection with restricted stock units (in shares)	'	'	122,108	'	'	'
Issuance of common stock upon ESPP purchase (in shares)	'	'	67,804	'	'	'
Issuance of common stock upon ESPP purchase	169	'	'	169	'	'
Issuance of common stock upon private placement offering	3,246	'	1	3,245	'	'
Issuance of common stock upon private placement offering (in shares)	'	'	2,922,337	'	'	'
Issuance of common stock upon underwritten public offering	44,096	'	14	44,082	'	'
Issuance of common stock upon underwritten public offering (in shares)	'	'	14,375,000	'	'	'
Change in unrealized gains and losses on investments, net of taxes	1	'	'	'	'	1
Net loss	-33,363	'	'	'	-33,363	'
Ending balance at Dec. 31, 2012	33,847	'	37	155,836	-122,027	1
Ending balance (in shares) at Dec. 31, 2012	'	'	37,055,027	'	'	'
Issuance of Warrants	1,130	'	'	1,130	'	'
Issuance of Warrants (in shares)	'	'	'	'	'	'
Stock-based compensation	3,479	'	'	3,479	'	'
Issuance of common stock upon exercise of stock options and in connection with restricted stock units	1,277	'	1	1,276	'	'
Issuance of common stock upon exercise of stock options and in connection with restricted stock units (in shares)	'	'	520,365	'	'	'
Issuance of common stock upon exercise of stock warrants	8,690	'	1	8,689	'	'
Issuance of common stock upon the exercise of common stock warrants (in shares)	808,078	'	1,050,062	'	'	'
Issuance of common stock upon ESPP purchase (in shares)	'	'	55,126	'	'	'
Issuance of common stock upon ESPP purchase	219	'	'	219	'	'
Issuance of common stock upon underwritten public offering	47,943	'	4	47,939	'	'
Issuance of common stock upon underwritten public offering (in shares)	'	'	-4,370,000	'	'	'
Change in unrealized gains and losses on investments, net of taxes	'	'	'	'	'	'
Net loss	-23,426	'	'	'	-23,426	'
Ending balance at Dec. 31, 2013	$73,159	'	$43	$218,568	($145,453)	$1
Ending balance (in shares) at Dec. 31, 2013	'	'	43,050,580	'	'	'

Statements_of_Convertible_Pref1

Statements of Convertible Preferred Stock and Stockholders' Equity (Deficit) (Parenthetical) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Statement Of Stockholders Equity [Abstract]	'	'	'
Issuance of common stock upon IPO, offering-related costs	'	'	$5.10
Issuance of common stock, offering-related costs	'	0.9	'
Issuance of common stock, offering-related costs	$3	$3.50	'

Statements_of_Cash_Flows

Statements of Cash Flows (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
CASH FLOWS FROM OPERATING ACTIVITIES:	'	'	'
Net loss	($23,426)	($33,363)	($20,101)
Adjustments to reconcile net loss to net cash used in operating activities:	'	'	'
Depreciation and amortization	593	605	513
Amortization of premium/discount on investments, net	202	380	195
Interest expense related to debt financing	442	647	1,619
Stock-based compensation	3,479	2,150	1,833
Revaluation of convertible preferred stock warrant, call option, put option and PIPE warrant liabilities	14,071	1,439	-1,512
Loss on extinguishment of debt	1,202	'	'
Other	'	43	'
Changes in operating assets and liabilities:	'	'	'
Prepaid expenses and other assets	1,132	429	-434
Restricted cash	-45	'	'
Accounts payable	106	705	987
Accrued liabilities	-760	2,029	1,788
Deferred revenue	2,630	'	'
Deferred rent	-113	354	-175
Net cash used in operating activities	-487	-24,582	-15,287
CASH FLOWS FROM INVESTING ACTIVITIES:	'	'	'
Purchase of property and equipment	-3,287	-826	-2,019
Purchase of investments	-28,009	-27,167	-39,367
Proceeds from sales of investments	'	'	2,082
Proceeds from maturities of investments	24,376	42,948	9,725
Net cash provided by (used in) investing activities	-6,920	14,955	-29,579
CASH FLOWS FROM FINANCING ACTIVITIES:	'	'	'
Proceeds from issuance of common stock in equity offerings, net of offering costs	47,943	53,174	34,939
Proceeds from the issuance of long-term debt	14,958	'	19,762
Payment of long-term debt	-16,345	-3,655	-5,297
Extinguishment of debt	-437	'	'
Net proceeds from issuance of common stock through equity plans and exercise of warrants	1,757	246	201
Net cash provided by financing activities	47,876	49,765	49,605
NET INCREASE IN CASH AND CASH EQUIVALENTS	40,469	40,138	4,739
CASH AND CASH EQUIVALENTS-Beginning of period	47,932	7,794	3,055
CASH AND CASH EQUIVALENTS-End of period	88,401	47,932	7,794
SUPPLEMENTAL DISCLOSURES OF CASH FLOW INFORMATION:	'	'	'
Cash paid for interest	1,105	1,632	1,162
NONCASH INVESTING AND FINANCING ACTIVITIES:	'	'	'
Conversion of convertible promissory notes into common stock	'	'	8,137
Issuance of common stock upon cashless exercise of warrants	8,428	'	536
Reclassification of warrant liability and call option liability to equity	'	'	906
Issuance of warrants for common stock	1,130	5,828	967
Contingent put option liability	334	'	232
Purchases of property and equipment in Accrued Liabilities	$725	'	'

Organization_and_Summary_of_Si

Organization and Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2013
Accounting Policies [Abstract]	'
Organization and Summary of Significant Accounting Policies	'
	1. Organization and Summary of Significant Accounting Policies
	The Company
	AcelRx Pharmaceuticals, Inc., or the Company or AcelRx, was incorporated in Delaware on July 13, 2005 as SuRx, Inc., and in January 2006, the Company changed its name to AcelRx Pharmaceuticals, Inc. The Company’s operations are based in Redwood City, California.
	AcelRx is a specialty pharmaceutical company focused on the development and commercialization of innovative therapies for the treatment of acute and breakthrough pain. AcelRx intends to commercialize its product candidates in the United States and license the development and commercialization rights to its product candidates for sale outside of the United States through strategic partnerships and collaborations. The Company’s lead product candidate, ZalvisoTM, formerly known as the Sufentanil NanoTab PCA System, or ARX-01, is currently under review by the FDA for marketing approval, and is designed to improve the management of moderate-to-severe acute pain in patients in the hospital setting. In addition, in December 2013, the Company entered into a collaboration agreement with Grünenthal for the commercialization of Zalviso in Europe and Australia.
	The Company has incurred recurring operating losses and negative cash flows from operating activities since inception and expects to continue to incur negative cash flows until its product candidates are approved for marketing in the United States and other countries, in which it has and intends to license its products, which may never occur. In previous years, prior to the completion of the clinical development program for Zalviso and the commercial collaboration of Zalviso, AcelRx was considered a development stage company.
	The Company has one business activity, which is the development and commercialization of product candidates for the treatment of pain, and a single reporting and operating unit structure.
	Basis of Presentation
	The preparation of financial statements in conformity with generally accepted accounting principles requires management to make estimates and assumptions that affect the amounts reported in the financial statements and the accompanying notes. Actual results could differ from those estimates.
	Concentration of Risk
	The Company invests cash that is currently not being used for operational purposes in accordance with its investment policy in debt securities of the U.S. Treasury and U.S. government sponsored agencies and overnight deposits. The Company is exposed to credit risk in the event of default by the institutions holding the cash equivalents and available-for-sale securities to the extent recorded on the balance sheet. Our cash and cash equivalent balances can be in excess of federally insured amounts.
	Cash, Cash Equivalents and Marketable Securities
	The Company considers all highly liquid investments with an original maturity (at date of purchase) of three months or less to be cash equivalents. Cash and cash equivalents consist of cash on deposit with banks and money market instruments.
	All marketable securities are classified as available-for-sale and consist of U.S. Treasury and U.S. government sponsored enterprise debt securities. These securities are carried at estimated fair value, which is based on quoted market prices or observable market inputs of almost identical assets, with unrealized gains and losses included in accumulated other comprehensive income (loss). The amortized cost of securities is adjusted for amortization of premiums and accretion of discounts to maturity. Such amortization and accretion is included in interest income or expense. The cost of securities sold is based on specific identification. The Company’s investments are subject to a periodic impairment review for other-than-temporary declines in fair value. The Company’s review includes the consideration of the cause of the impairment including the creditworthiness of the security issuers, the number of securities in an unrealized loss position, the severity and duration of the unrealized losses and the Company’s intent and ability to hold the investment for a period of time sufficient to allow for any anticipated recovery in the market value. When the Company determines that the decline in fair value of an investment is below its accounting basis and this decline is other-than-temporary, it reduces the carrying value of the security it holds and records a loss in the amount of such decline.
	Property and Equipment
	Property and equipment are stated at cost less accumulated depreciation and amortization. Depreciation is calculated using the straight-line method over the estimated useful lives of the assets, generally three to five years. Leasehold improvements are amortized over the shorter of the estimated useful life of the improvements or the remaining lease term.
	Impairment of Long-Lived Assets
	The Company periodically assesses the impairment of long-lived assets and, if indicators of asset impairment exist, the Company assesses the recoverability of the affected long-lived assets by determining whether the carrying value of such assets can be recovered through an analysis of the undiscounted future expected operating cash flows. If impairment is indicated, the Company records the amount of such impairment for the excess of the carrying value of the asset over its estimated fair value. For example, purchased equipment and manufacturing-related facility improvements the Company has made at Patheon’s facility in Ohio, are utilized for continued research and development, and potential commercial manufacturing of our product candidates. If the Company does not receive regulatory approval for our product candidates, the Company may determine that it is no longer probable that the Company will realize the future economic benefit associated with the costs of these assets through future manufacturing activities, and if so, the Company would record an impairment charge associated with these assets. As of December 31, 2013, the Company has not written down any of its long-lived assets as a result of impairment.
	Restricted Cash
	Under the Company’s facility lease and corporate credit card agreements, the Company is required to maintain letters of credit as security for performance under these agreements. The letters of credit are secured by certificates of deposit in amounts equal to the letters of credit, which are classified as restricted cash on the balance sheet.
	Revenue Recognition
	The Company recognizes revenue when all of the following criteria are met: persuasive evidence of an arrangement exists; delivery has occurred or services have been rendered; the fee is fixed or determinable; and collectability is reasonably assured.
	Collaboration Revenue
	Collaboration revenue, which is earned under license agreements with third parties, may include nonrefundable license fees, cost reimbursements, research and development services, commercial manufacturing services, contingent development and commercial milestones and royalties.
	In October 2009, the Financial Accounting Standards Board, or FASB, issued Accounting Standards Update, or ASU, 2009-13 Revenue Arrangements with Multiple Deliverables, or ASU 2009-13, which amended the accounting standards for certain multiple element revenue arrangements to:
		•	provide updated guidance on whether multiple elements exist, how the elements in an arrangement should be separated, and how the arrangement consideration should be allocated to the separate elements;
		•	require an entity to allocate arrangement consideration to each element based on a selling price hierarchy, also called the relative selling price method, where the selling price for an element is based on vendor-specific objective evidence (“VSOE”), if available; third-party evidence (“TPE”), if available and VSOE is not available; or the best estimate of selling price (“ESP”), if neither VSOE nor TPE is available; and
		•	eliminate the use of the residual method and require an entity to allocate arrangement consideration using the selling price hierarchy.
	The revenue allocated to each element is then recognized when the basic revenue recognition criteria are met for that element.
	VSOE is based on the price charged when the element is sold separately and is the price actually charged for that deliverable. Establishing VSOE may not be possible for the elements of a license arrangement because each arrangement is unique, an arrangement typically consists of multiple elements and AcelRx has limited history of entering into license arrangements.
	When VSOE cannot be established, AcelRx attempts to establish the selling price of the elements of a license arrangement based on TPE. TPE is determined based on a competitor’s price for similar deliverables when sold separately. AcelRx may not be able to determine TPE for license arrangements, as they contain a significant level of differentiation such that the comparable pricing of a competitor’s license arrangement with similar functionality cannot be obtained, and AcelRx is therefore unable to reliably determine what a similar competitor’s license arrangement’s selling price would be on a standalone basis.
	When AcelRx is unable to establish the selling price of an element using VSOE or TPE, ESP is utilized in the allocation of the elements of the arrangement. The objective of the ESP is to determine the price at which AcelRx would transact a sale if the element of the license arrangement were sold on a standalone basis.
	The process for determining ESPs involves management’s judgment. Our process considers multiple factors such as discounted cash flows, estimated direct expenses and other costs and available data, which may vary over time, depending upon the circumstances, and relate to each deliverable. If the estimated obligation period of one or more deliverables should change, the future amortization of the revenue would also change.
	AcelRx recognizes a contingent milestone payment as revenue in its entirety upon our achievement of the milestone. A milestone is substantive if the consideration earned from the achievement of the milestone (i) is consistent with performance required to achieve the milestone or the increase in value to the delivered item, (ii) relates solely to past performance and (iii) is reasonable relative to all of the other deliverables and payments within the arrangement.
	Research Grant Revenue
	In May 2011, the Company entered into an award contract with the US Army Medical Research and Materiel Command, or USAMRMC, to support the development of the Company’s new product candidate, ARX-04, a Sufentanil NanoTab for the treatment of moderate-to-severe acute pain. The grant provides for the reimbursement of qualified expenses for research and development activities as defined under the terms of the grant agreement. Revenue under the grant agreement is recognized when the related qualified research expenses are incurred.
	Research and Development Expenses
	Research and development costs are charged to expense when incurred. Research and development expenses include salaries, employee benefits, including stock-based compensation, consultant fees, laboratory supplies, costs associated with clinical trials and manufacturing, including contract research organization fees, other professional services and allocations of corporate costs. The Company reviews and accrues clinical trial expenses based on work performed, which relies on estimates of total costs incurred based on patient enrollment, completion of patient studies and other events.
	Comprehensive Loss
	Comprehensive loss is comprised of net loss and other comprehensive income (loss) and is disclosed in the Statement of Comprehensive Loss. For the Company, other comprehensive income (loss) consists of changes in unrealized gains and losses on the Company’s investments.
	Fair Value of Financial Instruments
	The Company measures and reports its cash equivalents, investments and financial liabilities at fair value. Fair value is defined as the exchange price that would be received for an asset or an exit price paid to transfer a liability in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants on the measurement date. Valuation techniques used to measure fair value must maximize the use of observable inputs and minimize the use of unobservable inputs. The fair value hierarchy defines a three-level valuation hierarchy for disclosure of fair value measurements as follows:
	Level I—Unadjusted quoted prices in active markets for identical assets or liabilities;
	Level II—Inputs other than quoted prices included within Level I that are observable, unadjusted quoted prices in markets that are not active, or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the related assets or liabilities; and
	Level III—Unobservable inputs that are supported by little or no market activity for the related assets or liabilities.
	The categorization of a financial instrument within the valuation hierarchy is based upon the lowest level of input that is significant to the fair value measurement.
	Income Taxes
	Deferred tax assets and liabilities are measured based on differences between the financial reporting and tax basis of assets and liabilities using enacted rates and laws that are expected to be in effect when the differences are expected to reverse. The Company records a valuation allowance for the full amount of deferred assets, which would otherwise be recorded for tax benefits relating to operating loss and tax credit carryforwards, as realization of such deferred tax assets cannot be determined to be more likely than not.
	Stock-Based Compensation
	Compensation expense for all share-based payment awards made to employees and directors, including employee stock options, restricted stock units and employee share purchases related to the 2011 Employee Stock Purchase Plan, or ESPP, is based on estimated fair values at grant date. The Company determines the grant date fair value of the awards using the Black-Scholes option-pricing model and generally recognizes the fair value as stock-based compensation expense on a straight-line basis over the vesting period of the respective awards.
	The Black-Scholes option pricing model requires inputs such as expected term, expected volatility and risk-free interest rate. These inputs are subjective and generally require significant analysis and judgment to develop. Estimates of expected life are primarily determined using the simplified method in accordance with guidance provided by the SEC. Such method was utilized as the Company did not believe its historical option exercise experience, which was limited, provided a reasonable basis upon which to estimate expected term. Volatility is derived from historical volatilities of several public companies within AcelRx’s industry that are deemed to be comparable to AcelRx’s business because AcelRx’s has limited information on the volatility of its common stock since there was no trading history prior to completion of AcelRx’s Initial Public Offering, or IPO, in February 2011. The risk-free rate is based on the U.S. Treasury yield curve in effect at the time of grant commensurate with the expected life assumption. Further, the Company estimates forfeitures at the time of grant and revises those estimates in subsequent periods if actual forfeitures differ from those estimates.
	Net Loss per Share of Common Stock
	The Company’s basic net loss per share of common stock is calculated by dividing the net loss by the weighted average number of shares of common stock outstanding for the period. The diluted net loss per share of common stock is computed by giving effect to all potential common stock equivalents outstanding for the period determined using the treasury stock method. For purposes of this calculation, convertible preferred stock, options to purchase common stock, restricted stock subject to repurchase, warrants to purchase convertible preferred stock and warrants to purchase common stock were considered to be common stock equivalents. In periods with a reported net loss, such common stock equivalents are excluded from the calculation of diluted net loss per share of common stock as their effect is antidilutive.
	Segment Information
	The Company operates in one operating segment and has operations solely in the United States.
	Recently Issued Accounting Pronouncements
	In February 2013, Accounting Standards Codification Topic 220, Comprehensive Income was amended to require companies to report, in one place, information about reclassifications out of accumulated other comprehensive income. Accordingly, a company can present this information on the face of the financial statements, if certain requirements are met, or the information must be presented in the notes to the financial statements. The Company adopted this guidance as of January 1, 2013, on a retrospective basis, and the items reclassified out of accumulated other comprehensive income are not material for all periods presented.

Investments_and_Fair_Value_Mea

Investments and Fair Value Measurement	12 Months Ended
	Dec. 31, 2013
Text Block [Abstract]	'
Investments and Fair Value Measurement	'
	2. Investments and Fair Value Measurement
	Investments
	The Company classifies its marketable securities as available-for-sale and records its investments at fair value. Available-for-sale securities are carried at estimated fair value based on quoted market prices or observable market inputs of almost identical assets, with the unrealized holding gains and losses included in accumulated other comprehensive income. Marketable securities which have maturities beyond one year as of the end of the reporting period are classified as non-current.
	The table below summarizes the Company’s cash, cash equivalents and investments (in thousands):
		As of December 31, 2013
		Amortized Cost			Gross Unrealized			Gross Unrealized		Fair
					Gains			Losses		Value
	Cash and cash equivalents:
	Cash	$	88,390		$	—		$	—	$	88,390
	Money market funds		11			—			—		11
	Total cash and cash equivalents		88,401			—			—		88,401
	Marketable securities:
	U.S. government agency securities		15,261			1			—		15,262
	Total marketable securities		15,261			1			—		15,262
	Total cash, cash equivalents and investments		103,662			1			—		103,663
		As of December 31, 2012
		Amortized Cost			Gross Unrealized			Gross Unrealized		Fair
					Gains			Losses		Value
	Cash and cash equivalents:
	Cash	$	44,440		$	—		$	—	$	44,440
	Money market funds		2,086			—			—		2,086
	U.S. government agency securities		1,406			—			—		1,406
	Total cash and cash equivalents		47,932			—			—		47,932
	Marketable securities:
	U.S. government agency securities		11,830			1			—		11,831
	Total marketable securities		11,830			1			—		11,831
	Total cash, cash equivalents and investments	$	59,762		$	1		$	—	$	59,763
	None of the available-for-sale securities held by the Company had material unrealized losses and there were no realized losses for the years ended December 31, 2013 and 2012. There were no other-than-temporary impairments for these securities as of December 31, 2013 or 2012.
	As of December 31, 2013 and 2012, the contractual maturity of all investments held was less than one year.
	Fair Value Measurement
	The Company’s financial instruments consist of Level I and Level II assets and Level III liabilities. Level I securities include highly liquid money market funds and are valued based on quoted market prices. For Level II instruments, the Company estimates fair value by utilizing third party pricing services in developing fair value measurements where fair value is based on valuation methodologies such as models using observable market inputs, including benchmark yields, reported trades, broker/dealer quotes, bids, offers and other reference data. Such Level II instruments typically include U.S. treasury and U.S. government agency obligations. As of December 31, 2013 and December 31, 2012, the Company held, in addition to Level I and Level II assets, a contingent put option liability associated with the Company’s loan and security agreement with Hercules Technology II, L.P. and Hercules Technology Growth Capital, Inc., collectively referred to as Hercules, which was classified as a Level III liability. The Company’s estimate of fair value of the contingent put option liability was determined by using a risk-neutral valuation model, wherein the fair value of the underlying debt facility is estimated both with and without the presence of the default provisions, holding all other assumptions constant. The resulting difference between the two estimated fair values is the estimated fair value of the default provisions, or the contingent put option. The fair value of the underlying debt facility is estimated by calculating the expected cash flows in consideration of an estimated probability of default and expected recovery rate in default, and discounting such cash flows back to the reporting date using a risk-free rate. As of December 31, 2013 and 2012, the Company also held a Level III liability associated with warrants, or PIPE warrants, issued in connection with the Company’s private placement equity offering, completed in June 2012. For a detailed description, see Note 10 “Stockholders’ Equity.” The PIPE warrants are considered a liability and are valued using the Black-Scholes option-pricing model, the inputs for which include exercise price of the PIPE warrants, market price of the underlying common shares, expected term, volatility based on a group of the Company’s peers and the risk-free rate corresponding to the expected term of the PIPE warrants. Changes to any of the inputs can have a significant impact to the estimated fair value of the PIPE warrants.
	The following table sets forth the fair value of the Company’s financial assets and liabilities by level within the fair value hierarchy (in thousands):
		As of December 31, 2013
		Fair Value			Level I			Level II		Level III
	Assets
	Money market funds	$	11		$	11		$	—	$	—
	U.S. government agency obligations		15,262			—			15,262		—
	Total assets measured at fair value	$	15,273		$	11		$	15,262	$	—
	Liabilities
	PIPE warrant	$	13,111		$	—		$	—	$	13,111
	Contingent put option		334			—			—		334
	Total liabilities measured at fair value	$	13,445		$	—		$	—	$	13,445
		As of December 31, 2012
		Fair Value			Level I			Level II		Level III
	Assets
	Money market funds	$	2,086		$	2,086		$	—	$	—
	U.S. government agency obligations		13,237			—			13,237		—
	Total assets measured at fair value	$	15,323		$	2,086		$	13,237	$	—
	Liabilities
	PIPE warrant	$	7,418			—			—	$	7,418
	Contingent put option		82			—			—		82
	Total liabilities measured at fair value	$	7,500		$	—		$	—	$	7,500
	The following table sets forth the assumptions used in the Black-Scholes option-pricing model to estimate the fair value of the PIPE warrants as of December 31, 2013 and 2012:
		As of December 31,			As of December 31,
		2013			2012
	Market Price	$	11.31		$	4.26
	Exercise Price	$	3.4		$	3.4
	Risk-free interest rate		1.27	%		0.72	%
	Expected volatility		69	%		78	%
	Expected life (in years)		3.92			4.9
	Expected dividend yield		0	%		0	%
	The following table sets forth a summary of the changes in the fair value of the Company’s Level III financial liabilities for the years ended December 31, 2013 and 2012 (in thousands):
		Year Ended
December 31,
2013
Fair value—beginning of period	$	7,500
Change in fair value of PIPE warrants		5,693
Change in fair value of contingent put option associated with 2011 loan and security agreement with Hercules		(82	)
Addition of contingent put option associated with 2013 loan and security agreement with Hercules		334
Fair value—end of period	$	13,445
	Year Ended
	December 31,
	2012
Fair value—beginning of period	$	232
Addition of PIPE warrants in June 2012		5,828
Change in fair value of PIPE warrants		1,590
Change in fair value of contingent put option		(150	)
Fair value—end of period	$	7,500

Property_and_Equipment

Property and Equipment	12 Months Ended
	Dec. 31, 2013
Property Plant And Equipment [Abstract]	'
Property and Equipment	'
	3. Property and Equipment
	Property and equipment consist of the following (in thousands):
		As of December 31,
		2013			2012
	Research equipment	$	2,014		$	2,014
	Leasehold improvements		1,425			1,418
	Computer equipment and software		189			167
	Construction in process		3,277			—
	Tooling		318			337
	Furniture and fixtures		59			59
	Total property, plant and equipment		7,282			3,995
	Less accumulated depreciation and amortization		(2,103	)		(1,510	)
		$	5,179		$	2,485
	Depreciation and amortization expense was $0.6 million, $0.6 million and $0.5 million during the years ended December 31, 2013, 2012 and 2011. Construction in process includes $2.5 million related to certain modifications the Company is making at Patheon’s Cincinnati facility under the terms of a capital and equipment agreement related to the manufacture of the Company’s product candidates.

Research_Grant

Research Grant	12 Months Ended
	Dec. 31, 2013
Research And Development [Abstract]	'
Research Grant	'
	4. Research Grant
	In May 2011, AcelRx received a grant from the US Army Medical Research and Materiel Command, or USAMRMC, in which the USAMRMC granted $5.6 million to the Company in order to support the development of a new product candidate, ARX-04, a Sufentanil NanoTab for the treatment of moderate-to-severe acute pain. Under the terms of the grant, the USAMRMC will reimburse the Company for development, manufacturing and clinical costs necessary to prepare for and complete the planned Phase 2 dose-finding trial in a study of acute moderate-to-severe pain, and to prepare to enter Phase 3 development. The grant gives the USAMRMC the option to extend the term of the grant and provide additional funding for the research. As of December 31, 2013, the full amount of the grant, $5.6 million, had been recognized as revenue.
	Revenue is recognized based on expenses incurred by AcelRx in conducting research and development activities set forth in the agreement. Revenue attributable to the research and development performed under the USAMRMC grant was $2.1 million, $2.4 million and $1.1 million for the years ended December 31, 2013, 2012, 2011, respectively.

Collaboration

Collaboration	12 Months Ended
	Dec. 31, 2013
Organization Consolidation And Presentation Of Financial Statements [Abstract]	'
Collaboration	'
	5. Collaboration
	On December 16, 2013, AcelRx and Grünenthal GmbH, or Grünenthal, entered into a Collaboration and License Agreement (the “License Agreement”) and related Manufacture and Supply Agreement (the “Manufacturing Agreement” and together with the License Agreement, the “Agreements”). The License Agreement grants Grünenthal rights to commercialize Zalviso the Company’s novel sublingual patient-controlled analgesia (PCA) system (the “Product”), in the countries of the European Union, Switzerland, Liechtenstein, Iceland, Norway and Australia (the “Territory”), for human use in pain treatment within or dispensed by hospitals hospices, nursing homes and other medically-supervised settings (the “Field”). The Company retains rights with respect to the Product in countries outside the Territory, including the U.S., Asia and Latin America. Under the Supply Agreement, the Company will exclusively manufacture and supply the Product to Grünenthal for the Field in the Territory.
	License Agreement
	Under the terms of the License Agreement, Grünenthal has the exclusive right to commercialize the Product in the Field in the Territory. The Company retains control of clinical development, while Grünenthal and the Company will be responsible for certain development activities pursuant to a development plan as agreed between the parties. The Company will not receive separate payment for such development activities. Grünenthal is exclusively responsible for marketing approval applications and other regulatory filings relating to the sufentanil drug cartridge for the Product in the Field in the Territory, while the Company is responsible for the CE Mark and other regulatory filings relating to device portions of the Product.
	The Company received an upfront non-refundable cash payment of $30.0 million, and is eligible to receive up to $220.0 million in additional payments contingent upon research, development, regulatory and manufacturing efforts and specified net sales target milestones. Grünenthal will also make tiered royalty and supply and trademark fee payments in the mid-teens up to the mid-twenties percent range on net sales of Product in the Territory.
	Unless earlier terminated, the License Agreement continues in effect until the expiration of the obligation of Grünenthal to make royalty and supply and trademark fee payments, which supply and trademark fee continues for so long as the Company continues to supply the Product to Grünenthal. The License Agreement is subject to earlier termination in the event the parties mutually agree, by a party in the event of an uncured material breach by the other party, upon the bankruptcy or insolvency of either party, or by Grünenthal for convenience.
	Manufacturing Agreement
	Under the terms of the Manufacturing Agreement, the Company will manufacture and supply the Product for use in the Field for the Territory exclusively for Grünenthal. Grünenthal shall purchase from AcelRx, during the first five years after the effective date of the Manufacturing Agreement, 100% and thereafter 80% of Grünenthal’s and its sublicensees’ and distributors’ requirements of Product for use in the Field for the Territory. The Product will be supplied at the Company’s fully burdened manufacturing cost (as defined in the Manufacturing Agreement). The Manufacturing Agreement requires the Company to use commercially reasonable efforts to enter stand-by contracts with third parties providing significant supply and manufacturing services and under certain specified conditions permits Grünenthal to use a third party back-up manufacturer to manufacture the Product for Grünenthal’s commercial sale in the Territory.
	Unless earlier terminated, the Manufacturing Agreement continues in effect until the later of the expiration of the obligation of Grünenthal to make royalty and supply and trademark fee payments or the end of any transition period for manufacturing obligations due to the expiration or termination of the License Agreement. The Manufacturing Agreement is subject to earlier termination in connection with certain termination events in the License Agreement, in the event the parties mutually agree, by a party in the event of an uncured material breach by the other party or upon the bankruptcy or insolvency of either party.
	The Company identified the following four significant non-contingent performance deliverables under the agreements: 1) intellectual property (license), 2) the obligation to provide research and development services, 3) the significant and incremental discount on the manufacturing of Zalviso for commercial purposes, and 4) the obligation to participate on the joint steering committee.
	The Company considered the provisions of the multiple-element arrangement guidance in determining whether the deliverables outlined above have standalone value and thus should be treated as separate units of accounting. Company’s management determined that the license has standalone value and represents a separate unit of accounting because the rights conveyed permit Grünenthal to perform all efforts necessary to commercialize and begin selling the product upon regulatory approval. In addition, Grünenthal has the appropriate development, regulatory and commercial expertise with products similar to the product licensed under the agreement and has the ability to engage third parties to manufacture the product allowing Grünenthal to realize the value of the license without receiving any of the remaining deliverables. Grünenthal can also sublicense its license rights to third parties. Also, the Company’s management determined that the research services, committee participation and implied discount associated with the manufacturing services each represent individual units of accounting as Grünenthal could perform such services and/or could acquire these on a separate basis.
	The Company developed best estimates of selling prices for each deliverable in order to allocate the noncontingent arrangement consideration to the four units of accounting.
	The Company’s management determined the best estimate of selling price for the license based on Grünenthal’s estimated future cash flows arising from the arrangement. Embedded in the estimate were significant assumptions regarding regulatory expenses, revenue, including potential customer market for the product and product price, costs to manufacture the product and the discount rate. The Company’s management determined the best estimate of selling price of the research and development services and committee participation based on the nature and timing of the services to be performed and in consideration of personnel and other costs incurred in the delivery of the services. For the discount on manufacturing services, Company’s management estimated the selling price based on the market level of contract manufacturing margin it could have received if it were engaged to supply products to a customer in a separate transaction.
	The Agreements entitle the Company to receive additional payments upon the achievement of certain development and sales milestones. Based on ASC Topic 605-28, Revenue Recognition — Milestone Method, the Company evaluates contingent milestones at inception of the agreement, and recognizes consideration that is contingent upon the achievement of a milestone in its entirety as revenue in the period in which the milestone is achieved only if the milestone is considered substantive in its entirety. Milestones are events which have the following characteristics: (i) they can be achieved based in whole or in part on either the Company’s performance or on the occurrence of a specific outcome resulting from the Company’s performance, (ii) there was substantive uncertainty at the date the agreement was entered into that the event would be achieved and, (iii) they would result in additional payments due to the Company. A milestone is considered substantive if the following criteria are met: (i) the consideration is commensurate with either (1) the entity’s performance to achieve the milestone, or (2) the enhancement of the value of the delivered item (s) as a result of a specific outcome resulting from the entity’s performance to achieve the milestone, , (ii) the consideration relates solely to past performance and, (iii) the consideration is reasonable relative to all of the other deliverables and payment terms, including other potential milestone consideration, within the arrangement.
	The substantive milestone payments will be recognized as revenue in their entirety upon the achievement of each substantive milestone. Based on the criteria noted above, the identified substantive milestones in the agreement pertain to post approval product enhancements, expanded market opportunities and manufacturing efficiencies for Zalviso. Each of these potential achievements is based primarily on the Company’s performance and involves substantive uncertainty as achievement of these milestones require future research, development and regulatory activities, which are inherently uncertain in nature. The Company determined that the consideration for each milestone was commensurate with the Company’s performance to achieve the milestone, including future research, development, manufacturing and regulatory activities and that the consideration is reasonable relative to all of the other deliverables and payments within the arrangement. Aggregate potential payments for these milestones total $28.5 million.
	In addition to substantive milestones, two milestones associated with the Agreements were deemed not to be substantive. These milestones pertain to regulatory developments for Zalviso in Europe, which Company’s management deemed to be not substantive due to the level of performance associated with future achievement of these milestones. Aggregate potential payments for these milestones total $20.0 million. When achieved, the value of these milestones will be allocated to the four separate units of accounting based on estimated selling prices and recognized as revenue in the period of achievement to the extent the services underlying the separate units of accounting have been performed. The Company anticipates receiving the first milestone payment of $5.0 million in 2014, for the submission of the Marketing Authorization Application for Zalviso to the European Medicines Agency.
	The Agreement also include milestone payments related to specified net sales targets, totaling $171.5 million. The sales-based milestones do not meet the definition of a milestone under ASU 2010-17 because the achievement of these milestones is solely dependent on counter-party performance and not on any performance obligations of the Company.
	The Company allocated the $30.0 million upfront fee across the four deliverables based on estimated selling prices.
	Based on the relative estimated selling price method, the amount of consideration allocated to the license was $27.4 million, which was recognized as revenue for the year ended December 31, 2013, as the license had been delivered. The remaining upfront consideration, of $2.6 million, was allocated to the remaining deliverables and recorded as deferred revenue as of December 31, 2013.

LongTerm_Debt

Long-Term Debt	12 Months Ended
	Dec. 31, 2013
Debt Disclosure [Abstract]	'
Long-Term Debt	'
	6. Long-Term Debt
	Hercules Loan and Security Agreements
	In June 2011, AcelRx entered into a loan and security agreement with Hercules, under which AcelRx borrowed $20.0 million in two tranches of $10.0 million each, represented by secured convertible term promissory notes. The Company’s obligations associated with the agreement are secured by a security interest in substantially all of its assets, other than its intellectual property.
	The Company borrowed the first tranche of $10.0 million upon the closing of the transaction on June 29, 2011 and borrowed the second tranche of $10.0 million in December 2011. The Company used a portion of the proceeds from the first tranche to repay the remaining obligations under that certain loan and security agreement between the Company and Pinnacle Ventures, L.L.C., or Pinnacle Ventures, dated September 16, 2008. The agreement with Pinnacle Ventures is described further below. The interest rate for each tranche was 8.50%. In connection with the loan, the Company issued Hercules seven-year warrants to purchase an aggregate of 274,508 shares of common stock at a price of $3.06 per share. See Note 8 “Warrants,” for further description.
	On December 16, 2013, AcelRx entered into an Amended and Restated Loan and Security Agreement (the “Loan Agreement”) with Hercules Technology II, L.P. and Hercules Technology Growth Capital, Inc. (together, the “Lenders”) under which the Company may borrow up to $40.0 million in three tranches. The loans are represented by secured convertible term promissory notes (collectively, the “Notes”). The Loan Agreement amends and restates the Loan and Security Agreement between the Company and the Lenders dated as of June 29, 2011, (the Original Loan Agreement), as noted above. The Company borrowed the first tranche of $15.0 million upon closing of the transaction on December 16, 2013. The Company used approximately $8.6 million of the proceeds from the first tranche to repay its obligations under the Original Loan Agreement.
	In accordance with ASC Topic No. 470, “Debt – Modifications and Extinguishments” (Topic No. 470), the amendment noted above was determined to be an extinguishment of the existing debt and an issuance of new debt. The Company reached this conclusion based on a comparison of discounted remaining cash flows of the original loan agreement compared to the amended loan agreement, the result of which was a greater than 10% difference in discounted cash flows. The Company determined this difference to be significant. The Company has recorded the new debt at estimated fair value and, as of December 31, 2013, the balance was $14.3 million.
	As a result of the extinguishment, AcelRx recorded a $1.2 million loss on extinguishment of debt which was recorded as other income / expense on the Statement of Comprehensive Loss. The loss on extinguishment was a non-cash write off, consisting of deferred debt charges, the unamortized portion of the original issue discount related to the Original Loan Agreement and other fees associated with extinguishing the debt, including the estimated fair value of warrants issued in connection with the amended loan agreement, facility and legal fees associated with the amended loan agreement and the value of the contingent put option liability associated with the original loan agreement at the time of the amendment.
	The second tranche of the amended loan agreement of up to $10.0 million can be drawn, at the Company’s option, anytime prior to June 30, 2014. The third tranche, of up to $15.0 million, can be drawn at anytime between December 15, 2014 and March 15, 2015, but only if the Company has obtained approval for Zalviso from the U.S. Food and Drug Administration (the “Milestone”). The interest rate for each tranche will be calculated at a rate equal to the greater of either (i) 9.10% plus the prime rate as reported from time to time in The Wall Street Journal minus 5.25%, and (ii) 9.10%. Payments under the Loan Agreement are interest only until April 1, 2015 (which will be extended until January 1, 2016 if the Company achieves the Milestone on or before April 1, 2015) followed by equal monthly payments of principal and interest through the scheduled maturity date on October 1, 2017 (which would be extended until January 1, 2018 if the Company achieves the Milestone on or prior to April 1, 2015) (the “Loan Maturity Date”). In addition, a final payment equal to $1,700,000 will be due on the Loan Maturity Date, or such earlier date specified in the Loan Agreement. The Company’s obligations under the Loan Agreement are secured by a security interest in substantially all of its assets, other than its intellectual property.
	If the Company prepays the loan prior to maturity, it will pay the Lenders a prepayment charge, based on a percentage of the then outstanding principal balance, equal to 3% if the prepayment occurs prior to December 16, 2014, 2% if the prepayment occurs after December 16, 2014, but prior to December 16, 2015, or 1% if the prepayment occurs after December 16, 2015.
	Subject to certain conditions and limitations set forth in the Loan Agreement, the Company has the right to convert up to $5.0 million of scheduled principal installments under the Notes into freely tradeable shares of the Company’s common stock (“Common Stock”). The number of shares of Common Stock that would be issued upon conversion of the Notes would be equal to the number determined by dividing (x) the product of (A) the principal amount to be paid in shares of Common Stock and (B) 103%, by (y) $9.30 (subject to certain proportional adjustments as provided for in the Loan Agreement).
	The Loan Agreement includes customary affirmative and restrictive covenants, but does not include any financial maintenance covenants, and also includes standard events of default, including payment defaults, breaches of covenants following any applicable cure period, a material impairment in the perfection or priority of Lenders’ security interest or in the value of the collateral, and events relating to bankruptcy or insolvency. Upon the occurrence of an event of default, a default interest rate of an additional 5% may be applied to the outstanding loan balances, and the Lenders may declare all outstanding obligations immediately due and payable and take such other actions as set forth in the Loan Agreement.
	In connection with the Loan Agreement, the Company issued a warrant to each Lender which together are exercisable for an aggregate of 176,730 shares of Common Stock and each carry an exercise price of $6.79 (the “Warrants”). Each Warrant may be exercised on a cashless basis. The Warrants are exercisable for a term beginning on the date of issuance and ending on the earlier to occur of five years from the date of issuance or the consummation of certain acquisitions of the Company as set forth in the Warrants. The number of shares for which the Warrants are exercisable and the associated exercise price are subject to certain proportional adjustments as set forth in the Warrants.
	Upon an event of default, including a change of control, Hercules has the option to accelerate repayment of the loan, including payment of any applicable prepayment charges, which range from 1%-3% of the outstanding loan balance and accrued interest, as well as a final payment fee of $1.7 million. This option is considered a contingent put option liability as the holder of the loan may exercise the option in the event of default and, is considered an embedded derivative which must be valued and separately accounted for in the Company’s financial statements. As the amendment of the loan agreement was considered an extinguishment, the contingent put option liability associated with the original loan agreement, which had an estimated fair value of $32,000 at the time of the amendment, was written off as a part of the loss on extinguishment, and a new contingent put option liability was established. As of December 31, 2013, 2012 and 2011, the estimated fair value of the contingent put option liability was $334,000, $82,000 and $232,000, respectively which was determined by using a risk-neutral valuation model, wherein the fair value of the underlying debt facility is estimated both with and without the presence of the default provisions, holding all other assumptions constant. The resulting difference between the two estimated fair values is the estimated fair value of the default provisions, or the contingent put option. The fair value of the underlying debt facility is estimated by calculating the expected cash flows in consideration of an estimated probability of default and expected recovery rate in default, and discounting such cash flows back to the reporting date using a risk-free rate. The contingent put option liability was recorded as a debt discount to the loan and consequently a reduction to the carrying value of the loan. The contingent put option liability will be revalued at the end of each reporting period and any change in the fair value will be recognized in the statement of operations.
	As of December 31, 2013, the Company had outstanding borrowings under the amended Hercules loan and security agreement of $15.0 million. Amortization of the debt discount prior to amending the Hercules loan and security agreement in December 2013, which was recorded as interest expense, was $0.4 million for the year ended December 31, 2013.
	As of December 31, 2012, the Company had outstanding borrowings under the Hercules loan and security agreement of $16.0 million, net of debt discount of $0.5 million. Amortization of the debt discount, which was recorded as interest expense, was $0.5 million for the year ended December 31, 2012.
	Amortization of the debt discount, which was recorded as Interest Expense, was $254,000 for the year ended December 31, 2011.
	Pinnacle Loan and Security Agreement
	In September 2008, the Company entered into a $12.0 million loan and security agreement with Pinnacle. In November 2008, the Company drew down all $12.0 million of the loan facility. On June 29, 2011, upon execution of the Hercules loan and security agreement, the Pinnacle agreement was terminated and the outstanding balance of $2.8 million was repaid. The unamortized portion of the final balloon payment and deferred financing costs were recorded to interest expense upon termination of the agreement.
	Future Payments on Long-Term Debt
	The following table summarizes our outstanding future payments associated with the Company’s long-term debt as of December 31, 2013 (in thousands):
				Payment by Period
	Obligations:	Total		Less than 1		1-3 years		3-5 years		More than 5
				year						years
	Principal Payments	$	15,000	$	—	$	10,106	$	4,894		—
	Interest Payments		3,533		1,327		2,015	$	191		—
	Balloon Payments		1,900		200		—	$	1,700		—
	Total	$	20,433	$	1,527	$	12,121	$	6,785		—

Convertible_Notes

Convertible Notes	12 Months Ended
	Dec. 31, 2013
Text Block [Abstract]	'
Convertible Notes	'
	7. Convertible Notes
	2010 Convertible Notes
	On September 14, 2010, the Company sold convertible promissory notes, or the 2010 Convertible Notes, to certain existing investors for an aggregate purchase price of $8.0 million. The 2010 Convertible Notes bore interest at a rate of 4.0% per annum and had a maturity date of the earlier of (1) September 14, 2011 or (2) an event of default. In connection with the IPO, the outstanding principal and accrued interest under the 2010 Convertible Notes automatically converted into 2,034,438 shares of common stock immediately prior to the closing of the IPO.
	Upon the election of the holders of a majority of the aggregate principal amount payable under the 2010 Convertible Notes outstanding, the Company was required to sell an additional $4.0 million of 2010 Convertible Notes. This additional $4.0 million was determined to be a call option that was recorded at its fair value of $476,000 as a debt discount that would have been amortized to interest expense over the one-year term of the 2010 Convertible Notes. The fair value of the call option was determined by evaluating multiple potential scenarios using a market approach and an income approach depending on the scenario and discounting these values back to the appropriate date while applying estimated probabilities to each scenario value. These scenarios included a potential initial public offering, merger or sale of the Company at different times during 2011 and 2012 as well as remaining private. The fair value of the call option as of December 31, 2010 was $596,000. During the three months ended March 31, 2011, the 2010 Convertible Notes were amended so that the note holders’ option to invest the second tranche of $4.0 million expired upon the closing of the IPO. The call option was revalued to its fair value as of the IPO date and was written off upon its expiration with a benefit of $596,000 being recognized through other income (expense). In addition, the unamortized debt discount in the amount of $1.1 million at the time of the IPO was recognized as interest expense in connection with the conversion of the notes.

Warrants

Warrants	12 Months Ended
	Dec. 31, 2013
Text Block [Abstract]	'
Warrants	'
	8. Warrants
	Series A Warrants
	In March 2007, the Company entered into an equipment financing agreement in which the Company issued immediately exercisable and fully vested warrants to purchase 2,500 shares of its Series A convertible preferred stock, or the Series A warrants, with an exercise price of $10.00 per share. The fair value of the Series A warrants on the date of issuance was $1,000, as determined using the Black-Scholes option-pricing model. This fair value was recorded as a convertible preferred stock warrant liability and as a deferred financing cost in other assets. The fair value was remeasured at the end of each reporting period. In connection with the IPO, the Series A warrants were automatically converted into warrants to purchase 3,425 shares of common stock. As a result of the conversion, these common stock warrants were no longer recorded as liabilities and were, therefore, no longer remeasured as of the end of each reporting period.
	As of December 31, 2013, warrants to purchase 3,425 shares of common stock had not been exercised and were still outstanding. These warrants expire in March 2017.
	Series B and Series C Warrants
	In September 2008, the Company entered into a $12.0 million loan and security agreement with Pinnacle Ventures. In November 2008, the Company drew down all $12.0 million of the loan facility. In connection with the loan and security agreement, the Company issued immediately exercisable and fully vested warrants, or the Series B warrants, to purchase 56,250 shares of Series B convertible preferred stock with an exercise price of $16.00 per share. Upon the closing of the Series C convertible preferred stock financing during the year ended December 31, 2009, the Series B warrants underlying the loan and security agreement became exercisable for 228,264 shares of Series C convertible preferred stock with an exercise price of $3.94 per share, or the Series C warrants. The Company determined the fair value of the Series B warrants and Series C warrants on the dates of issuance to be $162,000, as determined using the Black-Scholes option-pricing model which was recorded as a convertible preferred stock warrant liability and as a deferred financing cost in other assets. The Company revalued the convertible preferred stock warrant liability related to the Series B warrants and Series C warrants during each reporting period using the Black-Scholes option-pricing model. The fair value of the convertible preferred stock warrant liability related to these Series B warrants and Series C warrants was estimated to be $894,000 and $1.2 million as of the IPO date in February 2011 and December 31, 2010.
	In connection with the Company’s IPO in February 2011, the Series C warrants were automatically converted into warrants to purchase 228,264 shares of common stock with an exercise price of $3.94 per share. Immediately before the conversion to common stock warrants, the Series C warrants were remeasured to fair value with the change in the fair value of these warrants of $323,000 being recorded as a benefit through other income (expense), net during the three months ended March 31, 2011. Immediately after the conversion to common stock warrants, the remaining liability of $894,000 was reclassified to additional paid-in capital. As a result of the conversion, these common stock warrants were no longer recorded as liabilities and were therefore no longer remeasured as of the end of each reporting period.
	In February 2013, warrants to purchase 228,264 shares were net exercised, for 58,580 shares of common stock. As of December 31, 2013, no warrants to purchase shares of common stock issued to Pinnacle were outstanding.
	2010 Warrants
	The Company issued warrants in connection with the 2010 Convertible Notes in September 2010, or the 2010 Warrants. The 2010 Warrants were exercisable into shares of convertible preferred stock. The 2010 Warrants would have terminated if not exercised immediately prior to the IPO. The 2010 Warrants allowed for cashless exercises.
	The Company determined the fair value of the 2010 Warrants to be $1.2 million upon issuance, as determined using the Black-Scholes option-pricing model which was recorded as a convertible preferred stock warrant liability and a debt discount. As of December 31, 2010, the related warrant liability was $1.3 million. In connection with the IPO, the 2010 Warrants were net exercised into shares of Series C convertible preferred stock, which shares were automatically converted to 107,246 shares of common stock immediately prior to the IPO. Immediately before the exercise into Series C convertible preferred stock, the 2010 Warrants were remeasured to fair value with the change in the fair value of these warrants of $763,000 being recorded as a benefit through other income (expense), net during the three months ended March 31, 2011. Immediately after the exercise into Series C convertible preferred stock, the remaining liability of $536,000 was reclassified to additional paid-in capital.
	Hercules Warrants
	In connection with the Amended Loan Agreement, executed in December 2013, the Company issued warrants to Hercules which are exercisable for an aggregate of 176,730 shares of Common Stock and each carry an exercise price of $6.79 (the “Warrants”). Each Warrant may be exercised on a cashless basis. The Warrants are exercisable for a term beginning on the date of issuance and ending on the earlier to occur of five years from the date of issuance or the consummation of certain acquisitions of the Company as set forth in the Warrants. The number of shares for which the Warrants are exercisable and the associated exercise price are subject to certain proportional adjustments as set forth in the Warrants. The Company estimated the fair value of these warrants as of the issuance date to be $1.1 million, which was used in the estimating the fair value of the amended debt instrument and was recorded as equity. The fair value of the warrants was calculated using the Black-Scholes option-valuation model, and was based on the strike price of $6.79, the stock price at issuance of $9.67, the five-year contractual term of the warrants, a risk-free interest rate of 1.55%, expected volatility of 71% and 0% expected dividend yield.
	As of December 31, 2013, warrants to purchase 176,730 shares of common stock issued to Hercules had not been exercised and were still outstanding. These warrants expire in December 2018.
	In connection with the original loan and security agreement with Hercules, executed in June 2011, the Company issued to Hercules warrants to purchase an aggregate of 274,508 shares of common stock at a price of $3.06 per share. The warrants may be exercised on a cashless basis. The warrants are exercisable for a term beginning on the date of issuance and ending on the earlier to occur of seven years from the date of issuance or the consummation of certain acquisitions of the Company as set forth in the warrants. The Company estimated the fair value of these warrants as of the issuance date to be $967,000, which was recorded as a debt discount to the loan and consequently a reduction to the carrying value of the loan. The fair value of the warrants was calculated using the Black-Scholes option-valuation model, and was based on the seven-year contractual term of the warrants, a risk-free interest rate of 2.44%, expected volatility of 79% and 0% expected dividend yield. During June and July 2013, warrants to purchase 274,508 shares were net exercised, for 183,404 shares of common stock.
	2012 Private Placement Warrants
	In connection with the Private Placement, completed in June 2012, the Company issued PIPE warrants to purchase up to 2,630,103 shares of common stock. The per share exercise price of the PIPE warrants was $3.40 which equals the closing consolidated bid price of the Company’s common stock on May 29, 2012, the effective date of the Purchase Agreement. The PIPE warrants issued in the Private Placement became exercisable six months after the issuance date, and expire on the five year anniversary of the initial exercisability date. Under the terms of the PIPE warrants, upon certain transactions, including a merger, tender offer, sale of all or substantially all of the assets of the Company or if a person or group shall become the owner of 50% of the Company’s issued and outstanding common stock, which is outside of the Company’s control, each PIPE warrant holder may elect to receive a cash payment in exchange for the warrant, in an amount determined by application of the Black-Scholes option-pricing model. Accordingly, the PIPE warrants were recorded as a liability at fair value, as determined by the Black-Scholes option-pricing model, and then marked to fair value each reporting period, with changes in estimated fair value recorded through the Statement of Comprehensive Loss in other income or expense. The Black-Scholes assumptions used to value the PIPE warrants are disclosed in Note 2.
	Upon execution of the Purchase Agreement, the fair value of the PIPE warrants was estimated to be $5.8 million, which was recorded as a liability. As of December 31, 2013, the fair value of the PIPE warrants was estimated to be $13.1 million. The change in fair value for the year ended December 31, 2013 and December 31, 2012, which was recorded as other expense, was $14.1 million and $1.6 million, respectively.
	During the year ended December 31, 2013, warrants to purchase 1,135,589 shares were net exercised, for 808,078 shares of common stock. As of December 31, 2013, PIPE warrants to purchase 1,494,514 shares of common stock issued in connection with the Private Placement had not been exercised and were outstanding. These warrants expire in November 2017.

Commitments_and_Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2013
Commitments And Contingencies Disclosure [Abstract]	'
Commitments and Contingencies	'
	9. Commitments and Contingencies
	Operating Leases
	In December 2011, the Company entered into a non-cancelable lease agreement for approximately 13,787 square feet of office and laboratory facilities in Redwood City, California, which serve as the Company headquarters, effective April 2012. The lease agreement expires in May 2016. Rent expense from the facility lease is recognized on a straight-line basis from the inception of the lease in December 2011, the early access date, through the end of the lease.
	Prior to April 2012, the Company was subject to a non-cancelable lease agreement for approximately 11,305 square feet of office and laboratory facilities in Redwood City, California, which served as the Company headquarters for the duration of the lease term. The lease term commenced in April 2007 and expired in April 2012. Rent expense from the facility lease was recognized on a straight-line basis from the inception of the lease in January 2007, the early access date, through the end of the lease.
	Rent expense was $0.3 million, $0.3 million and $0.2 million during the years ended December 31, 2013, 2012 and 2011, respectively.
	Future minimum payments under the lease agreement as of December 31, 2013 are as follows (in thousands):
	Year Ending December 31:
	2014		392
	2015		404
	2016		142
	Total minimum payments	$	938
	Litigation
	The Company is not a party to any litigation and does not have contingent liabilities established for any litigation matters.
	Manufacturing Agreements
	Patheon
	In January 2013, the Company and Patheon Pharmaceuticals Inc., or Patheon, entered into a Manufacturing Services Agreement, or the Services Agreement, and a related Amended and Restated Capital Expenditure and Equipment Agreement, or the Capital Agreement, relating to the manufacture of Sufentanil NanoTabs, or the Product, for use with the Company’s Sufentanil NanoTab PCA System, or ARX-01.
	Under the terms of the Services Agreement, the Company has agreed to purchase, subject to Patheon’s continued material compliance with the terms of the Services Agreement, all of its Product requirements for the United States, Canada and Mexico from Patheon during the Initial Term of the Services Agreement (as defined below), and at least eighty percent (80%) of its Product requirements for such territories after the Initial Term.
	The term of the Services Agreement extends until December 31, 2017, or the Initial Term, and will automatically renew thereafter for periods of two years, unless terminated by either party upon eighteen months’ prior written notice; provided, however, that the Services Agreement may not be terminated without cause prior to the end of the Initial Term.
	The Company also entered into a Capital Expenditure and Equipment Agreement, or the Capital Agreement. Under the terms of the Capital Agreement, the second amendment for which was entered into in January 2014, the Company has made and has the option to make certain future modifications to Patheon’s Cincinnati facility, the aggregate cost of which is expected to be less than $4.4 million and which would be the responsibility of the Company. If additional equipment and facility modifications are required to meet the Company’s Product needs, the Company may be required to contribute to the cost of such additional equipment and facility modifications. The Capital Agreement also requires that the Company make payments in 2012 and 2013 totaling $480,000, which the Company made, to Patheon to partially offset taxes incurred and paid by Patheon in connection with facility modifications already completed by Patheon. The Company can seek reimbursement from Patheon for this payment if it receives approval from the U.S. Food and Drug Administration for ARX-01. The Capital Agreement further requires that the Company pay a maximum “overhead fee” of $200,000 annually during the term of the Services Agreement, which amount may be reduced to $0 based on the amount of annual revenues earned by Patheon under the Services Agreement and the pre-existing development agreements. No fee was due in 2013 based on the amount of revenues earned by Patheon from the Company.
	Expenditures associated with the aforementioned agreements are primarily driven by the potential commercial requirements and demand for the Company’s products, none of which have been approved for commercialization; accordingly, the amounts and timing of such future expenditures cannot be determined at this time.
	Grünenthal
	On December 16, 2013, AcelRx Pharmaceuticals, Inc. (the “Company”) and Grünenthal GmbH (“Grünenthal”) entered into a Collaboration and License Agreement (the “License Agreement”) and related Manufacture and Supply Agreement (the “Manufacturing Agreement” and together with the License Agreement, the “Agreements”). The License Agreement grants Grünenthal rights to commercialize ZalvisoTM (formerly known as ARX-01) the Company’s novel sublingual patient-controlled analgesia (PCA) system (the “Product”), in the countries of the European Union, Switzerland, Liechtenstein, Iceland, Norway and Australia (the “Territory”), for human use in pain treatment within or dispensed by hospitals hospices, nursing homes and other medically-supervised settings (the “Field”).
	Under the terms of the Manufacturing Agreement, the Company will manufacture and supply the Product for use in the Field for the Territory exclusively for Grünenthal. Grünenthal shall purchase from AcelRx, during the first five years after the effective date of the Manufacturing Agreement, 100% and thereafter 80% of Grünenthal’s and its sublicensees’ and distributors’ requirements of Product for use in the Field for the Territory. The Product will be supplied at the Company’s fully burdened manufacturing cost (as defined in the Manufacturing Agreement). The Manufacturing Agreement requires the Company to use commercially reasonable efforts to enter stand-by contracts with third parties providing significant supply and manufacturing services and under certain specified conditions permits Grünenthal to use a third party back-up manufacturer to manufacture the Product for Grünenthal’s commercial sale in the Territory.
	Unless earlier terminated, the Manufacturing Agreement continues in effect until the later of the expiration of the obligation of Grünenthal to make royalty and supply and trademark fee payments or the end of any transition period for manufacturing obligations due to the expiration or termination of the License Agreement. The Manufacturing Agreement is subject to earlier termination in connection with certain termination events in the License Agreement, in the event the parties mutually agree, by a party in the event of an uncured material breach by the other party or upon the bankruptcy or insolvency of either party.
	Under the Supply Agreement, the Company will exclusively manufacture and supply the Product to Grünenthal for the Field in the Territory.
	Expenditures associated with the aforementioned agreements are primarily driven by the potential commercial requirements and demand for the Company’s products, none of which are currently approved for commercial use; accordingly, the amounts and timing of such future expenditures cannot be determined at this time.

Stockholders_Equity

Stockholders' Equity	12 Months Ended
	Dec. 31, 2013
Equity [Abstract]	'
Stockholders' Equity	'
	10. Stockholders’ Equity
	Common Stock
	Public Offerings
	On July 23, 2013, AcelRx completed an underwritten public offering of 4,370,000 shares of common stock, at a price of $11.65 per share to the public. The total gross proceeds of this offering were $50.9 million with net proceeds to AcelRx of $47.9 million after deducting underwriting discounts and commissions and other expenses payable by AcelRx.
	In December 2012, AcelRx completed an underwritten public offering, in which the Company sold an aggregate of 14,375,000 shares of its common stock at a public offering price of $3.31 per share, resulting in net proceeds of $44.1 million, after deducting underwriting discounts and commissions and other offering related expenses totaling $3.5 million.
	Private Placement Offering
	On June 1, 2012, or the Issuance Date, the Company issued an aggregate of 2,922,337 shares of common stock and warrants to purchase up to 2,630,103 shares of common stock, or the PIPE warrants, for aggregate gross proceeds of $10.0 million, or the Private Placement. Costs related to the offering were $0.9 million. The shares of common stock and PIPE warrants issued in the Private Placement were sold pursuant to a Securities Purchase Agreement, or Purchase Agreement, dated May 29, 2012, between the Company and certain purchasers, including certain entities affiliated with Mark Wan and Stephen J. Hoffman, members of the Company’s board of directors. Pursuant to the Purchase Agreement, AcelRx sold shares of common stock and PIPE warrants to purchase common stock in immediately separable “Units,” with each Unit consisting of (i) one share of common stock and (ii) a PIPE warrant to purchase 0.9 of a share of common stock. The per share exercise price of the PIPE warrants was $3.40. The offering price per Unit was $3.40 for non-affiliated investors, and $3.5125 for affiliated investors, which equals the sum of (i) $3.40, the closing consolidated bid price of the Company’s common stock on May 29, 2012, plus (ii) $0.1125 (which is equal to $0.125 per PIPE warrant share, multiplied by 0.9), for an aggregate amount of $10.0 million. The PIPE warrants issued in the Private Placement became exercisable six months after the Issuance Date, and expire on the five year anniversary of the initial exercisability date.
	In connection with the Private Placement, the Company filed a registration statement with the U.S. Securities and Exchange Commission, or SEC, registering for resale the shares of common stock and shares of common stock issuable upon exercise of the warrants sold in the Private Placement. The registration statement was declared effective by the SEC in July 2012.
	2012 ATM Agreement
	On August 31, 2012, the Company entered into an At Market Issuance Sales Agreement, or Sales Agreement, or ATM, with MLV & Co. LLC, or MLV, pursuant to which the Company may elect to issue and sell shares of its common stock having an aggregate offering price equal to the lesser of (i) the amount that the Company may continue to offer and sell under the eligibility requirements for use of Form S-3 (including, if applicable, Instruction I.B.6 thereof) or (ii) $7,500,000. The Company is not obligated to make any sales of common stock under the Sales Agreement. Unless earlier terminated, the Sales Agreement will automatically terminate upon the earlier of (1) the sale of all common stock subject to the Sales Agreement or (2) August 31, 2015. The Company will pay MLV an aggregate commission rate equal to up to 3.0% of the gross proceeds for common stock sold through MLV under the Sales Agreement. The Company has also provided MLV with customary indemnification rights and expense reimbursements for up to $25,000 of expenses. As of December 31, 2013, the Company has not sold any shares of common stock pursuant to the ATM.
	Initial Public Offering
	On February 10, 2011, the Company sold 8,000,000 shares of common stock at a price of $5.00 per share in an IPO. The shares began trading on the NASDAQ Global Market on February 11, 2011. The Company received $34.9 million in net proceeds from the IPO, after deducting underwriting discounts and commissions and other offering expenses totaling $5.1 million. Upon the closing of the offering, all outstanding shares of convertible preferred stock converted into common stock. The convertible preferred stock converted into 8,555,713 shares of common stock. In addition, the principal and accrued interest under the 2010 Convertible Notes converted into 2,034,438 shares of common stock upon the closing of the Company’s IPO and the 2010 Warrants were net exercised for 107,246 shares of Series C convertible preferred stock, which shares were converted to common stock upon the closing of the Company’s IPO. All other outstanding warrants to purchase convertible preferred stock became exercisable into shares of common stock. Concurrently, the Company increased the number of authorized shares of common stock to 100,000,000 with a par value of $0.001 per share and decreased the number of authorized shares of preferred stock to 10,000,000 with a par value of $0.001 per share.
	Convertible Preferred Stock
	Upon the closing of the Company’s IPO in February 2011, all outstanding shares of convertible preferred stock converted into common stock, as described further above, under Initial Public Offering.
	Stock Plans
	2011 Equity Incentive Plan
	In January 2011, the board of directors adopted, and the Company’s stockholders approved, the 2011 Equity Incentive Plan, or 2011 Incentive Plan, as a successor to the 2006 Plan. The 2011 Incentive Plan became effective immediately upon the execution and delivery of the underwriting agreement for the IPO on February 10, 2011. As of February 10, 2011, no more awards may be granted under the 2006 Plan, although all outstanding stock options and other stock awards previously granted under the 2006 Plan will continue to remain subject to the terms of the 2006 Plan. The 51,693 shares reserved under the 2006 Plan that remained available for future grant at the time of the IPO were transferred to the share reserve of the 2011 Incentive Plan.
	The initial aggregate number of shares of the Company’s common stock that may be issued pursuant to stock awards under the 2011 Incentive Plan is 1,875,000 shares, which number was the sum of (i) 51,693 shares remaining available for future grant under the 2006 Plan at the time of the execution and delivery of the underwriting agreement for the Company’s IPO, and (ii) an additional 1,823,307 new shares. Then, the number of shares of common stock reserved for issuance under the 2011 Incentive Plan will automatically increase on January 1st each year, starting on January 1, 2012 and continuing through January 1, 2020, by 4% of the total number of shares of the Company’s common stock outstanding on December 31 of the preceding calendar year, or such lesser number of shares of common stock as determined by the board of directors. In January 2013 and 2012, an additional 1,482,201 and 782,711 shares, were authorized for issuance under the 2011 Incentive Plan, respectively.
	2011 Employee Stock Purchase Plan
	Additionally, in January 2011, the board of directors adopted, and the Company’s stockholders approved, the 2011 Employee Stock Purchase Plan, or the ESPP, which also became effective immediately upon the execution and delivery of the underwriting agreement for the IPO.
	Initially, 250,000 shares of the Company’s common stock were authorized for issuance under the ESPP pursuant to purchase rights granted to the Company’s employees or to employees of any of its designated affiliates. The number of shares of the Company’s common stock reserved for issuance will automatically increase on January 1st each year, starting January 1, 2012 and continuing through January 1, 2020, in an amount equal to the lower of (1) 2% of the total number of shares of the Company’s common stock outstanding on December 31 of the preceding calendar year, or (2) a number of shares of common stock as determined by the board of directors. If a purchase right granted under the ESPP terminates without having been exercised, the shares of the Company’s common stock not purchased under such purchase right will be available for issuance under the ESPP. No additional shares were authorized for issuance under the ESPP in 2013, and in January 2012, an additional 391,355 were authorized for issuance under the ESPP.
	2006 Stock Plan
	In August 2006, the Company established the 2006 Plan in which 342,000 shares of common stock were originally reserved for the issuance of incentive stock options, or ISOs, and nonstatutory stock options, or NSOs, to employees, directors or consultants of the Company. In February 2008, an additional 375,000 shares of common stock were reserved for issuance under the 2006 Plan and, in November 2009, an additional 1,376,059 shares of common stock were reserved for issuance under the 2006 Plan. Per the 2006 Plan, the exercise price of ISOs and NSOs granted to a stockholder who at the time of grant owns stock representing more than 10% of the voting power of all classes of the stock of the Company could not be less than 110% of the fair value per share of the underlying common stock on the date of grant. Effective upon the execution and delivery of the underwriting agreement for the Company’s IPO, no additional stock options or other stock awards may be granted under the 2006 Plan.

StockBased_Compensation

Stock-Based Compensation	12 Months Ended
	Dec. 31, 2013
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]	'
Stock-Based Compensation	'
	11. Stock-Based Compensation
	The Company recorded total stock-based compensation expense for stock options, stock awards and the ESPP as follows (in thousands):
		Year Ended December 31,
		2013			2012		2011
	Research and development	$	1,657		$	998	$	785
	General and administrative		1,822			1,152		1,048
	Total	$	3,479		$	2,150	$	1,833
	The following table summarizes option activity under the 2011 Plan and 2006 Plan:
		Number			Weighted-		Weighted-		Aggregate
		of Stock Options			Average		Average		Intrinsic
		Outstanding			Exercise		Remaining		Value
					Price		Contractual
							Life (Years)
									(in thousands)
	December 31, 2010		2,008,797		$	2.91
	Granted		514,958			3.48
	Forfeited		(58,022	)		3.32
	Exercised		(69,765	)		1.2
	December 31, 2011		2,395,968		$	3.08
	Granted		1,213,391			3.36
	Forfeited		(165,781	)		3.23
	Exercised		(43,767	)		2.32
	December 31, 2012		3,399,811		$	3.18
	Granted		1,958,727			5.99
	Forfeited		(17,917	)		8.82
	Exercised		(431,216	)		3.03
	December 31, 2013		4,909,405		$	4.29		7.9		34,452
	Vested and exercisable options—December 31, 2013		2,161,400		$	3.17		6.7	$	17,589
	Vested and expected to vest—December 31, 2013		4,718,574		$	4.25		7.8	$	33,322
	As of December 31, 2013, there were 273,290 shares available for future grant under the 2011 Plan. In January 2014, an additional 1,722,023 shares were authorized for issuance under the 2011 Incentive Plan.
	Additional information regarding the Company’s stock options outstanding and vested and exercisable as of December 31, 2013 is summarized below:
		Options Outstanding							Options Vested and Exercisable
	Exercise Prices	Number of			Weighted-Average		Weighted-Average		Shares Subject		Weighted-Average
		Stock Options			Remaining		Exercise Price  per		to Stock		Exercise Price  per
		Outstanding			Contractual  Life		Share		Options		Share
					(Years)
	$1.20-$2.56		613,875			5.9	$	2.22		613,874	$	2.22
	$2.5601-$4.00		2,088,053			7.4	$	3.23		1,299,298	$	3.16
	$4.22-$6.34		1,962,477			8.7	$	5.31		236,353	$	5.32
	$8.18-$10.55		245,000			9.7	$	10.4		11,875	$	10.55
			4,909,405			7.9	$	4.29		2,161,400	$	3.17
	The weighted average grant-date fair value of options granted during the years ended December 31, 2013, 2012, 2011 was $4.15, $2.25 and $2.45 per share. As of December 31, 2013, total stock-based compensation expense related to unvested options to be recognized in future periods was $8.2 million which is expected to be recognized over a weighted-average period of 2.8 years. The grant date fair value of shares vested during the years ended December 31, 2013, 2012 and 2011 was $1.9 million, $1.3 million and $1.1 million, respectively. The total intrinsic value of options exercised during the years ended December 31, 2013, 2012 and 2011 was $3.6 million, $85,000 and $204,000, respectively.
	The Company used the following assumptions to calculate the fair value of each employee stock option:
		Year Ended December 31,
		2013		2012	2011
	Expected term (in years)	5.75-6.25		5.75-6.25	5.75-6.25
	Risk-free interest rate	1.02%-2.96%		0.6%-1.74%	1.1%-2.5%
	Expected volatility	80%		80%	79%
	Expected dividend rate	0%		0%	0%
	Restricted Stock Units
	In March 2011, the Company granted 343,815 Restricted Stock Units, or RSUs, to employees and directors under the 2011 Plan at a grant date fair value of $3.45. The fair value of the RSUs was determined on the date of grant based on the market price of the Company’s common stock. RSUs are recognized as expense ratably over the vesting period and the Company’s RSU’s generally vest over three years as follows: 25% on the 6 month anniversary of the vesting commencement date, 25% on the 12 month anniversary of the vesting commencement date, 25% on the 24 month anniversary of the vesting commencement date and 25% on the 36 month anniversary of the vesting commencement date, so long as the RSU recipient continues to provide services to the Company. As of December 31, 2013, there were 65,765 RSUs outstanding. The expense related to RSUs during the years ended December 31, 2013, 2012 and 2011 was $290,000, $315,000 and $492,000, respectively.

Net_Loss_per_Share_of_Common_S

Net Loss per Share of Common Stock	12 Months Ended
	Dec. 31, 2013
Earnings Per Share [Abstract]	'
Net Loss per Share of Common Stock	'
	12. Net Loss per Share of Common Stock
	The following table sets forth the computation of the Company’s basic and diluted net loss per share of common stock during the years ended December 31, 2012, 2011 and 2010 (in thousands, except for share and per share amounts):
		Year Ended December 31,
		2013			2012			2011
	Net loss	$	(23,426	)	$	(33,363	)	$	(20,101	)
	Shares used in computing net loss per share of common stock, basic and diluted		39,746,678			22,124,637			17,344,727
	Net loss per share of common stock, basic and diluted	$	(0.59	)	$	(1.51	)	$	(1.16	)
	The following outstanding shares of common stock equivalents were excluded from the computation of diluted net loss per share of common stock for the periods presented because including them would have been antidilutive:
		Year Ended December 31,
		2013			2012			2011
	Stock options to purchase common stock		4,909,405			3,399,811			2,395,968
	Restricted Stock Units		65,765			161,096			257,868
	Common stock warrants		1,674,669			3,136,300			506,197

Accounts_Payable_and_Accrued_L

Accounts Payable and Accrued Liabilities	12 Months Ended
	Dec. 31, 2013
Payables And Accruals [Abstract]	'
Accounts Payable and Accrued Liabilities	'
	13. Accounts Payable and Accrued Liabilities
	Accounts payable and accrued liabilities consist of the following (in thousands):
		December 31,
		2013		2012
	Accounts payable	$	2,341	$	2,235
	Accrued compensation and employee benefits		2,397		1,613
	Accrued research and development expenses		248		2,371
	Accrued liabilities associated with property and equipment		725		—
	Professional fees		230		361
	Interest payable		61		119
	Other		243		189
	Total accounts payable and accrued liabilities	$	6,245	$	6,888

401k_Plan

401(k) Plan	12 Months Ended
	Dec. 31, 2013
Text Block [Abstract]	'
401(k) Plan	'
	14. 401(k) Plan
	The Company sponsors a 401(k) plan that stipulates that eligible employees can elect to contribute to the 401(k) plan, subject to certain limitations. Pursuant to the 401(k) plan, the Company makes a discretionary safe harbor contribution equal to 3% of the related compensation. Eligible employees are 100% vested in this safe harbor contribution regardless of whether they make salary deferrals into the 401(k) plan. Company contributions were $143,000, $120,000 and $107,000 for the years ended December 31, 2013, 2012 and 2011.

Income_Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2013
Income Tax Disclosure [Abstract]	'
Income Taxes	'
	15. Income Taxes
	The Company did not record a provision for income taxes during the years ended December 31, 2013, 2012 and 2011. Net deferred tax assets as of December 31, 2013 and 2012 consist of the following (in thousands):
		December 31,			December 31,
		2013			2012
	Deferred tax assets:
	Accruals and other	$	2,172		$	802
	Research credits		3,553			2,050
	Net operating loss carryforward		36,279			35,730
	Section 59(e) R&D expenditures		10,339			8,572
	Total deferred tax assets		52,343			47,154
	Valuation allowance	$	(52,343	)	$	(47,154	)
	Net deferred tax assets	$	—		$	—
	Reconciliations of the statutory federal income tax to the Company’s effective tax during the years ended December 31, 2013, 2012 and 2011 are as follows (in thousands):
		Year Ended December 31,
		2013			2012			2011
	Tax at statutory federal rate	$	(7,965	)	$	(11,343	)	$	(6,834	)
	State tax—net of federal benefit		(716	)		(1,953	)		(1,104	)
	PIPE Warrant liability		4,898			540			—
	General Business credits		(1,326	)		—			—
	Other		(80	)		1,807			161
	Change in valuation allowance		5,189			11,949			7,777
	Provision (benefit) for income taxes	$	—		$	—		$	—
	ASC 740 requires that the tax benefit of net operating losses, temporary differences and credit carryforwards be recorded as an asset to the extent that management assesses that realization is “more likely than not.” Realization of deferred tax assets is dependent on future taxable income, if any, the timing and the amount of which are uncertain. Accordingly, the deferred tax assets have been fully offset by a valuation allowance. The valuation allowance increased by $5.2 million, $11.9 million and $7.8 million during the years ended December 31, 2013, 2012 and 2011, respectively. The amount of the valuation allowance for deferred tax assets associated with excess tax deduction from stock based compensation arrangement that is allocated to contributed capital if the future tax benefits are subsequently recognized is $1.1 million.
	As of December 31, 2013, 2012 and 2011, the Company had federal net operating loss carryforwards of $91.1 million, $89.7 million and $82.2 million, respectively, which begin to expire in 2025. As of December 31, 2013, 2012, and 2011, the Company had state net operating loss carryforwards of $91.0 million, $89.7 million and $80.6 million, respectively, which begin to expire in 2015.
	As of December 31, 2013, 2012 and 2011, the Company had federal research credit carryovers of $2.6 million, $1.3 million and $1.3 million, respectively, which begin to expire in 2026. As of December 31, 2013, 2012 and 2011, the Company had state research credit carryovers of $1.4 million, $1.1 million and $0.9 million, respectively, which will carryforward indefinitely.
	Under Section 382 of the Internal Revenue Code of 1986, as amended, if a corporation undergoes an “ownership change”, generally defined as a greater than 50% change (by value) in its equity ownership over a three year period, the corporation’s ability to use its pre-change net operating loss carryforwards and other pre-change tax attributes, such as research credits, to offset its post-change income may be limited. Based on an analysis performed by the Company as of December 31, 2013, it was determined that two ownership changes have occurred since inception of the Company. The first ownership change occurred in 2006 at the time of the Series A financing and, as a result of the change, $1.4 million in federal and state net operating loss carryforwards will expire unutilized. In addition, $26,000 in federal and state research and development credits will expire unutilized. The second ownership change occurred in July 2013 at the time of the underwritten public offering; however, the Company believes the resulting annual imposed limitation on use of pre-change tax attributes is sufficiently high that the limit itself will not result in unutilized pre-change tax attributes.
	Uncertain Tax Positions
	A reconciliation of the beginning and ending balances of the unrecognized tax benefits during the years ended December 31, 2013, 2012 and 2011 is as follows (in thousands):
		Year Ended December 31,
		2013			2012			2011
	Unrecognized benefit—beginning of period	$	810		$	748		$	603
	Gross decreases—prior period tax positions		221			(17	)		—
	Gross increases—current period tax positions		310			79			145
	Unrecognized benefit—end of period	$	1,341		$	810		$	748
	The entire amount of the unrecognized tax benefits would not impact the Company’s effective tax rate if recognized.
	Accrued interest and penalties related to unrecognized tax benefits are classified as income tax expense and were immaterial. The Company files income tax returns in the United States and in California. The tax years 2007 through 2013 remain open in both jurisdictions. The Company is not currently under examination by income tax authorities in federal, state or other foreign jurisdictions.

Unaudited_Quarterly_Financial_

Unaudited Quarterly Financial Data	12 Months Ended
	Dec. 31, 2013
Quarterly Financial Information Disclosure [Abstract]	'
Unaudited Quarterly Financial Data	'
	16. Unaudited Quarterly Financial Data (in thousands, except per share amounts)
	The following table sets forth certain unaudited quarterly financial data for the eight quarters ended December 31, 2013. The unaudited information set forth below has been prepared on the same basis as the audited information and includes all adjustments necessary to present fairly the information set forth herein. The operating results for any quarter are not indicative of results for any future period. All data is in thousands except per share data.
		2013											2012
		Q1			Q2			Q3			Q4		Q1			Q2			Q3			Q4
	Revenues	$	940		$	407		$	548		$	27,607	$	329		$	224		$	166		$	1,675
	Operating Expenses	$	11,509		$	8,178		$	8,858		$	7,624	$	6,875		$	7,170		$	8,358		$	9,704
	Net income / (loss)	$	(12,762	)	$	(17,447	)	$	(10,986	)	$	17,769	$	(7,065	)	$	(7,194	)	$	(8,582	)	$	(10,522	)
	Net income / (loss) per share (basic)	$	(0.34	)	$	(0.47	)	$	(0.26	)	$	0.41	$	(0.36	)	$	(0.35	)	$	(0.38	)	$	(0.41	)
	Diluted income for the fourth quarter of 2013 was $0.39 per share. For all other periods presented, basic and diluted loss per share were the same.

Organization_and_Summary_of_Si1

Organization and Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2013
Accounting Policies [Abstract]	'
The Company	'
	The Company
	AcelRx Pharmaceuticals, Inc., or the Company or AcelRx, was incorporated in Delaware on July 13, 2005 as SuRx, Inc., and in January 2006, the Company changed its name to AcelRx Pharmaceuticals, Inc. The Company’s operations are based in Redwood City, California.
	AcelRx is a specialty pharmaceutical company focused on the development and commercialization of innovative therapies for the treatment of acute and breakthrough pain. AcelRx intends to commercialize its product candidates in the United States and license the development and commercialization rights to its product candidates for sale outside of the United States through strategic partnerships and collaborations. The Company’s lead product candidate, ZalvisoTM, formerly known as the Sufentanil NanoTab PCA System, or ARX-01, is currently under review by the FDA for marketing approval, and is designed to improve the management of moderate-to-severe acute pain in patients in the hospital setting. In addition, in December 2013, the Company entered into a collaboration agreement with Grünenthal for the commercialization of Zalviso in Europe and Australia.
	The Company has incurred recurring operating losses and negative cash flows from operating activities since inception and expects to continue to incur negative cash flows until its product candidates are approved for marketing in the United States and other countries, in which it has and intends to license its products, which may never occur. In previous years, prior to the completion of the clinical development program for Zalviso and the commercial collaboration of Zalviso, AcelRx was considered a development stage company.
	The Company has one business activity, which is the development and commercialization of product candidates for the treatment of pain, and a single reporting and operating unit structure.
Basis of Presentation	'
	Basis of Presentation
	The preparation of financial statements in conformity with generally accepted accounting principles requires management to make estimates and assumptions that affect the amounts reported in the financial statements and the accompanying notes. Actual results could differ from those estimates.
Concentration of Risk	'
	Concentration of Risk
	The Company invests cash that is currently not being used for operational purposes in accordance with its investment policy in debt securities of the U.S. Treasury and U.S. government sponsored agencies and overnight deposits. The Company is exposed to credit risk in the event of default by the institutions holding the cash equivalents and available-for-sale securities to the extent recorded on the balance sheet. Our cash and cash equivalent balances can be in excess of federally insured amounts.
Cash, Cash Equivalents and Marketable Securities	'
	Cash, Cash Equivalents and Marketable Securities
	The Company considers all highly liquid investments with an original maturity (at date of purchase) of three months or less to be cash equivalents. Cash and cash equivalents consist of cash on deposit with banks and money market instruments.
	All marketable securities are classified as available-for-sale and consist of U.S. Treasury and U.S. government sponsored enterprise debt securities. These securities are carried at estimated fair value, which is based on quoted market prices or observable market inputs of almost identical assets, with unrealized gains and losses included in accumulated other comprehensive income (loss). The amortized cost of securities is adjusted for amortization of premiums and accretion of discounts to maturity. Such amortization and accretion is included in interest income or expense. The cost of securities sold is based on specific identification. The Company’s investments are subject to a periodic impairment review for other-than-temporary declines in fair value. The Company’s review includes the consideration of the cause of the impairment including the creditworthiness of the security issuers, the number of securities in an unrealized loss position, the severity and duration of the unrealized losses and the Company’s intent and ability to hold the investment for a period of time sufficient to allow for any anticipated recovery in the market value. When the Company determines that the decline in fair value of an investment is below its accounting basis and this decline is other-than-temporary, it reduces the carrying value of the security it holds and records a loss in the amount of such decline.
Property and Equipment	'
	Property and Equipment
	Property and equipment are stated at cost less accumulated depreciation and amortization. Depreciation is calculated using the straight-line method over the estimated useful lives of the assets, generally three to five years. Leasehold improvements are amortized over the shorter of the estimated useful life of the improvements or the remaining lease term.
Impairment of Long-Lived Assets	'
	Impairment of Long-Lived Assets
	The Company periodically assesses the impairment of long-lived assets and, if indicators of asset impairment exist, the Company assesses the recoverability of the affected long-lived assets by determining whether the carrying value of such assets can be recovered through an analysis of the undiscounted future expected operating cash flows. If impairment is indicated, the Company records the amount of such impairment for the excess of the carrying value of the asset over its estimated fair value. For example, purchased equipment and manufacturing-related facility improvements the Company has made at Patheon’s facility in Ohio, are utilized for continued research and development, and potential commercial manufacturing of our product candidates. If the Company does not receive regulatory approval for our product candidates, the Company may determine that it is no longer probable that the Company will realize the future economic benefit associated with the costs of these assets through future manufacturing activities, and if so, the Company would record an impairment charge associated with these assets. As of December 31, 2013, the Company has not written down any of its long-lived assets as a result of impairment.
Restricted Cash	'
	Restricted Cash
	Under the Company’s facility lease and corporate credit card agreements, the Company is required to maintain letters of credit as security for performance under these agreements. The letters of credit are secured by certificates of deposit in amounts equal to the letters of credit, which are classified as restricted cash on the balance sheet.
Revenue Recognition	'
	Revenue Recognition
	The Company recognizes revenue when all of the following criteria are met: persuasive evidence of an arrangement exists; delivery has occurred or services have been rendered; the fee is fixed or determinable; and collectability is reasonably assured.
Collaboration Revenue	'
	Collaboration Revenue
	Collaboration revenue, which is earned under license agreements with third parties, may include nonrefundable license fees, cost reimbursements, research and development services, commercial manufacturing services, contingent development and commercial milestones and royalties.
	In October 2009, the Financial Accounting Standards Board, or FASB, issued Accounting Standards Update, or ASU, 2009-13 Revenue Arrangements with Multiple Deliverables, or ASU 2009-13, which amended the accounting standards for certain multiple element revenue arrangements to:
		•	provide updated guidance on whether multiple elements exist, how the elements in an arrangement should be separated, and how the arrangement consideration should be allocated to the separate elements;
		•	require an entity to allocate arrangement consideration to each element based on a selling price hierarchy, also called the relative selling price method, where the selling price for an element is based on vendor-specific objective evidence (“VSOE”), if available; third-party evidence (“TPE”), if available and VSOE is not available; or the best estimate of selling price (“ESP”), if neither VSOE nor TPE is available; and
		•	eliminate the use of the residual method and require an entity to allocate arrangement consideration using the selling price hierarchy.
	The revenue allocated to each element is then recognized when the basic revenue recognition criteria are met for that element.
	VSOE is based on the price charged when the element is sold separately and is the price actually charged for that deliverable. Establishing VSOE may not be possible for the elements of a license arrangement because each arrangement is unique, an arrangement typically consists of multiple elements and AcelRx has limited history of entering into license arrangements.
	When VSOE cannot be established, AcelRx attempts to establish the selling price of the elements of a license arrangement based on TPE. TPE is determined based on a competitor’s price for similar deliverables when sold separately. AcelRx may not be able to determine TPE for license arrangements, as they contain a significant level of differentiation such that the comparable pricing of a competitor’s license arrangement with similar functionality cannot be obtained, and AcelRx is therefore unable to reliably determine what a similar competitor’s license arrangement’s selling price would be on a standalone basis.
	When AcelRx is unable to establish the selling price of an element using VSOE or TPE, ESP is utilized in the allocation of the elements of the arrangement. The objective of the ESP is to determine the price at which AcelRx would transact a sale if the element of the license arrangement were sold on a standalone basis.
	The process for determining ESPs involves management’s judgment. Our process considers multiple factors such as discounted cash flows, estimated direct expenses and other costs and available data, which may vary over time, depending upon the circumstances, and relate to each deliverable. If the estimated obligation period of one or more deliverables should change, the future amortization of the revenue would also change.
	AcelRx recognizes a contingent milestone payment as revenue in its entirety upon our achievement of the milestone. A milestone is substantive if the consideration earned from the achievement of the milestone (i) is consistent with performance required to achieve the milestone or the increase in value to the delivered item, (ii) relates solely to past performance and (iii) is reasonable relative to all of the other deliverables and payments within the arrangement.
Research Grant Revenue	'
	Research Grant Revenue
	In May 2011, the Company entered into an award contract with the US Army Medical Research and Materiel Command, or USAMRMC, to support the development of the Company’s new product candidate, ARX-04, a Sufentanil NanoTab for the treatment of moderate-to-severe acute pain. The grant provides for the reimbursement of qualified expenses for research and development activities as defined under the terms of the grant agreement. Revenue under the grant agreement is recognized when the related qualified research expenses are incurred.
Research and Development Expenses	'
	Research and Development Expenses
	Research and development costs are charged to expense when incurred. Research and development expenses include salaries, employee benefits, including stock-based compensation, consultant fees, laboratory supplies, costs associated with clinical trials and manufacturing, including contract research organization fees, other professional services and allocations of corporate costs. The Company reviews and accrues clinical trial expenses based on work performed, which relies on estimates of total costs incurred based on patient enrollment, completion of patient studies and other events.
Comprehensive Loss	'
	Comprehensive Loss
	Comprehensive loss is comprised of net loss and other comprehensive income (loss) and is disclosed in the Statement of Comprehensive Loss. For the Company, other comprehensive income (loss) consists of changes in unrealized gains and losses on the Company’s investments.
Fair Value of Financial Instruments	'
	Fair Value of Financial Instruments
	The Company measures and reports its cash equivalents, investments and financial liabilities at fair value. Fair value is defined as the exchange price that would be received for an asset or an exit price paid to transfer a liability in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants on the measurement date. Valuation techniques used to measure fair value must maximize the use of observable inputs and minimize the use of unobservable inputs. The fair value hierarchy defines a three-level valuation hierarchy for disclosure of fair value measurements as follows:
	Level I—Unadjusted quoted prices in active markets for identical assets or liabilities;
	Level II—Inputs other than quoted prices included within Level I that are observable, unadjusted quoted prices in markets that are not active, or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the related assets or liabilities; and
	Level III—Unobservable inputs that are supported by little or no market activity for the related assets or liabilities.
	The categorization of a financial instrument within the valuation hierarchy is based upon the lowest level of input that is significant to the fair value measurement.
Income Taxes	'
	Income Taxes
	Deferred tax assets and liabilities are measured based on differences between the financial reporting and tax basis of assets and liabilities using enacted rates and laws that are expected to be in effect when the differences are expected to reverse. The Company records a valuation allowance for the full amount of deferred assets, which would otherwise be recorded for tax benefits relating to operating loss and tax credit carryforwards, as realization of such deferred tax assets cannot be determined to be more likely than not.
Stock-Based Compensation	'
	Stock-Based Compensation
	Compensation expense for all share-based payment awards made to employees and directors, including employee stock options, restricted stock units and employee share purchases related to the 2011 Employee Stock Purchase Plan, or ESPP, is based on estimated fair values at grant date. The Company determines the grant date fair value of the awards using the Black-Scholes option-pricing model and generally recognizes the fair value as stock-based compensation expense on a straight-line basis over the vesting period of the respective awards.
	The Black-Scholes option pricing model requires inputs such as expected term, expected volatility and risk-free interest rate. These inputs are subjective and generally require significant analysis and judgment to develop. Estimates of expected life are primarily determined using the simplified method in accordance with guidance provided by the SEC. Such method was utilized as the Company did not believe its historical option exercise experience, which was limited, provided a reasonable basis upon which to estimate expected term. Volatility is derived from historical volatilities of several public companies within AcelRx’s industry that are deemed to be comparable to AcelRx’s business because AcelRx’s has limited information on the volatility of its common stock since there was no trading history prior to completion of AcelRx’s Initial Public Offering, or IPO, in February 2011. The risk-free rate is based on the U.S. Treasury yield curve in effect at the time of grant commensurate with the expected life assumption. Further, the Company estimates forfeitures at the time of grant and revises those estimates in subsequent periods if actual forfeitures differ from those estimates.
Net Loss per Share of Common Stock	'
	Net Loss per Share of Common Stock
	The Company’s basic net loss per share of common stock is calculated by dividing the net loss by the weighted average number of shares of common stock outstanding for the period. The diluted net loss per share of common stock is computed by giving effect to all potential common stock equivalents outstanding for the period determined using the treasury stock method. For purposes of this calculation, convertible preferred stock, options to purchase common stock, restricted stock subject to repurchase, warrants to purchase convertible preferred stock and warrants to purchase common stock were considered to be common stock equivalents. In periods with a reported net loss, such common stock equivalents are excluded from the calculation of diluted net loss per share of common stock as their effect is antidilutive.
Segment Information	'
	Segment Information
	The Company operates in one operating segment and has operations solely in the United States.
Recently Issued Accounting Pronouncements	'
	Recently Issued Accounting Pronouncements
	In February 2013, Accounting Standards Codification Topic 220, Comprehensive Income was amended to require companies to report, in one place, information about reclassifications out of accumulated other comprehensive income. Accordingly, a company can present this information on the face of the financial statements, if certain requirements are met, or the information must be presented in the notes to the financial statements. The Company adopted this guidance as of January 1, 2013, on a retrospective basis, and the items reclassified out of accumulated other comprehensive income are not material for all periods presented.

Investments_and_Fair_Value_Mea1

Investments and Fair Value Measurement (Tables)	12 Months Ended
	Dec. 31, 2013
Text Block [Abstract]	'
Summary of Cash, Cash Equivalents and Investments	'
	The table below summarizes the Company’s cash, cash equivalents and investments (in thousands):
		As of December 31, 2013
		Amortized Cost			Gross Unrealized			Gross Unrealized		Fair
					Gains			Losses		Value
	Cash and cash equivalents:
	Cash	$	88,390		$	—		$	—	$	88,390
	Money market funds		11			—			—		11
	Total cash and cash equivalents		88,401			—			—		88,401
	Marketable securities:
	U.S. government agency securities		15,261			1			—		15,262
	Total marketable securities		15,261			1			—		15,262
	Total cash, cash equivalents and investments		103,662			1			—		103,663
		As of December 31, 2012
		Amortized Cost			Gross Unrealized			Gross Unrealized		Fair
					Gains			Losses		Value
	Cash and cash equivalents:
	Cash	$	44,440		$	—		$	—	$	44,440
	Money market funds		2,086			—			—		2,086
	U.S. government agency securities		1,406			—			—		1,406
	Total cash and cash equivalents		47,932			—			—		47,932
	Marketable securities:
	U.S. government agency securities		11,830			1			—		11,831
	Total marketable securities		11,830			1			—		11,831
	Total cash, cash equivalents and investments	$	59,762		$	1		$	—	$	59,763
Fair Value of Financial Assets and Liabilities by Level within Fair Value Hierarchy	'
	The following table sets forth the fair value of the Company’s financial assets and liabilities by level within the fair value hierarchy (in thousands):
		As of December 31, 2013
		Fair Value			Level I			Level II		Level III
	Assets
	Money market funds	$	11		$	11		$	—	$	—
	U.S. government agency obligations		15,262			—			15,262		—
	Total assets measured at fair value	$	15,273		$	11		$	15,262	$	—
	Liabilities
	PIPE warrant	$	13,111		$	—		$	—	$	13,111
	Contingent put option		334			—			—		334
	Total liabilities measured at fair value	$	13,445		$	—		$	—	$	13,445
		As of December 31, 2012
		Fair Value			Level I			Level II		Level III
	Assets
	Money market funds	$	2,086		$	2,086		$	—	$	—
	U.S. government agency obligations		13,237			—			13,237		—
	Total assets measured at fair value	$	15,323		$	2,086		$	13,237	$	—
	Liabilities
	PIPE warrant	$	7,418			—			—	$	7,418
	Contingent put option		82			—			—		82
	Total liabilities measured at fair value	$	7,500		$	—		$	—	$	7,500
Assumptions Used in Black-Scholes Option-Pricing Model to Estimate Fair Value of PIPE Warrants	'
	The following table sets forth the assumptions used in the Black-Scholes option-pricing model to estimate the fair value of the PIPE warrants as of December 31, 2013 and 2012:
		As of December 31,			As of December 31,
		2013			2012
	Market Price	$	11.31		$	4.26
	Exercise Price	$	3.4		$	3.4
	Risk-free interest rate		1.27	%		0.72	%
	Expected volatility		69	%		78	%
	Expected life (in years)		3.92			4.9
	Expected dividend yield		0	%		0	%
Summary of Changes in Fair Value of Level III Financial Liabilities	'
	The following table sets forth a summary of the changes in the fair value of the Company’s Level III financial liabilities for the years ended December 31, 2013 and 2012 (in thousands):
		Year Ended
		December 31,
		2013
	Fair value—beginning of period	$	7,500
	Change in fair value of PIPE warrants		5,693
	Change in fair value of contingent put option associated with 2011 loan and security agreement with Hercules		(82	)
	Addition of contingent put option associated with 2013 loan and security agreement with Hercules		334
	Fair value—end of period	$	13,445
		Year Ended
		December 31,
		2012
	Fair value—beginning of period	$	232
	Addition of PIPE warrants in June 2012		5,828
	Change in fair value of PIPE warrants		1,590
	Change in fair value of contingent put option		(150	)
	Fair value—end of period	$	7,500

Property_and_Equipment_Tables

Property and Equipment (Tables)	12 Months Ended
	Dec. 31, 2013
Property Plant And Equipment [Abstract]	'
Components of Property and Equipment	'
	Property and equipment consist of the following (in thousands):
		As of December 31,
		2013			2012
	Research equipment	$	2,014		$	2,014
	Leasehold improvements		1,425			1,418
	Computer equipment and software		189			167
	Construction in process		3,277			—
	Tooling		318			337
	Furniture and fixtures		59			59
	Total property, plant and equipment		7,282			3,995
	Less accumulated depreciation and amortization		(2,103	)		(1,510	)
		$	5,179		$	2,485

LongTerm_Debt_Tables

Long-Term Debt (Tables)	12 Months Ended
	Dec. 31, 2013
Debt Disclosure [Abstract]	'
Outstanding Future Payments of Long-Term Debt	'
	The following table summarizes our outstanding future payments associated with the Company’s long-term debt as of December 31, 2013 (in thousands):
				Payment by Period
	Obligations:	Total		Less than 1		1-3 years		3-5 years		More than 5
				year						years
	Principal Payments	$	15,000	$	—	$	10,106	$	4,894		—
	Interest Payments		3,533		1,327		2,015	$	191		—
	Balloon Payments		1,900		200		—	$	1,700		—
	Total	$	20,433	$	1,527	$	12,121	$	6,785		—

Commitments_and_Contingencies_

Commitments and Contingencies (Tables)	12 Months Ended
	Dec. 31, 2013
Commitments And Contingencies Disclosure [Abstract]	'
Future Minimum Payments under Lease Agreement	'
	Future minimum payments under the lease agreement as of December 31, 2013 are as follows (in thousands):
	Year Ending December 31:
	2014		392
	2015		404
	2016		142
	Total minimum payments	$	938

StockBased_Compensation_Tables

Stock-Based Compensation (Tables)	12 Months Ended
	Dec. 31, 2013
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]	'
Employee Stock Purchase Plan	'
	The Company recorded total stock-based compensation expense for stock options, stock awards and the ESPP as follows (in thousands):
		Year Ended December 31,
		2013			2012		2011
	Research and development	$	1,657		$	998	$	785
	General and administrative		1,822			1,152		1,048
	Total	$	3,479		$	2,150	$	1,833
Option Activity	'
	The following table summarizes option activity under the 2011 Plan and 2006 Plan:
		Number			Weighted-		Weighted-		Aggregate
		of Stock Options			Average		Average		Intrinsic
		Outstanding			Exercise		Remaining		Value
					Price		Contractual
							Life (Years)
									(in thousands)
	December 31, 2010		2,008,797		$	2.91
	Granted		514,958			3.48
	Forfeited		(58,022	)		3.32
	Exercised		(69,765	)		1.2
	December 31, 2011		2,395,968		$	3.08
	Granted		1,213,391			3.36
	Forfeited		(165,781	)		3.23
	Exercised		(43,767	)		2.32
	December 31, 2012		3,399,811		$	3.18
	Granted		1,958,727			5.99
	Forfeited		(17,917	)		8.82
	Exercised		(431,216	)		3.03
	December 31, 2013		4,909,405		$	4.29		7.9		34,452
	Vested and exercisable options—December 31, 2013		2,161,400		$	3.17		6.7	$	17,589
	Vested and expected to vest—December 31, 2013		4,718,574		$	4.25		7.8	$	33,322
Stock Options Outstanding, Vested and Exercisable	'
	Additional information regarding the Company’s stock options outstanding and vested and exercisable as of December 31, 2013 is summarized below:
		Options Outstanding							Options Vested and Exercisable
	Exercise Prices	Number of			Weighted-Average		Weighted-Average		Shares Subject		Weighted-Average
		Stock Options			Remaining		Exercise Price  per		to Stock		Exercise Price  per
		Outstanding			Contractual  Life		Share		Options		Share
					(Years)
	$1.20-$2.56		613,875			5.9	$	2.22		613,874	$	2.22
	$2.5601-$4.00		2,088,053			7.4	$	3.23		1,299,298	$	3.16
	$4.22-$6.34		1,962,477			8.7	$	5.31		236,353	$	5.32
	$8.18-$10.55		245,000			9.7	$	10.4		11,875	$	10.55
			4,909,405			7.9	$	4.29		2,161,400	$	3.17
Assumptions to Calculate Fair Value of Each Employee Stock Option	'
	The Company used the following assumptions to calculate the fair value of each employee stock option:
		Year Ended December 31,
		2013		2012	2011
	Expected term (in years)	5.75-6.25		5.75-6.25	5.75-6.25
	Risk-free interest rate	1.02%-2.96%		0.6%-1.74%	1.1%-2.5%
	Expected volatility	80%		80%	79%
	Expected dividend rate	0%		0%	0%

Net_Loss_per_Share_of_Common_S1

Net Loss per Share of Common Stock (Tables)	12 Months Ended
	Dec. 31, 2013
Earnings Per Share [Abstract]	'
Computation of Basic and Diluted Net Loss per Share of Common Stock	'
	The following table sets forth the computation of the Company’s basic and diluted net loss per share of common stock during the years ended December 31, 2012, 2011 and 2010 (in thousands, except for share and per share amounts):
		Year Ended December 31,
		2013			2012			2011
	Net loss	$	(23,426	)	$	(33,363	)	$	(20,101	)
	Shares used in computing net loss per share of common stock, basic and diluted		39,746,678			22,124,637			17,344,727
	Net loss per share of common stock, basic and diluted	$	(0.59	)	$	(1.51	)	$	(1.16	)
Outstanding Shares of Common Stock Equivalents Excluded from Computation of Diluted Net Loss per Share	'
	The following outstanding shares of common stock equivalents were excluded from the computation of diluted net loss per share of common stock for the periods presented because including them would have been antidilutive:
		Year Ended December 31,
		2013			2012			2011
	Stock options to purchase common stock		4,909,405			3,399,811			2,395,968
	Restricted Stock Units		65,765			161,096			257,868
	Common stock warrants		1,674,669			3,136,300			506,197

Accounts_Payable_and_Accrued_L1

Accounts Payable and Accrued Liabilities (Tables)	12 Months Ended
	Dec. 31, 2013
Payables And Accruals [Abstract]	'
Accounts Payable and Accrued Liabilities	'
	Accounts payable and accrued liabilities consist of the following (in thousands):
		December 31,
		2013		2012
	Accounts payable	$	2,341	$	2,235
	Accrued compensation and employee benefits		2,397		1,613
	Accrued research and development expenses		248		2,371
	Accrued liabilities associated with property and equipment		725		—
	Professional fees		230		361
	Interest payable		61		119
	Other		243		189
	Total accounts payable and accrued liabilities	$	6,245	$	6,888

Income_Taxes_Tables

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2013
Income Tax Disclosure [Abstract]	'
Components of Deferred Tax Assets	'
	Net deferred tax assets as of December 31, 2013 and 2012 consist of the following (in thousands):
		December 31,			December 31,
		2013			2012
	Deferred tax assets:
	Accruals and other	$	2,172		$	802
	Research credits		3,553			2,050
	Net operating loss carryforward		36,279			35,730
	Section 59(e) R&D expenditures		10,339			8,572
	Total deferred tax assets		52,343			47,154
	Valuation allowance	$	(52,343	)	$	(47,154	)
	Net deferred tax assets	$	—		$	—
Reconciliation of Statutory Federal Income Tax	'
	Reconciliations of the statutory federal income tax to the Company’s effective tax during the years ended December 31, 2013, 2012 and 2011 are as follows (in thousands):
		Year Ended December 31,
		2013			2012			2011
	Tax at statutory federal rate	$	(7,965	)	$	(11,343	)	$	(6,834	)
	State tax—net of federal benefit		(716	)		(1,953	)		(1,104	)
	PIPE Warrant liability		4,898			540			—
	General Business credits		(1,326	)		—			—
	Other		(80	)		1,807			161
	Change in valuation allowance		5,189			11,949			7,777
	Provision (benefit) for income taxes	$	—		$	—		$	—
Reconciliation of Beginning and Ending Balance of Unrecognized Tax Benefits	'
	A reconciliation of the beginning and ending balances of the unrecognized tax benefits during the years ended December 31, 2013, 2012 and 2011 is as follows (in thousands):
		Year Ended December 31,
		2013			2012			2011
	Unrecognized benefit—beginning of period	$	810		$	748		$	603
	Gross decreases—prior period tax positions		221			(17	)		—
	Gross increases—current period tax positions		310			79			145
	Unrecognized benefit—end of period	$	1,341		$	810		$	748

Unaudited_Quarterly_Financial_1

Unaudited Quarterly Financial Data (Tables)	12 Months Ended
	Dec. 31, 2013
Quarterly Financial Information Disclosure [Abstract]	'
Quarterly Financial Data	'
	All data is in thousands except per share data.
		2013											2012
		Q1			Q2			Q3			Q4		Q1			Q2			Q3			Q4
	Revenues	$	940		$	407		$	548		$	27,607	$	329		$	224		$	166		$	1,675
	Operating Expenses	$	11,509		$	8,178		$	8,858		$	7,624	$	6,875		$	7,170		$	8,358		$	9,704
	Net income / (loss)	$	(12,762	)	$	(17,447	)	$	(10,986	)	$	17,769	$	(7,065	)	$	(7,194	)	$	(8,582	)	$	(10,522	)
	Net income / (loss) per share (basic)	$	(0.34	)	$	(0.47	)	$	(0.26	)	$	0.41	$	(0.36	)	$	(0.35	)	$	(0.38	)	$	(0.41	)

Organization_and_Summary_of_Si2

Organization and Summary of Significant Accounting Policies - Additional Information (Detail) (USD $)	12 Months Ended
	Dec. 31, 2013
	Segment
Organization And Summary Of Significant Accounting Policies [Line Items]	'
Place of incorporation	'Delaware
Date of incorporation	13-Jul-05
Impairment of long-lived assets	$0
Operating segment	1
Minimum	'
Organization And Summary Of Significant Accounting Policies [Line Items]	'
Estimated useful lives	'3 years
Maximum	'
Organization And Summary Of Significant Accounting Policies [Line Items]	'
Estimated useful lives	'5 years

Investments_and_Fair_Value_Mea2

Investments and Fair Value Measurement - Additional Information (Detail) (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012
Investment Holdings [Line Items]	'	'
Maturity period of non-current marketable securities	'Beyond one year	'
Unrealized losses on available-for-sale securities	$0	$0
Realized losses from available-for-sale securities	0	0
Other than temporary impairment for available-for-sale securities	$0	$0
Maximum	'	'
Investment Holdings [Line Items]	'	'
Contractual maturity period for all investments	'1 year	'1 year

Summary_of_Cash_Cash_Equivalen

Summary of Cash, Cash Equivalents and Investments (Detail) (USD $)	Dec. 31, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Amortized Cost	$103,662	$59,762
Gross Unrealized Gains	1	1
Gross Unrealized Losses	'	'
Fair Value	103,663	59,763
Cash and Cash Equivalents	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Amortized Cost	88,401	47,932
Gross Unrealized Gains	'	'
Gross Unrealized Losses	'	'
Fair Value	88,401	47,932
Cash and Cash Equivalents | Cash	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Amortized Cost	88,390	44,440
Gross Unrealized Gains	'	'
Gross Unrealized Losses	'	'
Fair Value	88,390	44,440
Cash and Cash Equivalents | Money market funds	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Amortized Cost	11	2,086
Gross Unrealized Gains	'	'
Gross Unrealized Losses	'	'
Fair Value	11	2,086
Cash and Cash Equivalents | U.S. government agency securities	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Amortized Cost	'	1,406
Gross Unrealized Gains	'	'
Gross Unrealized Losses	'	'
Fair Value	'	1,406
Marketable securities	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Amortized Cost	15,261	11,830
Gross Unrealized Gains	1	1
Gross Unrealized Losses	'	'
Fair Value	15,262	11,831
Marketable securities | U.S. government agency securities	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Amortized Cost	15,261	11,830
Gross Unrealized Gains	1	1
Gross Unrealized Losses	'	'
Fair Value	$15,262	$11,831

Fair_Value_of_Financial_Assets

Fair Value of Financial Assets and Liabilities by Level within Fair Value Hierarchy (Detail) (USD $)	Dec. 31, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Total assets measured at fair value	$15,273	$15,323
Total liabilities measured at fair value	13,445	7,500
Contingent put option liability	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Total liabilities measured at fair value	334	82
PIPE warrants	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Total liabilities measured at fair value	13,111	7,418
Money market funds	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Total assets measured at fair value	11	2,086
U.S. government agency obligations	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Total assets measured at fair value	15,262	13,237
Level I	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Total assets measured at fair value	11	2,086
Total liabilities measured at fair value	'	'
Level I | Contingent put option liability	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Total liabilities measured at fair value	'	'
Level I | PIPE warrants	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Total liabilities measured at fair value	'	'
Level I | Money market funds	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Total assets measured at fair value	11	2,086
Level I | U.S. government agency obligations	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Total assets measured at fair value	'	'
Level II	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Total assets measured at fair value	15,262	13,237
Total liabilities measured at fair value	'	'
Level II | Contingent put option liability	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Total liabilities measured at fair value	'	'
Level II | PIPE warrants	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Total liabilities measured at fair value	'	'
Level II | Money market funds	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Total assets measured at fair value	'	'
Level II | U.S. government agency obligations	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Total assets measured at fair value	15,262	13,237
Level III	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Total assets measured at fair value	'	'
Total liabilities measured at fair value	13,445	7,500
Level III | Contingent put option liability	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Total liabilities measured at fair value	334	82
Level III | PIPE warrants	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Total liabilities measured at fair value	13,111	7,418
Level III | Money market funds	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Total assets measured at fair value	'	'
Level III | U.S. government agency obligations	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Total assets measured at fair value	'	'

Assumptions_Used_in_BlackSchol

Assumptions Used in Black-Scholes Option-Pricing Model to Estimate Fair Value of Pipe Warrants (Detail) (PIPE warrants, USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012
PIPE warrants	'	'
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]	'	'
Market Price	$11.31	$4.26
Exercise Price	$3.40	$3.40
Risk-free interest rate	1.27%	0.72%
Expected volatility	69.00%	78.00%
Expected life (in years)	'3 years 11 months 1 day	'4 years 10 months 24 days
Expected dividend yield	0.00%	0.00%

Summary_of_Changes_in_Fair_Val

Summary of Changes in Fair Value of Level III Financial Liabilities (Detail) (Level III, USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]	'	'
Fair value-beginning of period	$7,500	$232
Addition of PIPE warrants in June 2012	'	5,828
Change in fair value of PIPE warrants	5,693	1,590
Change in fair value of contingent put option	'	-150
Fair value-end of period	13,445	7,500
Hercules 2011 Loan and Security Agreement	'	'
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]	'	'
Change in fair value of contingent put option	-82	'
Hercules 2013 Loan and Security Agreement	'	'
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]	'	'
Change in fair value of contingent put option	$334	'

Components_of_Property_and_Equ

Components of Property and Equipment (Detail) (USD $)	Dec. 31, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified
Property, Plant and Equipment [Line Items]	'	'
Total property, plant and equipment	$7,282	$3,995
Less accumulated depreciation and amortization	-2,103	-1,510
Total property, plant and equipment net	5,179	2,485
Research Equipment	'	'
Property, Plant and Equipment [Line Items]	'	'
Total property, plant and equipment	2,014	2,014
Leasehold Improvements	'	'
Property, Plant and Equipment [Line Items]	'	'
Total property, plant and equipment	1,425	1,418
Computer Equipment And Software	'	'
Property, Plant and Equipment [Line Items]	'	'
Total property, plant and equipment	189	167
Construction in Process	'	'
Property, Plant and Equipment [Line Items]	'	'
Total property, plant and equipment	3,277	'
Tooling	'	'
Property, Plant and Equipment [Line Items]	'	'
Total property, plant and equipment	318	337
Furniture and Fixtures	'	'
Property, Plant and Equipment [Line Items]	'	'
Total property, plant and equipment	$59	$59

Property_and_Equipment_Additio

Property and Equipment - Additional Information (Detail) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Property, Plant and Equipment [Line Items]	'	'	'
Depreciation and amortization expense	$593	$605	$513
Property, plant and equipment	7,282	3,995	'
Construction in Process	'	'	'
Property, Plant and Equipment [Line Items]	'	'	'
Property, plant and equipment	3,277	'	'
Patheon's Cincinnati Facility | Construction in Process	'	'	'
Property, Plant and Equipment [Line Items]	'	'	'
Property, plant and equipment	$2,500	'	'

Research_Grant_Additional_Info

Research Grant - Additional Information (Detail) (USD $)	1 Months Ended	12 Months Ended
	31-May-11	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Research And Development [Abstract]	'	'	'	'
Attributable revenue for product development from US Army Medical Research and Material Command	$5,600,000	$5,600,000	'	'
Research grant revenue	'	$2,132,000	$2,394,000	$1,072,000

Collaboration_Additional_Infor

Collaboration - Additional Information (Detail) (USD $)	12 Months Ended
	Dec. 31, 2013
Revenue Recognition, Milestone Method [Line Items]	'
Aggregate potential payments	$30,000,000
Additional payments receivable	220,000,000
Manufacturing Agreement, percentage for five years	100.00%
Manufacturing Agreement, percentage thereafter	80.00%
Revenue recognition - milestone method	'Milestones are events which have the following characteristics: (i) they can be achieved based in whole or in part on either the Companybs performance or on the occurrence of a specific outcome resulting from the Companybs performance, (ii) there was substantive uncertainty at the date the agreement was entered into that the event would be achieved and, (iii) they would result in additional payments due to the Company. A milestone is considered substantive if the following criteria are met: (i) the consideration is commensurate with either (1) the entitybs performance to achieve the milestone, or (2) the enhancement of the value of the delivered item (s) as a result of a specific outcome resulting from the entitybs performance to achieve the milestone, , (ii) the consideration relates solely to past performance and, (iii) the consideration is reasonable relative to all of the other deliverables and payment terms, including other potential milestone consideration, within the arrangement.
Milestone payments related to net sales net sales target	171,500,000
Zalviso	'
Revenue Recognition, Milestone Method [Line Items]	'
Aggregate potential payments	28,500,000
Zalviso | Europe	'
Revenue Recognition, Milestone Method [Line Items]	'
Aggregate potential payments	20,000,000
First milestone payment to be received	5,000,000
Up Front Fee	'
Revenue Recognition, Milestone Method [Line Items]	'
License revenue recognized	27,400,000
Deferred revenue	$2,630,000

LongTerm_Debt_Additional_Infor

Long-Term Debt - Additional Information (Detail) (USD $)

0 Months Ended

12 Months Ended

1 Months Ended

2 Months Ended

12 Months Ended

12 Months Ended

12 Months Ended

12 Months Ended

12 Months Ended

0 Months Ended

Jun. 29, 2011

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2011

Sep. 14, 2010

Jun. 30, 2011

Jul. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2011

Dec. 16, 2013

Jun. 29, 2011

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Jun. 29, 2011

Dec. 31, 2011

Dec. 31, 2013

Nov. 30, 2008

Sep. 30, 2008

Dec. 31, 2013

Dec. 16, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 16, 2013

Dec. 31, 2013

Dec. 31, 2013

Hercules Warrants

Hercules Warrants

Hercules Warrants

Hercules Loan and Security Agreement

Hercules Loan and Security Agreement

Hercules Loan and Security Agreement

Hercules Loan and Security Agreement

Hercules Loan and Security Agreement

Hercules Loan and Security Agreement

Hercules Loan and Security Agreement

Hercules Loan and Security Agreement

Hercules Loan and Security Agreement

Hercules Loan and Security Agreement

Hercules Loan and Security Agreement

Hercules Loan and Security Agreement

Hercules Loan and Security Agreement

Pinnacle Loan and Security Agreement

Pinnacle Loan and Security Agreement

Amended and Restated Loan and Security Agreement

Amended and Restated Loan and Security Agreement

Amended and Restated Loan and Security Agreement

Amended and Restated Loan and Security Agreement

Amended and Restated Loan and Security Agreement

Amended and Restated Loan and Security Agreement

Amended and Restated Loan and Security Agreement

Tranche

Prior to December 16, 2014

After December 16, 2014, but Prior to December 16, 2015

After December 16, 2015

Minimum

Maximum

First Tranche

Second Tranche

Hercules Warrants

Prime Rate

Minimum

First Tranche

Second Tranche

Third Tranche

Debt Instrument [Line Items]

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Loan and security agreement

'

'

'

'

'

'

'

'

'

'

'

'

$20,000,000

'

'

'

'

'

$10,000,000

$10,000,000

'

'

'

'

'

'

'

$15,000,000

'

'

Number of tranches

'

'

'

'

'

'

'

'

'

'

'

'

2

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Warrants exercisable term

'

'

'

'

'

'7 years

'

'5 years

'5 years

'

'

'

'

'

'

'

'

'

'

'

'7 years

'

'

'

'

'

'

'

'

'

Debt, interest rate percentage

'

'

'

'

4.00%

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

8.50%

'

'

'

'

'

'

'

'

'

Warrants exercise price per share

'

'

'

'

'

$3.06

'

$6.79

$6.79

'

'

'

'

'

'

'

'

'

'

'

$3.06

'

'

'

'

'

'

'

'

'

Warrants to purchase common stock

'

'

'

'

'

274,508

'

'

'

'

'

'

'

'

'

'

'

'

'

'

274,508

'

'

'

'

'

'

'

'

'

Loan and security agreement, maximum potential borrowings

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

12,000,000

'

40,000,000

'

'

'

10,000,000

15,000,000

Proceeds used for repayment of obligation

'

16,345,000

3,655,000

5,297,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

8,600,000

'

'

Difference in discounted cash flows, percentage

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

10.00%

'

'

'

New debt at estimated fair value

'

14,300,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Loss on extinguishment of debt

'

1,202,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

1,200,000

'

'

'

'

'

'

Payment terms

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'Payments under the Loan Agreement are interest only until April 1, 2015 (which will be extended until January 1, 2016 if the Company achieves the Milestone on or before April 1, 2015) followed by equal monthly payments of principal and interest through the scheduled maturity date on October 1, 2017 (which would be extended until January 1, 2018 if the Company achieves the Milestone on or prior to April 1, 2015) (the "Loan Maturity Date").

'

'

'

'

'

'

Interest rate terms

'

'The interest rate for each tranche will be calculated at a rate equal to the greater of either (i) 9.10% plus the prime rate as reported from time to time in The Wall Street Journal minus 5.25%, and (ii) 9.10%.

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Interest rate

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

9.10%

'

'

'

'

Basis spread on variable interest rate

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

5.25%

'

'

'

'

Final payment due on maturity date

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

1,700,000

'

'

'

'

'

'

Prepayment terms

'

'

'

'

'

'

'

'

'If the Company prepays the loan prior to maturity, it will pay the Lenders a prepayment charge, based on a percentage of the then outstanding principal balance, equal to 3% if the prepayment occurs prior to December 16, 2014, 2% if the prepayment occurs after December 16, 2014, but prior to December 16, 2015, or 1% if the prepayment occurs after December 16, 2015.

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Prepayment charge on loan percentage

'

'

'

'

'

'

'

'

'

'

'

'

'

3.00%

2.00%

1.00%

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Convertible debt amount

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

5,000,000

'

'

'

'

'

'

'

'

'

'

'

'

Convertible debt terms

'

'

'

'

'

'

'

'

'Subject to certain conditions and limitations set forth in the Loan Agreement, the Company has the right to convert up to $5.0 million of scheduled principal installments under the Notes into freely tradeable shares of the Companybs common stock (bCommon Stockb). The number of shares of Common Stock that would be issued upon conversion of the Notes would be equal to the number determined by dividing (x) the product of (A) the principal amount to be paid in shares of Common Stock and (B) 103%, by (y) $9.30 (subject to certain proportional adjustments as provided for in the Loan Agreement).

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Default interest rate

'

'

'

'

'

'

'

'

5.00%

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Common stock warrants exercised

'

1,135,589

'

'

'

'

274,508

176,730

176,730

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Prepayment charges for accelerated repayment of credit facility, percentage of outstanding balance

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

1.00%

3.00%

'

'

'

'

'

'

'

'

'

'

'

'

Final payment fee for early repayment of facility

'

'

'

'

'

'

'

'

1,700,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Contingent put option liability

'

'

'

'

'

'

'

'

334,000

82,000

232,000

32,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Loan and security agreement, amount outstanding

'

'

'

'

'

'

'

'

15,000,000

16,000,000

'

'

'

'

'

'

'

'

'

'

'

12,000,000

'

'

'

'

'

'

'

'

Amortization of debt discounts

'

'

'

'

'

'

'

'

400,000

500,000

254,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Outstanding borrowings, debt discount

'

1,100,000

'

'

'

'

'

'

'

500,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Repayment of outstanding loan balance

$2,800,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Outstanding_Future_Payments_of

Outstanding Future Payments of Long-Term Debt (Detail) (USD $)	Dec. 31, 2013
In Thousands, unless otherwise specified
Debt Instrument [Line Items]	'
Principal Payments	$15,000
Interest Payments	3,533
Balloon Payments	1,900
Total	20,433
Less than 1 year	'
Debt Instrument [Line Items]	'
Interest Payments	1,327
Balloon Payments	200
Total	1,527
1-3 years	'
Debt Instrument [Line Items]	'
Principal Payments	10,106
Interest Payments	2,015
Total	12,121
3-5 years	'
Debt Instrument [Line Items]	'
Principal Payments	4,894
Interest Payments	191
Balloon Payments	1,700
Total	6,785
More than 5 years	'
Debt Instrument [Line Items]	'
Principal Payments	'
Interest Payments	'
Balloon Payments	'
Total	'

Convertible_Notes_Additional_I

Convertible Notes - Additional Information (Detail) (USD $)	0 Months Ended	12 Months Ended			1 Months Ended
	Sep. 14, 2011	Dec. 31, 2013	Dec. 31, 2010	Sep. 14, 2010	Mar. 31, 2011
					Second Tranche
Debt Instrument [Line Items]	'	'	'	'	'
Convertible promissory notes value	'	$4,000,000	'	$8,000,000	$4,000,000
Convertible promissory notes, interest rate	'	'	'	4.00%	'
Convertible promissory notes, maturity date description	'A maturity date of the earlier of (1) September 14, 2011 or (2) an event of default.	'	'	'	'
Common stock issued for conversion of promissory notes	2,034,438	'	'	'	'
Fair value of call option	'	476,000	596,000	'	'
Amortization period of interest expense	'	'1 year	'	'	'
Gain recognized from fair value valuation of call option	'	'	'	'	596,000
Unamortized debt discount	'	$1,100,000	'	'	'

Warrants_Additional_Informatio

Warrants - Additional Information (Detail) (USD $)

12 Months Ended

3 Months Ended

3 Months Ended

1 Months Ended

12 Months Ended

1 Months Ended

2 Months Ended

12 Months Ended

1 Months Ended

12 Months Ended

1 Months Ended

12 Months Ended

1 Months Ended

12 Months Ended

Dec. 31, 2013

Feb. 28, 2011

Nov. 30, 2008

Sep. 30, 2008

Mar. 31, 2011

Dec. 31, 2010

Mar. 31, 2011

Jun. 30, 2012

Dec. 31, 2013

Jun. 30, 2011

Jul. 31, 2013

Dec. 31, 2013

Mar. 31, 2007

Dec. 31, 2012

Mar. 31, 2007

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2009

Dec. 31, 2009

Feb. 28, 2013

Dec. 31, 2013

Feb. 28, 2011

Dec. 31, 2010

Mar. 31, 2011

Dec. 31, 2013

Dec. 31, 2012

Pinnacle Loan and Security Agreement

Pinnacle Loan and Security Agreement

2010 Warrants

2010 Warrants

2010 Warrants

PIPE warrants

PIPE warrants

Hercules Warrants

Hercules Warrants

Hercules Warrants

Series Warrants

Series Warrants

Series Warrants

Series Warrants

Series B Warrants

Series B Warrants

Series B and Series C Warrants

Series B and Series C Warrants

Series B and Series C Warrants

Series B Warrant

Series C Warrant

Series C Warrants

2012 Private Placement

2012 Private Placement

Series C Convertible Preferred Stock

Series A Preferred Stock

Common Stock

Series B Preferred Stock

Series C Convertible Preferred Stock

Pinnacle Loan and Security Agreement

Pinnacle Loan and Security Agreement

Class of Warrant or Right [Line Items]

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

PIPE warrants to purchase shares

'

'

'

'

'

'

107,246

'

'

274,508

'

'

'

3,425

2,500

'

56,250

228,264

'

'

'

'

'

'

'

'

PIPE warrants, exercise price per share

'

'

'

'

'

'

'

$3.40

'

$3.06

'

$6.79

$10

'

'

'

$16

$3.94

'

'

'

'

'

'

'

'

Fair value of warrants

'

'

'

'

'

$1,200,000

'

'

'

$967,000

'

$1,100,000

'

$1,000

'

'

'

'

$162,000

'

'

$894,000

$1,200,000

$323,000

'

'

PIPE warrants outstanding

'

'

'

'

'

'

'

2,630,103

'

'

'

176,730

'

'

'

3,425

'

'

'

'

0

'

'

'

1,494,514

'

Warrants, expiration date

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'2017-03-01

'

'

'

'

'

'

'

'

'

'

Loan and security agreement, maximum potential borrowings

'

'

'

12,000,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Loan and security agreement, amount outstanding

'

'

12,000,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Warrant liability

'

894,000

'

'

'

1,300,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Common stock warrants exercised

1,135,589

'

'

'

'

'

'

'

'

'

274,508

176,730

'

'

'

'

'

'

'

228,264

'

'

'

'

'

'

Common stock issued upon exercise of warrants

808,078

'

'

'

'

'

'

'

'

'

183,404

'

'

'

'

'

'

'

'

58,580

'

'

'

'

'

'

Liability reclassified to additional paid-in capital

'

'

'

'

536,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Other operating income (expense), net

'

'

'

'

763,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

PIPE warrant exercisable term

'

'

'

'

'

'

'

'

'6 months

'7 years

'

'5 years

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Warrants strike price

'

'

'

'

'

'

'

'

'

'

'

6.79

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Warrants stock issuance price

'

'

'

'

'

'

'

'

'

'

'

9.67

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Risk-free interest rate

'

'

'

'

'

'

'

'

'

2.44%

'

1.55%

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Expected volatility

'

'

'

'

'

'

'

'

'

79.00%

'

71.00%

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Expected dividend yield

'

'

'

'

'

'

'

'

'

0.00%

'

0.00%

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Warrants, expiration date

'

'

'

'

'

'

'

'

'

'

'

31-Dec-18

'

'

'

'

'

'

'

'

'

'

'

'

1-Nov-17

'

Warrant expiration period after the initial exercisability date

'

'

'

'

'

'

'

'

'5 years

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Exercise of warrants description

'

'

'

'

'

'

'

'

'Under the terms of the PIPE warrants, upon certain transactions, including a merger, tender offer, sale of all or substantially all of the assets of the Company or if a person or group shall become the owner of 50% of the Company's issued and outstanding common stock, which is outside of the Company's control, each PIPE warrant holder may elect to receive a cash payment in exchange for the warrant, in an amount determined by application of the Black-Scholes option-pricing model.

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Estimated fair value of PIPE warrants upon execution of Purchase Agreement

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

5,800,000

'

Estimated fair value of PIPE warrants at end of period

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

13,100,000

'

Expense recorded related to change in fair value of PIPE warrants

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

$14,100,000

$1,600,000

Commitments_and_Contingencies_1

Commitments and Contingencies - Additional Information (Detail) (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
	sqft		sqft
Other Commitments [Line Items]	'	'	'
Product requirement percentage under Services Agreement	80.00%	'	'
Service agreement expiration date	31-Dec-17	'	'
Services Agreement renewal period	'2 years	'	'
Services Agreement termination notice period	'18 months	'	'
Manufacturing Agreement, percentage for five years	100.00%	'	'
Manufacturing Agreement, percentage thereafter	80.00%	'	'
Number of products approved for commercial use	0	'	'
Redwood City, California facility	'	'	'
Other Commitments [Line Items]	'	'	'
Leased office and laboratory facilities, lease space	11,305	'	13,787
Leased office and laboratory facilities, lease term commence date	'2007-04	'	'2012-04
Leased office and laboratory facilities, lease expiration date	'2012-04	'	'2016-05
Leased office and laboratory facilities, rent expense	$300,000	$300,000	$200,000
Patheon Cincinnati facility	'	'	'
Other Commitments [Line Items]	'	'	'
Additional payments made under Capital Agreement	480,000	'	'
Overhead fee	0	'	'
Patheon Cincinnati facility | Minimum	'	'	'
Other Commitments [Line Items]	'	'	'
Maximum aggregate cost expected to incur under Capital Agreement	4,400,000	'	'
Overhead fee	0	'	'
Patheon Cincinnati facility | Maximum	'	'	'
Other Commitments [Line Items]	'	'	'
Overhead fee	$200,000	'	'

Future_Minimum_Payments_under_

Future Minimum Payments under Lease Agreement (Detail) (USD $)	Dec. 31, 2013
In Thousands, unless otherwise specified
Commitments And Contingencies Disclosure [Abstract]	'
2014	$392
2015	404
2016	142
Total minimum payments	$938

Stockholders_Equity_Additional

Stockholders' Equity - Additional Information (Detail) (USD $)

0 Months Ended

12 Months Ended

1 Months Ended

12 Months Ended

1 Months Ended

1 Months Ended

1 Months Ended

12 Months Ended

1 Months Ended

12 Months Ended

Feb. 10, 2011

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2011

Jul. 23, 2013

Dec. 31, 2012

Jun. 30, 2012

Aug. 31, 2012

Aug. 31, 2012

Feb. 10, 2011

Nov. 30, 2009

Feb. 29, 2008

Aug. 31, 2006

Aug. 31, 2006

Jan. 31, 2013

Jan. 31, 2012

Dec. 31, 2011

Jan. 31, 2012

Dec. 31, 2013

Public Offering

Public Offering

2012 Private Placement

2012 ATM Agreement

2012 ATM Agreement

2006 Equity Incentive Plan

2006 Equity Incentive Plan

2006 Equity Incentive Plan

2006 Equity Incentive Plan

2006 Equity Incentive Plan

2011 Equity Incentive Plan

2011 Equity Incentive Plan

2011 Equity Incentive Plan

Employee Stock Purchase Plan

Employee Stock Purchase Plan

Maximum

Maximum

Subsidiary, Sale of Stock [Line Items]

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Stock issued during period shares new issues

8,000,000

'

'

'

4,370,000

'

2,922,337

'

'

'

'

'

'

'

'

'

'

'

'

Common stock, par value

$0.00

$0.00

$0.00

'

$11.65

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Net proceeds from issuance of an IPO

$34,900,000

'

'

'

$50,900,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Net proceeds from offering of common stock

'

47,943,000

53,174,000

34,939,000

47,900,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Issuance of common stock shares upon underwritten public offering

'

'

'

'

'

14,375,000

'

'

'

'

'

'

'

'

'

'

'

'

'

Common stock underwritten public offering price per share

'

'

'

'

'

$3.31

'

'

'

'

'

'

'

'

'

'

'

'

'

Net proceed from issuance of common stock upon underwritten public offering

'

47,943,000

44,096,000

'

'

44,100,000

'

'

'

'

'

'

'

'

'

'

'

'

'

Common stock underwritten public offering related costs

'

'

'

'

'

3,500,000

'

'

'

'

'

'

'

'

'

'

'

'

'

Warrants issued to purchase common stock

'

'

'

'

'

'

2,630,103

'

'

'

'

'

'

'

'

'

'

'

'

Proceed from issuance of common stock and PIPE warrants

'

'

'

'

'

'

10,000,000

'

'

'

'

'

'

'

'

'

'

'

'

Issuance of common stock, offering-related costs

'

'

'

'

'

'

900,000

'

'

'

'

'

'

'

'

'

'

'

'

Purchase agreement date

'

'

'

'

'

'

29-May-12

'

'

'

'

'

'

'

'

'

'

'

'

Share issue under purchase agreement description

'

'

'

'

'

'

'Pursuant to the Purchase Agreement, AcelRx sold shares of common stock and PIPE warrants to purchase common stock in immediately separable ""Units,"," with each Unit consisting of (i)cone share of common stock and (ii)ca PIPE warrant to purchase 0.9 of a share of common stock. The per share exercise price of the PIPE warrants was $3.40. The offering price per Unit was $3.40 for non-affiliated investors, and $3.5125 for affiliated investors, which equals the sum of (i)c$3.40, the closing consolidated bid price of our common stock on Mayc29, 2012, plus (ii)c$0.1125 (which is equal to $0.125 per PIPE warrant share, multiplied by 0.9), for an aggregate amount of $10.0 million. The PIPE warrants issued in the Private Placement became exercisable six months after the Issuance Date, and expire on the five year anniversary of the initial exercisability date.

'

'

'

'

'

'

'

'

'

'

'

'

PIPE warrants to purchase a share of common stock

'

'

'

'

'

'

0.9

'

'

'

'

'

'

'

'

'

'

'

'

PIPE warrants per share exercise price

'

'

'

'

'

'

3.4

'

'

'

'

'

'

'

'

'

'

'

'

Offering price per unit for non affiliated investors

'

'

'

'

'

'

$3.40

'

'

'

'

'

'

'

'

'

'

'

'

Offering price per unit for affiliated investors

'

'

'

'

'

'

$3.51

'

'

'

'

'

'

'

'

'

'

'

'

Consolidated closing bid price of common stock

'

'

'

'

'

'

$3.40

'

'

'

'

'

'

'

'

'

'

'

'

Bid price per PIPE warrant

'

'

'

'

'

'

$0.11

'

'

'

'

'

'

'

'

'

'

'

'

PIPE warrant exercisable term

'

'

'

'

'

'

'6 months

'

'

'

'

'

'

'

'

'

'

'

'

PIPE warrant expiration period

'

'

'

'

'

'

'5 years

'

'

'

'

'

'

'

'

'

'

'

'

Aggregate offering price on issuance and sell of shares

'

'

'

'

'

'

'

'

7,500,000

'

'

'

'

'

'

'

'

'

'

Sales agreement termination date

'

'

'

'

'

'

'

31-Aug-15

'

'

'

'

'

'

'

'

'

'

'

Maximum aggregate commission rate on gross proceeds for common stock sold

'

'

'

'

'

'

'

'

3.00%

'

'

'

'

'

'

'

'

'

'

Customary indemnification rights and expense reimbursements

'

'

'

'

'

'

'

'

25,000

'

'

'

'

'

'

'

'

'

'

Stock issued during period per share

$5

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Underwriters discounts and commissions paid on initial public offering

$5,100,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Convertible preferred stock converted into common stock

8,555,713

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

2010 Convertible Notes converted into common stock

2,034,438

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Common stock issued on exercise of warrant

107,246

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Common stock, shares authorized

100,000,000

100,000,000

100,000,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Preferred stock, shares authorized

10,000,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Preferred stock, par value

$0.00

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Number of shares outstanding in share based compensation plan

'

'

'

'

'

'

'

'

'

51,693

'

'

'

'

'

'

1,875,000

'

'

Common stock shares authorized for issuance

'

'

'

'

'

'

'

'

'

'

'

'

342,000

'

'

'

1,823,307

'

250,000

Increased percentage of common stock outstanding

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

4.00%

'

'

Additional shares authorized for issuance

'

'

'

'

'

'

'

'

'

'

1,376,059

375,000

'

'

1,482,201

782,711

'

391,355

'

Share based compensation common stock reserved for issuance description

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'The number of shares of the Company's common stock reserved for issuance will automatically increase on January 1st each year, starting January 1, 2012 and continuing through January 1, 2020, in an amount equal to the lower of (1) 2% of the total number of shares of the Company's common stock outstanding on December 31 of the preceding calendar year, or (2) a number of shares of common stock as determined by the board of directors.

Voting power percentage

'

'

'

'

'

'

'

'

'

'

'

'

'

10.00%

'

'

'

'

'

Fair value per share of the underlying common stock

'

'

'

'

'

'

'

'

'

'

'

'

'

110.00%

'

'

'

'

'

Employee_Stock_Purchase_Plan_D

Employee Stock Purchase Plan (Detail) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'	'	'
Stock-based compensation expense	$3,479	$2,150	$1,833
Research and Development	'	'	'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'	'	'
Stock-based compensation expense	1,657	998	785
General and Administrative	'	'	'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'	'	'
Stock-based compensation expense	$1,822	$1,152	$1,048

Option_Activity_Detail

Option Activity (Detail) (USD $)	12 Months Ended
In Thousands, except Share data, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
	Y
Number of Stock Options Outstanding	'	'	'
Beginning balance	3,399,811	2,395,968	2,008,797
Granted	1,958,727	1,213,391	514,958
Forfeited	-17,917	-165,781	-58,022
Exercised	-431,216	-43,767	-69,765
Ending balance	4,909,405	3,399,811	2,395,968
Vested and exercisable options-December 31, 2013	2,161,400	'	'
Weighted-Average Exercise Price	'	'	'
Beginning balance	$3.18	$3.08	$2.91
Granted	$5.99	$3.36	$3.48
Forfeited	$8.82	$3.23	$3.32
Exercised	$3.03	$2.32	$1.20
Ending balance	$4.29	$3.18	$3.08
Vested and exercisable options-December 31, 2013	$3.17	'	'
Vested and expected to vest-December 31, 2013	$4.25	'	'
Vested and expected to vest-December 31, 2013	4,718,574	'	'
Weighted Average-Remaining Contractual Life (Years)	'	'	'
Ending balance	'7 years 10 months 24 days	'	'
Vested and exercisable options-December 31, 2013	6.7	'	'
Vested and expected to vest-December 31, 2013	'7 years 9 months 18 days	'	'
Aggregate Intrinsic Value	'	'	'
Ending balance	$34,452	'	'
Vested and exercisable options-December 31, 2013	17,589	'	'
Vested and expected to vest-December 31, 2013	$33,322	'	'

StockBased_Compensation_Additi

Stock-Based Compensation - Additional Information (Detail) (USD $)	1 Months Ended	12 Months Ended			1 Months Ended
	Mar. 31, 2011	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Jan. 31, 2014
					Subsequent Event
Share based Compensation Arrangement Assumptions Used to Estimate Fair Values of Share Options Granted [Line Items]	'	'	'	'	'
Shares available for grant	'	273,290	'	'	'
Additional shares available for grant	'	'	'	'	1,722,023
Weighted average grant date fair value of option granted	'	$4.15	$2.25	$2.45	'
Stock based compensation related to unvested option based on grant date fair value	'	$8,200,000	'	'	'
Stock based compensation recognized over a weighted average period	'	'2 years 9 months 18 days	'	'	'
Share based compensation grant date fair value of option granted	'	1,900,000	1,300,000	1,100,000	'
Total intrinsic value of option exercised	'	3,600,000	85,000	204,000	'
Restricted stock unit granted	343,815	'	'	'	'
Restricted stock unit grant date fair value	$3.45	'	'	'	'
Restricted stock unit vesting, Percentage	25.00%	'	'	'	'
Restricted stock unit vesting, Percentage, year one	25.00%	'	'	'	'
Restricted stock unit vesting, Percentage, year two	25.00%	'	'	'	'
Restricted stock unit vesting, Percentage, year three	25.00%	'	'	'	'
Restricted stock unit outstanding	'	65,765	'	'	'
Expenses related to restricted stock units	'	$290,000	$315,000	$492,000	'

Stock_Options_Outstanding_Vest

Stock Options Outstanding, Vested and Exercisable (Detail) (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'	'	'	'
Number of Stock Options Outstanding	4,909,405	3,399,811	2,395,968	2,008,797
Options Outstanding Weighted-Average Remaining Contractual Life (Years)	'7 years 10 months 24 days	'	'	'
Options Outstanding Weighted-Average Exercise Price per Share	$4.29	$3.18	$3.08	$2.91
Options Vested and Exercisable Shares Subject to Stock Options	2,161,400	'	'	'
Options Vested and Exercisable Weighted-Average Exercise Price per Share	$3.17	'	'	'
$1.20-$2.56	'	'	'	'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'	'	'	'
Exercise Prices Lower Limit	$1.20	'	'	'
Exercise Prices Upper Limit	$2.56	'	'	'
Number of Stock Options Outstanding	613,875	'	'	'
Options Outstanding Weighted-Average Remaining Contractual Life (Years)	'5 years 10 months 24 days	'	'	'
Options Outstanding Weighted-Average Exercise Price per Share	$2.22	'	'	'
Options Vested and Exercisable Shares Subject to Stock Options	613,874	'	'	'
Options Vested and Exercisable Weighted-Average Exercise Price per Share	$2.22	'	'	'
$2.5601-$4.00	'	'	'	'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'	'	'	'
Exercise Prices Lower Limit	$2.56	'	'	'
Exercise Prices Upper Limit	$4	'	'	'
Number of Stock Options Outstanding	2,088,053	'	'	'
Options Outstanding Weighted-Average Remaining Contractual Life (Years)	'7 years 4 months 24 days	'	'	'
Options Outstanding Weighted-Average Exercise Price per Share	$3.23	'	'	'
Options Vested and Exercisable Shares Subject to Stock Options	1,299,298	'	'	'
Options Vested and Exercisable Weighted-Average Exercise Price per Share	$3.16	'	'	'
$4.22-$6.34	'	'	'	'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'	'	'	'
Exercise Prices Lower Limit	$4.22	'	'	'
Exercise Prices Upper Limit	$6.34	'	'	'
Number of Stock Options Outstanding	1,962,477	'	'	'
Options Outstanding Weighted-Average Remaining Contractual Life (Years)	'8 years 8 months 12 days	'	'	'
Options Outstanding Weighted-Average Exercise Price per Share	$5.31	'	'	'
Options Vested and Exercisable Shares Subject to Stock Options	236,353	'	'	'
Options Vested and Exercisable Weighted-Average Exercise Price per Share	$5.32	'	'	'
$8.18-$10.55	'	'	'	'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'	'	'	'
Exercise Prices Lower Limit	$8.18	'	'	'
Exercise Prices Upper Limit	$10.55	'	'	'
Number of Stock Options Outstanding	245,000	'	'	'
Options Outstanding Weighted-Average Remaining Contractual Life (Years)	'9 years 8 months 12 days	'	'	'
Options Outstanding Weighted-Average Exercise Price per Share	$10.40	'	'	'
Options Vested and Exercisable Shares Subject to Stock Options	11,875	'	'	'
Options Vested and Exercisable Weighted-Average Exercise Price per Share	$10.55	'	'	'

Assumptions_to_Calculate_Fair_

Assumptions to Calculate Fair Value of Each Employee Stock Option (Detail)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'	'	'
Risk-free interest rate, minimum	1.02%	0.60%	1.10%
Risk-free interest rate, maximum	2.96%	1.74%	2.50%
Expected volatility	80.00%	80.00%	79.00%
Expected dividend rate	0.00%	0.00%	0.00%
Minimum	'	'	'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'	'	'
Expected term (in years)	'5 years 9 months	'5 years 9 months	'5 years 9 months
Maximum	'	'	'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'	'	'
Expected term (in years)	'6 years 3 months	'6 years 3 months	'6 years 3 months

Computation_of_Basic_and_Dilut

Computation of Basic and Diluted Net Loss per Share of Common Stock (Detail) (USD $)	3 Months Ended								12 Months Ended
In Thousands, except Share data, unless otherwise specified	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Earnings Per Share [Abstract]	'	'	'	'	'	'	'	'	'	'	'
Net loss	$17,769	($10,986)	($17,447)	($12,762)	($10,522)	($8,582)	($7,194)	($7,065)	($23,426)	($33,363)	($20,101)
Shares used in computing net loss per share of common stock, basic and diluted	'	'	'	'	'	'	'	'	39,746,678	22,124,637	17,344,727
Net loss per share of common stock, basic and diluted	'	'	'	'	'	'	'	'	($0.59)	($1.51)	($1.16)

Outstanding_Shares_of_Common_S

Outstanding Shares of Common Stock Equivalents Excluded from Computation of Diluted Net Loss per Share (Detail)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Stock Options to Purchase Common Stock	'	'	'
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]	'	'	'
Shares of common stock equivalents excluded from the computation of diluted net loss per share of common stock	4,909,405	3,399,811	2,395,968
Restricted Stock Units	'	'	'
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]	'	'	'
Shares of common stock equivalents excluded from the computation of diluted net loss per share of common stock	65,765	161,096	257,868
Common Stock Warrants	'	'	'
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]	'	'	'
Shares of common stock equivalents excluded from the computation of diluted net loss per share of common stock	1,674,669	3,136,300	506,197

Accounts_Payable_and_Accrued_L2

Accounts Payable and Accrued Liabilities (Detail) (USD $)	Dec. 31, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified
Accounts Payable and Accrued Liabilities [Line Items]	'	'
Accounts payable	$2,341	$2,235
Accrued compensation and employee benefits	2,397	1,613
Accrued research and development expenses	248	2,371
Professional fees	230	361
Interest payable	61	119
Other	243	189
Total accounts payable and accrued liabilities	6,245	6,888
Property and Equipment	'	'
Accounts Payable and Accrued Liabilities [Line Items]	'	'
Accrued liabilities associated with property and equipment	$725	'

401k_Plan_Additional_Informati

401(k) Plan - Additional Information (Detail) (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Compensation And Retirement Disclosure [Abstract]	'	'	'
Company's contribution to employee benefits plan	$143,000	$120,000	$107,000
Discretionary contribution by employer for 100% vested eligible employees	3.00%	'	'
Discretionary contribution by employer for eligible employees, vesting percentage	100.00%	'	'

Income_Taxes_Additional_Inform

Income Taxes - Additional Information (Detail) (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Income Tax Disclosure [Line Items]	'	'	'
Provision for income taxes	$0	$0	$0
Increase in valuation allowance	5,200,000	11,900,000	7,800,000
Valuation allowance for deferred tax assets from stock based compensation arrangement	1,100,000	'	'
Operating loss carry forwards description	'Under Section 382 of the Internal Revenue Code of 1986, as amended, if a corporation undergoes an "ownership change", generally defined as a greater than 50% change (by value) in its equity ownership over a three year period, the corporation's ability to use its pre-change net operating loss carryforwards and other pre-change tax attributes, such as research credits, to offset its post-change income may be limited.	'	'
Federal	'	'	'
Income Tax Disclosure [Line Items]	'	'	'
Net operating loss carry-forwards	91,100,000	89,700,000	82,200,000
Net operating loss carry-forwards, Expiry year	'2025	'	'
Research credit carryovers	2,600,000	1,300,000	1,300,000
Federal research credit carryovers, expiry year	'2026	'	'
State	'	'	'
Income Tax Disclosure [Line Items]	'	'	'
Net operating loss carry-forwards	91,000,000	89,700,000	80,600,000
Net operating loss carry-forwards, Expiry year	'2015	'	'
Research credit carryovers	1,400,000	1,100,000	900,000
Subject to expiration	'	'	'
Income Tax Disclosure [Line Items]	'	'	'
Net operating loss carry-forwards	1,400,000	'	'
Research credit carryovers	$26,000	'	'

Net_Deferred_Tax_Assets_Detail

Net Deferred Tax Assets (Detail) (USD $)	Dec. 31, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified
Income Tax Disclosure [Abstract]	'	'
Accruals and other	$2,172	$802
Research credits	3,553	2,050
Net operating loss carryforward	36,279	35,730
Section 59(e) R&D expenditures	10,339	8,572
Total deferred tax assets	52,343	47,154
Valuation allowance	-52,343	-47,154
Net deferred tax assets	'	'

Reconciliation_of_Statutory_Fe

Reconciliation of Statutory Federal Income Tax (Detail) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Income Tax Disclosure [Abstract]	'	'	'
Tax at statutory federal rate	($7,965)	($11,343)	($6,834)
State tax-net of federal benefit	-716	-1,953	-1,104
PIPE Warrant liability	4,898	540	'
General Business credits	-1,326	'	'
Other	-80	1,807	161
Change in valuation allowance	5,189	11,949	7,777
Provision (benefit) for income taxes	$0	$0	$0

Reconciliation_of_Beginning_an

Reconciliation of Beginning and Ending Balance of Unrecognized Tax Benefits (Detail) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Income Tax Disclosure [Abstract]	'	'	'
Unrecognized benefit-beginning of period	$810	$748	$603
Gross decreases-prior period tax positions	221	-17	'
Gross increases-current period tax positions	310	79	145
Unrecognized benefit-end of period	$1,341	$810	$748

Unaudited_Quarterly_Financial_2

Unaudited Quarterly Financial Data (Detail) (USD $)	3 Months Ended								12 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Quarterly Financial Information Disclosure [Abstract]	'	'	'	'	'	'	'	'	'	'	'
Revenues	$27,607	$548	$407	$940	$1,675	$166	$224	$329	$29,502	$2,394	$1,072
Operating Expenses	7,624	8,858	8,178	11,509	9,704	8,358	7,170	6,875	36,169	32,107	20,424
Net income / (loss)	$17,769	($10,986)	($17,447)	($12,762)	($10,522)	($8,582)	($7,194)	($7,065)	($23,426)	($33,363)	($20,101)
Net income / (loss) per share (basic)	$0.41	($0.26)	($0.47)	($0.34)	($0.41)	($0.38)	($0.35)	($0.36)	'	'	'

Unaudited_Quarterly_Financial_3

Unaudited Quarterly Financial Data - Additional Information (Detail) (USD $)	3 Months Ended
	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012
Quarterly Financial Information Disclosure [Abstract]	'	'	'	'	'	'	'	'
Diluted income	$0.39	($0.26)	($0.47)	($0.34)	($0.41)	($0.38)	($0.35)	($0.36)