Amphastar Pharmaceuticals (AMPH) 10-Q 9 May 22 2022 Q1 Quarterly report Financial data

Document And Entity Information

Document And Entity Information - shares	3 Months Ended
	Mar. 31, 2022	May 03, 2022
Document and Entity Information [Abstract]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Mar. 31, 2022
Document Transition Report	false
Entity File Number	001-36509
Entity Registrant Name	Amphastar Pharmaceuticals, Inc.
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	33-0702205
Entity Address, Address Line One	11570 6th Street
Entity Address, City or Town	Rancho Cucamonga
Entity Address, State or Province	CA
Entity Address, Postal Zip Code	91730
City Area Code	909
Local Phone Number	980-9484
Title of 12(b) Security	Common Stock, par value $0.0001 per share
Trading Symbol	AMPH
Security Exchange Name	NASDAQ
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		48,829,793
Entity Central Index Key	0001297184
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2022
Document Fiscal Period Focus	Q1
Amendment Flag	false

CONSOLIDATED BALANCE SHEETS

CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Current Assets:
Cash and cash equivalents	$ 172,627	$ 126,353
Restricted cash	235	235
Short-term investments	14,383	10,320
Restricted short-term investments	2,200	2,200
Accounts receivable, net	73,166	78,804
Inventories	95,147	92,807
Income tax refunds and deposits	223	126
Prepaid expenses and other assets	6,434	7,274
Total current assets	364,415	318,119
Property, plant, and equipment, net	243,248	244,244
Finance lease right-of-use assets	278	353
Operating lease right-of-use assets	27,843	26,894
Investment in unconsolidated affiliate	3,318	3,985
Goodwill and intangible assets, net	38,436	38,870
Other assets	16,301	16,665
Deferred tax assets	22,399	22,399
Total assets	716,238	671,529
Current Liabilities:
Accounts payable and accrued liabilities	95,810	89,545
Income taxes payable	13,116	9,081
Current portion of long-term debt	2,159	2,202
Current portion of operating lease liabilities	3,279	2,982
Total current liabilities	114,364	103,810
Long-term reserve for income tax liabilities	6,531	6,531
Long-term debt, net of current portion and unamortized debt costs	74,348	74,776
Long-term operating lease liabilities, net of current portion	25,489	24,703
Deferred tax liabilities	487	534
Other long-term liabilities	15,494	15,653
Total liabilities	236,713	226,007
Commitments and Contingencies
Stockholders' equity:
Preferred stock: par value $0.0001; 20,000,000 shares authorized; no shares issued and outstanding
Common stock: par value $0.0001; 300,000,000 shares authorized; 57,495,402 and 48,752,175 shares issued and outstanding as of March 31, 2022 and 56,440,202 and 47,714,912 shares issued and outstanding as of December 31, 2021, respectively	6	6
Additional paid-in capital	433,454	422,423
Retained earnings	204,590	180,337
Accumulated other comprehensive loss	(7,245)	(6,765)
Treasury stock	(151,280)	(150,479)
Total equity	479,525	445,522
Total liabilities and stockholders' equity	$ 716,238	$ 671,529

CONSOLIDATED BALANCE SHEETS (Pa

CONSOLIDATED BALANCE SHEETS (Parenthetical) - $ / shares	Mar. 31, 2022	Dec. 31, 2021
CONSOLIDATED BALANCE SHEETS
Preferred stock, par value (in dollars per share)	$ 0.0001	$ 0.0001
Preferred stock, shares authorized	20,000,000	20,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value (in dollars per share)	$ 0.0001	$ 0.0001
Common stock; shares authorized	300,000,000	300,000,000
Common stock; shares issued	57,495,402	56,440,202
Common stock; shares outstanding	48,752,175	47,714,912

CONSOLIDATED STATEMENTS OF OPER

CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
CONSOLIDATED STATEMENTS OF OPERATIONS
Net revenues	$ 120,368	$ 103,020
Cost of revenues	64,542	58,074
Gross profit	55,826	44,946
Operating (income) expenses:
Selling, distribution, and marketing	5,519	4,537
General and administrative	12,470	15,338
Research and development	16,223	14,765
Total operating expenses	34,212	34,640
Income (loss) from operations	21,614	10,306
Non-operating income (expenses):
Interest income	181	161
Interest expense	(355)	(104)
Other income (expenses), net	7,593	(5,249)
Total non-operating income (expenses), net	7,419	(5,192)
Income (loss) before income taxes	29,033	5,114
Income tax provision (benefit)	4,077	1,155
Income before equity in losses of unconsolidated affiliate	24,956	3,959
Equity in losses of unconsolidated affiliates	(703)
Net income (loss)	24,253	3,959
Net income (loss) attributable to non-controlling interests		(1,082)
Net income (loss) attributable to Amphastar Pharmaceuticals, Inc.	$ 24,253	$ 5,041
Net income (loss) per share attributable to Amphastar Pharmaceuticals, Inc. stockholders:
Basic (in Dollars per share)	$ 0.50	$ 0.11
Diluted (in Dollars per share)	$ 0.47	$ 0.10
Weighted-average shares used to compute net income (loss) per share attributable to Amphastar Pharmaceuticals, Inc. stockholders:
Basic (in Shares)	48,138	47,520
Diluted (in Shares)	51,979	49,518

CONSOLIDATED STATEMENTS OF COMP

CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS)
Net income (loss) attributable to Amphastar Pharmaceuticals, Inc.	$ 24,253	$ 5,041
Other comprehensive income (loss) attributable to Amphastar Pharmaceuticals, Inc., net of income taxes
Foreign currency translation adjustment	(480)	(1,921)
Total other comprehensive income (loss) attributable to Amphastar Pharmaceuticals, Inc.	(480)	(1,921)
Total comprehensive income (loss) attributable to Amphastar Pharmaceuticals, Inc.	$ 23,773	$ 3,120

CONSOLIDATED STATEMENTS OF STOC

CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY - USD ($) $ in Thousands	Common Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Treasury Stock [Member]	Total Amphastar Stockholders' Equity [Member]	Non-controlling Interest [Member]	Total
Balance at Dec. 31, 2020	$ 5	$ 410,061	$ 117,773	$ (3,721)	$ (121,812)	$ 402,306	$ 46,417
Balance at Dec. 31, 2020								$ 448,723
Balance at Dec. 31, 2020	54,760,922				(7,265,483)
Changes in Stockholders' Equity
Net income (loss) attributable to Amphastar Pharmaceuticals, Inc.			5,041			5,041		5,041
Other comprehensive income (loss) attributable to Amphastar Pharmaceuticals, Inc.				(1,921)		(1,921)		(1,921)
Net income (loss) attributable to non-controlling interest							(1,082)	(1,082)
Purchase of treasury stock					$ (3,783)	(3,783)		(3,783)
Purchase of treasury stock (in shares)					(204,698)
Issuance of treasury stock in connection with the Company's equity plans		(49)			$ 49
Issuance of treasury stock in connection with the Company's equity plans (in Shares)					4,184
Issuance of common stock in connection with the Company's equity plans	$ 1	(853)				(852)		(852)
Issuance of common stock in connection with the Company's equity plans (in Shares)	423,078
Share-based compensation expense		4,767				4,767	67	4,834
Balance at Mar. 31, 2021	$ 6	413,926	122,814	(5,642)	$ (125,546)	405,558	$ 45,402
Balance at Mar. 31, 2021								450,960
Balance at Mar. 31, 2021	55,184,000				(7,465,997)
Balance at Dec. 31, 2021	$ 6	422,423	180,337	(6,765)	$ (150,479)	445,522
Balance at Dec. 31, 2021								$ 445,522
Balance at Dec. 31, 2021	56,440,202				(8,725,290)			47,714,912
Changes in Stockholders' Equity
Net income (loss) attributable to Amphastar Pharmaceuticals, Inc.			24,253			24,253		$ 24,253
Other comprehensive income (loss) attributable to Amphastar Pharmaceuticals, Inc.				(480)		(480)		(480)
Purchase of treasury stock					$ (1,229)	(1,229)		(1,229)
Purchase of treasury stock (in shares)					(51,168)
Issuance of treasury stock in connection with the Company's equity plans		(428)			$ 428
Issuance of treasury stock in connection with the Company's equity plans (in Shares)					33,231
Issuance of common stock in connection with the Company's equity plans		6,437				6,437		6,437
Issuance of common stock in connection with the Company's equity plans (in Shares)	1,055,200
Share-based compensation expense		5,022				5,022		5,022
Balance at Mar. 31, 2022	$ 6	$ 433,454	$ 204,590	$ (7,245)	$ (151,280)	$ 479,525
Balance at Mar. 31, 2022								$ 479,525
Balance at Mar. 31, 2022	57,495,402				(8,743,227)			48,752,175

CONSOLIDATED STATEMENTS OF CASH

CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Cash Flows From Operating Activities:
Net income (loss)	$ 24,253	$ 3,959
Reconciliation to net cash provided by operating activities:
Loss (gain) on impairment and disposal of assets	1	6
Loss (gain) on interest rate swaps	(3,013)	(179)
Depreciation of property, plant, and equipment	5,615	5,686
Amortization of product rights, trademarks, and patents	352	276
Operating lease right-of-use asset amortization	828	863
Equity in losses of unconsolidated affiliate	703
Share-based compensation	5,022	4,834
Changes in operating assets and liabilities:
Accounts receivable, net	5,598	(12,078)
Inventories	(2,687)	(1,144)
Prepaid expenses and other assets	1,420	1,119
Income tax refunds, deposits, and payables, net	3,926	1,182
Operating lease liabilities	(695)	(754)
Accounts payable and accrued liabilities	9,442	19,055
Net cash provided by operating activities	50,765	22,825
Cash Flows From Investing Activities:
Purchases and construction of property, plant, and equipment	(6,139)	(7,618)
Purchase of investments	(5,317)	(4,501)
Maturity of investments	2,535	3,944
Payment of deposits and other assets	(189)	(520)
Net cash used in investing activities	(9,110)	(8,695)
Cash Flows From Financing Activities:
Proceeds from equity plans, net of withholding tax payments	6,437	(854)
Purchase of treasury stock	(1,229)	(3,783)
Debt issuance costs	(22)
Principal payments on long-term debt	(538)	(2,002)
Net cash provided by (used in) financing activities	4,648	(6,639)
Effect of exchange rate changes on cash	(29)	(162)
Net increase (decrease) in cash, cash equivalents and restricted cash	46,274	7,329
Cash, cash equivalents, and restricted cash at beginning of period	126,588	94,507
Cash, cash equivalents, and restricted cash at end of period	172,862	101,836
Noncash Investing and Financing Activities:
Capital expenditure included in accounts payable	6,709	6,238
Operating lease right-of-use assets in exchange for operating lease liabilities	1,777	103
Equipment acquired under finance leases		74
Supplemental Disclosures of Cash Flow Information:
Interest paid, net of capitalized interest	579	508
Income taxes paid	$ 183	$ 30

General

General	3 Months Ended
	Mar. 31, 2022
General
General	Note 1. Genera l ​ Amphastar Pharmaceuticals, Inc., a Delaware corporation (together with its subsidiaries, hereinafter referred to as the “Company”) is a bio-pharmaceutical company that develops, manufactures, markets, and sells generic and proprietary injectable, inhalation, and intranasal products, including products with high technical barriers to market entry. Additionally, the Company sells insulin active pharmaceutical ingredient, or API, products. Most of the Company’s products are used in hospital or urgent care clinical settings and are primarily contracted and distributed through group purchasing organizations and drug wholesalers. The Company’s insulin API products are sold to other pharmaceutical companies for use in their own products and are being used by the Company in the development of injectable finished pharmaceutical products. The Company’s inhalation product, Primatene Mist ® ​ The accompanying unaudited condensed consolidated financial statements should be read in conjunction with the audited consolidated financial statements of the Company for the year ended December 31, 2021 and the notes thereto as filed with the Securities and Exchange Commission, or SEC, in the Company’s Annual Report on Form 10-K for the year ended December 31, 2021. Certain information and footnote disclosures normally included in annual financial statements prepared in accordance with United States generally accepted accounting principles, or GAAP, have been condensed or omitted from the accompanying condensed consolidated financial statements. The accompanying year-end condensed consolidated balance sheet was derived from the audited financial statements. The accompanying interim financial statements are unaudited, but reflect all adjustments which are, in the opinion of management, necessary for a fair statement of the Company’s consolidated financial position, results of operations, comprehensive income (loss), stockholders’ equity, and cash flows for the periods presented. Unless otherwise noted, all such adjustments are of a normal, recurring nature. The Company’s results of operations, comprehensive income (loss) and cash flows for the interim periods are not necessarily indicative of the results of operations and cash flows that it may achieve in future periods.

Summary of Significant Accounti

Summary of Significant Accounting Policies	3 Months Ended
	Mar. 31, 2022
Summary of Significant Accounting Policies
Summary of Significant Accounting Policies	Note 2. Summary of Significant Accounting Policies ​ Basis of Presentation ​ The unaudited condensed consolidated financial statements include the accounts of the Company and its subsidiaries, and are prepared in accordance with GAAP. Certain prior period amounts have been reclassified within the operating activities of the condensed consolidated statements of cash flows to conform to the current period presentation. All intercompany activity has been eliminated in the preparation of the condensed consolidated financial statements. ​ The Company’s subsidiaries include: (1) International Medication Systems, Limited, or IMS, (2) Armstrong Pharmaceuticals, Inc., or Armstrong, (3) Amphastar Nanjing Pharmaceuticals Inc., or ANP, (4) Amphastar France Pharmaceuticals, S.A.S., or AFP, (5) Amphastar UK Ltd., or AUK, and (6) International Medication Systems (UK) Limited, or IMS UK. ​ COVID-19 Pandemic ​ The Company is subject to risks and uncertainties as a result of the ongoing novel coronavirus pandemic, or COVID-19. The complete extent of the impact of the COVID-19 pandemic on the Company’s business is highly uncertain and difficult to predict, as the information is constantly evolving. The Company considered the impact of COVID - ​ All of the Company’s production facilities continued to operate during the quarter as they had prior to the COVID-19 pandemic with very little change, other than for enhanced safety measures intended to prevent the spread of the virus. Recent increases in COVID-19 cases in Shanghai, China, have led to shutdowns and delays at the ports in Shanghai, which could have an impact on the Company’s operations. However, the extent of the impact of this shutdown and delay is highly uncertain and difficult to predict. ​ It is not possible at this time to estimate the complete impact that COVID-19 could have on the Company’s business, including its customers and suppliers, as the impact will depend on future developments, which are highly uncertain and cannot be predicted. The Company will continue to monitor the impact of COVID-19 on all aspects of its business. ​ Use of Estimates ​ The preparation of condensed consolidated financial statements in accordance with GAAP requires management to make estimates and assumptions that affect the amounts reported in the condensed consolidated financial statements and accompanying notes. Actual results could differ from those estimates. The principal accounting estimates include: determination of allowances for credit losses, fair value of financial instruments, allowance for discounts, provision for chargebacks and rebates, provision for product returns, adjustment of inventory to its net realizable values, impairment of investments, long-lived and intangible assets and goodwill, accrual for workers’ compensation liabilities, litigation reserves, stock price volatility for share-based compensation expense, valuation allowances for deferred tax assets, and liabilities for uncertain income tax positions. ​ Foreign Currency ​ The functional currency of the Company, its domestic subsidiaries, its Chinese subsidiary, ANP, and its U.K. subsidiary, AUK, is the U.S. Dollar, or USD. ANP maintains its books of record in Chinese yuan. These books are remeasured into the functional currency, USD, using the current or historical exchange rates. The resulting currency remeasurement adjustments and other transactional foreign currency exchange gains and losses are reflected in the Company’s condensed consolidated statements of operations. ​ The Company’s French subsidiary, AFP, maintains its book of record in euros. AUK’s subsidiary, IMS UK, maintains its book of record in British pounds. These local currencies have been determined to be the subsidiaries’ respective functional currencies. Activity in the statement of operations is translated to USD using average exchange rates during the period. Assets and liabilities are translated at the rate of exchange prevailing on the balance sheet date. Equity is translated at the prevailing rate of exchange at the date of the equity transactions. Translation adjustments are reflected in stockholders’ equity and are included as a component of other accumulated comprehensive income (loss). The unrealized gains or losses of intercompany foreign currency transactions that are of a long-term investment nature are reported in other accumulated comprehensive income (loss). ​ The unrealized gains and losses of intercompany foreign currency transactions that are of a long-term investment nature for the three months ended March 31, 2022 and 2021 were $0.6 million loss and $1.5 million loss, respectively. ​ Comprehensive Income ​ For the three months ended March 31, 2022 and 2021, the Company included its foreign currency translation gain or loss as part of its comprehensive income. ​ Advertising Expense ​ Advertising expenses, primarily associated with Primatene Mist ® commercial or campaign is first presented, and are reflected as a component of selling, distribution and marketing in the Company’s condensed consolidated statement of operations. For the three months ended March 31, 2022 and 2021, advertising expenses were $2.4 million and $2.2 million, respectively. ​ Financial Instruments ​ The carrying amounts of cash and cash equivalents, short-term investments, restricted cash and short-term investments, accounts receivable, accounts payable, accrued expenses, and short-term borrowings approximate fair value due to the short maturity of these items. The majority of the Company’s long-term obligations consist of variable rate debt, and their carrying value approximates fair value as the stated borrowing rates are comparable to rates currently offered to the Company for instruments with similar maturities. The Company at times enters into fixed interest rate swap contracts to exchange the variable interest rates for fixed interest rates. Such interest rate swap contracts are recorded at their fair values. ​ Cash and Cash Equivalents ​ Cash and cash equivalents consist of cash, money market accounts, certificates of deposit and highly liquid investments purchased with original maturities of three months or less. ​ Investments ​ Investments as of March 31, 2022 and December 31, 2021 consisted of certificates of deposit and investment grade corporate and municipal bonds with original maturity dates between three and fifteen months. ​ Restricted Cash ​ Restricted cash is collateral required for the Company to guarantee certain vendor payments in France. As of each of March 31, 2022 and December 31, 2021, the restricted cash balance was $0.2 million. ​ Restricted Short-Term Investments ​ Restricted short-term investments consist of certificates of deposit that are collateral for standby letters of credit to qualify for workers’ compensation self-insurance. The certificates of deposit have original maturities greater than three months, but less than one year. As of March 31, 2022 and December 31, 2021, the balance of restricted short-term investments was $2.2 million. ​ Deferred Income Taxes ​ The Company utilizes the liability method of accounting for income taxes, under which deferred taxes are determined based on the temporary differences between the financial statements and the tax basis of assets and liabilities using enacted tax rates. A valuation allowance is recorded when it is more likely than not that the deferred tax assets will not be realized. ​ Litigation, Commitments and Contingencies ​ Litigation, commitments and contingencies are accrued when management, after considering the facts and circumstances of each matter as then known to management, has determined it is probable a liability will be found to have been incurred and the amount of the loss can be reasonably estimated. When only a range of amounts is reasonably estimable and no amount within the range is more likely than another, the low end of the range is recorded. Legal fees are expensed as incurred. Due to the inherent uncertainties surrounding gain contingencies, the Company generally does not recognize potential gains until realized. ​ Recent Accounting Pronouncements ​ The Company does not believe that any recently issued effective pronouncements, or pronouncements issued but not yet effective, if adopted, would have a material effect on the accompanying condensed consolidated financial statements.

ANP Restructuring

ANP Restructuring	3 Months Ended
	Mar. 31, 2022
ANP Restructuring
ANP Restructuring	Note 3. ANP Restructuring ​ As a result of the ANP restructuring that was completed during the third quarter of 2021, and subsequent investments by other equity holders of Hanxin, the Company has a 14% noncontrolling investment in Hanxin that is accounted for as an equity method investment. ​ In addition to the retained noncontrolling investment in Hanxin, the Company maintains a seat on Hanxin’s board of directors, and Henry Zhang, a relative of Dr. Jack Zhang and Dr. Mary Luo, is an equity holder, general manager, and chairman of the board of directors of Hanxin. As a result, it was determined that the Company has significant influence over Hanxin and the retained noncontrolling investment in Hanxin is accounted for as an equity method investment. ​ Hanxin continues to be a related party after the deconsolidation.

Revenue Recognition

Revenue Recognition	3 Months Ended
	Mar. 31, 2022
Revenue Recognition
Revenue Recognition	Note 4. Revenue Recognition ​ In accordance with Accounting Standard Codification, or ASC, 606 Revenue from Contracts with Customers ​ Generally, revenue is recognized at the time of product delivery to the Company’s customers. In some cases, revenue is recognized at the time of shipment when stipulated by the terms of the sale agreements. ​ The consideration the Company receives in exchange for its goods or services is only recognized when it is probable that a significant reversal will not occur. The consideration to which the Company expects to be entitled includes a stated list price, less various forms of variable consideration. The Company makes significant estimates for related variable consideration at the point of sale, including chargebacks, rebates, product returns, other discounts and allowances. ​ The Company’s payment terms vary by types and locations of customers and the products or services offered. Payment terms differ by jurisdiction and customers, but payment is generally required in a term ranging from 30 to 75 days from date of shipment or satisfaction of the performance obligation. For certain products or services and certain customer types, we may require payment before products are delivered or services are rendered to customers. ​ Provisions for estimated chargebacks, rebates, discounts, product returns and credit losses are made at the time of sale and are analyzed and adjusted, if necessary, at each balance sheet date. ​ Revenues derived from contract manufacturing services are recognized when third-party products are shipped to customers, and after the customer has accepted test samples of the products to be shipped. ​ The Company’s accounting policy is to review each agreement involving contract development and manufacturing services to determine if there are multiple revenue-generating activities that constitute more than one unit of accounting. Revenues are recognized for each unit of accounting based on revenue recognition criteria relevant to that unit. The Company does not have any revenue arrangements with multiple performance obligations. ​ Service revenues derived from research and development contracts is recognized over time based on progress toward satisfaction of the performance obligation. For each performance obligation satisfied over time, the Company assesses the proper method to be used for revenue recognition, either an input method to measure progress toward the satisfaction of services or an output method of determining the progress of completion of performance obligation. For the three months ended March 31, 2022, and 2021, revenues from research and development services at ANP were $0.6 million and $0.3 million, respectively. ​ Provision for Chargebacks and Rebates ​ The provision for chargebacks and rebates is a significant estimate used in the recognition of revenue. Wholesaler chargebacks relate to sales terms under which the Company agrees to reimburse wholesalers for differences between the gross sales prices at which the Company sells its products to wholesalers and the actual prices of such products that wholesalers resell under the Company’s various contractual arrangements with third parties such as hospitals and group purchasing organizations in the United States. Rebates include primarily amounts paid to retailers, payers, and providers in the United States, including those paid to state Medicaid programs, and are based on contractual arrangements or statutory requirements. The Company estimates chargebacks and rebates using the expected value method at the time of sale to wholesalers based on wholesaler inventory stocking levels, historic chargeback and rebate rates, and current contract pricing. ​ The provision for chargebacks and rebates is reflected as a component of net revenues. The following table is an analysis of the chargeback and rebate provision: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended ​ ​ March 31, ​ ​ ​ 2022 ​ 2021 ​ ​ (in thousands) Beginning balance $ 20,167 $ 20,380 ​ Provision for chargebacks and rebates ​ 46,779 ​ 47,031 ​ Credits and payments issued to third parties ​ (48,394) ​ (46,881) ​ Ending balance ​ $ 18,552 ​ $ 20,530 ​ ​ Changes in the chargeback provision from period to period are primarily dependent on the Company’s sales to its wholesalers, the level of inventory held by wholesalers, and the wholesalers’ customer mix. Changes in the rebate provision from period to period are primarily dependent on retailer’s and other indirect customers’ purchases. The approach that the Company uses to estimate chargebacks has been consistently applied for all periods presented. Variations in estimates have been historically small. The Company continually monitors the provision for chargebacks and rebates and makes adjustments when it believes that the actual chargebacks and rebates may differ from the estimates. The settlement of chargebacks and rebates generally occurs within 20 days to 60 days after the sale to wholesalers. Accounts receivable and/or accounts payable and accrued liabilities are reduced and/or increased by the chargebacks and rebate amounts depending on whether the Company has the right to offset with the customer. Of the provision for chargebacks and rebates as of March 31, 2022 and December 31, 2021, $14.1 million and $15.6 million were included as a reduction to accounts receivable, net, on the condensed consolidated balance sheets, respectively. The remaining provision as of March 31, 2022 and December 31, 2021 of $4.5 million and $4.6 million, respectively, were included in accounts payable and accrued liabilities. ​ Accrual for Product Returns ​ The Company offers most customers the right to return qualified excess or expired inventory for partial credit; however, API product sales are generally non-returnable. The Company’s product returns primarily consist of the returns of expired products from sales made in prior periods. Returned products cannot be resold. At the time product revenue is recognized, the Company records an accrual for product returns estimated using the expected value method. The accrual is based, in part, upon the historical relationship of product returns to sales and customer contract terms. The Company also assesses other factors that could affect product returns including market conditions, product obsolescence, and new competition. Although these factors do not normally give the Company’s customers the right to return products outside of the regular return policy, the Company realizes that such factors could ultimately lead to increased returns. The Company analyzes these situations on a case-by-case basis and makes adjustments to the product return reserve as appropriate. ​ The provision for product returns is reflected as a component of net revenues. The following table is an analysis of the product return liability: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended ​ ​ March 31, ​ ​ ​ 2022 ​ 2021 ​ ​ (in thousands) Beginning balance $ 21,677 $ 14,204 ​ Provision for product returns ​ 1,192 ​ 3,233 ​ Credits issued to third parties ​ (1,480) ​ (2,517) ​ Ending balance ​ $ 21,389 ​ $ 14,920 ​ ​ Of the provision of product returns as of March 31, 2022 and December 31, 2021, $15.9 million and $16.0 million were included in accounts payable and accrued liabilities on the condensed consolidated balance sheets, respectively. The remaining provision as of March 31, 2022 and December 31, 2021 of $5.5 million and $5.7 million, respectively, were included in other long-term liabilities. For the three months ended March 31, 2022 and 2021, the Company’s aggregate product return rates were 1.6% and 1.4% of qualified sales, respectively.

Income per Share Attributable t

Income per Share Attributable to Amphastar Pharmaceuticals, Inc. Stockholders	3 Months Ended
	Mar. 31, 2022
Income per Share Attributable to Amphastar Pharmaceuticals, Inc. Stockholders
Income per Share Attributable to Amphastar Pharmaceuticals, Inc. Stockholders	Note 5. Income per Share Attributable to Amphastar Pharmaceuticals, Inc. Stockholders ​ Basic net income per share attributable to Amphastar Pharmaceuticals, Inc. stockholders is calculated based upon the weighted-average number of shares outstanding during the period. Diluted net income per share attributable to Amphastar Pharmaceuticals, Inc. stockholders gives effect to all potential dilutive shares outstanding during the period, such as stock options, non-vested restricted stock units and shares issuable under the Company’s Employee Stock Purchase Plan, or ESPP. ​ For the three months ended March 31, 2022, options to purchase 706,740 shares of stock with a weighted-average exercise price of $34.74 per share were excluded in the computation of diluted net income per share attributable to Amphastar Pharmaceuticals, Inc. stockholders because the effect would be anti-dilutive. ​ For the three months ended March 31, 2021, options to purchase 1,899,833 shares of stock with a weighted-average exercise price of $20.85 per share, and the reallocation of net loss attributable to non-controlling interest were excluded in the computation of diluted net income per share attributable to Amphastar Pharmaceuticals, Inc. stockholders because the effect would be anti-dilutive. ​ The following table provides the calculation of basic and diluted net income per share attributable to Amphastar Pharmaceuticals, Inc. stockholders for each of the periods presented: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended ​ ​ ​ March 31, ​ ​ ​ 2022 ​ 2021 ​ ​ ​ (in thousands, except per share data) ​ Basic and dilutive numerator: ​ ​ Net income attributable to Amphastar Pharmaceuticals, Inc. ​ $ 24,253 ​ $ 5,041 ​ Denominator: ​ ​ ​ ​ ​ ​ ​ Weighted-average shares outstanding — basic ​ 48,138 ​ ​ 47,520 ​ ​ ​ ​ ​ ​ ​ ​ ​ Net effect of dilutive securities: ​ ​ ​ ​ ​ ​ ​ Incremental shares from equity awards ​ 3,841 ​ ​ 1,998 ​ Weighted-average shares outstanding — diluted ​ 51,979 ​ 49,518 ​ Net income per share attributable to Amphastar Pharmaceuticals, Inc. stockholders — basic ​ $ 0.50 ​ $ 0.11 ​ Net income per share attributable to Amphastar Pharmaceuticals, Inc. stockholders — diluted ​ $ 0.47 ​ $ 0.10 ​ ​

Segment Reporting

Segment Reporting	3 Months Ended
	Mar. 31, 2022
Segment Reporting
Segment Reporting	Note 6. Segment Reporting ​ The Company’s business is the development, manufacture, and marketing of pharmaceutical products. The Company has identified two reporting segments that each report to the Chief Operating Decision Maker, or CODM, as defined in ASC 280, Segment Reporting. The Company’s performance is assessed and resources are allocated by the CODM based on the following two reportable segments: ​ ● Finished pharmaceutical products ● APIs ​ The finished pharmaceutical products segment manufactures, markets and distributes Primatene Mist ® ​ Selected financial information by reporting segment is presented below: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended ​ ​ March 31, ​ ​ ​ 2022 ​ 2021 ​ ​ (in thousands) Net revenues: ​ ​ ​ Finished pharmaceutical products ​ $ 116,546 ​ $ 97,882 ​ API ​ 3,822 ​ ​ 5,138 ​ Total net revenues ​ 120,368 ​ 103,020 ​ ​ ​ ​ ​ ​ ​ ​ ​ Gross profit (loss): ​ ​ ​ ​ ​ ​ ​ Finished pharmaceutical products ​ 56,939 ​ 45,286 ​ API ​ (1,113) ​ ​ (340) ​ Total gross profit ​ 55,826 ​ 44,946 ​ ​ ​ ​ ​ ​ ​ ​ ​ Operating expenses ​ 34,212 ​ 34,640 ​ ​ ​ ​ ​ ​ ​ ​ ​ Income from operations ​ 21,614 ​ 10,306 ​ Non-operating income (expenses) ​ 7,419 ​ (5,192) ​ ​ ​ ​ ​ ​ ​ ​ ​ Income before income taxes ​ $ 29,033 ​ $ 5,114 ​ ​ The Company manages its business segments to the gross profit level and manages its operating and other costs on a company-wide basis. The Company does not identify total assets by segment for internal purposes, as the Company’s CODM does not assess performance, make strategic decisions, or allocate resources based on assets. ​ The amount of net revenues in the finished pharmaceutical product segment is presented below: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended ​ ​ March 31, ​ ​ ​ 2022 ​ 2021 ​ ​ (in thousands) Finished pharmaceutical products net revenues: ​ ​ ​ Primatene Mist ® ​ $ 24,697 ​ $ 18,383 ​ Epinephrine ​ ​ 15,156 ​ ​ 15,578 ​ Glucagon ​ ​ 10,984 ​ ​ 7,984 ​ Lidocaine ​ ​ 10,590 ​ ​ 9,071 ​ Phytonadione ​ 10,475 ​ 9,565 ​ Enoxaparin ​ ​ 10,124 ​ ​ 10,658 ​ Naloxone ​ ​ 7,413 ​ ​ 6,341 ​ Other finished pharmaceutical products ​ 27,107 ​ 20,302 ​ Total finished pharmaceutical products net revenues ​ $ 116,546 ​ $ 97,882 ​ ​ ​ The amount of depreciation and amortization expense included in cost of revenues, by reporting segments is presented below: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended ​ ​ ​ March 31, ​ ​ ​ 2022 ​ 2021 ​ ​ ​ (in thousands) ​ Depreciation and amortization expense ​ ​ Finished pharmaceutical products ​ $ 1,794 ​ $ 1,435 ​ API ​ 948 ​ 1,048 ​ Total depreciation and amortization expense ​ $ 2,742 ​ $ 2,483 ​ ​ Net revenues and carrying values of long-lived assets by geographic regions are as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Net Revenue ​ Long-Lived Assets ​ ​ Three Months Ended ​ ​ ​ ​ ​ ​ ​ ​ March 31, ​ March 31, ​ December 31, ​ ​ ​ 2022 ​ 2021 ​ 2022 ​ 2021 ​ ​ (in thousands) United States $ 117,114 $ 99,170 $ 137,423 $ 134,731 ​ China ​ 933 ​ ​ 1,121 ​ 90,770 ​ 91,876 ​ France ​ 2,321 ​ ​ 2,729 ​ 43,176 ​ 44,884 ​ Total ​ $ 120,368 ​ $ 103,020 ​ $ 271,369 ​ $ 271,491 ​ ​

Customer and Supplier Concentra

Customer and Supplier Concentration	3 Months Ended
	Mar. 31, 2022
Customer and Supplier Concentration
Customer and Supplier Concentration	Note 7. Customer and Supplier Concentration ​ Customer Concentrations ​ Three large wholesale drug distributors, AmerisourceBergen Corporation, or AmerisourceBergen, Cardinal Health, Inc., or Cardinal, and McKesson Corporation, or McKesson, are all distributors of the Company’s products, as well as suppliers of a broad range of health care products. The Company considers these three customers to be its major customers, as each individually, and these customers collectively, represented a significant percentage of the Company’s net revenue for the three months ended March 31, 2022 and 2021 and accounts receivable as of March 31, 2022 and December 31, 2021, respectively. The following table provides accounts receivable and net revenue information for these major customers: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ % of Total Accounts ​ % of Net ​ ​ ​ Receivable ​ Revenue ​ ​ ​ ​ ​ Three Months Ended ​ ​ ​ March 31, ​ December 31, ​ March 31, ​ ​ 2022 2021 2022 2021 AmerisourceBergen 13 % 13 % 22 % 25 % McKesson 23 % 30 % 18 % 20 % Cardinal Health 22 % 20 % 16 % 15 % ​ Supplier Concentrations ​ The Company depends on suppliers for raw materials, APIs, and other components that are subject to stringent FDA requirements. Some of these materials may only be available from one or a limited number of sources. Establishing additional or replacement suppliers for these materials may take a substantial period of time, as suppliers must be approved by the FDA. Furthermore, a significant portion of raw materials may only be available from foreign sources. If the Company is unable to secure, on a timely basis, sufficient quantities of the materials it depends on to manufacture and market its products, it could have a materially adverse effect on the Company’s business, financial condition, and results of operations.

Fair Value Measurements

Fair Value Measurements	3 Months Ended
	Mar. 31, 2022
Fair Value Measurements
Fair Value Measurements	Note 8. Fair Value Measurements ​ GAAP defines fair value as the price that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants in the principal or most advantageous market for the asset or liability at the measurement date (an exit price). These standards also establish a hierarchy that prioritizes observable and unobservable inputs used in measuring fair value of an asset or liability, as described below: ​ ● Level 1 – Inputs to measure fair value are based on quoted prices (unadjusted) in active markets on identical assets or liabilities; ​ ● Level 2 – Inputs to measure fair value are based on the following: a) quoted prices in active markets on similar assets or liabilities, b) quoted prices for identical or similar instruments in inactive markets, or c) observable (other than quoted prices) or collaborated observable market data used in a pricing model from which the fair value is derived; and ​ ● Level 3 – Inputs to measure fair value are unobservable and the assets or liabilities have little, if any, market activity; these inputs reflect the Company’s own assumptions about the assumptions that market participants would use in pricing the assets or liabilities based on best information available in the circumstances. ​ As of March 31, 2022, cash equivalents include money market accounts. Investments consist of certificates of deposit as well as investment-grade municipal bonds with original maturity dates between three and fifteen months. The certificates of deposit are carried at amortized cost in the Company’s condensed consolidated balance sheet, which approximates their fair value determined based on Level 2 inputs. The corporate and municipal bonds are classified as held-to-maturity and are carried at amortized cost net of allowance for credit losses, which approximates their fair value determined based on Level 2 inputs. The restrictions on restricted cash and investments have a negligible effect on the fair value of these financial assets. ​ The fair value of the Company’s financial assets and liabilities measured on a recurring basis as of March 31, 2022 and December 31, 2021, are as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total (Level 1) (Level 2) (Level 3) ​ ​ (in thousands) Cash equivalents - money market ​ $ 140,991 ​ $ 140,991 ​ $ — ​ $ — ​ Restricted cash - money market ​ ​ 235 ​ ​ 235 ​ ​ — ​ ​ — ​ Short-term investments - certificates of deposit ​ ​ 4,600 ​ ​ — ​ ​ 4,600 ​ ​ — ​ Restricted short-term investments - certificates of deposit ​ 2,200 ​ — ​ 2,200 ​ — ​ Corporate and municipal bonds ​ ​ 9,676 ​ ​ — ​ ​ 9,676 ​ ​ — ​ Interest rate swap related to variable rate loans ​ ​ 3,609 ​ ​ — ​ ​ 3,609 ​ ​ — ​ Fair value measurement as of March 31, 2022 ​ $ 161,311 ​ $ 141,226 ​ $ 20,085 ​ $ — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Cash equivalents - money market ​ $ 102,863 ​ $ 102,863 ​ $ — ​ $ — ​ Restricted cash - money market ​ ​ 235 ​ ​ 235 ​ ​ — ​ ​ — ​ Short-term investments - certificates of deposit ​ ​ 5,103 ​ ​ — ​ ​ 5,103 ​ ​ — ​ Restricted short-term investments - certificates of deposit ​ 2,200 ​ — ​ 2,200 ​ — ​ Corporate and municipal bonds ​ ​ 6,984 ​ ​ — ​ ​ 6,984 ​ ​ — ​ Interest rate swap related to variable rate loans ​ ​ 596 ​ ​ — ​ ​ 596 ​ ​ — ​ Fair value measurement as of December 31, 2021 ​ $ 117,981 ​ $ 103,098 ​ $ 14,883 ​ $ — ​ ​ The Company does not hold any Level 3 instruments that are measured at fair value on a recurring basis. ​ Nonfinancial assets and liabilities are not measured at fair value on a recurring basis but are subject to fair value adjustments in certain circumstances. These items primarily include investments in unconsolidated affiliates, long-lived assets, goodwill, and intangible assets for which the fair value is determined as part of the related impairment test. As of March 31, 2022 and December 31, 2021, there were no significant adjustments to fair value for nonfinancial assets or liabilities. ​ The deferred compensation plan assets are valued using the cash surrender value of the life insurance policies and are not included in the table above.

Investments

Investments	3 Months Ended
	Mar. 31, 2022
Investments
Investments	Note 9. Investments ​ A summary of the Company’s investments that are classified as held-to-maturity are as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Gross ​ Gross ​ ​ ​ ​ Amortized ​ Unrealized ​ Unrealized ​ Fair ​ Cost Gains Losses Value ​ ​ (in thousands) Corporate bonds (due within 1 year) ​ $ 5,557 ​ $ — ​ $ (30) ​ $ 5,527 Municipal bonds (due within 1 year) ​ ​ 4,162 ​ ​ — ​ ​ (13) ​ ​ 4,149 Total investments as of March 31, 2022 ​ $ 9,719 ​ $ — ​ $ (43) ​ $ 9,676 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Corporate bonds (due within 1 year) ​ $ 2,481 ​ $ — ​ $ (3) ​ $ 2,478 Corporate bonds (due within 1 to 3 years) ​ ​ 1,248 ​ ​ — ​ ​ (3) ​ ​ 1,245 Municipal bonds (due within 1 year) ​ ​ 3,263 ​ ​ — ​ ​ (2) ​ ​ 3,261 Total investments as of December 31, 2021 ​ $ 6,992 ​ $ — ​ $ (8) ​ $ 6,984 ​ At each reporting period, the Company evaluates securities for impairment when the fair value of the investment is less than its amortized cost. The Company evaluated the underlying credit quality and credit ratings of the issuers, noting neither a significant deterioration since purchase nor any other factors that would indicate a material credit loss. ​ The Company measures expected credit losses on held-to-maturity investments on a collective basis. All the Company’s held-to-maturity investments were considered to be one pool. The estimate for credit losses considers historical loss information that is adjusted for current conditions and reasonable and supportable forecasts. Expected credit losses on held-to-maturity investments were not material to the condensed consolidated financial statements . ​ Investment in unconsolidated affiliate ​ The Company accounts for its share of the earnings or losses of its unconsolidated affiliate (Hanxin) with a reporting lag of three months, as the financial statements of Hanxin are not completed on a basis that is sufficient for the Company to apply the equity method on a current basis. The Company’s share of Hanxin’s losses for the three months ended March 31, 2022 was $0.7 million, which was recorded in the “Equity in losses of unconsolidated affiliate” line on the consolidated statement of operations.

Goodwill and Intangible Assets

Goodwill and Intangible Assets	3 Months Ended
	Mar. 31, 2022
Goodwill and Intangible Assets
Goodwill and Intangible Assets	Note 10. Goodwill and Intangible Assets ​ The table below shows the weighted-average life, original cost, accumulated amortization, and net book value by major intangible asset classification: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted-Average ​ ​ ​ ​ Accumulated ​ ​ ​ ​ Life (Years) Original Cost Amortization Net Book Value ​ ​ (in thousands) Definite-lived intangible assets ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ IMS (UK) international product rights ​ 10 ​ $ 9,182 ​ $ 5,203 ​ $ 3,979 ​ Patents 12 ​ 486 ​ ​ 350 ​ 136 ​ Land-use rights 39 ​ 2,540 ​ ​ 700 ​ 1,840 ​ Subtotal 12 ​ 12,208 ​ 6,253 ​ 5,955 ​ Indefinite-lived intangible assets ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Trademark * ​ 29,225 ​ — ​ 29,225 ​ Goodwill - Finished pharmaceutical products * ​ 3,256 ​ — ​ 3,256 ​ Subtotal * ​ 32,481 ​ — ​ 32,481 ​ As of March 31, 2022 * ​ $ 44,689 ​ $ 6,253 ​ $ 38,436 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted-Average ​ ​ ​ ​ Accumulated ​ ​ ​ ​ Life (Years) Original Cost Amortization Net Book Value ​ ​ (in thousands) Definite-lived intangible assets ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ IMS (UK) international product rights ​ 10 ​ $ 9,445 ​ $ 5,116 ​ $ 4,329 ​ Patents 12 ​ 486 ​ ​ 340 ​ 146 ​ Land-use rights 39 ​ 2,540 ​ ​ 683 ​ 1,857 ​ Subtotal 12 ​ 12,471 ​ 6,139 ​ 6,332 ​ Indefinite-lived intangible assets ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Trademark * ​ 29,225 ​ — ​ 29,225 ​ Goodwill - Finished pharmaceutical products * ​ 3,313 ​ — ​ 3,313 ​ Subtotal * ​ 32,538 ​ — ​ 32,538 ​ As of December 31, 2021 * ​ $ 45,009 ​ $ 6,139 ​ $ 38,870 ​ * Intangible assets with indefinite lives have an indeterminable average life. ​ Goodwill ​ The changes in the carrying amounts of goodwill were as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ March 31, ​ December 31, ​ ​ 2022 ​ 2021 ​ ​ (in thousands) Beginning balance $ 3,313 $ 3,940 ​ ANP restructuring ​ ​ — ​ ​ (374) ​ Currency translation ​ (57) ​ (253) ​ Ending balance ​ $ 3,256 ​ $ 3,313 ​ ​ Primatene ® Trademark ​ In January 2009, the Company acquired the exclusive rights to the trademark, domain name, website and domestic marketing, distribution and selling rights related to Primatene Mist ® ​ The trademark was determined to have an indefinite life. In determining its indefinite life, the Company considered the following: the expected use of the intangible; the longevity of the brand; the legal, regulatory and contractual provisions that affect their maximum useful life; the Company’s ability to renew or extend the asset’s legal or contractual life without substantial costs; effects of the regulatory environment; expected changes in distribution channels; maintenance expenditures required to obtain the expected future cash flows from the asset; and considerations for obsolescence, demand, competition and other economic factors.

Inventories

Inventories	3 Months Ended
	Mar. 31, 2022
Inventories
Inventories	Note 11. Inventories ​ Inventories consist of the following: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ March 31, ​ December 31, ​ ​ 2022 ​ 2021 ​ ​ (in thousands) Raw materials and supplies $ 40,358 $ 41,853 ​ Work in process ​ 40,264 ​ 33,298 ​ Finished goods ​ 14,525 ​ 17,656 ​ Total inventories ​ $ 95,147 ​ $ 92,807 ​ ​ Charges of $8.0 million and $9.5 million were included in the cost of revenues in the Company’s condensed consolidated statements of operations for the three months ended March 31, 2022 and 2021, respectively, to adjust the Company’s inventory and related firm purchase commitments to their net realizable value. ​ Losses on firm purchase commitments related to raw materials on order were $6.4 million and $8.2 million as of March 31, 2022 and 2021, respectively.

Property, Plant, and Equipment

Property, Plant, and Equipment	3 Months Ended
	Mar. 31, 2022
Property, Plant, and Equipment
Property, Plant, and Equipment	Note 12. Property, Plant, and Equipment ​ Property, plant, and equipment consist of the following: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ March 31, ​ December 31, ​ ​ 2022 ​ 2021 ​ ​ (in thousands) Buildings $ 130,364 $ 130,582 ​ Leasehold improvements ​ 29,221 ​ 29,221 ​ Land ​ 7,592 ​ 7,615 ​ Machinery and equipment ​ 207,006 ​ 207,883 ​ Furniture, fixtures, and automobiles ​ 27,635 ​ 27,376 ​ Construction in progress ​ 44,685 ​ 41,186 ​ Total property, plant, and equipment ​ 446,503 ​ 443,863 ​ Less accumulated depreciation ​ (203,255) ​ (199,619) ​ Total property, plant, and equipment, net ​ $ 243,248 ​ $ 244,244 ​ ​

Accounts Payable and Accrued Li

Accounts Payable and Accrued Liabilities	3 Months Ended
	Mar. 31, 2022
Accounts Payable and Accrued Liabilities.
Accounts Payable and Accrued Liabilities	Note 13. Accounts Payable and Accrued Liabilities ​ Accounts payable and accrued liabilities consisted of the following: ​ ​ ​ ​ ​ ​ ​ ​ March 31, ​ December 31, ​ 2022 ​ 2021 ​ (in thousands) Accrued customer fees and rebates $ 12,903 ​ $ 12,121 Accrued payroll and related benefits ​ 24,178 ​ ​ 23,256 Accrued product returns, current portion ​ 15,898 ​ ​ 16,028 Accrued loss on firm purchase commitments ​ 9,779 ​ ​ 7,133 Other accrued liabilities ​ 9,209 ​ ​ 8,793 Total accrued liabilities 71,967 ​ 67,331 Accounts payable 23,843 ​ 22,214 Total accounts payable and accrued liabilities $ 95,810 ​ $ 89,545 ​

Debt

Debt	3 Months Ended
	Mar. 31, 2022
Debt
Debt	Note 14. Debt ​ Debt consists of the following: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ March 31, ​ December 31, ​ ​ 2022 ​ 2021 ​ ​ (in thousands) Line of Credit Facilities ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Line of credit facility with China Merchant Bank ​ $ — ​ $ — ​ Revolving line of credit facility with Capital One N.A. due August 2026 ​ ​ — ​ ​ — ​ ​ ​ ​ ​ ​ ​ ​ ​ Term Loan ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Term loan with Capital One N.A. due August 2026 ​ ​ 69,125 ​ ​ 69,563 ​ ​ ​ ​ ​ ​ ​ ​ ​ Mortgage Loans ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Mortgage payable with East West Bank due June 2027 ​ ​ 8,313 ​ ​ 8,353 ​ ​ ​ ​ ​ ​ ​ ​ ​ Other Loans and Payment Obligations ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ French government loans due December 2026 ​ ​ 267 ​ ​ 269 ​ ​ ​ ​ ​ ​ ​ ​ ​ Equipment under Finance Leases ​ 337 ​ 398 ​ Total debt ​ 78,042 ​ 78,583 ​ Less current portion of long-term debt ​ 2,159 ​ 2,202 ​ Less: Loan issuance costs ​ ​ 1,535 ​ ​ 1,605 ​ Long-term debt, net of current portion and unamortized debt issuance costs ​ $ 74,348 ​ $ 74,776 ​ ​ As of March 31, 2022, the fair value of the loans listed above approximated their carrying amount. The interest rate used in the fair value estimation was determined to be a Level 2 input. For the mortgage loan with East West Bank, as well as the term loan with Capital One N.A., the Company has entered into fixed interest rate swap contracts to exchange the variable interest rates for a fixed interest rates. ​ Covenants ​ At March 31, 2022 and December 31, 2021, the Company was in compliance with all of its debt covenants.

Income Taxes

Income Taxes	3 Months Ended
	Mar. 31, 2022
Income Taxes
Income Taxes	Note 15. Income Taxes ​ The following table sets forth the Company’s income tax provision for the periods indicated: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended ​ ​ ​ March 31, ​ ​ 2022 2021 ​ ​ (in thousands) ​ Income before taxes ​ $ 29,033 ​ $ 5,114 ​ Income tax provision ​ ​ 4,077 ​ 1,155 ​ Income before equity in losses of unconsolidated affiliate ​ $ 24,956 ​ $ 3,959 ​ Income tax provision as a percentage of income before income taxes ​ ​ 14.0 % 22.6 % ​ The change in the Company’s effective tax rate for the three months ended March 31, 2022 was primarily due to differences in pre-tax income positions and timing of discrete tax items. ​ Valuation Allowance ​ In assessing the need for a valuation allowance, management considers whether it is more likely than not that some portion or all of the deferred income tax assets will be realized. Ultimately, realization depends on the existence of future taxable income. Management considers sources of taxable income such as income in prior carryback periods, future reversal of existing deferred taxable temporary differences, tax-planning strategies, and projected future taxable income. ​ The Company continues to record a full valuation allowance on AFP’s net deferred income tax assets and will continue to do so until AFP generates sufficient taxable income to realize its deferred income tax assets. ​ For purposes of computing its annual effective tax rate, the Company did not benefit from its losses in the states where it files separately. This increased the Company’s income tax expense by an immaterial amount during the three months ended March 31, 2022 and 2021.

Stockholders' Equity

Stockholders' Equity	3 Months Ended
	Mar. 31, 2022
Stockholders' Equity
Stockholders' Equity	Note 16. Stockholders' Equity ​ Share Buyback Program ​ Pursuant to the Company’s existing share buyback program, the Company purchased 51,168 and 204,698 shares of its common stock during the three months ended March 31, 2022 and 2021, totaling $1.2 million and $3.8 million, respectively. ​ In May 2022, the Company’s Board of Directors authorized a $25.0 million increase to the Company’s share buyback program, which is expected to continue for an indefinite period of time. Since the inception of the program, the Company’s Board of Directors have authorized an aggregate of $185.0 million to the Company’s share buyback program. The primary goal of the program is to offset dilution created by the Company’s equity compensation programs. ​ Purchases are made through open market and private block transactions pursuant to Rule 10b5-1 plans, privately negotiated transactions or other means as determined by the Company’s management and in accordance with the requirements of the SEC and applicable laws. The timing and actual number of treasury share purchases will depend on a variety of factors including price, corporate and regulatory requirements, and other conditions. These treasury share purchases are accounted for under the cost method and are included as a component of treasury stock in the Company’s condensed consolidated balance sheets. ​ Amended and Restated 2015 Equity Incentive Plan ​ As of March 31, 2022, the Company reserved an aggregate of 6,462,223 shares of common stock for future issuance under the Amended and Restated 2015 Equity Incentive Plan, or the 2015 Plan, including 1,192,873 shares, which were reserved in January 2022 pursuant to the evergreen provision in the 2015 Plan. ​ 2014 Employee Stock Purchase Plan ​ As of March 31, 2022, the Company has issued 954,456 shares of common stock under the ESPP and 1,045,544 shares of its common stock remain available for issuance under the ESPP. ​ For the three months ended March 31, 2022 and 2021, the Company recorded ESPP expenses of $0.2 million and $0.1 million, respectively. ​ Share-Based Award Activity and Balances (excluding the ANP Equity Plan) ​ The Company accounts for share-based compensation payments in accordance with ASC 718, which requires measurement and recognition of compensation expense at fair value for all share-based payment awards made to employees and directors. Under these standards, the fair value of option awards and the option components of the ESPP awards are estimated at the grant date using the Black-Scholes option-pricing model. The fair value of RSUs is estimated at the grant date using the Company’s common share price. Compensation cost for all share-based payments granted with service-based graded vesting schedules is recognized using the straight-line method over the requisite service period. ​ The weighted-averages for key assumptions used in determining the fair value of options granted during the three months ended March 31, 2022 and 2021, are as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended ​ ​ ​ March 31, ​ ​ 2022 2021 Average volatility 41.1 % 42.2 % Average risk-free interest rate 2.2 % 1.3 % Weighted-average expected life in years 6.3 ​ 6.3 ​ Dividend yield rate — % — % ​ A summary of option activity for the three months ended March 31, 2022, is presented below: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted-Average ​ ​ ​ ​ ​ ​ ​ Weighted-Average ​ Remaining ​ Aggregate ​ ​ ​ ​ Exercise ​ Contractual ​ Intrinsic ​ ​ Options ​ Price ​ Term (Years) ​ Value (1) ​ ​ ​ ​ ​ ​ ​ ​ ​ (in thousands) Outstanding as of December 31, 2021 8,455,721 ​ $ 15.67 ​ ​ Options granted 706,740 ​ ​ 34.74 ​ ​ ​ ​ ​ ​ Options exercised (795,795) ​ ​ 14.43 ​ ​ ​ ​ ​ ​ Options cancelled (7,646) ​ ​ 17.19 ​ ​ ​ ​ ​ ​ Options expired (3,914) ​ ​ 13.35 ​ ​ ​ ​ ​ ​ Outstanding as of March 31, 2022 8,355,106 ​ $ 17.40 ​ 5.58 ​ $ 154,559 ​ Exercisable as of March 31, 2022 5,816,368 ​ $ 15.53 ​ 4.23 ​ $ 118,506 ​ Vested and expected to vest as of March 31, 2022 ​ 8,071,696 ​ $ 17.20 ​ 5.46 ​ $ 150,955 ​ (1) The aggregate intrinsic value is calculated as the difference between the exercise price of the underlying awards and the estimated fair value of the Company’s common stock for those awards that have an exercise price below the estimated fair value at March 31, 2022. ​ For the three months ended March 31, 2022 and 2021, the Company recorded an expense of $2.5 million and $2.4 million, respectively, related to stock options granted under all plans. ​ Information relating to option grants and exercises is as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended ​ ​ March 31, ​ ​ 2022 2021 ​ ​ (in thousands, except per share data) Weighted-average grant date fair value per option share ​ $ 15.06 ​ $ 7.66 ​ Intrinsic value of options exercised ​ 12,200 ​ 1,029 ​ Cash received from options exercised ​ 12,450 ​ 2,169 ​ Total fair value of the options vested during the period ​ 6,987 ​ 6,772 ​ ​ A summary of the status of the Company’s non-vested options as of March 31, 2022, and changes during the three months ended March 31, 2022, is presented below: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted-Average ​ ​ ​ ​ Grant Date ​ ​ Options ​ Fair Value Non-vested as of December 31, 2021 ​ 2,848,934 ​ $ 6.95 ​ Options granted 706,740 ​ ​ 15.06 ​ Options vested (1,009,290) ​ ​ 6.92 ​ Options forfeited (7,646) ​ ​ 7.34 ​ Non-vested as of March 31, 2022 2,538,738 ​ 9.22 ​ ​ As of March 31, 2022, there was $18.8 million of total unrecognized compensation cost, net of forfeitures, related to non-vested stock option based compensation arrangements granted under all plans. The cost is expected to be recognized over a weighted-average period of 3.1 years and will be adjusted for future changes in estimated forfeitures. ​ Restricted Stock Units ​ The Company grants restricted stock units, or RSUs, to certain employees and members of the Board of Directors with a vesting period of up to five years. The grantee receives one share of common stock at a specified future date for each RSU awarded. The RSUs may not be sold or otherwise transferred until certificates of common stock have been issued, recorded, and delivered to the participant. The RSUs do not have any voting or dividend rights prior to the issuance of certificates of the underlying common stock. The share-based expense associated with these grants was based on the Company’s common stock fair value at the time of grant and is amortized over the requisite service period, which generally is the vesting period using the straight-line method. During the three months ended March 31, 2022 and 2021, the Company recorded expenses of $2.4 million and $2.2 million, respectively, related to RSU awards granted under all plans. ​ As of March 31, 2022, there was $20.0 million of total unrecognized compensation cost, net of forfeitures, related to non-vested RSU stock-based compensation arrangements granted under all plans. The cost is expected to be recognized over a weighted-average period of 3.1 years and will be adjusted for future changes in estimated forfeitures. ​ Information relating to RSU grants and deliveries is as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total Fair Market ​ ​ Total RSUs ​ Value of RSUs ​ Issued Issued (1) ​ ​ ​ ​ (in thousands) RSUs outstanding at December 31, 2021 1,184,842 ​ ​ ​ ​ RSUs granted 306,080 ​ $ 10,633 ​ RSUs forfeited (3,259) ​ ​ ​ ​ RSUs vested (2) (417,007) ​ ​ ​ ​ RSUs outstanding at March 31, 2022 1,070,656 ​ ​ ​ ​ (1) The total fair market value is derived from the number of RSUs granted times the current stock price on the date of grant. (2) Of the vested RSUs, 174,982 shares of common stock were surrendered to fulfill tax withholding obligations. ​ The 2018 ANP Equity Incentive Plan ​ In December 2018, ANP’s board of directors approved the 2018 Plan, which was set to expire in December 2023. The 2018 Plan permitted the grant of stock options and other equity awards in ANP shares to ANP employees. ​ During the second quarter of 2021, in connection with the ANP restructuring, the 2018 Plan was terminated. ​ Prior to the termination of the 2018 Plan, during the three months ended March 31, 2021, the Company recorded expense of $0.1 million related to stock options issued by ANP under the 2018 Plan. ​ Share-based Compensation Expense ​ The Company recorded share-based compensation expense, which is included in the Company’s condensed consolidated statement of operations as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended ​ ​ March 31, ​ ​ 2022 ​ 2021 ​ ​ (in thousands) Cost of revenues $ 1,385 $ 1,146 Operating expenses: ​ ​ ​ ​ ​ ​ Selling, distribution, and marketing ​ 168 ​ 127 General and administrative ​ 2,861 ​ 2,968 Research and development ​ 608 ​ 593 Total share-based compensation ​ $ 5,022 ​ $ 4,834 ​

Employee Benefits

Employee Benefits	3 Months Ended
	Mar. 31, 2022
Employee Benefits
Employee Benefits	Note 17. Employee Benefits ​ 401(k) Plan ​ The Company has a defined contribution 401(k) plan, or the Plan, whereby eligible employees voluntarily contribute up to a defined percentage of their annual compensation. The Company matches contributions at a rate of 50% on the first 6% of employee contributions, and pays the administrative costs of the Plan. Total employer contributions for the three months ended March 31, 2022 and 2021, were approximately $0.6 million and $0.5 million, respectively. ​ Defined Benefit Pension Plan ​ The Company’s subsidiary, AFP, has an obligation associated with a defined-benefit plan for its eligible employees. This plan provides benefits to the employees from the date of retirement and is based on the employee’s length of time employed by the Company. The calculation is based on a statistical calculation combining a number of factors that include the employee’s age, length of service, and AFP employee turnover rate. ​ The liability under the plan is based on a discount rate of 1.00% as of March 31, 2022 and December 31, 2021. The liability is included in other long-term liabilities in the accompanying condensed consolidated balance sheets. The plan is currently unfunded, and the benefit obligation under the plan was $2.7 million at March 31, 2022 and December 31, 2021. The Company recorded an immaterial amount of expense under the plan for the three months ended March 31, 2022 and 2021. ​ Non-qualified Deferred Compensation Plan ​ In December 2019, the Company established a non-qualified deferred compensation plan. The plan allows certain eligible participants to defer a portion of their cash compensation and provides a matching contribution at the discretion of the Company. The plan obligations are payable upon retirement, termination of employment and/or certain other times in a lump-sum distribution or in installments, as elected by the participant in accordance with the plan. Participants can allocate their deferred compensation amongst various investment options with earnings accruing to the participant. The Company has established a Rabbi Trust to fund the plan obligations and to hold the plan assets. Eligible participants began contributing to the plan in January 2020. The plan assets were valued at approximately $3.5 million and $3.4 million as of March 31, 2022 and December 31, 2021, respectively. The plan liabilities were valued at approximately $3.6 million and $3.5 million as of March 31, 2022 and December 31, 2021, respectively. The plan assets and liabilities are included in other long-term assets and other long-term liabilities, respectively, on the Company’s condensed consolidated balance sheets.

Commitments and Contingencies

Commitments and Contingencies	3 Months Ended
	Mar. 31, 2022
Commitments and Contingencies
Commitments and Contingencies	Note 18. Commitments and Contingencies ​ Purchase Commitments ​ As of March 31, 2022, the Company has entered into commitments to purchase equipment and raw materials for an aggregate amount of approximately $72.9 million. The Company anticipates that most of these commitments with a remaining term in excess of one year will be fulfilled by 2023.

Litigation

Litigation	3 Months Ended
	Mar. 31, 2022
Litigation
Litigation	Note 19. Litigation ​ Hatch-Waxman Litigations ​ Regadenoson (0.4 mg/5 mL, 0.08 mg/mL) Patent Litigation ​ On February 25, 2020, Astellas US LLC, Astellas Pharma US, Inc., and Gilead Sciences, Inc. (collectively, “Astellas-Gilead”) filed a Complaint in the United States District Court for the District of Delaware against IMS for infringement of U.S. Patent Nos. 8,106,183 (the “‘183 patent”), RE47,301 (the “‘301 patent”), and 8,524,883 (the “‘883 patent”) (collectively, “Astellas-Gilead Patents”) with regard to IMS’s ANDA No. 214,252 for approval to manufacture and sell 0.4 mg/5 mL (0.08 mg/mL) intravenous solution of Regadenoson. On March 4, 2020, IMS filed its Answer and Counterclaims. On March 30, 2020, the Court issued an Order allowing the Company to join pending consolidated litigation with five other generic Regadenoson ANDA filers involving similar claims. The Company’s 30-month FDA stay expires August 10, 2022. On January 26, 2022, the Company and Astellas-Gilead reached an agreement to resolve the lawsuit. The parties submitted, and the Court granted on January 27, 2022, a Motion to Dismiss Without Prejudice for Astellas-Gilead’s complaint of infringement against IMS. Under the terms of the agreement, the Company received $5.4 million from Astellas constituting saved litigation expenses. The Company recorded the settlement amount as other income (expenses), in its condensed consolidated statement of operations for the three months ended March 31, 2022. ​ Other Litigation ​ The Company is also subject to various other claims, arbitrations, investigations, and lawsuits from time to time arising in the ordinary course of business. In addition, third parties may, from time to time, assert claims against the Company in the forms of letters and other communications. ​ The Company records a provision for contingent losses when it is both probable that a liability has been incurred and the amount of the loss can be reasonably estimated. In the opinion of management, the ultimate resolution of any such matters is not expected to have a material adverse effect on its financial position, results of operations, or cash flows; however, the results of litigation and claims are inherently unpredictable and the Company’s view of these matters may change in the future. Regardless of the outcome, litigation can have an adverse impact on the Company because of defense and settlement costs, diversion of management resources, and other factors.

Subsequent Events

Subsequent Events	3 Months Ended
	Mar. 31, 2022
Subsequent Events
Subsequent Events	Note 20. Subsequent Event ​ In April 2022, the Company’s Chinese subsidiary, ANP, entered into a contract manufacturing agreement with Hanxin, which is a related party, whereby Hanxin will develop several active pharmaceutical ingredients and finished products for the Chinese market and will engage ANP to manufacture the products on a cost-plus basis. Hanxin will commit to purchase certain quantities from ANP subject to the terms and conditions set forth in the agreement, including Hanxin filing for and obtaining any required marketing authorizations. ​

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	3 Months Ended
	Mar. 31, 2022
Summary of Significant Accounting Policies
Basis of Presentation	Basis of Presentation ​ The unaudited condensed consolidated financial statements include the accounts of the Company and its subsidiaries, and are prepared in accordance with GAAP. Certain prior period amounts have been reclassified within the operating activities of the condensed consolidated statements of cash flows to conform to the current period presentation. All intercompany activity has been eliminated in the preparation of the condensed consolidated financial statements. ​ The Company’s subsidiaries include: (1) International Medication Systems, Limited, or IMS, (2) Armstrong Pharmaceuticals, Inc., or Armstrong, (3) Amphastar Nanjing Pharmaceuticals Inc., or ANP, (4) Amphastar France Pharmaceuticals, S.A.S., or AFP, (5) Amphastar UK Ltd., or AUK, and (6) International Medication Systems (UK) Limited, or IMS UK. ​
COVID-19 Pandemic	COVID-19 Pandemic ​ The Company is subject to risks and uncertainties as a result of the ongoing novel coronavirus pandemic, or COVID-19. The complete extent of the impact of the COVID-19 pandemic on the Company’s business is highly uncertain and difficult to predict, as the information is constantly evolving. The Company considered the impact of COVID - ​ All of the Company’s production facilities continued to operate during the quarter as they had prior to the COVID-19 pandemic with very little change, other than for enhanced safety measures intended to prevent the spread of the virus. Recent increases in COVID-19 cases in Shanghai, China, have led to shutdowns and delays at the ports in Shanghai, which could have an impact on the Company’s operations. However, the extent of the impact of this shutdown and delay is highly uncertain and difficult to predict. ​ It is not possible at this time to estimate the complete impact that COVID-19 could have on the Company’s business, including its customers and suppliers, as the impact will depend on future developments, which are highly uncertain and cannot be predicted. The Company will continue to monitor the impact of COVID-19 on all aspects of its business.
Use of Estimates	Use of Estimates ​ The preparation of condensed consolidated financial statements in accordance with GAAP requires management to make estimates and assumptions that affect the amounts reported in the condensed consolidated financial statements and accompanying notes. Actual results could differ from those estimates. The principal accounting estimates include: determination of allowances for credit losses, fair value of financial instruments, allowance for discounts, provision for chargebacks and rebates, provision for product returns, adjustment of inventory to its net realizable values, impairment of investments, long-lived and intangible assets and goodwill, accrual for workers’ compensation liabilities, litigation reserves, stock price volatility for share-based compensation expense, valuation allowances for deferred tax assets, and liabilities for uncertain income tax positions.
Foreign Currency	Foreign Currency ​ The functional currency of the Company, its domestic subsidiaries, its Chinese subsidiary, ANP, and its U.K. subsidiary, AUK, is the U.S. Dollar, or USD. ANP maintains its books of record in Chinese yuan. These books are remeasured into the functional currency, USD, using the current or historical exchange rates. The resulting currency remeasurement adjustments and other transactional foreign currency exchange gains and losses are reflected in the Company’s condensed consolidated statements of operations. ​ The Company’s French subsidiary, AFP, maintains its book of record in euros. AUK’s subsidiary, IMS UK, maintains its book of record in British pounds. These local currencies have been determined to be the subsidiaries’ respective functional currencies. Activity in the statement of operations is translated to USD using average exchange rates during the period. Assets and liabilities are translated at the rate of exchange prevailing on the balance sheet date. Equity is translated at the prevailing rate of exchange at the date of the equity transactions. Translation adjustments are reflected in stockholders’ equity and are included as a component of other accumulated comprehensive income (loss). The unrealized gains or losses of intercompany foreign currency transactions that are of a long-term investment nature are reported in other accumulated comprehensive income (loss). ​ The unrealized gains and losses of intercompany foreign currency transactions that are of a long-term investment nature for the three months ended March 31, 2022 and 2021 were $0.6 million loss and $1.5 million loss, respectively.
Comprehensive Income (Loss)	Comprehensive Income ​ For the three months ended March 31, 2022 and 2021, the Company included its foreign currency translation gain or loss as part of its comprehensive income.
Advertising Expense	Advertising Expense ​ Advertising expenses, primarily associated with Primatene Mist ® commercial or campaign is first presented, and are reflected as a component of selling, distribution and marketing in the Company’s condensed consolidated statement of operations. For the three months ended March 31, 2022 and 2021, advertising expenses were $2.4 million and $2.2 million, respectively.
Financial Instruments	Financial Instruments ​ The carrying amounts of cash and cash equivalents, short-term investments, restricted cash and short-term investments, accounts receivable, accounts payable, accrued expenses, and short-term borrowings approximate fair value due to the short maturity of these items. The majority of the Company’s long-term obligations consist of variable rate debt, and their carrying value approximates fair value as the stated borrowing rates are comparable to rates currently offered to the Company for instruments with similar maturities. The Company at times enters into fixed interest rate swap contracts to exchange the variable interest rates for fixed interest rates. Such interest rate swap contracts are recorded at their fair values.
Cash and Cash Equivalents	Cash and Cash Equivalents ​ Cash and cash equivalents consist of cash, money market accounts, certificates of deposit and highly liquid investments purchased with original maturities of three months or less. ​
Investments	Investments ​ Investments as of March 31, 2022 and December 31, 2021 consisted of certificates of deposit and investment grade corporate and municipal bonds with original maturity dates between three and fifteen months.
Restricted Cash	Restricted Cash ​ Restricted cash is collateral required for the Company to guarantee certain vendor payments in France. As of each of March 31, 2022 and December 31, 2021, the restricted cash balance was $0.2 million. ​
Restricted Short-Term Investments	Restricted Short-Term Investments ​ Restricted short-term investments consist of certificates of deposit that are collateral for standby letters of credit to qualify for workers’ compensation self-insurance. The certificates of deposit have original maturities greater than three months, but less than one year. As of March 31, 2022 and December 31, 2021, the balance of restricted short-term investments was $2.2 million.
Deferred Income Taxes	Deferred Income Taxes ​ The Company utilizes the liability method of accounting for income taxes, under which deferred taxes are determined based on the temporary differences between the financial statements and the tax basis of assets and liabilities using enacted tax rates. A valuation allowance is recorded when it is more likely than not that the deferred tax assets will not be realized. ​
Litigation, Commitments and Contingencies	Litigation, Commitments and Contingencies ​ Litigation, commitments and contingencies are accrued when management, after considering the facts and circumstances of each matter as then known to management, has determined it is probable a liability will be found to have been incurred and the amount of the loss can be reasonably estimated. When only a range of amounts is reasonably estimable and no amount within the range is more likely than another, the low end of the range is recorded. Legal fees are expensed as incurred. Due to the inherent uncertainties surrounding gain contingencies, the Company generally does not recognize potential gains until realized. ​ Recent Accounting Pronouncements ​ The Company does not believe that any recently issued effective pronouncements, or pronouncements issued but not yet effective, if adopted, would have a material effect on the accompanying condensed consolidated financial statements.
Recent Accounting Pronouncements	​

Revenue Recognition (Tables)

Revenue Recognition (Tables)	3 Months Ended
	Mar. 31, 2022
Revenue Recognition
Schedule of chargeback and rebates provision analysis	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended ​ ​ March 31, ​ ​ ​ 2022 ​ 2021 ​ ​ (in thousands) Beginning balance $ 20,167 $ 20,380 ​ Provision for chargebacks and rebates ​ 46,779 ​ 47,031 ​ Credits and payments issued to third parties ​ (48,394) ​ (46,881) ​ Ending balance ​ $ 18,552 ​ $ 20,530 ​
Schedule of product return liability analysis	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended ​ ​ March 31, ​ ​ ​ 2022 ​ 2021 ​ ​ (in thousands) Beginning balance $ 21,677 $ 14,204 ​ Provision for product returns ​ 1,192 ​ 3,233 ​ Credits issued to third parties ​ (1,480) ​ (2,517) ​ Ending balance ​ $ 21,389 ​ $ 14,920 ​

Income per Share Attributable_2

Income per Share Attributable to Amphastar Pharmaceuticals, Inc. Stockholders (Tables)	3 Months Ended
	Mar. 31, 2022
Income per Share Attributable to Amphastar Pharmaceuticals, Inc. Stockholders
Schedule of basic and diluted net income (loss) per share calculation	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended ​ ​ ​ March 31, ​ ​ ​ 2022 ​ 2021 ​ ​ ​ (in thousands, except per share data) ​ Basic and dilutive numerator: ​ ​ Net income attributable to Amphastar Pharmaceuticals, Inc. ​ $ 24,253 ​ $ 5,041 ​ Denominator: ​ ​ ​ ​ ​ ​ ​ Weighted-average shares outstanding — basic ​ 48,138 ​ ​ 47,520 ​ ​ ​ ​ ​ ​ ​ ​ ​ Net effect of dilutive securities: ​ ​ ​ ​ ​ ​ ​ Incremental shares from equity awards ​ 3,841 ​ ​ 1,998 ​ Weighted-average shares outstanding — diluted ​ 51,979 ​ 49,518 ​ Net income per share attributable to Amphastar Pharmaceuticals, Inc. stockholders — basic ​ $ 0.50 ​ $ 0.11 ​ Net income per share attributable to Amphastar Pharmaceuticals, Inc. stockholders — diluted ​ $ 0.47 ​ $ 0.10 ​

Segment Reporting (Tables)

Segment Reporting (Tables)	3 Months Ended
	Mar. 31, 2022
Segment Reporting
Schedule of financial information by reporting segment	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended ​ ​ March 31, ​ ​ ​ 2022 ​ 2021 ​ ​ (in thousands) Net revenues: ​ ​ ​ Finished pharmaceutical products ​ $ 116,546 ​ $ 97,882 ​ API ​ 3,822 ​ ​ 5,138 ​ Total net revenues ​ 120,368 ​ 103,020 ​ ​ ​ ​ ​ ​ ​ ​ ​ Gross profit (loss): ​ ​ ​ ​ ​ ​ ​ Finished pharmaceutical products ​ 56,939 ​ 45,286 ​ API ​ (1,113) ​ ​ (340) ​ Total gross profit ​ 55,826 ​ 44,946 ​ ​ ​ ​ ​ ​ ​ ​ ​ Operating expenses ​ 34,212 ​ 34,640 ​ ​ ​ ​ ​ ​ ​ ​ ​ Income from operations ​ 21,614 ​ 10,306 ​ Non-operating income (expenses) ​ 7,419 ​ (5,192) ​ ​ ​ ​ ​ ​ ​ ​ ​ Income before income taxes ​ $ 29,033 ​ $ 5,114 ​
Schedule of net revenues in the finished pharmaceutical products segment	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended ​ ​ March 31, ​ ​ ​ 2022 ​ 2021 ​ ​ (in thousands) Finished pharmaceutical products net revenues: ​ ​ ​ Primatene Mist ® ​ $ 24,697 ​ $ 18,383 ​ Epinephrine ​ ​ 15,156 ​ ​ 15,578 ​ Glucagon ​ ​ 10,984 ​ ​ 7,984 ​ Lidocaine ​ ​ 10,590 ​ ​ 9,071 ​ Phytonadione ​ 10,475 ​ 9,565 ​ Enoxaparin ​ ​ 10,124 ​ ​ 10,658 ​ Naloxone ​ ​ 7,413 ​ ​ 6,341 ​ Other finished pharmaceutical products ​ 27,107 ​ 20,302 ​ Total finished pharmaceutical products net revenues ​ $ 116,546 ​ $ 97,882 ​
Schedule of depreciation and amortization expense by reporting segment	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended ​ ​ ​ March 31, ​ ​ ​ 2022 ​ 2021 ​ ​ ​ (in thousands) ​ Depreciation and amortization expense ​ ​ Finished pharmaceutical products ​ $ 1,794 ​ $ 1,435 ​ API ​ 948 ​ 1,048 ​ Total depreciation and amortization expense ​ $ 2,742 ​ $ 2,483 ​
Schedule of net revenues and carrying values of long-lived assets by geographic region	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Net Revenue ​ Long-Lived Assets ​ ​ Three Months Ended ​ ​ ​ ​ ​ ​ ​ ​ March 31, ​ March 31, ​ December 31, ​ ​ ​ 2022 ​ 2021 ​ 2022 ​ 2021 ​ ​ (in thousands) United States $ 117,114 $ 99,170 $ 137,423 $ 134,731 ​ China ​ 933 ​ ​ 1,121 ​ 90,770 ​ 91,876 ​ France ​ 2,321 ​ ​ 2,729 ​ 43,176 ​ 44,884 ​ Total ​ $ 120,368 ​ $ 103,020 ​ $ 271,369 ​ $ 271,491 ​

Customer and Supplier Concent_2

Customer and Supplier Concentration (Tables)	3 Months Ended
	Mar. 31, 2022
Customer and Supplier Concentration
Schedule of accounts receivable and net revenues by major customer	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ % of Total Accounts ​ % of Net ​ ​ ​ Receivable ​ Revenue ​ ​ ​ ​ ​ Three Months Ended ​ ​ ​ March 31, ​ December 31, ​ March 31, ​ ​ 2022 2021 2022 2021 AmerisourceBergen 13 % 13 % 22 % 25 % McKesson 23 % 30 % 18 % 20 % Cardinal Health 22 % 20 % 16 % 15 %

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	3 Months Ended
	Mar. 31, 2022
Fair Value Measurements
Schedule of financial assets and liabilities measured on a recurring basis	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total (Level 1) (Level 2) (Level 3) ​ ​ (in thousands) Cash equivalents - money market ​ $ 140,991 ​ $ 140,991 ​ $ — ​ $ — ​ Restricted cash - money market ​ ​ 235 ​ ​ 235 ​ ​ — ​ ​ — ​ Short-term investments - certificates of deposit ​ ​ 4,600 ​ ​ — ​ ​ 4,600 ​ ​ — ​ Restricted short-term investments - certificates of deposit ​ 2,200 ​ — ​ 2,200 ​ — ​ Corporate and municipal bonds ​ ​ 9,676 ​ ​ — ​ ​ 9,676 ​ ​ — ​ Interest rate swap related to variable rate loans ​ ​ 3,609 ​ ​ — ​ ​ 3,609 ​ ​ — ​ Fair value measurement as of March 31, 2022 ​ $ 161,311 ​ $ 141,226 ​ $ 20,085 ​ $ — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Cash equivalents - money market ​ $ 102,863 ​ $ 102,863 ​ $ — ​ $ — ​ Restricted cash - money market ​ ​ 235 ​ ​ 235 ​ ​ — ​ ​ — ​ Short-term investments - certificates of deposit ​ ​ 5,103 ​ ​ — ​ ​ 5,103 ​ ​ — ​ Restricted short-term investments - certificates of deposit ​ 2,200 ​ — ​ 2,200 ​ — ​ Corporate and municipal bonds ​ ​ 6,984 ​ ​ — ​ ​ 6,984 ​ ​ — ​ Interest rate swap related to variable rate loans ​ ​ 596 ​ ​ — ​ ​ 596 ​ ​ — ​ Fair value measurement as of December 31, 2021 ​ $ 117,981 ​ $ 103,098 ​ $ 14,883 ​ $ — ​

Investments (Tables)

Investments (Tables)	3 Months Ended
	Mar. 31, 2022
Investments
Schedule of securities classified as held-to-maturity	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Gross ​ Gross ​ ​ ​ ​ Amortized ​ Unrealized ​ Unrealized ​ Fair ​ Cost Gains Losses Value ​ ​ (in thousands) Corporate bonds (due within 1 year) ​ $ 5,557 ​ $ — ​ $ (30) ​ $ 5,527 Municipal bonds (due within 1 year) ​ ​ 4,162 ​ ​ — ​ ​ (13) ​ ​ 4,149 Total investments as of March 31, 2022 ​ $ 9,719 ​ $ — ​ $ (43) ​ $ 9,676 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Corporate bonds (due within 1 year) ​ $ 2,481 ​ $ — ​ $ (3) ​ $ 2,478 Corporate bonds (due within 1 to 3 years) ​ ​ 1,248 ​ ​ — ​ ​ (3) ​ ​ 1,245 Municipal bonds (due within 1 year) ​ ​ 3,263 ​ ​ — ​ ​ (2) ​ ​ 3,261 Total investments as of December 31, 2021 ​ $ 6,992 ​ $ — ​ $ (8) ​ $ 6,984

Goodwill and Intangible Assets

Goodwill and Intangible Assets (Tables)	3 Months Ended
	Mar. 31, 2022
Goodwill and Intangible Assets
Schedule of weighted-average life, original cost, accumulated amortization and net book value by major class	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted-Average ​ ​ ​ ​ Accumulated ​ ​ ​ ​ Life (Years) Original Cost Amortization Net Book Value ​ ​ (in thousands) Definite-lived intangible assets ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ IMS (UK) international product rights ​ 10 ​ $ 9,182 ​ $ 5,203 ​ $ 3,979 ​ Patents 12 ​ 486 ​ ​ 350 ​ 136 ​ Land-use rights 39 ​ 2,540 ​ ​ 700 ​ 1,840 ​ Subtotal 12 ​ 12,208 ​ 6,253 ​ 5,955 ​ Indefinite-lived intangible assets ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Trademark * ​ 29,225 ​ — ​ 29,225 ​ Goodwill - Finished pharmaceutical products * ​ 3,256 ​ — ​ 3,256 ​ Subtotal * ​ 32,481 ​ — ​ 32,481 ​ As of March 31, 2022 * ​ $ 44,689 ​ $ 6,253 ​ $ 38,436 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted-Average ​ ​ ​ ​ Accumulated ​ ​ ​ ​ Life (Years) Original Cost Amortization Net Book Value ​ ​ (in thousands) Definite-lived intangible assets ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ IMS (UK) international product rights ​ 10 ​ $ 9,445 ​ $ 5,116 ​ $ 4,329 ​ Patents 12 ​ 486 ​ ​ 340 ​ 146 ​ Land-use rights 39 ​ 2,540 ​ ​ 683 ​ 1,857 ​ Subtotal 12 ​ 12,471 ​ 6,139 ​ 6,332 ​ Indefinite-lived intangible assets ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Trademark * ​ 29,225 ​ — ​ 29,225 ​ Goodwill - Finished pharmaceutical products * ​ 3,313 ​ — ​ 3,313 ​ Subtotal * ​ 32,538 ​ — ​ 32,538 ​ As of December 31, 2021 * ​ $ 45,009 ​ $ 6,139 ​ $ 38,870 ​ * Intangible assets with indefinite lives have an indeterminable average life.
Schedule of changes in carrying amounts of goodwill	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ March 31, ​ December 31, ​ ​ 2022 ​ 2021 ​ ​ (in thousands) Beginning balance $ 3,313 $ 3,940 ​ ANP restructuring ​ ​ — ​ ​ (374) ​ Currency translation ​ (57) ​ (253) ​ Ending balance ​ $ 3,256 ​ $ 3,313 ​

Inventories (Tables)

Inventories (Tables)	3 Months Ended
	Mar. 31, 2022
Inventories
Schedule of inventories	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ March 31, ​ December 31, ​ ​ 2022 ​ 2021 ​ ​ (in thousands) Raw materials and supplies $ 40,358 $ 41,853 ​ Work in process ​ 40,264 ​ 33,298 ​ Finished goods ​ 14,525 ​ 17,656 ​ Total inventories ​ $ 95,147 ​ $ 92,807 ​

Property, Plant, and Equipment

Property, Plant, and Equipment (Tables)	3 Months Ended
	Mar. 31, 2022
Property, Plant, and Equipment
Schedule of property, plant, and equipment	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ March 31, ​ December 31, ​ ​ 2022 ​ 2021 ​ ​ (in thousands) Buildings $ 130,364 $ 130,582 ​ Leasehold improvements ​ 29,221 ​ 29,221 ​ Land ​ 7,592 ​ 7,615 ​ Machinery and equipment ​ 207,006 ​ 207,883 ​ Furniture, fixtures, and automobiles ​ 27,635 ​ 27,376 ​ Construction in progress ​ 44,685 ​ 41,186 ​ Total property, plant, and equipment ​ 446,503 ​ 443,863 ​ Less accumulated depreciation ​ (203,255) ​ (199,619) ​ Total property, plant, and equipment, net ​ $ 243,248 ​ $ 244,244 ​

Accounts Payable and Accrued _2

Accounts Payable and Accrued Liabilities (Tables)	3 Months Ended
	Mar. 31, 2022
Accounts Payable and Accrued Liabilities.
Schedule of accounts payable and accrued liabilities	​ ​ ​ ​ ​ ​ ​ ​ March 31, ​ December 31, ​ 2022 ​ 2021 ​ (in thousands) Accrued customer fees and rebates $ 12,903 ​ $ 12,121 Accrued payroll and related benefits ​ 24,178 ​ ​ 23,256 Accrued product returns, current portion ​ 15,898 ​ ​ 16,028 Accrued loss on firm purchase commitments ​ 9,779 ​ ​ 7,133 Other accrued liabilities ​ 9,209 ​ ​ 8,793 Total accrued liabilities 71,967 ​ 67,331 Accounts payable 23,843 ​ 22,214 Total accounts payable and accrued liabilities $ 95,810 ​ $ 89,545

Debt (Tables)

Debt (Tables)	3 Months Ended
	Mar. 31, 2022
Debt
Schedule of debt	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ March 31, ​ December 31, ​ ​ 2022 ​ 2021 ​ ​ (in thousands) Line of Credit Facilities ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Line of credit facility with China Merchant Bank ​ $ — ​ $ — ​ Revolving line of credit facility with Capital One N.A. due August 2026 ​ ​ — ​ ​ — ​ ​ ​ ​ ​ ​ ​ ​ ​ Term Loan ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Term loan with Capital One N.A. due August 2026 ​ ​ 69,125 ​ ​ 69,563 ​ ​ ​ ​ ​ ​ ​ ​ ​ Mortgage Loans ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Mortgage payable with East West Bank due June 2027 ​ ​ 8,313 ​ ​ 8,353 ​ ​ ​ ​ ​ ​ ​ ​ ​ Other Loans and Payment Obligations ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ French government loans due December 2026 ​ ​ 267 ​ ​ 269 ​ ​ ​ ​ ​ ​ ​ ​ ​ Equipment under Finance Leases ​ 337 ​ 398 ​ Total debt ​ 78,042 ​ 78,583 ​ Less current portion of long-term debt ​ 2,159 ​ 2,202 ​ Less: Loan issuance costs ​ ​ 1,535 ​ ​ 1,605 ​ Long-term debt, net of current portion and unamortized debt issuance costs ​ $ 74,348 ​ $ 74,776 ​

Income Taxes (Tables)

Income Taxes (Tables)	3 Months Ended
	Mar. 31, 2022
Income Taxes
Schedule of reconciliation of the statutory federal income tax rate	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended ​ ​ ​ March 31, ​ ​ 2022 2021 ​ ​ (in thousands) ​ Income before taxes ​ $ 29,033 ​ $ 5,114 ​ Income tax provision ​ ​ 4,077 ​ 1,155 ​ Income before equity in losses of unconsolidated affiliate ​ $ 24,956 ​ $ 3,959 ​ Income tax provision as a percentage of income before income taxes ​ ​ 14.0 % 22.6 %

Stockholders' Equity (Tables)

Stockholders' Equity (Tables)	3 Months Ended
	Mar. 31, 2022
Stockholders' Equity
Schedule of key assumptions to determine fair value of options	​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended ​ ​ ​ March 31, ​ ​ 2022 2021 Average volatility 41.1 % 42.2 % Average risk-free interest rate 2.2 % 1.3 % Weighted-average expected life in years 6.3 ​ 6.3 ​ Dividend yield rate — % — %
Schedule of the summary of option activity under all plans	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted-Average ​ ​ ​ ​ ​ ​ ​ Weighted-Average ​ Remaining ​ Aggregate ​ ​ ​ ​ Exercise ​ Contractual ​ Intrinsic ​ ​ Options ​ Price ​ Term (Years) ​ Value (1) ​ ​ ​ ​ ​ ​ ​ ​ ​ (in thousands) Outstanding as of December 31, 2021 8,455,721 ​ $ 15.67 ​ ​ Options granted 706,740 ​ ​ 34.74 ​ ​ ​ ​ ​ ​ Options exercised (795,795) ​ ​ 14.43 ​ ​ ​ ​ ​ ​ Options cancelled (7,646) ​ ​ 17.19 ​ ​ ​ ​ ​ ​ Options expired (3,914) ​ ​ 13.35 ​ ​ ​ ​ ​ ​ Outstanding as of March 31, 2022 8,355,106 ​ $ 17.40 ​ 5.58 ​ $ 154,559 ​ Exercisable as of March 31, 2022 5,816,368 ​ $ 15.53 ​ 4.23 ​ $ 118,506 ​ Vested and expected to vest as of March 31, 2022 ​ 8,071,696 ​ $ 17.20 ​ 5.46 ​ $ 150,955 ​ (1) The aggregate intrinsic value is calculated as the difference between the exercise price of the underlying awards and the estimated fair value of the Company’s common stock for those awards that have an exercise price below the estimated fair value at March 31, 2022.
Schedule of information relating to options grants	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended ​ ​ March 31, ​ ​ 2022 2021 ​ ​ (in thousands, except per share data) Weighted-average grant date fair value per option share ​ $ 15.06 ​ $ 7.66 ​ Intrinsic value of options exercised ​ 12,200 ​ 1,029 ​ Cash received from options exercised ​ 12,450 ​ 2,169 ​ Total fair value of the options vested during the period ​ 6,987 ​ 6,772 ​
Schedule of the summary of nonvested options status	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted-Average ​ ​ ​ ​ Grant Date ​ ​ Options ​ Fair Value Non-vested as of December 31, 2021 ​ 2,848,934 ​ $ 6.95 ​ Options granted 706,740 ​ ​ 15.06 ​ Options vested (1,009,290) ​ ​ 6.92 ​ Options forfeited (7,646) ​ ​ 7.34 ​ Non-vested as of March 31, 2022 2,538,738 ​ 9.22 ​
Schedule of information relating to RSU grants and deliveries	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total Fair Market ​ ​ Total RSUs ​ Value of RSUs ​ Issued Issued (1) ​ ​ ​ ​ (in thousands) RSUs outstanding at December 31, 2021 1,184,842 ​ ​ ​ ​ RSUs granted 306,080 ​ $ 10,633 ​ RSUs forfeited (3,259) ​ ​ ​ ​ RSUs vested (2) (417,007) ​ ​ ​ ​ RSUs outstanding at March 31, 2022 1,070,656 ​ ​ ​ ​ (1) The total fair market value is derived from the number of RSUs granted times the current stock price on the date of grant. (2) Of the vested RSUs, 174,982 shares of common stock were surrendered to fulfill tax withholding obligations.
Schedule of recorded share-based compensation expense under all plans	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended ​ ​ March 31, ​ ​ 2022 ​ 2021 ​ ​ (in thousands) Cost of revenues $ 1,385 $ 1,146 Operating expenses: ​ ​ ​ ​ ​ ​ Selling, distribution, and marketing ​ 168 ​ 127 General and administrative ​ 2,861 ​ 2,968 Research and development ​ 608 ​ 593 Total share-based compensation ​ $ 5,022 ​ $ 4,834

Summary of Significant Accoun_3

Summary of Significant Accounting Policies (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021	Dec. 31, 2021
Gains and (losses) of intercompany foreign currency transactions	$ (600)	$ (1,500)
Restricted cash	235		$ 235
Certificates of deposit	2,200		$ 2,200
Finished Pharmaceutical Products Segment [Member] | Primatene Mist
Advertising expense	$ 2,400	$ 2,200

ANP Restructuring (Details)

ANP Restructuring (Details)	Sep. 30, 2021
ANP | Hanxin
Restructuring and Related Cost [Line Items]
Ownership after transaction	14.00%

Revenue Recognition (Analysis o

Revenue Recognition (Analysis of the Chargeback Provision) (Details) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2022	Mar. 31, 2021	Dec. 31, 2021
Revenue	$ 120,368	$ 103,020
Beginning balance	20,167	20,380	$ 20,380
Provision for chargebacks and rebates	46,779	47,031
Credits and payments issued to third parties	(48,394)	(46,881)
Ending balance	18,552	20,530	20,167
Research and development services | ANP
Revenue	$ 600	$ 300
Minimum
Payment terms	30 days
Settlement of chargebacks and rebates terms	20 days
Maximum
Payment terms	75 days
Settlement of chargebacks and rebates terms	60 days
Accounts Receivable, Net
Provision for chargebacks and rebates	$ 14,100		15,600
Accounts Payable and Accrued Liabilities
Provision for chargebacks and rebates	$ 4,500		$ 4,600

Revenue Recognition (Analysis_2

Revenue Recognition (Analysis of Product Return Liability) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021	Dec. 31, 2021
Aggregate product return rate	1.60%	1.40%
Return accrual included in accounts payable and accrued liabilities	$ 15,898		$ 16,028
Return accrual included in other long-term liabilities	5,500		$ 5,700
Product returns
Beginning balance	21,677	$ 14,204
Provision for product returns	1,192	3,233
Credits issued to third parties	(1,480)	(2,517)
Ending balance	$ 21,389	$ 14,920

Income per Share Attributable_3

Income per Share Attributable to Amphastar Pharmaceuticals, Inc. Stockholders (Narrative) (Details) - Employee and Non-Employee Stock Options [Member] - $ / shares	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Shares	706,740	1,899,833
Antidilutive Securities Excluded from Computation of Earnings Per Share, Exercise Price of Excluded Securities	$ 34.74	$ 20.85

Income per Share Attributable_4

Income per Share Attributable to Amphastar Pharmaceuticals, Inc. Stockholders (Calculation of Basic and Diluted Net Income (Loss) Per Share) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Basic and dilutive numerator:
Net Income (Loss) Attributable to Parent	$ 24,253	$ 5,041
Denominator:
Weighted-average shares outstanding-basic	48,138	47,520
Net effect of dilutive securities:
Incremental shares from equity awards	3,841	1,998
Weighted-average shares outstanding - diluted	51,979	49,518
Net income (loss) per share - basic	$ 0.50	$ 0.11
Net income (loss) per share - diluted	$ 0.47	$ 0.10

Segment Reporting (Selected Fin

Segment Reporting (Selected Financial Information by Reporting Segment) (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2022USD ($)segment	Mar. 31, 2021USD ($)
Segment Reporting Information [Line Items]
Number of Reportable Segments | segment	2
Net revenues:
Net revenues	$ 120,368	$ 103,020
Gross profit (loss):
Gross Profit	55,826	44,946
Operating expenses	34,212	34,640
Income (loss) from operations	21,614	10,306
Non-operating income (expenses)	7,419	(5,192)
Income (loss) before income taxes	29,033	5,114
Finished Pharmaceutical Products Segment [Member]
Net revenues:
Net revenues	116,546	97,882
Gross profit (loss):
Gross Profit	56,939	45,286
Active Pharmaceutical Ingredient Segment [Member]
Net revenues:
Net revenues	3,822	5,138
Gross profit (loss):
Gross Profit	$ (1,113)	$ (340)

Segment Reporting (Summary of N

Segment Reporting (Summary of Net Revenues by Product Segment) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Segment Reporting Information, Revenue for Reportable Segment [Abstract]
Net revenues	$ 120,368	$ 103,020
Finished Pharmaceutical Products Segment [Member]
Segment Reporting Information, Revenue for Reportable Segment [Abstract]
Net revenues	116,546	97,882
Finished Pharmaceutical Products Segment [Member] | Exclusive Marketing Rights for Enoxaparin [Member]
Segment Reporting Information, Revenue for Reportable Segment [Abstract]
Net revenues	10,124	10,658
Finished Pharmaceutical Products Segment [Member] | Lidocaine
Segment Reporting Information, Revenue for Reportable Segment [Abstract]
Net revenues	10,590	9,071
Finished Pharmaceutical Products Segment [Member] | Phytonadione
Segment Reporting Information, Revenue for Reportable Segment [Abstract]
Net revenues	10,475	9,565
Finished Pharmaceutical Products Segment [Member] | Naloxone
Segment Reporting Information, Revenue for Reportable Segment [Abstract]
Net revenues	7,413	6,341
Finished Pharmaceutical Products Segment [Member] | Epinephrine
Segment Reporting Information, Revenue for Reportable Segment [Abstract]
Net revenues	15,156	15,578
Finished Pharmaceutical Products Segment [Member] | Primatene Mist
Segment Reporting Information, Revenue for Reportable Segment [Abstract]
Net revenues	24,697	18,383
Finished Pharmaceutical Products Segment [Member] | Glucagon
Segment Reporting Information, Revenue for Reportable Segment [Abstract]
Net revenues	10,984	7,984
Finished Pharmaceutical Products Segment [Member] | Other Finished Pharmaceutical Products
Segment Reporting Information, Revenue for Reportable Segment [Abstract]
Net revenues	$ 27,107	$ 20,302

Segment Reporting (Depreciation

Segment Reporting (Depreciation and Amortization Expense by Reporting Segment) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Segment Reporting Information [Line Items]
Depreciation and amortization expense	$ 2,742	$ 2,483
Finished Pharmaceutical Products Segment [Member]
Segment Reporting Information [Line Items]
Depreciation and amortization expense	1,794	1,435
Active Pharmaceutical Ingredient Segment [Member]
Segment Reporting Information [Line Items]
Depreciation and amortization expense	$ 948	$ 1,048

Segment Reporting (Summary of R

Segment Reporting (Summary of Revenues and Long-Lived Assets by Geographic Region) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021	Dec. 31, 2021
Revenues from External Customers and Long-Lived Assets [Line Items]
Net revenues	$ 120,368	$ 103,020
Long-Lived Assets	271,369		$ 271,491
UNITED STATES
Revenues from External Customers and Long-Lived Assets [Line Items]
Net revenues	117,114	99,170
Long-Lived Assets	137,423		134,731
CHINA
Revenues from External Customers and Long-Lived Assets [Line Items]
Net revenues	933	1,121
Long-Lived Assets	90,770		91,876
FRANCE
Revenues from External Customers and Long-Lived Assets [Line Items]
Net revenues	2,321	$ 2,729
Long-Lived Assets	$ 43,176		$ 44,884

Customer and Supplier Concent_3

Customer and Supplier Concentration (Details) - Customer Concentration Risk [Member] - item	3 Months Ended		12 Months Ended
	Mar. 31, 2022	Mar. 31, 2021	Dec. 31, 2021
Revenue, Major Customer [Line Items]
Number of major customers that are wholesale distributors	3
Accounts Receivable, Net
Revenue, Major Customer [Line Items]
Number of major customers	3		3
Net Revenue
Revenue, Major Customer [Line Items]
Number of major customers	3	3
AmerisourceBergen [Member] | Accounts Receivable, Net
Revenue, Major Customer [Line Items]
Major Customers	13.00%		13.00%
AmerisourceBergen [Member] | Net Revenue
Revenue, Major Customer [Line Items]
Major Customers	22.00%	25.00%
Cardinal Health [Member] | Accounts Receivable, Net
Revenue, Major Customer [Line Items]
Major Customers	22.00%		20.00%
Cardinal Health [Member] | Net Revenue
Revenue, Major Customer [Line Items]
Major Customers	16.00%	15.00%
McKesson [Member] | Accounts Receivable, Net
Revenue, Major Customer [Line Items]
Major Customers	23.00%		30.00%
McKesson [Member] | Net Revenue
Revenue, Major Customer [Line Items]
Major Customers	18.00%	20.00%

Fair Value Measurements (Fair V

Fair Value Measurements (Fair Values of the Company's Financial Assets and Liabilities) (Details) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Recurring Basis
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value measurement	$ 161,311	$ 117,981
Recurring Basis | Interest rate swaps
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Interest rate swaps related to variable rate loans	3,609	596
Recurring Basis | Corporate bonds (due within 1 to 3 years)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Corporate and municipal bonds	9,676	6,984
Recurring Basis | Certificates of deposit
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments	4,600	5,103
Restricted short-term investments	2,200	2,200
Recurring Basis | Money market
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	140,991	102,863
Restricted cash	235	235
Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value measurement	141,226	103,098
Level 1 | Money market
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	140,991	102,863
Restricted cash	235	235
Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value measurement	20,085	14,883
Level 2 | Interest rate swaps
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Interest rate swaps related to variable rate loans	3,609	596
Level 2 | Corporate bonds (due within 1 to 3 years)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Corporate and municipal bonds	9,676	6,984
Level 2 | Certificates of deposit
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments	4,600	5,103
Restricted short-term investments	$ 2,200	$ 2,200

Investments (Held-to_Maturity)

Investments (Held-to_Maturity) (Details) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	$ 9,719	$ 6,992
Gross Unrealized Losses	(43)	(8)
Fair Value	9,676	6,984
Corporate Bonds (due within 1 year)
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	5,557	2,481
Gross Unrealized Losses	(30)	(3)
Fair Value	5,527	2,478
Corporate bonds (due within 1 to 3 years)
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost		1,248
Gross Unrealized Losses		(3)
Fair Value		1,245
Municipal Bonds [Member]
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	4,162	3,263
Gross Unrealized Losses	(13)	(2)
Fair Value	$ 4,149	$ 3,261

Investments (Equity Method Inve

Investments (Equity Method Investment) (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2022USD ($)
Restructuring and Related Cost
Income (Loss) from Equity Method Investments	$ (703)
Hanxin | Nonconsolidated investee
Restructuring and Related Cost
Income (Loss) from Equity Method Investments	$ (700)

Goodwill and Intangible Asset_2

Goodwill and Intangible Assets (Summary of Intangible Assets) (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Definite-lived intangible assets
Weighted-Average Life (Years)	12 years	12 years
Finite-Lived Intangible Assets, Gross	$ 12,208	$ 12,471
Accumulated Amortization	6,253	6,139
Finite-Lived Intangible Assets, Net	5,955	6,332
Indefinite-lived intangible assets
Goodwill recognized	3,256	3,313	$ 3,940
Subtotal, Original Cost	32,481	32,538
Subtotal, Net Book Value	32,481	32,538
Balance, Original Cost	44,689	45,009
Balance, Net Book Value	38,436	38,870
Finished Pharmaceutical Products Segment [Member]
Indefinite-lived intangible assets
Goodwill recognized	3,256	3,313
Trademarks
Indefinite-lived intangible assets
Indefinite-lived intangible assets	$ 29,225	$ 29,225
Patents
Definite-lived intangible assets
Weighted-Average Life (Years)	12 years	12 years
Finite-Lived Intangible Assets, Gross	$ 486	$ 486
Accumulated Amortization	350	340
Finite-Lived Intangible Assets, Net	$ 136	$ 146
Land-Use Rights [Member]
Definite-lived intangible assets
Weighted-Average Life (Years)	39 years	39 years
Finite-Lived Intangible Assets, Gross	$ 2,540	$ 2,540
Accumulated Amortization	700	683
Finite-Lived Intangible Assets, Net	$ 1,840	$ 1,857
International Medication Systems (UK) Limited | Acquired international product rights
Definite-lived intangible assets
Weighted-Average Life (Years)	10 years	10 years
Finite-Lived Intangible Assets, Gross	$ 9,182	$ 9,445
Accumulated Amortization	5,203	5,116
Finite-Lived Intangible Assets, Net	$ 3,979	$ 4,329

Goodwill and Intangible Asset_3

Goodwill and Intangible Assets (Summary of Changes in the Carrying Amount of Goodwill) (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2022	Dec. 31, 2021
Beginning balance	$ 3,313	$ 3,940
Currency translation and other adjustments	(57)	(253)
Ending balance	$ 3,256	3,313
ANP
Disposal Group, Not Discontinued Operation, Loss (Gain) on Write-down		$ (374)

Inventories (Details)

Inventories (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021	Dec. 31, 2021
Raw materials and supplies	$ 40,358		$ 41,853
Work in process	40,264		33,298
Finished goods	14,525		17,656
Total inventory, net	95,147		$ 92,807
Inventory adjustment to reflect net realizable value	8,000	$ 9,500
Exclusive Marketing Rights for Enoxaparin [Member]
Inventory, Firm Purchase Commitment, Loss	$ 6,400	$ 8,200

Property, Plant, and Equipmen_2

Property, Plant, and Equipment (Summary of Property, Plant, and Equipment) (Details) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Property, Plant and Equipment [Line Items]
Total property, plant, and equipment	$ 446,503	$ 443,863
Less accumulated depreciation and amortization	(203,255)	(199,619)
Total property, plant, and equipment, net	243,248	244,244
Building [Member]
Property, Plant and Equipment [Line Items]
Total property, plant, and equipment	130,364	130,582
Leasehold Improvements [Member]
Property, Plant and Equipment [Line Items]
Total property, plant, and equipment	29,221	29,221
Land
Property, Plant and Equipment [Line Items]
Total property, plant, and equipment	7,592	7,615
Machinery and Equipment [Member]
Property, Plant and Equipment [Line Items]
Total property, plant, and equipment	207,006	207,883
Furniture, fixtures, and automobiles
Property, Plant and Equipment [Line Items]
Total property, plant, and equipment	27,635	27,376
Construction in progress
Property, Plant and Equipment [Line Items]
Total property, plant, and equipment	$ 44,685	$ 41,186

Accounts Payable and Accrued _3

Accounts Payable and Accrued Liabilities (Details) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Accounts Payable and Accrued Liabilities.
Accrued customer fees and rebates	$ 12,903	$ 12,121
Accrued payroll and related benefits	24,178	23,256
Accrued product returns, current portion	15,898	16,028
Accrued loss on firm purchase commitments	9,779	7,133
Other accrued liabilities	9,209	8,793
Total accrued liabilities	71,967	67,331
Accounts payable	23,843	22,214
Total accounts payable and accrued liabilities	$ 95,810	$ 89,545

Debt (Schedule of Debt) (Detail

Debt (Schedule of Debt) (Details) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Debt Instrument
Unamortized Debt Issuance Expense	$ 1,535	$ 1,605
Equipment under Finance Leases	$ 337	398
Finance Lease, Liability, Noncurrent, Statement of Financial Position [Extensible Enumeration]	Long-term debt, net of current portion and unamortized debt costs
Total debt	$ 78,042	78,583
Less current portion of long-term debt and finance leases	2,159	2,202
Long-term debt, net of current portion and unamortized debt costs	74,348	74,776
Term Loan - Due August 2026 | Capital One, N.A.
Debt Instrument
Long Term Debt	69,125	69,563
French Government Loan 4 - Due December 2026 | Seine-Normandie Water Agency [Member]
Debt Instrument
Long Term Debt	267	269
Mortgage Payable - Due June 2027 | East West Bank [Member]
Debt Instrument
Long Term Debt	$ 8,313	$ 8,353

Income Taxes (Summary of Income

Income Taxes (Summary of Income (Loss) Before Income Taxes) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Income (loss) before income taxes:
Income (loss) before income taxes	$ 29,033	$ 5,114
Income tax provision (benefit)	4,077	1,155
Income before equity in losses of unconsolidated affiliate	$ 24,956	$ 3,959
Income tax provision as a percentage of income before income taxes	14.00%	22.60%
Other Effective Tax Rate Provision (Benefit)	$ 0	$ 0

Stockholders' Equity (Share Buy

Stockholders' Equity (Share Buyback Program) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021	May 05, 2022
Equity, Class of Treasury Stock [Line Items]
Treasury Stock, Value, Acquired, Cost Method	$ 1,229	$ 3,783
November 2014 Share Repurchase Plan
Equity, Class of Treasury Stock [Line Items]
Treasury Stock, Shares, Acquired (in Shares)	51,168	204,698
Treasury Stock, Value, Acquired, Cost Method	$ 1,200	$ 3,800
Subsequent Event [Member]
Equity, Class of Treasury Stock [Line Items]
Stock buyback program, authorized amount			$ 185,000
Subsequent Event [Member] | November 2014 Share Repurchase Plan
Equity, Class of Treasury Stock [Line Items]
Increase authorized for share buyback program			$ 25,000

Stockholders' Equity (The 2015

Stockholders' Equity (The 2015 Equity Incentive Plan) (Details) - The 2015 Equity Incentive Plan [Member] - shares	1 Months Ended
	Jan. 31, 2022	Mar. 31, 2022
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Authorized (in Shares)		6,462,223
Share-based Compensation Arrangement by Share-based Payment Award, Number of Additional Shares Authorized	1,192,873

Stockholders' Equity (2014 Empl

Stockholders' Equity (2014 Employee Stock Purchase Plan) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Allocated share based compensation	$ 5,022	$ 4,834
2014 Employee Stock Purchase Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock Issued During Period, Shares, Employee Stock Purchase Plans (in Shares)	954,456
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Available for Grant (in Shares)	1,045,544
Allocated share based compensation	$ 200	$ 100

Stockholders' Equity (Key Assum

Stockholders' Equity (Key Assumptions Used in Determining Fair Value of Options Granted) (Details)	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Stockholders' Equity
Average volatility	41.10%	42.20%
Average risk-free interest rate	2.20%	1.30%
Weighted-average expected life in years	6 years 3 months 18 days	6 years 3 months 18 days
Dividend yield rate	0.00%	0.00%

Stockholders' Equity (Summary o

Stockholders' Equity (Summary of Option Activity) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Options
Outstanding Options, Beginning of period	8,455,721
Options granted	706,740
Options exercised	(795,795)
Options cancelled	(7,646)
Options expired	(3,914)
Outstanding Options, End of period	8,355,106
Exercisable at the end of period	5,816,368
Vested and expected to vest, at the end of period	8,071,696
Weighted-Average Exercise Price
Outstanding Exercise Price (in dollars per share)	$ 15.67
Options granted (in dollars per share)	34.74
Options exercised (in dollars per share)	14.43
Options cancelled (in dollars per share)	17.19
Options expired (in dollars per share)	13.35
Outstanding Exercise Price (in dollars per share)	17.40
Exercisable at the end of period (in dollars per share)	15.53
Vested and expected to vest at end of period (in dollars per share)	$ 17.20
Additional Disclosures
Outstanding Intrinsic Value	$ 154,559
Exercisable aggregate intrinsic value	118,506
Allocated share based compensation	5,022	$ 4,834
Vested and expected to vest aggregate intrinsic value	$ 150,955
Vested and expected to vest weighted average remaining contractual term	5 years 5 months 15 days
Employee Stock Options [Member]
Additional Disclosures
Contractual term	5 years 6 months 29 days
Exercisable remaining contractual term (in Years)	4 years 2 months 23 days
Allocated share based compensation	$ 2,500	$ 2,400

Stockholders' Equity (Informati

Stockholders' Equity (Information Relating to Option Grants and Exercises) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Stockholders' Equity
Weighted-average grant date fair value (in Dollars per share)	$ 15.06	$ 7.66
Intrinsic value of options exercised	$ 12,200	$ 1,029
Cash received from options exercised	12,450	2,169
Total fair value of the options vested during the period	$ 6,987	$ 6,772

Stockholders' Equity (Summary_2

Stockholders' Equity (Summary of Nonvested Options) (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Options
Nonvested at beginning of period	2,848,934
Options granted	706,740
Options vested	(1,009,290)
Options forfeited	(7,646)
Nonvested at end of period	2,538,738
Weighted-Average Grant Date Fair Value
Nonvested at beginning of period (in dollars per share)	$ 6.95
Options granted (in dollars per share)	15.06	$ 7.66
Options vested (in dollars per share)	6.92
Options forfeited (in dollars per share)	7.34
Nonvested at end of period (in dollars per share)	$ 9.22
Employee Stock Option [Member]
Weighted-Average Grant Date Fair Value
Employee Service Share-based Compensation, Nonvested Awards, Compensation Not yet Recognized, Stock Options	$ 18.8
Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized, Period for Recognition	3 years 1 month 6 days

Stockholders' Equity (Restricte

Stockholders' Equity (Restricted Stock Units) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Allocated share based compensation	$ 5,022	$ 4,834
Restricted Stock Units (RSUs)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period	5 years
Allocated share based compensation	$ 2,400	$ 2,200
Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized, Period for Recognition	3 years 1 month 6 days
Share-based Compensation Arrangement by Share-based Payment Award, Restricted Stock Units, Number of Shares of Common Stock Per Award (in Shares)	1
Service Share-based Compensation, Nonvested Awards, Compensation Not yet Recognized, Share-based Awards Other than Options	$ 20,000

Stockholders' Equity (Informa_2

Stockholders' Equity (Information Relating to RSU Grants and Deliveries) (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2022USD ($)shares
Restricted Stock Units (RSUs)
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Total RSUs outstanding at the beginning of the period	1,184,842
RSUs granted	306,080
RSUs forfeited	(3,259)
RSUs vested	(417,007)
Total RSUs outstanding at the end of the period	1,070,656
Stock surrendered to fulfill tax withholding obligations	174,982
Restricted Stock Units Issued as Compensation [Member]
Total Fair Market Value of RSUs Issued
RSUs granted (in Dollars) | $	$ 10,633

Stockholders' Equity (The 2018

Stockholders' Equity (The 2018 ANP Equity Incentive Plan) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Allocated share based compensation	$ 5,022	$ 4,834
The 2018 ANP Equity Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Allocated share based compensation		$ 100

Stockholders' Equity (Share-Bas

Stockholders' Equity (Share-Based Compensation Expense Included in the Statement of Operations) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Allocated share based compensation	$ 5,022	$ 4,834
Cost Of Revenues [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Allocated share based compensation	1,385	1,146
Selling, Distribution And Marketing [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Allocated share based compensation	168	127
General and Administrative Expense [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Allocated share based compensation	2,861	2,968
Research and Development Expense [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Allocated share based compensation	$ 608	$ 593

Employee Benefits (Details)

Employee Benefits (Details) - USD ($) $ in Millions	3 Months Ended		12 Months Ended
	Mar. 31, 2022	Mar. 31, 2021	Dec. 31, 2021
Employee Benefits
Defined Contribution Plan, Employer Matching Contribution, Percent of Match	50.00%
Defined Contribution Plan, Employer Matching Contribution, Percent of Employees' Gross Pay	6.00%
Defined Contribution Plan, Employer Discretionary Contribution Amount	$ 0.6	$ 0.5
Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation, Discount Rate	1.00%		1.00%
Defined Benefit Plan, Benefit Obligation	$ 2.7		$ 2.7
Pension Cost	0		0
Deferred compensation plan assets	3.5		3.4
Deferred compensation plan liabilities	$ 3.6		$ 3.5

Commitments and Contingencies (

Commitments and Contingencies (Purchase Commitments) (Details) $ in Millions	3 Months Ended
	Mar. 31, 2022USD ($)
Commitments to Purchase Equipment and Raw Materials [Member]
Purchase Commitment, Excluding Long-term Commitment [Line Items]
Long-term Purchase Commitment, Amount	$ 72.9

Litigation (Details)

Litigation (Details) $ in Millions	3 Months Ended
	Mar. 31, 2022USD ($)
Settled Litigation [Member] | Amphastar Pharmaceuticals vs Astellas-Gilead
Loss Contingencies [Line Items]
Litigation Settlement, amount paid to the Company	$ 5.4