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                                                                    EXHIBIT 10.4



                      SECOND AMENDMENT TO CREDIT AGREEMENT

      THIS SECOND AMENDMENT TO CREDIT AGREEMENT  (this "Amendment") is entered 
into as of November 1, 1998, by and between NEXSTAR PHARMACEUTICALS, INC., a 
Delaware corporation ("Borrower"), and WELLS FARGO BANK, NATIONAL ASSOCIATION 
("Bank").


                                    RECITALS

      WHEREAS, Borrower is currently indebted to Bank pursuant to the terms and 
conditions of that certain Credit Agreement between Borrower and Bank dated as 
of September 1, 1997, as amended from time to time ("Credit Agreement").

      WHEREAS, Bank and Borrower have agreed to certain changes in the terms 
and conditions set forth in the Credit Agreement and have agreed to amend the 
Credit Agreement to reflect said changes.

      NOW, THEREFORE, for valuable consideration, the receipt and sufficiency 
of which are hereby acknowledged, the parties hereto agree that the Credit 
Agreement shall be amended as follows:

      1. Section 1.1.(a) is hereby amended by deleting "November 1, 1998" as 
the last day on which Bank will make advances under the Line of Credit, and by 
substituting for said date "November 1, 1999," with such change to be effective 
upon the execution and delivery to Bank of a promissory note substantially in 
the form of Exhibit A attached hereto (which promissory note shall replace and 
be deemed the Line of Credit Note defined in and made pursuant to the Credit 
Agreement) and all other contracts, instruments and documents required by Bank 
to evidence such change.

      2. Section 1.2.(a) is hereby amended (a) by deleting "September 1, 1998" 
as the last day on which the Bank will enter into foreign exchange contracts 
for the account of Borrower, and by substituting for said date "November 1, 
1999," (b) by deleting "November 1, 1998" as the last day any foreign exchange 
contract may expire, and by substituting for said date "January 1, 2000", (c) 
by deleting "Fifty Million United States Dollars (US$50,000,000.00)" as the 
maximum amount of all outstanding foreign exchange contracts under the Foreign 
Exchange Facility, and by substituting for said amount "Sixty-five Million 
United States Dollars (US$65,000,000.00) and (d) by deleting "Ten Million 
United States Dollars (US$10,000,000.00) as the maximum Delivery Limit under 
the Foreign Exchange Facility, and by substituting for said amount "Thirteen 
Million United States Dollars (US$13,000,000.00)."




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     3.  Borrower shall pay to Bank a non-refundable commitment fee for the 
Line or Credit equal to $5,200.00, which fee shall be due and payable in full 
upon execution of this amendment.

     4.  Except as specifically provided herein, all terms and conditions of 
the Credit Agreement remain in full force and effect, without waiver or 
modification. All terms defined in the Credit Agreement shall have the same 
meaning when used in this Amendment. This Amendment and the Credit Agreement 
shall be read together, as one document.

     5.  Borrower hereby remakes all representations and warranties contained 
in the Credit Agreement and reaffirms all covenants set forth therein. Borrower 
further certifies that as of the date of this Amendment there exists no Event 
of Default as defined in the Credit Agreement, nor any condition, act or event 
which with the giving of notice or the passage of time or both would constitute 
any such Event of Default.

     IN WITNESS WHEREOF, the parties hereto have caused this Amendment to be 
executed as of the day and year first written above.

                                        WELLS FARGO BANK,
NEXSTAR PHARMACEUTICALS, INC.             NATIONAL ASSOCIATION


By: /s/  MICHAEL E. HART                By: /s/  TRACEY HANSON
   --------------------------               -----------------------
         Michael E. Hart                    Tracey Hanson
                                            Vice President

Title: VP/CFO
      -----------------------

By:
   --------------------------

Title:
      -----------------------
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                         REVOLVING LINE OF CREDIT NOTE

$10,000,000.00                                                  Denver, Colorado
                                                                November 1, 1998

     FOR VALUE RECEIVED, the undersigned NEXSTAR PHARMACEUTICALS, INC. 
("Borrower") promises to pay to the order of WELLS FARGO BANK, NATIONAL 
ASSOCIATION ("Bank") at its office at Colorado RCBO, 633 17th Street, Denver, 
Colorado, or at such other place as the holder hereof may designate, in lawful 
money of the United States of America and in immediately available funds, the 
principal sum of Ten Million Dollars ($10,000,000.00), or so much thereof as 
may be advanced and be outstanding, with interest thereon, to be computed on 
each advance from the date of its disbursement as set forth herein.

DEFINITIONS:

     As used herein, the following terms shall have the meanings set forth 
after each, and any other term defined in this Note shall have the meaning set 
forth at the place defined:

     (a)  "Business Day" means any day except a Saturday, Sunday or any other 
day on which commercial banks in Colorado are authorized or required by law to 
close.

     (b)  "Fixed Rate Term" means a period commencing on a Business Day and 
continuing for one (1), two (2), three (3) or six (6) months, as designated by 
Borrower, during which all or a portion of the outstanding principal balance of 
this Note bears interest determined in relation to LIBOR; provided however, 
that no Fixed Rate Term may be selected for a principal amount less than Two 
Hundred Fifty Thousand Dollars ($250,000.00); and provided further, that no 
Fixed Rate Term shall extent beyond the scheduled maturity date hereof. If any 
Fixed Rate Term would end on a day which is not a Business Day, then such Fixed 
Rate Term shall be extended to the next succeeding Business Day.

     (c)  "LIBOR" means the rate per annum (rounded upward, if necessary, to 
the nearest whole 1/8 of 1%) and determined pursuant to the following formula:

                        Base LIBOR 
     LIBOR =  _______________________________

              100% - LIBOR Reserve Percentage

     (i)  "Base LIBOR" means the rate per annum for United States dollar 
deposits quoted by Bank as the Inter-Bank Market Offered Rate, with the 
understanding that such rate is quoted by Bank for the purpose of calculating 
effective rates of interest for loans making reference thereto, on the first 
day of a Fixed Rate Term for delivery of funds on said date for a period of 
time approximately equal to the number of days in such Fixed Rate Term

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the limitations, terms and conditions of this Note and of any document executed 
in connection with or governing this Note; provided however, that the total 
outstanding borrowings under this Note shall not at any time exceed the 
principal amount stated above. The unpaid principal balance of this obligation 
at any time shall be the total amounts advanced hereunder by the holder hereof 
less the amount of principal payments made hereon by or for Borrower, which 
balance may be endorsed hereon from time to time by the holder. The outstanding 
principal balance of this Note shall be due and payable in full on November 1, 
1999.

     (b)  Advances. Advances hereunder, to the total amount of the principal 
sum stated above, may be made by the holder at the oral or written request of 
(i) Michael E. Hart, any one acting alone, who are authorized to request 
advances and direct the disposition of any advances until written notice of the 
revocation of such authority is received by the holder at the office designated 
above, or (ii) any person, with respect to advances deposited to the credit of 
any account of Borrower with the holder, which advances, when so deposited, 
shall be conclusively presumed to have been made to or for the benefit of 
Borrower regardless of the fact that persons other than those authorized to 
request advances may have authority to draw against such account. The holder 
shall have no obligation to determine whether any person requesting an advance 
is or has been authorized by Borrower.

     (c)  Application of Payments. Each payment made on this Note shall be 
credited first, to any interest then due and second, to the outstanding 
principal balance hereof. All payments credited to principal shall be applied 
first, to the outstanding principal balance of this Note which bears interest 
determined in relation to the Prime Rate, if any, and second, to the 
outstanding principal balance of this Note which bears interest determined in 
relation to LIBOR, with such payments applied to the oldest Fixed Rate Term 
first.

PREPAYMENT:

     (a)  Prime Rate. Borrower may prepay principal on any portion of this Note 
which bears interest determined in relation to the Prime Rate at any time, in 
any amount and without penalty.

     (b)  LIBOR. Borrower may prepay principal on any portion of this Note 
which bears interest determined in relation to LIBOR at any time and in the 
minimum amount of Two Hundred Fifty Thousand Dollars ($250,000.00); provided 
however, that if the outstanding principal balance of such portion of this Note 
is less than said amount, the minimum prepayment amount shall be the entire 
outstanding principal balance thereof. In consideration of Bank providing this 
prepayment option to Borrower, or if any such portion of this Note shall become 
due and payable at any time prior to the last day of the Fixed Rate Term 
applicable thereto 
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by acceleration or otherwise, Borrower shall pay to Bank immediately upon demand
a fee which is the sum of the discounted monthly differences for each month from
the month of prepayment through the month in which such Fixed Rate Term matures,
calculated as follows for each such month;

     (i)     Determine the amount of interest which would have accrued each
             month on the amount prepaid at the interest rate applicable to such
             amount had it remained outstanding until the last day of the Fixed
             Rate Term applicable thereto.

     (ii)    Subtract from the amount determined in (i) above the amount of
             interest which would have accrued for the same month on the amount
             prepaid for the remaining term of such Fixed Rate Term at an
             interest rate equal to (a) LIBOR in effect on the date of
             prepayment for new loans made for such term and in a principal
             amount equal to the amount prepaid, plus (b) the LIBOR Margin
             applicable to such amount prepaid had it remained outstanding until
             the last day of the Fixed Rate Term applicable thereto.

     (iii)   If the result obtained in (ii) for any month is greater than zero,
             discount that difference by LIBOR used in (ii) above.

Borrower acknowledges that prepayment of such amount may result in Bank
incurring additional costs, expenses and/or liabilities, and that it is
difficult to ascertain the full extent of such costs, expenses and/or
liabilities. Borrower, therefore, agrees to pay the above-described prepayment
fee and agrees that said amount represents a reasonable estimate of the
prepayment costs, expenses and/or liabilities of Bank. If Borrower fails to pay
any prepayment fee when due, the amount of such prepayment fee shall thereafter
bear interest until paid at a rate per annum two percent (2.0%) above the Prime
Rate in effect from time to time (computed on the basis of a 360-day year,
actual days elapsed). Each change in the rate of interest on any such past due
prepayment fee shall become effective on the date each Prime Rate change is
announced within Bank.

EVENTS OF DEFAULT:

     This Note is made pursuant to and is subject to the terms and conditions 
of the Credit Agreement. Any default in the payment or performance of any 
obligation under this Note, or any defined event of default under the Credit 
Agreement, shall constitute an "Event of Default" under this Note.  
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MISCELLANEOUS:

        (a)     Remedies. Upon the occurrence of any Event of Default, the 
holder of this Note, at the holder's option, may declare all sums of principal 
and interest outstanding hereunder to be immediately due and payable without 
presentment, demand, notice of nonperformance, notice of protest, protest or 
notice of dishonor, all of which are expressly waived by Borrower, and the 
obligation, if any, of the holder to extend any further credit hereunder shall 
immediately cease and terminate. Borrower shall pay to the holder immediately 
upon demand the full amount of all payments, advances, charges, costs and 
expenses, including reasonable attorneys' fees (to include outside counsel fees 
and all allocated costs of the holder's in-house counsel), expended or incurred 
by the holder in connection with the enforcement of the holder's rights and/or 
the collection of any amounts which become due to the holder under this Note, 
and the prosecution or defense of any action in any way related to this Note, 
including without limitation, any action for declaratory relief, whether 
incurred at the trial or appellate level, in an arbitration proceeding or 
otherwise, and including any of the foregoing incurred in connection with any 
bankruptcy proceeding (including without limitation, any adversary proceeding, 
contested matter or motion brought by Bank or any other person) relating to 
Borrower or any other person or entity.

        (b)     Governing Law. This Note shall be governed by and construed in 
accordance with the laws of the State of Colorado.

        IN WITNESS WHEREOF, the undersigned has executed this Note as of the 
date first written above.

NEXSTAR PHARMACEUTICALS, INC.

By: /s/ MICHAEL E. HART
    ---------------------------------
Title: VP/CEO
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By:
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Title: 
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