<PAGE>

                   AMENDMENT NO. 6 TO BUSINESS LOAN AGREEMENT


         This Amendment No. 6 (this "Amendment") dated as of November 13, 1998
is between Dura Pharmaceuticals, Inc. (the "Borrower") and Bank of America
National Trust and Savings Association (the "Bank").

                                    RECITALS

         A. The Bank and the Borrower entered into that certain Business Loan
Agreement dated as of April 14, 1997, as modified by amendments dated May 8,
1997, July 30, 1997, October 28, 1997, June 25, 1998, and October 12, 1998 (as
amended, the "Agreement").

         B. The Bank and the Borrower desire to amend the Agreement on the terms
and conditions set forth below:

                                    AGREEMENT

         1.       DEFINITIONS.  Capitalized terms used but not defined in this
Amendment shall have the meanings given to them in the Agreement.

         2. AMENDMENTS. Effective as of September 28, 1998, the Agreement is
hereby amended as follows:

                  2.1      The following is added as a new Article 3A:

                           "3A  COLLATERAL

                           3A.1 Stock of Certain Subsidiaries: Upon consummation
                  of the transactions described in Paragraph 6.24 below, the
                  Borrower's obligations under this Agreement will be secured by
                  the following property:

                                    (a) Sixty-six percent (66%) of the issued
                           and outstanding common stock of Dura (Barbados)
                           Holding Company Ltd.;

                                    (b) Sixty-six percent (66%) of the issued
                           and outstanding common stock of Dura (Barbados) Ltd.;
                           and

                                    (c) Sixty-six percent (66%) of the issued
                           and outstanding common stock of Dura (Burmuda)
                           Trading Company Ltd.

                  2.2      The following is added as a new Paragraph 5.14:

                           "5.14 TAXES ON INCOME FROM FOREIGN SUBSIDIARIES. 
         Income received by the Borrower from its Foreign Subsidiaries (as
         defined in Paragraph 6.6 below) is subject only to taxation by the
         United States Internal Revenue Service and other state and local taxing
         authorities within the United States of America."

                  2.3       Paragraph 6.3 is amended and restated in its
         entirety to read as follows:

                                         1
<PAGE>

                           "6.3 NET WORTH. To maintain on a consolidated basis
                  for each quarterly accounting period Net Worth equal to, on a
                  cumulative basis, at least the sum of:

                           (a) Four Hundred Thirty Million Dollars
                  ($430,000,000); plus

                           (b) the sum of 50% of the net income after income
                  taxes (without subtracting losses) earned in each quarterly
                  accounting period commencing with the quarter ended September
                  30, 1998; PLUS

                           (c) the net proceeds from any equity securities
                  (including shares issued upon the exercise of stock options)
                  issued in each quarterly accounting period commencing with the
                  quarter ended September 30, 1998; plus

                           (d) any increase in stockholders' equity resulting
                  from the conversion of debt securities to equity securities
                  issued in each quarterly accounting period commencing with the
                  quarter ended September 30, 1998; MINUS

                           (e) the amount of treasury stock held by the Borrower
                  not to exceed Fifty Million Dollars ($50,000,000).

                           `Net Worth' means the gross book value of the
                  Borrower's assets less total liabilities, including but not
                  limited to accrued and deferred income taxes, and any reserves
                  against assets."

                  2.4     Paragraph 6.4 is amended and restated in its entirety 
         to read as follows:

                           "6.4 MAXIMUM ADJUSTED FUNDED DEBT TO EBITDA. To
                  maintain on a consolidated basis a ratio of (i) funded debt,
                  including all interest bearing obligations, less the sum of
                  the following up to an amount equal to the face amount of the
                  Notes issued pursuant to and as defined in the Indenture: (A)
                  domestic cash and domestic cash equivalents, (B) one hundred
                  percent (100%) of offshore cash balances up to an amount equal
                  to the capital directly or indirectly contributed to Dura
                  (Burmuda) Trading Company Ltd. (as of the date hereof, this
                  amount is Sixty Million Dollars ($60,000,000)), and (C) fifty
                  percent (50%) of such offshore cash balances in excess of such
                  capital contributions, to (ii) EBITDA of not greater than 1.75
                  to 1.00.

                           Upon the Bank's request from time to time , the
                  Borrower shall provide evidence acceptable to the Bank of cash
                  equivalents. For purposes of this Agreement, cash equivalents
                  means:

                                    (a) domestic certificates of deposit or
                           domestic time deposits;

                                    (b) U.S. treasury bills and other direct
                           obligations of the federal government;

                                    (c) shares in domestic money market funds;

                                         2
<PAGE>

                                    (d) readily marketable obligations of an
                           agency of the United States of America that are
                           generally considered in the securities industry to be
                           implicit obligations of the federal government;

                                    (e) prime bankers' acceptances and
                           commercial paper issued by financial institutions
                           rated as least A-1 by Standard & Poors Ratings Group
                           or at least P-1 by Moody's Investors Service, Inc.;
                           and

                                    (f) repurchase agreements covering U.S.
                           government securities.

                           For purposes of this Agreement, `EBITDA' means net
                  income for such period, LESS, to the extent added in
                  determining such net income, interest income, PLUS, to the
                  extent deducted in determining such net income, (i) interest
                  expense, (ii) depreciation, (iii) depletion, (iv)
                  amortization, and (v) all federal, state, local and foreign
                  income taxes. This ratio will be calculated at the end of each
                  fiscal quarter using the results of that quarter and each of
                  the three immediately preceding quarters."

                  2.5    Paragraph 6.5 is amended and restated in its entirety
         to read as follows:

                           "6.5 MINIMUM EBIT; MINIMUM U.S. EBIT. To maintain for
                  each quarterly accounting period (i) on a consolidated basis
                  EBIT of not less than zero dollars ($0); and (ii) on
                  consolidated basis only for the Borrower and its Domestic
                  Subsidiaries EBIT of not less than a NEGATIVE Six Million
                  Dollars (-$6,000,000) for the fiscal quarter ended September
                  30, 1998, and not less than a NEGATIVE One Million Dollars
                  (-$1,000,000) for each fiscal quarter thereafter.

                           For purposes of this Agreement: `EBIT' means net
                  income for such period, LESS, to the extent added in
                  determining such net income, interest income, PLUS, to the
                  extent deducted in determining such net income, (i) interest
                  expense and (ii) all federal, state, local and foreign income
                  taxes; `Domestic Subsidiaries' means direct or indirect
                  subsidiaries of the Borrower that is incorporated or otherwise
                  organized under the laws of (x) the United States of America,
                  (y) any state, territory, or possession of the United States
                  of America, or (z) any other jurisdiction located within
                  either the United States of America or any state, territory,
                  or possession of the United States of America; individually, a
                  `Domestic Subsidiary.'"

                  2.6    Paragraph 6.6 is amended and restated in its entirety
         to read as follows:

                           "6.6 ADDITIONAL GUARANTIES. If at any time after the
                  date of this Agreement a subsidiary of the Borrower or any
                  guarantor becomes a Significant Subsidiary, to cause such
                  Significant Subsidiary to execute and deliver to the Bank, as
                  soon as reasonably practicable but not later than thirty (30)
                  days after the Bank's request therefor, a continuing guaranty
                  in the principal amount of at least Fifty Million Dollars
                  ($50,000,000) and otherwise in form and substance acceptable
                  to the Bank, together with satisfactory 

                                         3
<PAGE>

                  evidence of such Significant Subsidiary's authority to execute
                  and deliver such guaranty. For purposes of this Agreement 
                  `Significant Subsidiary' means a corporation (i) that is 
                  wholly-owned by the Borrower or any guarantor and (ii) that 
                  owns twenty percent (20%) or more of the Borrower's total 
                  consolidated assets or twenty percent (20%) or more of the 
                  Borrower's total consolidated sales for any fiscal quarter. 
                  Notwithstanding the foregoing, `Significant Subsidiary' shall 
                  not include any Foreign Subsidiary. `Foreign Subsidiary' means
                  any direct or indirect subsidiary of the Borrower that is not 
                  a Domestic Subsidiary."
                  
                  2.7     The following is added as a new Paragraph 6.24:

                           "6.24 PLEDGES OF STOCK. On or before December 15,
                  1998, to take all actions and execute and deliver to the Bank
                  all documentation (including without limitation opinion of
                  counsel), in form and substance satisfactory to the Bank, and
                  to cause all subsidiaries to take such actions and execute and
                  deliver to the Bank such documentation, necessary to grant to
                  the Bank a first position perfected security interest in and
                  to the following shares of stock: sixty-six percent (66%) of
                  the issued and outstanding shares of the common stock of Dura
                  (Barbados) Holding Company Ltd. owned by the Borrower;
                  sixty-six percent (66%) of the issued and outstanding shares
                  of common stock of Dura (Barbados) Ltd. owned by Dura
                  (Barbados) Holding Company Ltd.; and sixty-six percent (66%)
                  of the issued and outstanding shares of common stock of Dura
                  (Burmuda) Trading Company Ltd. owned by Dura (Barbados) Ltd.

                  2.8 The form of compliance certificate appearing as Exhibit A
         to Amendment No. 3 to the Agreement as referenced in Paragraph 6.2(d)
         is amended to read as set forth on Exhibit A to this Amendment.

         3. REPRESENTATIONS AND WARRANTIES. When the Borrower signs this
Amendment, the Borrower represents and warrants to the Bank that: (a) there is
no event which is, or with notice or lapse of time or both would be, a default
under the Agreement (b) the representations and warranties in the Agreement are
true as of the date of this Amendment as if made on the date of this Amendment,
(c) this Amendment is within the Borrower's powers, has been duly authorized,
and does not conflict with any of the Borrower's organizational papers, and (d)
this Amendment does not conflict with any law, agreement, or obligation by which
the Borrower is bound.

         4. EFFECT OF AMENDMENT. Except as provided in this Amendment, all of
the terms and conditions of the Agreement shall remain in full force and effect.





[Signatures continue on next page]

                                         4
<PAGE>


         This Amendment is executed as of the date stated at the beginning of
the Amendment.

                           BANK OF AMERICA NATIONAL TRUST AND SAVINGS
                           ASSOCIATION


                            By: /s/ Susan J. Pepping
                            --------------------------------------------------
                            Name:     Susan J. Pepping
                            Title:    Vice President



                            DURA PHARMACEUTICALS, INC.



                            By: /s/ Erle T. Mast
                            --------------------------------------------------

                            Name:     Erle T. Mast
                            --------------------------------------------------

                            Title:    Vice President, Finance
                            --------------------------------------------------


                            By: /s/ Mitchell R. Woodbury
                            --------------------------------------------------

                            Name: Mitchell R. Woodbury
                            --------------------------------------------------

                            Title  Senior V.P., General Counsel and Secretary
                            --------------------------------------------------



                                         5
<PAGE>

                                   EXHIBIT "A"

                             COMPLIANCE CERTIFICATE


To:    BANK OF AMERICA NATIONAL TRUST AND SAVINGS ASSOCIATION

       Reference is made to that certain Business Loan Agreement dated as of
April 14, 1997, as amended, between Bank of American National Trust and Savings
Association and Dura Pharmaceuticals, Inc., (the "Business Loan Agreement").
Capitalized terms not otherwise defined in this Certificate shall have the
meanings ascribed to them in the Business Loan Agreement. This Certificate is
delivered in accordance with Paragraph 6.2(d) of the Business Loan Agreement.

I.     COMPLIANCE WITH FINANCIAL COVENANTS

       Computations showing compliance with certain paragraphs of the Business
Loan Agreement are as follows:

       PARAGRAPH 6.3; NET WORTH.. As of the date of the attached financial
statements, the Borrower's Net Worth, on a consolidated and cumulative basis, is
at least the sum of:

<TABLE>

             <S>                                                                  <C>
             Calculated Net Worth from the immediately preceding
             fiscal quarter.  Net Worth amount as of the 6/30/98
             fiscal quarter shall begin with $430,000,000.                        $____________

             PLUS, in each quarterly accounting period, commencing with the
             quarter ended 9/30/98 the sum of:

                50% of net income after income taxes
                (without subtracting losses),                                     $____________

                PLUS the net proceeds from the issuance of any equity
                securities (including shares issued upon exercise
                of stock options),                                                $____________

                PLUS any increase in stockholders' equity resulting
                from the conversion of debt securities to equity
                securities                                                        $____________

                PLUS any increase in stockholders equity resulting from
                the transactions as described in the Form S-3 dated
                October 10, 1997                                                  $____________

             MINUS the amount of treasury stock held by the
             Borrower not to exceed $50,000,000.                                  $____________

             minimum permitted                                                    $____________

                                         
<PAGE>

Compliance Certificate
Page 2

             <S>                                                                  <C>
             actual Net Worth                                                     $____________


</TABLE>


       PARAGRAPH 6.4; ADJUSTED FUNDED DEBT TO EBITDA. As of the date of the
attached consolidated financial statements, the ratio of adjusted funded debt to
EBITDA was calculated as follows:

       (a)   The sum of:

<TABLE>

             <S>                                                                  <C>
             All funded debt (including interest bearing obligations)             $____________

             MINUS the sum of the following not to exceed the
             face amount of Notes issues under the Indenture:                     $_____________

                  domestic cash and domestic cash equivalents

                  100% of offshore cash balances not to exceed capital 
                  contributed to Dura (Burmuda) Trading Company Ltd.              $_____________

                  50% of other offshore cash balances                             $_____________
</TABLE>

             DIVIDED BY

       (b)    For the current fiscal quarter and each of the three immediately
              preceding quarters, the sum of :

<TABLE>

             <S>                                                                  <C>
             net income                                                           $_____________

             MINUS interest income                                                $(____________)

             PLUS interest expense                                                $_____________

             PLUS depreciation                                                    $_____________

             PLUS depletion                                                       $_____________

             PLUS amortization                                                    $_____________

             PLUS all federal, state, local and foreign income taxes              $_____________

             EBITDA                                                               $_____________

             EQUALS (EXPRESSED AS A RATIO)                                         __________:1.00


<PAGE>

Compliance Certificate
Page 3


             <S>                                                                  <C>
             maximum permitted:                                                   1.75 to 1.00
</TABLE>

       PARAGRAPH 6.5; MINIMUM EBIT; MINIMUM U.S. EBIT; For the fiscal quarter
ended as of the date of the attached consolidated financial statements,
consolidated EBIT was calculated as follows:

             (a)  the sum of:

<TABLE>

                  <S>                                                              <C>
                  net income                                                       $____________

                  MINUS interest income                                            ($___________)

                  PLUS interest expense                                            $____________

                  PLUS all federal, state, local and foreign income
                  taxes                                                            $____________

                  EQUALS                                                           $____________

                  minimum permitted:                                               $0

</TABLE>

       EBIT for the Borrower and its Domestic Subsidiaries was calculated as
follows:

             (a)  the sum of:
<TABLE>

             <S>                                                                  <C>
             U.S. net income                                                       $____________

             MINUS U.S. interest income                                            ($___________)

             PLUS U.S. interest expense                                            $____________

             PLUS all federal, state, local,
             and foreign taxes                                                     $____________

             EQUALS                                                                $____________

             minimum permitted:

                  quarter ended 9/30/98                                            ($6,000,000)

                  each quarter thereafter                                          ($1,000,000)
</TABLE>

             PARAGRAPH 6.7; OTHER INDEBTEDNESS. As of the date of the attached
       financial statements for the Borrower and its subsidiaries, the
       outstanding amount of debts for 

<PAGE>

Compliance Certificate
Page 4
 
       acquisition of fixed or capital assets permitted under Paragraph 
       6.7 (e) was $_______________.

<TABLE>

             <S>                                                                   <C>
             maximum permitted in any single fiscal year:                          $5,000,000
             (excludes debt pursuant to that certain Indenture
             dated as of July 30, 1997)
</TABLE>

             PARAGRAPH 6.8; LIENS. As of the date of the attached financial
       statements for the Borrower and its subsidiaries, the amount of
       obligations secured by a lien under the last provision of Paragraph 6.8
       was $______________.

<TABLE>
             <S>                                                                   <C>
             maximum permitted in any fiscal year:                                 $5,000,000

</TABLE>
             PARAGRAPH 6.9; CAPITAL EXPENDITURES. As of the date of the attached
       financial statements for the Borrower and its subsidiaries, the total
       amount expended year to date in fiscal year 1998 to acquire fixed or
       capital assets was $_____________.


<TABLE>
             <S>                                                                   <C>
             maximum permitted:                                                    $55,000,000
</TABLE>

             PARAGRAPH 6.11, DIVIDENDS.  As of the date of the attached 
       financial statements for the Borrower and its subsidiaries, the total 
       amount of treasury stock was $_______________.


<TABLE>
             <S>                                                                   <C>
             maximum permitted                                                     $50,000,000
</TABLE>

             PARAGRAPH 6.12; LOANS TO AFFILIATED COMPANIES. Since the date of
       the Business Loan Agreement, the total amount of loans or other
       extensions of credit made by the Borrower or any Domestic Subsidiary
       (including subsidiaries of the Borrower) to its affiliates was
       $___________________;
       and the total investments in Foreign Subsidiaries was $___________;
       and the total Loans to Dura (Bermuda) Trading
       Company, Ltd. was $________________.

<TABLE>
             <S>                                                                   <C>
             maximum permitted:                                                    $10,000,000
             Investments in Foreign Subsidiaries permitted                         $90,000,000
             Loans to Dura (Bermuda) Trading Company, Ltd.
             permitted                                                             $190,000,000
</TABLE>

             PARAGRAPH 6.21 (h); ASSET ACQUISITIONS. Since the date of the
       Business Loan Agreement, the total amount of asset acquisitions,
       including license agreements and product rights, permitted under
       Paragraph 6.21 (h) was $__________________.

<TABLE>
             <S>                                                                   <C>
             Maximum permitted in aggregate                                        $100,000,000
</TABLE>

<PAGE>

Compliance Certificate
Page 5

       II    PERFORMANCE OF OBLIGATIONS

             A review of the activities of Borrower during the fiscal period
       covered by this Certificate has been made under the supervision of the
       undersigned with a view to determining whether during such fiscal period
       Borrower performed and observed all of its obligations. The best
       knowledge of the undersigned, during the fiscal period covered by this
       Certificate, all covenants and conditions have been so performed and
       observed by Borrower and no Event of Default or event which with notice
       or lapse of time or both would be an Event of Default has occurred based
       on the activities of Borrower and is continuing, with any exceptions set
       forth below, in response to which Borrower has taken or propose to take
       the following actions (if none, so state). Without limiting the
       foregoing, the Borrower has no Significant Subsidiaries except those that
       have executed and delivered to Bank a guaranty as required under
       paragraph 6.6 of the Business Loan Agreement.

       III.  COMPLIANCE WITH INDENTURE

       To the best knowledge of the undersigned, no event or circumstance has
       occurred that constitutes violation of the Indenture Agreement, as
       evidenced by the attached copy of the most recent Indenture compliance
       certificate .

       IV.   NO MATERIAL ADVERSE CHANGE

             To the best knowledge of the undersigned, no event or circumstance
       has occurred that constitutes a Material Adverse Effect regarding
       Borrower under Paragraph 8.7 of the Business Loan Agreement since the
       date the most recent Certificate was executed and delivered, with any
       exceptions being set forth below (if none, so state):

<PAGE>

      This Certificate is executed on _________, 19___, by a responsible
       officer of Borrower. the undersigned hereby certify that each and every
       matter contained herein is derived from Borrower's books and records and
       is, to the best knowledge of the undersigned, true and correct.

             Dated: ____________, 19___

                                                 Dura Pharmaceuticals, Inc.


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