<PAGE>

                   AMENDMENT NO. 5 TO BUSINESS LOAN AGREEMENT

         This Amendment No.5 (the "Amendment") dated as of October 12, 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 of May 8, 1997,
July 30, 1997, October 28, 1997, and June 25, 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 meaning given to them in the Agreement.

         2. AMENDMENTS. The Agreement is hereby amended as follows:

                  2.1 In Paragraph 6.3 of the Agreement, the period is deleted
         from the end of subparagraph (g) and is replaced with "; MINUS" and the
         following is added as a new subparagraph (h):

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

                  2.2 Paragraph 6.11 of the Agreement is amended in full to read
         as follows:

                           "6.11 Dividends. Not to declare or pay any dividends
                  on any of its shares except dividends payable in capital stock
                  of the Borrower, and not to purchase, redeem or otherwise
                  acquire for value any of its shares, or create any sinking
                  fund in relation thereto; provided, however, that the Borrower
                  may acquire treasury stock in an amount not to exceed Fifty
                  Million Dollars ($50,000,000)."

                  2.3 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) except as
disclosed to the Bank by the Borrower in its letter dated October __, 1998,
there is no event which is, or with notice or lapse of time or both would be, a
default under the Agreement (b) except as disclosed to the Bank by the Borrower
in its letter dated October __, 1998, 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 
                                         1
<PAGE>

(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.

         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 Mast
                           -------------------------------
                           Name:     Erle Mast

                           Title:    Vice President, Finance


                           By: /s/ Mitchell R. Woodbury

                           Name: Mitchell R. Woodbury

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




                                         2
<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 and Domestic Subsidiaries' 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 6/30/97
             fiscal quarter shall begin with $450,000,000.                        $____________

             PLUS, in each quarterly accounting period, commencing with the
             quarter ended 6-30-97 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, cash and noncash charges for in-process technology
                purchased from Spiros Development Corporation and for any
                contribution to Spiros Development Corporation II, Inc., as
                described in the Form S-3 ( the "Spiros Charges"), up to a
                maximum of One Hundred Twenty Five Million
                Dollars ($125,000,000) in the aggregate;                          $_____________

<PAGE>

Compliance Certificate
Page 2

                <S>                                                               <C>
                MINUS any decrease in stockholders' equity resulting from the
                acquisition by the Borrower of Spiros Development Corporation or
                a cash contribution from the Borrower to Spiros Development
                Corporation II,
                Inc. as described in the Form S-3,                                $____________

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

             minimum permitted                                                    $_____________

             actual Net Worth                                                     $_____________

</TABLE>

       PARAGRAPH 6.4; ADJUSTED FUNDED DEBT TO ADJUSTED EBITDA. As of the date of
the attached financial statements for Borrower and its Domestic Subsidiaries,
the ratio of funded debt to adjusted EBITDA was calculated as follows:

       (a)   The sum of:

<TABLE>

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

             MINUS obligations owing to Procter & Gamble Pharmaceuticals, Inc.
             for Entex Products (maximum $20,000,000) less domestic cash and
             domestic cash equivalents up to an amount equal the face amount of
             the Notes issued pursuant to
             and as defined in the Indenture.                                     $_____________

             adjusted funded debt                                                 $_____________

             DIVIDED by

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

             net income                                                           $_____________

             MINUS interest income                                                $(____________)

             PLUS interest expense                                                $_____________

             PLUS depreciation                                                    $_____________

             PLUS depletion                                                       $____________

             PLUS amortization                                                    $_____________

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


<PAGE>

Compliance Certificate
Page 3

             <S>                                                                  <C>
             PLUS Spiros Charges (up to maximum of $125,000,000
             in aggregate)                                                        $_____________

             Adjusted EBITDA                                                      $_____________

             EQUALS (EXPRESSED AS A RATIO)                                         __________:1.00

             maximum permitted:

             Up to and including August 31, 1997                                  2.00 to 1.00

             From and including September 1, 1997 and thereafter                  1.75 to 1.00

</TABLE>

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

<TABLE>
             <S>                                                                  <C>
             (a)  the sum of:

                  net income                                                       $____________

                  minus interest income                                            $(____________)

                  plus interest expense                                            $____________

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

                  plus the Spiros Charges (maximum of $125,000,000
                  in aggregate)                                                    $_____________

                  equals                                                           $_____________

                  minimum permitted:                                               $(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 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>

<PAGE>

       Compliance Certificate
       Page 4

             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 to acquire fixed or capital assets was
       $_____________.


<TABLE>

             <S>                                                                   <C>
             maximum permitted during 1997 fiscal year:                            $30,000,000

             maximum permitted during 1998 fiscal year:                            $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>
<CAPTION>

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

       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.

<PAGE>

       Compliance Certificate
       Page 5

       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):

       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: