<PAGE>

THE SPECIAL COMMON STOCK, PAR VALUE $1.00, OF SPIROS DEVELOPMENT CORPORATION 
II, INC., A DELAWARE COMPANY (THE "COMPANY"), EVIDENCED HEREBY ENTITLES THE 
HOLDERS OF A MAJORITY OF THE SHARES OF SUCH SPECIAL COMMON STOCK TO PURCHASE 
ALL, BUT NOT LESS THAN ALL, OF THE OUTSTANDING SHARES OF THE COMPANY'S 
CALLABLE COMMON STOCK, PAR VALUE $0.001 PER SHARE (THE "CALLABLE COMMON 
STOCK"), EXERCISABLE BY NOTICE GIVEN AT ANY TIME BEGINNING ON THE CLOSING 
DATE OF THE OFFERING OF THE UNITS, EACH UNIT COMPRISED OF ONE SHARE OF 
CALLABLE COMMON STOCK AND ONE WARRANT TO PURCHASE ONE-FOURTH OF ONE SHARE OF 
THE COMMON STOCK OF DURA PHARMACEUTICALS, INC. AND ENDING ON THE EARLIER OF 
(i) DECEMBER 31, 2002, (ii) THE 90TH DAY AFTER THE DATE THE COMPANY PROVIDES 
SUCH HOLDER WITH QUARTERLY FINANCIAL STATEMENTS OF THE COMPANY SHOWING CASH 
OR CASH EQUIVALENTS OF LESS THAN $5,000,000 OR (iii) THE DATE OF TERMINATION 
BY THE COMPANY OF THAT CERTAIN TECHNOLOGY LICENSE AGREEMENT, DEVELOPMENT 
AGREEMENT OR MANUFACTURING AND MARKETING AGREEMENT DATED ON OR ABOUT DECEMBER 
22, 1997, ALL AS DESCRIBED IN THE AMENDED AND RESTATED CERTIFICATE OF 
INCORPORATION OF THE COMPANY.  COPIES OF THE AMENDED AND RESTATED CERTIFICATE 
OF INCORPORATION OF THE COMPANY ARE AVAILABLE AT THE OFFICES OF THE COMPANY, 
7475 LUSK BOULEVARD, SAN DIEGO, CALIFORNIA  92121, ATTENTION:  MITCHELL R. 
WOODBURY AND WILL BE FURNISHED TO ANY STOCKHOLDER OF THE COMPANY ON REQUEST 
AND WITHOUT COST.

THE SECURITIES REPRESENTED HEREBY HAVE NOT BEEN REGISTERED UNDER THE 
SECURITIES ACT OF 1933, AS AMENDED (THE "ACT"), AND MAY NOT BE OFFERED, SOLD 
OR OTHERWISE TRANSFERRED PLEDGED OR HYPOTHECATED IN THE ABSENCE OF A 
REGISTRATION STATEMENT IN EFFECT WITH RESPECT TO SUCH SECURITIES, OR DELIVERY 
OF AN OPINION OF COUNSEL IN FORM AND SUBSTANCE SATISFACTORY TO THE ISSUER OF 
THESE SECURITIES THAT SUCH OFFER, SALE OR TRANSFER, PLEDGE OR HYPOTHECATION 
IS IN COMPLIANCE WITH THE ACT.

THE COMPANY WILL FURNISH WITHOUT CHARGE TO EACH STOCKHOLDER WHO SO REQUESTS A 
COPY OF THE POWERS, DESIGNATIONS, PREFERENCES AND RELATIVE, PARTICIPATING 
OPTIONAL OR OTHER SPECIAL RIGHTS OF EACH CLASS OF SHARES OF THE COMPANY OR 
SERIES THEREOF, AND THE QUALIFICATIONS, LIMITATIONS OR RESTRICTIONS OF SUCH 
PREFERENCES AND/OR RIGHTS.

No. S-1                                           *1,000 shares*
                                          
                      SPIROS DEVELOPMENT CORPORATION II, INC.
                                          
                INCORPORATED UNDER THE LAWS OF THE STATE OF DELAWARE
                                          
                 FULLY PAID AND NON-ASSESSABLE SPECIAL COMMON STOCK
                                          
                             PAR VALUE $1.00 PER SHARE

          This certifies that Dura Pharmaceuticals, Inc. is the owner of One
Thousand (1,000) shares of Special Common Stock of Spiros Development
Corporation II, Inc., transferable on the books of the Company by the holder
thereof, in person or by duly authorized attorney, upon surrender of this
certificate properly endorsed.  This certificate and the shares represented
hereby are 

<PAGE>

subject to the laws of Delaware, and to the Amended and Restated Certificate 
of Incorporation of the Company as now or hereafter amended (copies of which 
are on file at the offices of the Company) which are made a part hereof with 
the same force and effect as if they were set forth herein, to all of which 
the holder, by acceptance hereof, assents.

          IN WITNESS WHEREOF, the Company has caused the signatures of its duly
authorized officers and its corporate seal to be hereunto affixed.  

Dated:  December 18, 1997



                                        

/s/David S. Kabakoff                   /s/ Mitchell R. Woodbury
--------------------                   ------------------------
President                              Secretary


<PAGE>


The following abbreviations, when used in the inscription on the first page of
this certificate, shall be construed as though they were written out in full
according to applicable laws or regulations:

TEN COM - as tenants in common

TEN ENT - as tenants by the entireties

JT TEN - as joint tenants with right of survivorship and not as tenants in
common

UNIF GIFT MIN ACT  . . . . . Custodian . . . . . . . . . . .  

                    (Cust)              (Minor)
                    under Uniform Gifts to Minors Act
                    . . . . . . . . . . . . . . . . .
                                              (State)


Additional abbreviations may also be used though not in the above list.


   For Value Received, _______________ hereby sells, assigns and transfers unto
                                                                 

_______________________________________________________________________________
                         (Please insert Social Security
                    or other identifying number of assignee)

                                          
_______________________________________________________________________________
                  (Please print or typewrite name and address
                     including postal zip code of assignee)


____________________________ shares of Special Common Stock represented by the
within certificate, and do hereby irrevocably constitute and appoint _________
______________________________________________________________________________
attorney, to transfer the said same on the books of the within named Company,
with full power of substitution in the premises.


Dated:________________________
                                                            
                              
                                       _______________________________________
                                       Signature

                                       _______________________________________
                                       Signature

                                 Notice:  The signature to this assignment must 
                          correspond with the name as written upon the face of 
                  the Certificate, in every particular, without alteration 
          or enlargement, or any change whatever.