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                                                                    Exhibit 4.10


                      SECOND AMENDMENT TO RIGHTS AGREEMENT
             AND CERTIFICATION OF COMPLIANCE WITH SECTION 27 THEREOF

         This Amendment, dated as of September 10, 2000 (the "Amendment"), to
the Rights Agreement, dated as of May 21, 1998 (as amended December 10, 1998,
the "Agreement"), between Dura Pharmaceuticals, Inc., a Delaware corporation
(the "Company"), and ChaseMellon Shareholder Services, L.L.C., a limited
liability company (the "Rights Agent"). Capitalized terms used in this Amendment
without definition shall have the respective meanings ascribed to them in
Agreement.

         Pursuant to Section 27 of the Agreement, this Amendment is being
executed by the Company and the Rights Agent for the purpose of amending the
Agreement as set forth below:

         The Agreement is hereby amended as follows:

         1.       Section 1(a) shall be amended by inserting the following at
the end of the definition of "Acquiring Person":

                  "Notwithstanding the foregoing, neither of Elan Corporation,
                  plc, a public limited company organized under the laws of
                  Ireland ("Acquiror"), or Carbon Acquisition Corp., a Delaware
                  corporation, or any subsidiary of Acquiror ("Merger Sub"),
                  shall be an Acquiring Person solely by virtue of the execution
                  of the Agreement and Plan of Merger, dated as of September 10,
                  2000 (the "Merger Agreement"), by and among Acquiror, Merger
                  Sub and the Company, or the consummation of the Merger (as
                  defined in the Merger Agreement)."

         2.       Section 1(aj) shall be amended by inserting the following at
the end of the definition of "Shares Acquisition Date":

                  "Notwithstanding the foregoing, no Shares Acquisition Date
                  shall occur solely by reason of the execution of the Merger
                  Agreement or the consummation of the Merger (as defined in the
                  Merger Agreement)."

         3.       Section 1(ao) shall be amended by inserting the following at
the end of the definition of "Triggering Event":

                  "Notwithstanding the foregoing, a "Triggering Event" shall not
                  occur solely by reason of the execution of the Merger
                  Agreement or the consummation of the Merger (as defined in the
                  Merger Agreement)."

         4.       Section 3(a) shall be amended by inserting the following at
the end of the section:

                  "Notwithstanding the foregoing or any provision to the
                  contrary in this Agreement, a Distribution Date shall not
                  occur solely by reason of the execution of the Merger
                  Agreement or the consummation of the Merger (as defined in the
                  Merger Agreement)."


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         5.       Section 7(a) shall be amended by inserting and deleting the
following into the definition of "Expiration Date":

                  deleting the word "or" immediately preceding clause (iii)
                  thereto and replacing all of clause (iii) and the text
                  following clause (iii), with "(iii) immediately prior to the
                  Effective Time (as defined in the Merger Agreement) or (iv)
                  the time at which such Rights are exchanged as provided in
                  Section 24 hereof (the earlier of (i), (ii), (iii) and (iv)
                  being the "Expiration Date"). The Company, upon having
                  knowledge thereof, will promptly notify the Rights Agent of
                  the anticipated Effective Time."

         6.       Section 13 shall be amended by inserting the following as
Section 13(f) at the end of Section 13:

                  "(f) Notwithstanding the foregoing, no Section 13 Event shall
                  occur solely by reason of the execution of the Merger
                  Agreement or the consummation of the Merger (as defined in the
                  Merger Agreement)."

         7.       This Amendment shall be deemed effective as of September 10,
2000 as if executed by both parties hereto on such date.

         8.       This Amendment shall be deemed to be a contract made under the
laws of the State of Delaware and for all purposes shall be governed by and
construed in accordance with the laws of such State applicable to contracts to
be made and performed entirely within such State.

         9.       This Amendment may be executed in any number of counterparts
and each of such counterparts shall for all purposes be deemed to be an
original, and all such counterparts shall together constitute but one and the
same instrument.

         10.      Except as amended hereby, the Agreement shall remain in full
force and effect.

         The undersigned officer of the Company, being an appropriate officer of
         the Company and authorized to do so by resolution of the Board of
         Directors of the Company dated as of September 8, 2000, hereby
         certifies to the Rights Agent that these amendments are in compliance
         with the terms of Section 27 of the Agreement.


                                       2
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         IN WITNESS WHEREOF, the parties have caused this Amendment to be
executed and attested, all as of the day and year first above written.



                                         DURA PHARMACEUTICALS, INC.


                                         By:  /s/ Erle T. Mast
                                            ------------------------------------
                                            Name: Erle T. Mast
                                            Title:   Vice President, Finance



ATTEST:


By:  /s/ John R. Cook
   -------------------------------------
   Name:  John R. Cook
   Title: Vice President, Associate General Counsel
          And Secretary



                                         CHASEMELLON SHAREHOLDER
                                         SERVICES, L.L.C., as Rights Agent


                                         By:  /s/ Sharon Knepper
                                            ------------------------------------
                                            Name:  Sharon Knepper
                                            Title: Vice President



ATTEST:


By:  /s/ Rosa Bautista
   --------------------------------------
   Name:  Rosa Bautista
   Title: Relationship Manager