<PAGE>   1
                                                                Exhibit 10.28 

                                   AMENDMENT

       This Amendment by and between Rhone-Poulenc Rorer Inc. (as successor to
Rorer Group Inc.) ("RPR") and Noven Pharmaceuticals, Inc. ("Noven") is entered
into as of this 6th day of May, 1996.

       WHEREAS, as of April 27, 1989, the parties entered into a license
agreement (hereafter the "License Agreement") and a related supply agreement,
pursuant to which they agreed to collaborate on the development and marketing of
the Licensed Product (as defined in the License Agreement);

       WHEREAS, on several occasions since April 27, 1989, the parties have
amended the License Agreement in various respects in order to reflect various
adjustments in their collaborative venture, including an Amendment dated as of
June 9, 1994 (hereafter the "June 1994 Amendment"); and

      WHEREAS, the parties now desire to enter into another amendment for the
purpose of modifying certain fee provisions of the License Agreement and the
June 1994 Amendment.

      NOW, THEREFORE, for valuable consideration and intending to be legally
bound, the parties agree as follows:

      1.     All capitalized items used in this Amendment shall have the
meaning ascribed to them in the License Agreement and the June 1994 Amendment,
unless otherwise specifically provided.

      2.     Subparagraphs (a), (b), (c), (d) and (e) of Article 5.2 of the
License Agreement, and subparagraphs (b), (c), (d) and (g)(iii) of Article 3 of
the June 1994 Amendment, are deleted in their entirety and replaced by the
following:

      "5.2  Fee

       (a)  RPR shall pay to Noven ************* of RPR's, its Affiliates' and
       Sublicensees' Net Sales, subject to the provisions set forth below in
       this Article 5.2.  To the extent that Noven engages in any **************
       of the Licensed Product, RPR shall pay Noven with respect to ********** 
       Licensed Product for which Noven performs the **************************
       of RPR's, its Affiliates' and Sublicensees' Net Sales, subject to the 
       provisions set forth below in this Article 5.2.

       * Confidential portions of this Exhibit have been omitted and filed
         separately with the Commission pursuant to a request for Confidential
         Treatment.
<PAGE>   2
       (b)  Notwithstanding anything else to the contrary, the fee to be paid
       under subparagraph (a) above with respect to Licensed Product for which
       **************************** shall be no less than *********************
       ****************************************** of Licensed Product; 
       provided, however, that for purposes of calculating such minimum fee, 
       RPR shall be deemed to obtain a fixed **********************************
       ****************************** provided by Noven, regardless of the 
       yield RPR actually obtains.  Such minimum fee shall therefore equate to 
       a minimum fee of *******************************************************
       ********* material provided by Noven.  Noven and RPR shall negotiate in 
       good faith to determine an acceptable minimum fee with respect to any 
       units of Licensed Product for which Noven performs *********************.

       (c) Notwithstanding the foregoing, if Noven's Cost of Licensed Product
       increases such that it is no longer commercially viable for Noven to
       manufacture the Licensed Product for the fee provided for in this Article
       5.2, or if RPR's weighted average gross margin for the Licensed Product
       with respect to any country, computed excluding samples and sales at or
       below cost, is reduced to a point that it is no longer commercially
       viable for RPR to continue to market the Licensed Product in that
       country, then RPR and Noven shall negotiate in good faith for a revised
       fee under this Article 5.2 with respect to the Licensed Product.  In the
       absence of the parties being able to reach a mutually satisfactory
       agreement, Noven shall grant RPR a non-exclusive license to manufacture
       Licensed Product under Noven's Technology and Noven's Patent Rights in
       return for a royalty of ******************************** of Net Sales, in
       addition to other terms and conditions as reasonably agreed by the
       parties.  Such license shall only be for sales of Licensed Product in the
       country or countries that occasioned the negotiation."

       3.     Article 5.4 of the License Agreement and subparagraphs (f) and
g(iv) of Article 3 of the June 1994 Amendment are deleted in their entirety and
replaced by the following:

       "5.4  Payments.  The fee due under Article 5.2(a) shall be payable as
       follows: (a) The minimum fee of Article 5.2(b) shall be due and payable
       within thirty (30) days of Noven's invoice for the applicable Licensed
       Product; and (b) within thirty (30) days after the end of each calendar
       quarter, RPR shall make a


                                       2
<PAGE>   3
       payment to Noven of the remaining fee, if any, due under Article 5.2(a)
       with respect to such quarter, based on Net Sales in the quarter and
       calculated as set forth in Exhibit A, attached and incorporated by
       reference."

       4.     Subparagraph (g)(i) of Article 3 of the June 1994 Amendment is
deleted in its entirety and replaced by the following:

       "g(i) RPR shall cause its Affiliate in Ireland to purchase *************
       of Licensed Product from Noven at a price equal to the minimum fee under
       Article 5.2(b) of the License Agreement, which purchase price shall be
       credited against the fee due Noven pursuant to Article 5.2(a) of the
       License Agreement."

       5.     This Amendment shall supersede and supplant any term or provision
of the License Agreement and/or the June 1994 Amendment that is in direct
conflict with an express term or provision of this Amendment. Except in the case
of such a conflict, the terms and provisions of the License Agreement and the
June 1994 Amendment shall remain in full force and effect and unchanged.

Noven Pharmaceuticals, Inc.               Rhone-Poulenc Rorer Inc.


By: /s/ Steven Sablotsky                  By:

   -----------------------------             ----------------------------------

Name:  Steven Sablotsky                   Name:
       -------------------------               --------------------------------

Title: President                          Title:
       -------------------------                -------------------------------







                                      3

<PAGE>   4


                                   EXHIBIT A


<TABLE>

<S>                                                            <C>
The total units of Licensed Product sold worldwide
 by RPR, its Affiliates or Sublicensees in the quarter         = X

Net Sales worldwide with respect to the quarter                = Y

Fee due under Article 5.2(a) of the License Agreement
 for the quarter = *****************                           = Z

Fee paid under Article 5.4(a) of the License Agreement
 with respect to Licensed Product sold in the quarter           **

Remaining fee payable to Noven for the quarter under
 Article 5.4(b) of the License Agreement                       = Z-B

In the event that Z-B is a negative number, no fee will be
 payable under Article 5.4(b) of the License Agreement
</TABLE>


<PAGE>   5



                                   AMENDMENT


       This Amendment to the License Agreement ("License Agreement") and the
Supply Agreement ("Supply Agreement"), each dated April 27, 1989, by and between
Rhone-Poulenc Rorer Inc. (as successor to Rorer Group Inc. ("RPR") and Noven
Pharmaceuticals, Inc. ("Noven") is entered into as of this 9th day of June,
1994.

       WHEREAS, as of April 27, 1989, the parties entered into the License
Agreement, pursuant to which they agreed to collaborate on the development and
marketing of the Licensed Product;

       WHEREAS, on that same date the parties entered into the Supply Agreement
(together with the License Agreement sometimes referred to herein as the "Prior
Agreements") which provided that, following regulatory approval, Noven would
manufacture the License Product and package it in final form for delivery to 
RPR for sale and distribution by RPR;

       WHEREAS, on several occasions since April 27, 1989, the parties have
amended the License Agreement in various respects in order to reflect various
adjustments in their collaborative venture; and

       WHEREAS, the parties now desire to enter into another amendment for the
purpose of modifying certain provisions of the Prior Agreements in order to
provide that ******************************************** may be done by RPR on
a non-exclusive basis under the terms and conditions of this Amendment.

       NOW, THEREFORE, for valuable consideration and intending to be legally
bound, the parties agree as following:

1.     Definitions.  All capitalized terms not defined herein shall have the
       meaning ascribed to them in the Prior Agreements.


                                     - 1 -

<PAGE>   6
2.     Effect of this Amendment.  This Amendment shall supersede and supplant
       any term or provision of the Prior Agreements that is in conflict with an
       express term of this Amendment.  Except in the case of such a conflict,
       the terms and provisions of the Prior Agreements shall remain in full
       force and effect and unchanged.

3.     Final Processing of Licensed Product.

       a.     Noven shall (i) manufacture the Licensed Product through the stage
              of production of **************************************** (ii)
              test, prepare and package such ************************ and (iii)
              supply and deliver them to RPR's facility in Nenagh, Ireland, or
              such other RPR facility as RPR shall designate.  Noven shall
              perform all such activities in accordance with the terms of the
              Prior Agreements, the specifications attached hereto as Exhibit A 
              (as may be amended by the parties from time to time) and all
              applicable laws and regulations.  RPR shall complete *************
              ****************** in accordance with the terms of the Prior
              Agreements and this Amendment.  Specifically, RPR shall be
              responsible for **************************************** received
              from Noven and **************************************************
              and releasing the Licensed Product ******************************
              ************. The price for Licensed Product delivered by Noven to
              RPR under this paragraph shall be as set forth in the Prior
              Agreements, as amended herein, and shall be ex Noven's factory.
              Title to and risk of loss to *************************** shall
              pass to RPR at Noven's factory, and RPR shall bear all costs and
              expenses for delivery of ************************ including, but
              not limited to, freight, insurance and duties.

       b.     Article 5.2(a) of the License Agreement is deleted in its entirety
              and replaced by the following: " (a) RPR shall pay to Noven
              **************** of RPR's, its Affiliates' and Sublicensees' Net
              Sales, subject to the provisions set forth in this Article 5.2.
              In the event ***************************************************
              ******************** then costs above the Standard Packaging Cost
              shall be allocated **********************************************
              ************************************

       c.     The fee calculated under Article 5.2 of the License Agreement, as
              amended by paragraph 3(b) of this


                                     - 2 -
<PAGE>   7
    Amendment, for each unit of Licensed Product that is *******************
    ************* under this Amendment, including the minimum and maximum fees
    set forth in Article 5.2(b), shall be reduced by an amount equal to
    ******************* as such amount is adjusted from time to time under
    paragraph 3(d) of this Amendment (the "Fee Reduction Amount").


d.  The Fee Reduction Amount shall be adjusted, up or down (but not below
    ($00.00), effective January 1 of each calendar year in accordance with
    the increase or decrease, as the case may be, during the previous calendar
    year of ******************************************************************
    ******************************************** in accordance with the terms of
    this Amendment; provided, however, that no upward adjustment under this
    subparagraph shall exceed, on a percentage basis, the percentage increase
    in the Consumer Price Index (as that term is defined in the License
    Agreement) over the corresponding period.

e.  Reflecting the fact that the fee provided for in Article 5.2(b) of the 
    License Agreement has been *************** approximately ******************
    (i.e., the **********************), each of the annual minimum fees provided
    for in Articles 5.3(a) and 5.3(b) of the License Agreement shall be *******
    by ************* provided, however, that to the extent Noven supplies RPR
    with Licensed Product in the final form for any market, then the foregoing
    ****************** shall be adjusted downward for such market(s), based
    upon the proportion, on a percentage basis, that such production by Noven
    of Licensed Product in final form has to all Licensed Product *************
    *********************** and *** for such market(s).

f.  The first sentence of Article 5.4 of the License Agreement is deleted in
    its entirety and replaced by the following:

     "   5.4 Payments.  The fee due hereunder shall be payable as follows:  The
         minimum price of Paragraph 5.2(b), subject to the adjustment set
         forth in Paragraph 5.2(c) and reduced, when applicable, by the *******
         ******************, shall be due and payable within thirty (30) days of
         Noven's invoice for such Licensed Product."




                                      3






<PAGE>   8
g.      (i)     The RPR Affiliate in Ireland shall purchase bulk rolls from
                Noven at the initial price of ******************************* 
                per unit (which reflects the adjustment for CPI and the ****** 
                **********************) for the first six months of production, 
                which purchase price shall be credited against the fee due 
                Noven pursuant to Article 5.2(a) of the License Agreement.

       (ii)     Noven will invoice the RPR Affiliate in Ireland based on the 
                number of *************************** delivered by Noven to RPR 
                pursuant to Paragraph 3(a) of this Amendment.

      (iii)     The amount to be invoiced by Noven for ********** shall 
                initially be based upon a production yield of *****************
                ***************************** yard for the first six months.

                After the first six months, the amount to be invoiced by Noven 
                for ************ shall be adjusted up or down based upon the 
                average actual ******************************************* for 
                the first six months.

                At the end of each calendar year thereafter, the amount to be 
                invoiced by Noven for ************* shall be adjusted up or 
                down based upon the average actual ************************* 
                for the previous calendar year.

                In the event that the average *********************************
                ******************************************************** upon 
                adjustment pursuant to this subparagraph g (iii), then the 
                parties shall negotiate in good faith to determine an acceptable
                price ****************** to be invoiced by Noven; provided, 
                however, that should the parties fail to reach agreement for a 
                price ********************************** within sixty (60) 
                days, then Noven shall supply RPR with Licensed Product 
                processed in final form in accordance with the terms and 
                pricing of the prior Agreements in lieu of ****************

       (iv)     Any balance of the fee due to Noven pursuant to Article 5.2 of 
                the License Agreement, as hereby amended, will be paid by RPR 
                within thirty (30) days after the end of each calendar quarter.


                                      4


<PAGE>   9
        (v)     In the event that Noven supplies bulk laminate rolls of 
                placebo material for educational or promotional purposes, such 
                material shall be supplied by Noven at an agreed upon price and
                no other fee or royalty shall be due from RPR with respect to 
                such material.

    h.  ************************ anything else to the contrary contained in this
        Amendment, Noven shall remain liable in accordance with the terms and
        pricing of the Prior Agreements to manufacture and supply all Licensed
        Product processed in final form **************, or *******************
        ********, or other conditions mutually agreed between RPR and Noven, **
        *************************** pursuant to the terms of this Amendment.

4.  Acquisition of Processing Technology and the Machine.
    
    a.  Noven shall construct and ship to RPR at its Nenagh, Ireland
        facility a die cutting and pouch packaging Machine (the "Machine")
        along with spare parts as set forth in Exhibit B capable of performing
        *******************************************************************
        shipped from Noven.  Noven warrants that said Machine will be capable
        of ************************************ and said Machine will meet the
        minimum specifications and output requirements set forth in Exhibit B.
        
        RPR shall be responsible for providing engineering/technical support 
        capable of installing and operating said Machine.

        Noven shall be responsible for packing the Machine suitable for
        transport and transporting same to RPR's Nenagh facility and Noven
        shall bear all costs and expenses for delivery of the Machine including
        packing, freight, insurance and duties.  Risk of loss or damage to the
        Machine shall remain with Noven until delivery at RPR's facility in
        Nenagh, Ireland.

        RPR shall be responsible for installation of the Machine and Noven 
        shall provide RPR with support in commissioning the Machine, as
        detailed in paragraphs 4.b.(i), (ii), and (iii), and training
        RPR's mechanics and operators in the proper maintenance and operation
        of the Machine.  Noven shall be responsible for demonstrating the
        Machine's ability to operate and perform in accordance with its agreed
        specifications and output requirements as set forth in Exhibit B.
                

                                    - 5 -
<PAGE>   10
       b.     Noven grants RPR a non-exclusive license to use the Machine in
              Ireland under Noven's Processing Technology and Noven's Patent
              Rights (as defined below), solely for RPR to perform *********
              ************************ under this Amendment with respect to the
              Licensed Product.  In addition, Noven shall provide RPR on an
              ongoing basis throughout the term of the Prior Agreements
              assistance and training on the following terms:

              (i)    On completion of the Machine, Noven shall provide to RPR
                     personnel up to two weeks training and instruction at a
                     mutually agreed time at Noven's Miami premises. RPR shall
                     bear the cost of travel, lodging, food and other out-of-
                     pocket expenses for its personnel.  Costs of and payment
                     for materials used in training and acceptance shall be
                     mutually agreed by both parties.

              (ii)   Noven shall provide at RPR's facility at Nenagh, Ireland,
                     and at Noven's expense, three (3) man weeks of technical
                     support to assist RPR in the commissioning of the Machine.

              (iii)  Subsequent to the assistance provided in subparagraph
                     4.b(ii) above, Noven shall provide additional assistance as
                     may reasonably be necessary including providing an
                     engineer/technician at RPR's facility in Nenagh, Ireland.
                     The cost of such additional assistance shall be borne by
                     RPR to the extent of the cost of incremental travel, food,
                     and lodging for an additional two week period for one
                     technician.  If further Noven technical assistance is
                     required at the RPR Nenagh facility beyond the additional
                     two (2) weeks, RPR shall pay to Noven ********************
                     per Noven employee in addition to paying for any
                     incremental travel costs, lodging and meals.

       c.     The term "Noven's Processing Technology" shall mean any and all
              data, information, technologies, know-how, processes, techniques,
              methods, skills, proprietary information, trade secrets,
              developments and discoveries, that are owned or controlled by
              Noven and specifically related to the ***************************
              ******************with respect to the Licensed Product, now
              existing or developed in the future.  The term "Noven's




                                      - 6-
<PAGE>   11
              Patent Rights" shall mean any and all patents conceived or reduced
              to practice prior to December 31, 1998, including but not limited
              to reissues, extensions and patents of additions, and patent
              applications, continuations, divisionals and continuations-in-
              part thereon that are owned or controlled by Noven and the claims
              of which cover the Machine with respect to the Licensed Product.
              No right or license to make, use or sell under Noven's Processing
              Technology or Noven's Patent Rights or right of resale, lease or
              transfer of any kind with respect to the Machine is granted herein
              except as provided herein or with reference to the Licensed
              Product. No right to make or manufacture, or have made or
              manufactured, the Licensed Product, is granted to RPR except to
              the extent stated herein.

       d.     With respect to the matters provided for in subparagraphs 4(a) and
              4(b) above, RPR shall pay Noven *********************************
              in four installments, which shall be due and payable as follows:

              (i)    *************************************************** paid in
                     advance, the receipt of which is hereby acknowledged by
                     Noven;

              (ii)   ******************************************************* due
                     upon the completion of the Machine to the stage of scoring,
                     die cutting and transferring of cut patches to the
                     inspection web area, as demonstrated to the satisfaction of
                     a representative of RPR.

              (iii)  ***************************************************** upon
                     delivery of the Machine to RPR's facility in Nenagh,
                     Ireland; and

              (iv)   ****************************************** upon the date of
                     completion of the installation of the machine and
                     confirmation of its operation in accordance with its
                     specifications and the terms of this Amendment.

       e.     Noven represents and warrants its title to the Machine, that such
              title is free from any security interests of third parties or
              other liens or ecumbrances and that Noven is authorized and
              lawfully permitted to transfer 


                                     - 7 -

<PAGE>   12
such title to RPR.



























                                     -8-

<PAGE>   13
       f.     Noven shall exercise due care and diligence in constructing the
              Machine.  Noven warrants that the Machine shall conform to all
              applicable federal, state and local laws and regulations, and be
              merchantable, fit for the purpose for which it is intended and
              free from defects in workmanship and materials used in its
              manufacture.  For a period of one year after acceptance of the
              Machine in Ireland Noven will repair or replace at its cost any
              defect in the machine arising out of errors in workmanship or
              materials.  For purchased-in components the OEM's warranties will
              apply.

       g.     Noven represents and warrants that it has no actual and present
              knowledge of any rightful claim of any third party by way of
              infringement or the like of any patent or other intellectual
              property rights related to the machine. Noven shall defend at its
              own cost and hold RPR harmless from any such claims provided that
              RPR provides it prompt notice and an opportunity to defend.

       h.     Noven's Processing Technology and Patent Rights shall be subject
              to the confidentiality obligations of Article VIII of the License
              Agreement.  RPR shall undertake all reasonable actions to restrict
              access to the Machine and Noven's Processing Technology to its
              employees on a need to know basis and who are bound to obligations
              of confidentiality to the same extent as RPR is bound to Noven.

       i.     In the event that RPR wishes to sell, lease or otherwise transfer
              or dispose of the Machine, Noven shall have an exclusive right of
              first refusal on such terms as may be mutually agreed upon by the
              parties acting in good faith.  If Noven does not agree to such
              terms within forty-five (45) days of receipt of a written offer
              from RPR, then RPR may sell, lease or otherwise transfer or
              dispose of the Machine to a third party on terms no less favorable
              to RPR than those proposed to Noven.

       j.     RPR shall not move the Machine from its manufacturing facility in
              Nenagh, Ireland, to another facility without having first given
              written notice to Noven.

       k.     RPR shall not copy, duplicate or otherwise reproduce.



                                     - 9 -

<PAGE>   14

              the Machine or components thereof.




       IN WITNESS WHEREOF the parties have caused this Amendment to be executed
by their duly authorized representatives as of the date first above written.



NOVEN PHARMACEUTICALS, INC.               RHONE-POULENC RORER INC.



By  /s/ Steven Sablotsky                  By  /s/ Giulio Perillo
    -------------------------                 ----------------------------

Name:   Steven Sablotsky                  Name:   Giulio Perillo
      -----------------------                   --------------------------

Title:  President                         Title:  Vice President,
      -----------------------                    Industrial Operations

















                                      10

<PAGE>   15









                                   EXHIBIT A





                          MENOREST BULK LAMINATE ROLL
                                 SPECIFICATION
<PAGE>   16




                          MENOREST PACKAGING MACHINE
                                 SPECIFICATION




                                   EXHIBIT B