Document:

<PAGE>

                                                                    Exhibit 10.9
                            FIRST AMENDMENT TO THE
                               PLEDGE AGREEMENT

     THIS FIRST AMENDMENT TO THE PLEDGE AGREEMENT, dated as of June 20, 2001
(this "Amendment"), by and between SENETEK DRUG DELIVERY TECHNOLOGIES (the
       ---------
"Pledgor"), and SILVER CREEK INVESTMENTS, LTD., a British Virgin Islands company
--------
(the "Secured Party"), in its capacity as Collateral Agent under that certain
      -------------
Collateral Agency Agreement dated as of April 14, 1999 as amended by the First
Amendment dated the date hereof by and among the Secured Party, Bomoseen
Investments, Ltd., a British Virgin Islands company ("Bomoseen"), Dandelion
                                                      --------
Investments, Ltd., a British Virgin Islands company ("Dandelion"), and Elstree
Holdings, Ltd., a British Virgin Islands company ("Elstree" and together with
                                                   -------
the Secured Party, Bomoseen and Dandelion, the "Original Purchasers") and
                                                -------------------
Wallington Investments Limited, a corporation organized under the laws of the
British Virgin Islands (the "Lender").
                             ------

     WHEREAS, Senetek plc, a corporation organized under the laws of England
(the "Company") and the Original Purchasers have entered into a Securities
      -------
Purchase Agreement dated as of April 14, 1999 (the "Original Purchase
                                                    -----------------
Agreement");
---------

     WHEREAS, the Pledgor is, directly or indirectly, a wholly owned Subsidiary
of the Company and entered into a Guaranty Agreement dated as of April 14, 1999
(the "Guaranty") guaranteeing all of the Company's Liabilities (as defined in
      --------
the Guaranty);

     WHEREAS, pursuant to the terms of the Pledge Agreement dated as of April
14, 1999 (the "Pledge Agreement") by and between the Pledgor and the Secured
               ----------------
Party (on behalf of the Original Purchasers), as collateral security for the
payment and performance of the Secured Obligations (as defined therein), the
Pledgor pledged and granted to the Secured Party for the ratable benefit of the
Original Purchasers a security interest the Pledged Stock (as defined in the
Pledge Agreement) including without limitation the Pledged Subsidiaries (as
defined in the Pledge Agreement); and

     WHEREAS, the Lender has agreed to extend certain financial accommodations
to the Company in connection with the financing of the working capital needs of
the Company and Lender is willing to extend such financial accommodations to the
Company pursuant to the terms of a Revolving Credit Agreement to be entered into
by the Company and Lender (the "Credit Agreement");
                                ----------------

     WHEREAS, as a condition to Lender entering into the Credit Agreement and
extending financial accommodations to the Company thereunder, and in
consideration thereof, the Company and the Original Purchasers are (i) entering
into a First Amendment to the Purchase Agreement dated the date hereof (the

"First Amendment"; the Original Purchase Agreement, as amended by the First
----------------
Amendment is referred to herein as the "Purchase Agreement") in order to modify
                                        ------------------
certain terms of the Original Purchase Agreement to, among other things, permit
the Company to enter into the Credit Agreement and (ii) amending the certain of
the Transaction
<PAGE>

Documents, including, without limitation, the Pledge Agreement, to include the
Lender as a secured party thereunder. Capitalized terms used but not otherwise
defined herein shall have the meaning set forth in the Purchase Agreement ;

     WHEREAS, the Lender is unwilling to enter into the Credit Agreement unless
the Company and the Secured Party on behalf of the Original Purchasers and the
Lender enter into this Amendment;

     NOW, THEREFORE, in consideration of the mutual promises hereinafter set
forth and for other good and valuable consideration, the receipt and sufficiency
of which are hereby acknowledged, the parties hereto, intending to be legally
bound hereby, do hereby agree as follows:

     1.   Amendments to the Pledge Agreement. (a) The heading of the Pledge
          ----------------------------------
Agreement shall be amended and restated to read as follows:

          "THIS PLEDGE AGREEMENT, dated as of April 14, 1999, as amended by the
     First Amendment dated June 20, 2001 (this "Agreement"), is made by and
                                                ---------
     between SENETEK DRUG DELIVERY TECHNOLOGIES, INC., (the "Pledgor"), and
                                                             -------
     Silver Creek Investments, Ltd., a British Virgin Islands company (the

     "Secured Party"), in its capacity as Collateral Agent under that certain
     --------------
     Collateral Agency Agreement dated as of April 14, 1999 as amended by the
     First Amendment dated as of June 20, 2001 by and among the Secured Party,
     Bomoseen Investments, Ltd., a British Virgin Islands company ("Bomoseen"),
     Dandelion Investments, Ltd., a British Virgin Islands company
     ("Dandelion"), and Elstree Holdings, Ltd., a British Virgin Islands company
     ("Elstree" and together with the Secured Party, Bomoseen and Dandelion, the
     "Original Purchasers") and Wallington Investments Limited, a corporation
     organized under the laws of the British Virgin Islands (the "Lender"). All
     capitalized terms used but not otherwise defined herein shall have the
     respective meanings assigned thereto in the Purchase Agreement (as defined
     below) except that (i) the term "Purchasers" as used herein shall in all
     cases be deemed to include both the Original Purchasers and the Lender and
     (ii) the term "Event of Default" as used herein shall in all cases be
     deemed to include both an Event of Default (as defined in the Purchase
     Agreement) and (ii) an Event of Default (as defined in the Credit
     Agreement)."

          (b)  The first paragraph of Section 1 (Pledge of Stock; Other
                                                 ----------------------
Collateral) of the Pledge Agreement is hereby amended and restated as follows:
----------

          "As collateral security for the payment, performance, and satisfaction
     of (i) all of the "Obligations" (as defined in the Purchase Agreement) (ii)
     all of the "Obligations" (as defined under the Credit Agreement) and (iii)
     all of the Pledgor's obligations under the Guaranty, as amended by the
     First Amendment to the Guaranty dated June 20, 2001 by and among the
     Pledgor and Carme

                                       2
<PAGE>

     Cosmeceutical Sciences, Inc. in favor of the Secured Party; (i), (ii) and
     (iii) collectively, the "Secured Obligations"), the Pledgor hereby pledges
                              -------------------
     and collaterally assigns to the Secured Party, and grants to the Secured
     Party a FIRST priority lien and security interest in, the Pledged Stock and
     all of the following, subject only to Permitted Liens:"

     2.   Conditions to Effectiveness.  This Amendment shall become effective
          ---------------------------
only upon the satisfaction or waiver of all of the following conditions
precedent:

     (a)  The parties hereto shall have duly executed and delivered this
Amendment.

     (b)  The Company shall have satisfied all conditions to effectiveness under
Section 6 of the First Amendment.

     (c)  The Company shall have paid all fees and expenses required to be paid
by it pursuant to Section 5 of the First Amendment.

     3.   Representations and Warranties.  In order to induce the Secured Party
          ------------------------------
to enter into this Amendment (on behalf of the Original Purchasers and the
Lender), the Pledgor hereby represents and warrants to the Original Purchasers
and the Lender that the Pledgor has full power, right and legal authority to
execute, deliver and perform its obligations under this Amendment.  The Pledgor
has taken all corporate action necessary to authorize the execution and delivery
of, and the performance of its obligations under, this Amendment.  This
Amendment constitutes a legal, valid and binding obligation of the Pledgor
enforceable against it in accordance with its terms, subject to the effect of
any applicable bankruptcy, insolvency, reorganization or moratorium or similar
laws affecting the rights of creditors generally. The Pledgor hereby ratifies
and reaffirms the Pledge Agreement (as amended hereby) and the other related
documents and all of the Pledgor's covenants, duties and liabilities thereunder.

     4.   Amendments. This Amendment may not be amended, modified or
          ----------
supplemented except by a subsequent written agreement signed by the parties
hereto.

     5.   Counterparts. This Amendment may be executed simultaneously in any
          ------------
number of counterparts.  Each counterpart shall be deemed to be an original, and
all such counterparts shall constitute one in the same instrument.

     6.   Governing Law.  This Amendment shall be governed by the laws of the
          -------------
State of New York (without giving effect to any conflicts of law rules or
principles).

     7.   Headings.   The headings of this Amendment are included herein for
          --------
convenience of reference only and shall not constitute a part of this Amendment
for any other purpose.

     8.   Survival of the Pledge Agreement.  Each reference in the Pledge
          --------------------------------
Agreement to "this Agreement," "hereunder," "hereof," "herein" or words of like
import, and each reference to the Pledge Agreement in any related document
(other than the Pledge Agreement) shall mean and be a

                                       3
<PAGE>

reference to the Pledge Agreement as amended hereby. Except as specifically
amended by this Amendment, the Pledge Agreement shall remain in full force and
effect and is hereby ratified, confirmed and acknowledged by the Pledgor. This
Amendment shall not be deemed to (i) be a consent to any waiver or modification
of any term or condition of the Pledge Agreement or any document delivered
pursuant thereto, except in each case as expressly provided herein, or (ii)
prejudice any right or rights the Original Purchasers or the Lender may now or
in the future have in connection with the Pledge Agreement.

       [Signature page follows, remainder of page is intentionally blank]

                                       4
<PAGE>

     IN WITNESS WHEREOF, the parties have duly executed this First Amendment to
the Pledge Agreement on the day and year first written above.

                              PLEDGOR:
                              -------

                              SENETEK DRUG DELIVERY TECHNOLOGIES, INC.
                              as the Pledgor

                              By: /s/ Frank J. Massino
                                  --------------------
                              Name: Frank J. Massino
                              Title: President

                              SECURED PARTY:
                              -------------

                              SILVER CREEK INVESTMENTS, LTD.,
                              as Collateral Agent for the Original Purchasers
                              and the Lender

                              By: /s/ Robert T. Tucker
                                  --------------------
                              Name: Robert T. Tucker
                              Title: Director

            [Signature page to First Amendment to Pledge Agreement]<PAGE>

                                                                   Exhibit 10.10
                            FIRST AMENDMENT TO THE
                              GUARANTY AGREEMENT

     THIS FIRST AMENDMENT TO THE GUARANTY AGREEMENT, dated as of June 20, 2001
(this "Amendment"), by and between by each of the undersigned (each a
       ---------
"Guarantor" and collectively the "Guarantors") to and in favor of Silver Creek
 ---------                        ----------
Investments, Ltd., a British Virgin Islands company (the "Collateral Agent"), in
                                                          ----------------
its capacity as Collateral Agent under that certain Collateral Agency Agreement
dated as of April 14, 1999 as amended by the First Amendment dated the date
hereof by and among the Collateral Agent, Bomoseen Investments, Ltd., a British
Virgin Islands company ("Bomoseen"), Dandelion Investments, Ltd., a British
                         --------
Virgin Islands company ("Dandelion"), and Elstree Holdings, Ltd., a British
                         ---------
Virgin Islands company ("Elstree" and together with the Collateral Agent,
                         -------
Bomoseen and Dandelion, the "Original Purchasers") and Wallington Investments
                             -------------------
Limited, a corporation organized under the laws of the British Virgin Islands
(the "Lender"). All capitalized terms used but not otherwise defined herein
      ------
shall have the respective meanings assigned thereto in the Purchase Agreement
(as defined below);

     WHEREAS, Senetek plc, a corporation organized under the laws of England
(the "Company") and the Original Purchasers entered into a Securities Purchase
      -------
Agreement dated as of April 14, 1999 (the "Original Purchase Agreement");
                                           ---------------------------

     WHEREAS, as a condition to the Original Purchasers entering into the
Original Purchase Agreement and purchasing the Securities thereunder, each
Guarantor guaranteed to the Original Purchasers payment of all of the Company's
obligations under the Original Purchase Agreement and the other Transaction
Documents (as defined in the Original Purchase Agreement) in accordance with the
terms of the Guaranty Agreement dated as of April 14, 1999 (the "Guaranty
                                                                 --------
Agreement") made by each of the Guarantors to and in favor of the Collateral
---------
Agent (for the benefit of the Original Purchasers);

     WHEREAS, the Lender, has agreed to extend certain financial accommodations
to the Company in connection with the financing of the working capital needs of
the Company, and Lender is willing to extend such financial accommodations to
the Company pursuant to the terms of a Revolving Credit Agreement to be entered
into by the Company and Lender (the "Credit Agreement");
                                     ----------------

     WHEREAS, as a condition to the Lender entering into the Credit Agreement
and extending financial accommodations to the Company thereunder, and in
consideration thereof, the Company and the Original Purchasers are (i) entering
into a First Amendment to the Original Purchase Agreement dated the date hereof
(the "First Amendment"; the Original Agreement, as amended by the First
      ---------------
Amendment is referred to herein as the "Purchase Agreement") in order to modify
                                        ------------------
certain terms of the Original Purchase Agreement to, among other things, permit
the Company to enter into the Credit Agreement and (ii) amending certain of the
Transaction
<PAGE>

Documents, including, without limitation, the Guaranty Agreement, to include
obligations of the Company under the Credit Agreement and the other Loan
Documents (as defined therein).

     WHEREAS, the Lender is unwilling to enter into the Credit Agreement unless
the Guarantors enter into this Amendment;

     NOW, THEREFORE, in consideration of the mutual promises hereinafter set
forth and for other good and valuable consideration, the receipt and sufficiency
of which are hereby acknowledged, the parties hereto, intending to be legally
bound hereby, do hereby agree as follows:

     1.   Amendments to the Guaranty Agreement. (a) The heading of the Guaranty
          ------------------------------------
Agreement shall be amended and restated to read as follows:

          "THIS GUARANTY AGREEMENT, dated as of April 14, 1999, as amended by
     the First Amendment dated June 20, 2001 (this "Guaranty"), by and between
                                                    --------
     by each of the undersigned (each a "Guarantor" and collectively the
                                         ---------
     "Guarantors") to and in favor of Silver Creek Investments, Ltd., a British
     -----------
     Virgin Islands company (the "Collateral Agent"), in its capacity as
                                  ----------------
     Collateral Agent under that certain Collateral Agency Agreement dated as of
     April 14, 1999 as amended by the First Amendment dated the date hereof by
     and among the Collateral Agent, Bomoseen Investments, Ltd., a British
     Virgin Islands company ("Bomoseen"), Dandelion Investments, Ltd., a British
                              --------
     Virgin Islands company ("Dandelion"), and Elstree Holdings, Ltd., a British
                              ---------
     Virgin Islands company ("Elstree" and together with the Collateral Agent,
                              -------
     Bomoseen and Dandelion, the "Original Purchasers") and Wallington
                                  -------------------
     Investments Limited, a corporation organized under the laws of the British
     Virgin Islands (the "Lender").  All capitalized terms used but not
                          ------
     otherwise defined herein shall have the respective meanings assigned
     thereto in the Purchase Agreement (as amended) except that (i) the term
     "Purchasers" as used herein shall in all cases be deemed to include both
     the Original Purchasers and the Lender and (ii) the term "Event of Default"
                                                               ----------------
     as used herein shall in all cases be deemed to include both an Event of
     Default (as defined in the Purchase Agreement) and (ii) an Event of Default
     (as defined in the Credit Agreement)."

          (b) The first paragraph of Section 1 (Guaranty) of the Guaranty
                                                --------
Agreement is hereby amended and restated as follows:

          "Each Guarantor hereby jointly and severally, unconditionally,
     absolutely, continually and irrevocably guarantees to the Collateral Agent
     for the benefit of the Purchasers, the payment and performance in full of
     the Company's Liabilities (as defined below).  For all purposes of this
     Guaranty, "Company's Liabilities" means: (a) the Company's prompt payment
                ---------------------
     in full, when due or declared due and at all such times, of all Obligations
     and all other amounts pursuant to the terms of the Credit Agreement, the
     Lender Note, the Purchase Agreement, the Securities,

                                       2
<PAGE>

     and all other Transaction Documents executed in connection with the
     Purchase Agreement or the Credit Agreement, now or at any time or times
     hereafter owing, arising, due or payable from the Company, including
     without limitation principal, interest, premium or fee (including, but not
     limited to, attorneys' fees and expenses); and (b) the Company's prompt,
     full and faithful performance, observance and discharge of each and every
     agreement, undertaking, covenant and provision to be performed, observed or
     discharged by the Company under the Credit Agreement, the Lender Note, the
     Purchase Agreement and all other Transaction Documents executed in
     connection therewith. The Guarantors' obligations to the Collateral Agent
     for the benefit of the Purchasers under this Guaranty are hereinafter
     collectively referred to as the "Guarantors' Obligations"; provided,
                                      -----------------------   --------
     however, that the liability of each Guarantor individually with respect to
     -------
     the Guarantors' Obligations shall be limited to an aggregate amount equal
     to the largest amount that would not render its obligations hereunder
     subject to avoidance under Section 548 of the United States Bankruptcy Code
     or any comparable provisions of any applicable state law. Each Guarantor
     agrees that it is jointly and severally, directly and primarily liable for
     the Company's Liabilities, and that the guaranties made hereunder are
     guaranties of payment."

     2.   Conditions to Effectiveness. This Amendment shall become effective
          ---------------------------
only upon the satisfaction or waiver of all of the following conditions
precedent:

     (a)  The parties hereto shall have duly executed and delivered this
Amendment.

     (b)  The Company shall have satisfied all conditions to effectiveness under
Section 6 of the First Amendment.

     (c)  The Company shall have paid all fees and expenses required to be paid
by it pursuant to Section 5 of the First Amendment.

     3.   Representations and Warranties. In order to induce the Collateral
          ------------------------------
Agent to enter into this Amendment (on behalf of the Original Purchasers and the
Lender), the Guarantors each hereby represents and warrants to the Original
Purchasers and the Lender that each of the Guarantors has full power, right and
legal authority to execute, deliver and perform its obligations under this
Amendment. Each Guarantor has taken all corporate action necessary to authorize
the execution and delivery of, and the performance of its obligations under,
this Amendment. This Amendment constitutes a legal, valid and binding obligation
of the Guarantor enforceable against it in accordance with its terms, subject to
the effect of any applicable bankruptcy, insolvency, reorganization or
moratorium or similar laws affecting the rights of creditors generally. The
Guarantor hereby ratifies and reaffirms the Guaranty (as amended hereby) and
each of the other related documents and all of the Company's covenants, duties
and liabilities thereunder.

     4.   Amendments. This Amendment may not be amended, modified or
          ----------
supplemented except by a subsequent written agreement signed by the parties
hereto.

                                       3
<PAGE>

     5.   Counterparts. This Amendment may be executed simultaneously in any
          ------------
number of counterparts. Each counterpart shall be deemed to be an original, and
all such counterparts shall constitute one in the same instrument.

     6.   Governing Law. This Amendment shall be governed by the laws of the
          -------------
State of New York (without giving effect to any conflicts of law rules or
principles).

     7.   Headings. The headings of this Amendment are included herein for
          --------
convenience of reference only and shall not constitute a part of this Amendment
for any other purpose.

     8.   Survival of the Guaranty Agreement. Each reference in the Guaranty
          ----------------------------------
Agreement to "this Agreement," "hereunder," "hereof," "herein" or words of like
import, and each reference to the Guaranty Agreement in any related document
(other than the Guaranty Agreement) shall mean and be a reference to the
Guaranty Agreement as amended hereby. Except as specifically amended by this
Amendment, the Guaranty Agreement shall remain in full force and effect and is
hereby ratified, confirmed and acknowledged by each of the Guarantors. This
Amendment shall not be deemed to (i) be a consent to any waiver or modification
of any term or condition of the Guaranty Agreement or any document delivered
pursuant thereto, except in each case as expressly provided herein, or (ii)
prejudice any right or rights the Original Purchasers or the Lender may now or
in the future have in connection with the Guaranty Agreement.

      [Signature page follows, remainder of page is intentionally blank]

                                       4
<PAGE>

     IN WITNESS WHEREOF, the parties have duly executed this First Amendment to
the Guaranty on the day and year first written above.

                         GUARANTORS:
                         ----------

                              SENETEK DRUG DELIVERY TECHNOLOGIES, INC.

                              By: /s/ Frank J. Massino
                                  --------------------
                              Name: Frank J. Massino
                              Title: President

                              CARME' COSMECEUTICAL
                              SCIENCES, INC.

                              By: /s/ Frank J. Massino
                                  --------------------
                              Name: Frank J. Massino
                              Title: President

                         SECURED PARTY:
                         -------------

                              SILVER CREEK INVESTMENTS, LTD.,
                              as Collateral Agent for the Original Purchasers
                              and the Lender

                              By: /s/ Robert T. Tucker
                                  --------------------
                              Name: Robert T. Tucker
                              Title: Director

            [Signature page to the First Amendment to the Guaranty]

                                       5

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