Document:

<PAGE>   1
                                                                    Exhibit 4.9

R. Boissonneault Series C No. W04
Execution Copy

     SUPPLEMENTAL AGREEMENT NO. 1 TO WARNER CHILCOTT PUBLIC LIMITED COMPANY
                               WARRANT CERTIFICATE

                  WHEREAS, ROGER BOISSONNEAULT (the "Warrant Holder") is the
holder of certain warrants (the "Warrants") of Warner Chilcott Public Limited
Company ("WC") as set forth in a certificate numbered SERIES C NO. W04 (the
"Warrant Certificate");

                  WHEREAS, on September 29, 2000 WC and Galen Holdings PLC
("Galen"), consummated a change of control transaction (the "Acquisition") by
means of a scheme of arrangement under the laws of the Republic of Ireland (the
"Scheme") whereby Galen exchanged all of the outstanding securities of WC for
ordinary shares in Galen; and

                  WHEREAS, unless otherwise defined herein, capitalized terms
used herein will have the meanings set forth in the Warrant Certificate.

                  NOW THEREFORE, the parties agree as follows:

                  1. Change in Number and Purchase Price of Warrants. Under the
Scheme, holders of warrants to purchase WC's American Depository Receipts
("ADR's"), evidencing WC's American Depository Shares ("ADS's") will, upon
exercise, receive ordinary shares of Warner Chilcott, each of which will
immediately be exchanged pursuant to the Scheme for 2.5 ordinary shares of
Galen, to be held in the form of Galen ADR's evidencing Galen ADS's. Each Galen
ADS currently represents four Galen ordinary shares. As a result, (a) each
holder of warrants to purchase WC ADR's will, upon such exercise and immediate
exchange, receive 0.625 Galen ADR's for each WC ADR, with fractions of ADR's
being rounded as appropriate, and (b) the effective purchase price for these
Galen ADR's shall be derived by dividing the Purchase Price of WC ADR's by
0.625. Therefore, the Warrant Certificate will hereinafter have the effect of
entitling the Warrant Holder to purchase 18,750 Galen ADR's at a purchase price
of $1.60.

                  2. Net Exercise. The following language shall be added to the
end of Section 2(e) of the Warrant Certificate:

                  "IN LIEU OF PAYMENT OF THE PURCHASE PRICE AS SET FORTH IN THE
                  FIRST SENTENCE OF THIS SECTION 2(e), THE WARRANT HOLDER MAY
                  EXERCISE THIS WARRANT BY DELIVERING A NOTICE OF NET EXERCISE
                  IN THE FORM OF EXHIBIT A HERETO ELECTING TO RECEIVE, WITHOUT
                  CASH PAYMENT BY THE WARRANT HOLDER OF ANY ADDITIONAL
                  CONSIDERATION, ORDINARY SHARES THAT WILL IMMEDIATELY BE
                  EXCHANGED FOR GALEN ADR'S EQUAL TO THE VALUE OF THE WARRANTS
                  (OR THE PORTION THEREOF BEING CANCELED) BY SURRENDER OF THIS
                  WARRANT CERTIFICATE TOGETHER WITH THE FORM OF NET EXERCISE
                  (ATTACHED HERETO AS EXHIBIT A) DULY EXECUTED, IN WHICH EVENT
                  THE COMPANY SHALL ISSUE TO THE WARRANT HOLDER HEREOF (UPON THE
                  IMMEDIATE EXCHANGE OF
<PAGE>   2
R. Boissonneault Series C No. W04
Execution Copy

                  ORDINARY SHARES PURSUANT TO THE SCHEME) A NUMBER GALEN ADR'S
                  COMPUTED USING THE FOLLOWING FORMULA:

                                   X= Y(A-B)
                                      ------
                                         A

                  WHERE:            X= THE NUMBER OF GALEN ADR'S TO BE ISSUED TO
                                    THE WARRANT HOLDER PURSUANT TO THIS NET
                                    EXERCISE;

                                    Y= THE NUMBER OF GALEN ADR'S IN RESPECT OF
                                    WHICH THE NET ISSUE ELECTION IS MADE;

                                    A= THE FAIR MARKET VALUE OF ONE GALEN ADR AT
                                    THE TIME THE NET ISSUE ELECTION IS MADE; AND

                                    B= THE PURCHASE PRICE (AS ADJUSTED TO THE
                                    DATE OF THE NET ISSUANCE) DIVIDED BY 0.625.

                  FOR PURPOSES OF THIS SECTION 2(e), THE FAIR MARKET VALUE OF
                  ONE GALEN ADR AS OF A PARTICULAR DATE SHALL BE DETERMINED BY
                  USING THE AVERAGE OF THE CLOSING PRICES OF THE GALEN ADR'S
                  TRADED ON THE NASDAQ NATIONAL MARKET (OR ANY SUCCESSOR UNITED
                  STATES NATIONAL MARKET THE GALEN ADR'S TRADE ON) OVER THE
                  TWENTY (20) DAY PERIOD ENDING THREE (3) DAYS PRIOR TO THE NET
                  EXERCISE ELECTION."

                  3. Deposit Agreement. The reference to "Deposit Agreement" in
Section 3 of the Warrant Certificate shall be amended so that it refers instead
to the Amended and Restated Deposit Agreement among WC, Galen and The Bank of
New York as Depositary, dated September 29, 2000.
<PAGE>   3
R. Boissonneault Series C No. W04
Execution Copy

                  IN WITNESS WHEREOF, the Company and Roger Boissonneault have
caused this Supplemental Agreement No. 1 to be signed by their duly authorized
signatories and to be dated as of September 29, 2000.

WARNER CHILCOTT PUBLIC LIMITED COMPANY

By: /s/ Paul Herendeen
   -------------------
Name:  Paul Herendeen
Title:  Executive Vice President and Chief Financial Officer

ROGER BOISSONNEAULT

By: /s/ Roger Boissonneault
   ------------------------
Print Name: Roger Boissonneault
<PAGE>   4
R. Boissonneault Series C No. W04
Execution Copy

EXHIBIT A

                             Notice of Net Exercise

                  The undersigned ______________________________________,
pursuant to the provisions of the Warrant Certificate, hereby elects to exchange
its Warrant pursuant to Section 2(e) of the Warrant Certificate.

Dated:________________

Signature:____________________________
Name of Holder (Print):
Title:
Address:<PAGE>   1
                                                                    Exhibit 4.10

P. Herendeen Series C No. W05
Execution Copy

     SUPPLEMENTAL AGREEMENT NO. 1 TO WARNER CHILCOTT PUBLIC LIMITED COMPANY
                               WARRANT CERTIFICATE

            WHEREAS, PAUL HERENDEEN (the "Warrant Holder") is the holder of
certain warrants (the "Warrants") of Warner Chilcott Public Limited Company
("WC") as set forth in a certificate numbered SERIES C NO. W05 (the "Warrant
Certificate");

            WHEREAS, on September 29, 2000 WC and Galen Holdings PLC ("Galen"),
consummated a change of control transaction (the "Acquisition") by means of a
scheme of arrangement under the laws of the Republic of Ireland (the "Scheme")
whereby Galen exchanged all of the outstanding securities of WC for ordinary
shares in Galen; and

            WHEREAS, unless otherwise defined herein, capitalized terms used
herein will have the meanings set forth in the Warrant Certificate.

            NOW THEREFORE, the parties agree as follows:

            1. Change in Number and Purchase Price of Warrants. Under the
Scheme, holders of warrants to purchase WC's American Depository Receipts
("ADR's"), evidencing WC's American Depository Shares ("ADS's") will, upon
exercise, receive ordinary shares of Warner Chilcott, each of which will
immediately be exchanged pursuant to the Scheme for 2.5 ordinary shares of
Galen, to be held in the form of Galen ADR's evidencing Galen ADS's. Each Galen
ADS currently represents four Galen ordinary shares. As a result, (a) each
holder of warrants to purchase WC ADR's will, upon such exercise and immediate
exchange, receive 0.625 Galen ADR's for each WC ADR, with fractions of ADR's
being rounded as appropriate, and (b) the effective purchase price for these
Galen ADR's shall be derived by dividing the Purchase Price of WC ADR's by
0.625. Therefore, the Warrant Certificate will hereinafter have the effect of
entitling the Warrant Holder to purchase 125,000 Galen ADR's at a purchase price
of $15.632.

            2. Net Exercise. The following language shall be added to the end of
Section 2(e) of the Warrant Certificate:

            "IN LIEU OF PAYMENT OF THE PURCHASE PRICE AS SET FORTH IN THE FIRST
            SENTENCE OF THIS SECTION 2(e), THE WARRANT HOLDER MAY EXERCISE THIS
            WARRANT BY DELIVERING A NOTICE OF NET EXERCISE IN THE FORM OF
            EXHIBIT A HERETO ELECTING TO RECEIVE, WITHOUT CASH PAYMENT BY THE
            WARRANT HOLDER OF ANY ADDITIONAL CONSIDERATION, ORDINARY SHARES THAT
            WILL IMMEDIATELY BE EXCHANGED FOR GALEN ADR'S EQUAL TO THE VALUE OF
            THE WARRANTS (OR THE PORTION THEREOF BEING CANCELED) BY SURRENDER OF
            THIS WARRANT CERTIFICATE TOGETHER WITH THE FORM OF NET EXERCISE
            (ATTACHED HERETO AS EXHIBIT A) DULY EXECUTED, IN WHICH EVENT THE
            COMPANY SHALL ISSUE TO THE WARRANT HOLDER HEREOF (UPON THE IMMEDIATE
            EXCHANGE OF
<PAGE>   2
P. Herendeen Series C No. W05
Execution Copy

            ORDINARY SHARES PURSUANT TO THE SCHEME) A NUMBER GALEN ADR'S
            COMPUTED USING THE FOLLOWING FORMULA:

                                   X= Y (A-B)
                                     ---------
                                         A

            WHERE:      X=THE NUMBER OF GALEN ADR'S TO BE ISSUED TO THE WARRANT
                        HOLDER PURSUANT TO THIS NET EXERCISE;

                        Y= THE NUMBER OF GALEN ADR'S IN RESPECT OF WHICH THE NET
                        ISSUE ELECTION IS MADE;

                        A= THE FAIR MARKET VALUE OF ONE GALEN ADR AT THE TIME
                        THE NET ISSUE ELECTION IS MADE; AND

                        B= THE PURCHASE PRICE (AS ADJUSTED TO THE DATE OF THE
                        NET ISSUANCE) DIVIDED BY 0.625.

            FOR PURPOSES OF THIS SECTION 2(e), THE FAIR MARKET VALUE OF ONE
            GALEN ADR AS OF A PARTICULAR DATE SHALL BE DETERMINED BY USING THE
            AVERAGE OF THE CLOSING PRICES OF THE GALEN ADR'S TRADED ON THE
            NASDAQ NATIONAL MARKET (OR ANY SUCCESSOR UNITED STATES NATIONAL
            MARKET THE GALEN ADR'S TRADE ON) OVER THE TWENTY (20) DAY PERIOD
            ENDING THREE (3) DAYS PRIOR TO THE NET EXERCISE ELECTION."

            3. Deposit Agreement. The reference to "Deposit Agreement" in
Section 3 of the Warrant Certificate shall be amended so that it refers instead
to the Amended and Restated Deposit Agreement among WC, Galen and The Bank of
New York as Depositary, dated September 29, 2000.
<PAGE>   3
P. Herendeen Series C No. W05
Execution Copy

            IN WITNESS WHEREOF, the Company and Paul Herendeen have caused this
Supplemental Agreement No. 1 to be signed by their duly authorized signatories
and to be dated as of September 29, 2000.

WARNER CHILCOTT PUBLIC LIMITED COMPANY

By: /s/ Roger Boissonneault
   ------------------------------
Name:  Roger Boissonneault
Title: President and Chief Operating Officer

PAUL HERENDEEN

By: /s/ Paul Herendeen
   ------------------------------
Print Name:  Paul Herendeen
<PAGE>   4
P. Herendeen Series C No. W05
Execution Copy

EXHIBIT A

                             Notice of Net Exercise

            The undersigned ______________________________________, pursuant to
the provisions of the Warrant Certificate, hereby elects to exchange its Warrant
pursuant to Section 2(e) of the Warrant Certificate.

Dated:________________

Signature:____________________________
Name of Holder (Print):
Title:
Address:

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