<PAGE>

                                                                    Exhibit 10.2

THIS NOTE HAS NOT BEEN REGISTERED UNDER THE UNITED STATES SECURITIES ACT OF
1933, AS AMENDED. THIS NOTE MAY NOT BE SOLD OR TRANSFERRED IN THE ABSENCE OF
SUCH REGISTRATION OR AN EXEMPTION THEREFROM UNDER SUCH ACT. THIS NOTE IS SUBJECT
IN ALL RESPECTS TO THE PROVISIONS OF THE SECURITIES PURCHASE AGREEMENT DESCRIBED
BELOW.


                                   SENETEK PLC
                              AMENDED AND RESTATED
                     SENIOR SECURED NOTE DUE APRIL 14, 2004

No. [_____]                                                       April 14, 1999
$[____________]

          FOR VALUE RECEIVED, the undersigned, SENETEK PLC, a corporation
organized and existing under the laws of England (herein called the "Company"),
hereby promises to pay to [________________________________] ("[___________]")
at such bank or other financial institution and account therein as shall be
designated by the Holder, the principal sum of
[______________________________________________________] ($[___________]) with
the aggregate principal amount due and payable on April 14, 2004, with interest
(computed on the basis of a 360-day year of twelve 30-day months and compounded
daily) on the unpaid balance thereof from the date hereof at the rate of 8.0%
per annum, payable semi-annually on the last day of June and December in each
year until the principal hereof shall have become due and payable, and on the
maturity date hereof.  Interest not paid on the due date for payment thereof
shall be capitalized and added to the principal amount outstanding under this
Note.  The Company will pay interest on any overdue payment (including any
overdue prepayment) of principal and any overdue payment of interest, payable
semi-annually as aforesaid (or, at the option of the registered holder hereof,
on aforesaid or, at the option of the registered holder hereof, on demand) at a
rate equal to 12% per annum.

     1.   Definitions. Capitalized terms used herein and not otherwise defined
          -----------
shall have the meaning ascribed to them in the Securities Purchase Agreement,
dated as of April 14, 1999, as amended (the "Purchase Agreement"), between the
Company and Silver Creek Investments, Ltd., Dandelion Investments, Ltd.,
Bomoseen Investments, Ltd., and Elstree Holdings, Ltd. (the "Investors").

     2.   Payments.
          --------

     (a)  Payments of principal are to be made in immediately available funds in
     the manner provided for in the Purchase Agreement, in lawful money of the
     United States of America.

     (b)  Payments of interest are to be made (i) in immediately available funds
     in the manner provided for in the Purchase Agreement, in lawful money of
     the United States of
<PAGE>

     America or at the Company's option (ii) by the issuance on the applicable
     interest payment date of such number of Ordinary Shares, which Ordinary
     Shares shall be registered under the Securities Act of 1933, as amended,
     pursuant to an effective registration statement, which when each Ordinary
     Share is multiplied by its Fair Market Value the product shall equal the
     amount of interest due under this Note on the applicable interest payment
     date. For purposes of the preceding sentence, "Fair Market Value" shall
     mean the average of the daily closing sales price for Ordinary Shares for
     the five (5) consecutive trading days commencing eight (8) trading days
     prior to the date interest is to be paid in accordance with this Section
     2(b), as reported in The Wall Street Journal, or if not reported therein,
     as reported in another newspaper of national circulation chosen by the
     Board of Directors or as reported by the National Association of Securities
     Dealers, Inc. Automated Quotations System, or if the Ordinary Shares are
     not on the National Market List, the average of the closing reported bid
     and asked prices on such day in the over-the counter market, as furnished
     by the National Quotation Bureau, Inc., or, if such firm at the time is not
     engaged in the business of reporting such prices, as furnished by any
     similar firm then engaged in such business and selected by the Company or,
     if there is no such firm, as furnished by any member of the National
     Association of Securities Dealers, Inc., selected by the Company.


     3.   Issuance. This Note is one of a series of Senior Secured Notes (herein
          --------
called the "Notes") issued pursuant to the Purchase Agreement.  The obligations
of the Company evidenced by this Note are secured on a parri passu basis
pursuant to the Security Agreement, the Pledge Agreement, the Guaranty and the
Patent and Trademark Security Agreement; provided, that any liability in
connection with any issue or proposed issue of Ordinary Shares by the Company in
satisfaction of interest payments pursuant to this Note shall not be subject to
such security interest.  The holder of this Note is entitled to the benefits of
the Purchase Agreement, the Security Agreement, the Pledge Agreement, the
Guaranty, the U.K. Security Agreement and the Patent and Trademark Security
Agreement and is bound by their provisions.

     4.   Usury. Notwithstanding any provision to the contrary contained in this
          -----
Note or any of the other Transaction Documents, it is expressly provided that in
no case or event shall the aggregate of (i) all interest on the unpaid balance
of the Notes, accrued or paid from the date hereof and (ii) any other amounts
accrued or paid pursuant to the Notes or any of the other Transaction Documents,
which under applicable laws are or may be deemed to constitute interest upon the
indebtedness evidenced by the Notes from the date hereof, ever exceed the
maximum nonusurious rate of interest permitted for that day under the applicable
law (the "Ceiling Rate").  By acceptance of this Note, the Company and the
holder of this Note agree that it is their common and overriding intent to
contract in strict compliance with applicable federal and New York usury laws
(and the usury laws of any other jurisdiction whose usury laws are deemed to
apply to the Notes or any of the other Transaction Documents despite the
intention and desire of the parties to apply the usury laws of the State of New
York, including, without limitation, the laws of the State of California).  In
furtherance thereof, none of the terms of the Notes or any of the other
Transaction Documents shall ever be construed to create a contract to pay, as
consideration for the use, forbearance or detention of money, interest at a rate
in excess of the Ceiling Rate.  The Company or other parties now or hereafter
becoming liable for payment of the indebtedness evidenced by the Notes shall
never be liable for interest in excess of the Ceiling
<PAGE>

Rate. If, for any reason whatever, the interest paid or received on the Notes
during their full term produces a rate which exceeds the Ceiling Rate, the
holders of the Notes shall credit against the principal of the Notes (or, if
such indebtedness shall have been paid in full, shall refund to the payor of
such interest) such portion of said interest as shall be necessary to cause the
interest paid on the Notes to produce a rate equal to the Ceiling Rate. All sums
paid or agreed to be paid to the holders of the Notes for the use, forbearance
or detention of the indebtedness evidenced hereby shall, to the extent permitted
by applicable law, be amortized, prorated, allocated and spread in equal parts
throughout the full term of the Notes, so that the interest rate is uniform
throughout the full term of the Notes. The provisions of this Section 4 shall
control all agreements, whether now or hereafter existing and whether written or
oral, between the Company and the holder of this Note.

     5.   Loss, Destruction of Notes. Upon receipt of evidence satisfactory to
          --------------------------
the Company of the loss, theft, mutilation or destruction of this Note, and in
the case of any such loss, theft or destruction upon delivery of a bond of
indemnity in such form and amount as shall be reasonably satisfactory to the
Company (the original Noteholder's indemnity being satisfactory indemnity in the
event of loss, theft or destruction of any Notes owned by such holder), or in
the event of such mutilation upon surrender and cancellation of this Note, the
Company will make and deliver a new Note, of like tenor, as provided for in such
lost, stolen, destroyed or mutilated Note, in lieu of such lost, stolen,
destroyed or mutilated Note.  Any Notes issued under the provisions of this
Section 5 in lieu of any Note alleged to be lost, destroyed or stolen, or of any
mutilated Note, shall constitute an original contractual obligation on the part
of the Company.

     6.   Registered Note. This Note is a registered Note and, to the extent
          ---------------
provided in and subject to the terms of the Purchase Agreement, upon surrender
of this Note for registration of transfer, duly endorsed, or accompanied by a
written instrument of transfer duly executed, by the registered holder hereof or
such holder's attorney duly authorized in writing, a new Note for a like
principal amount will be issued to, and registered in the name of, the
transferee.  Prior to due presentment for registration of transfer, the Company
shall treat the person in whose name this Note is registered as the owner hereof
for the purpose of receiving payment and for all other purposes, and the Company
shall not be affected by any notice to the contrary.

     7.   Default. In case an Event of Default, as defined in the Agreement,
          -------
shall occur, the principal of this Note may be declared or otherwise become due
and payable in the manner and with the effect provided in the Purchase
Agreement.

     8.   Amendments. Neither this Note nor any term hereof may be changed,
          ----------
waived, discharged or terminated orally or in writing, provided that any term of
this Note may be amended or the observance of such term may be waived (either
generally or in a particular instance and either retroactively or prospectively)
with, but only with, the written consent of the Company and the holders of the
Notes that represent in the aggregate at least a majority of the total principal
amount of the Notes then outstanding (whether or not the Holder of this Note
consents).

     9.   Severability. If in any jurisdiction, any provision of this Agreement
          ------------
or its
<PAGE>

application to any party or circumstance is restricted, prohibited or
unenforceable, such provision shall, as to such jurisdiction, be ineffective
only to the extent of such restriction, prohibition or unenforceability without
invalidating the remaining provisions hereof and without affecting the validity
or enforceability of such provision in any other jurisdiction or its application
to other parties or circumstances.

     10.  Notice. Any notice or document required or permitted by this
          ------
Agreement to be given to a party hereto shall be in writing and is sufficiently
given if delivered personally, or if sent by prepaid certified mail, return
receipt requested, to such party addressed as follows:

     (i)  If to the Company:  Senetek Plc
                              620 Airport Road
                              Napa, California 94558
                              Attention: President

          copy to:            Latham & Watkins
                              505 Montgomery Street, Suite 1900
                              San Francisco, California 94111
                              Attention: Jeff Pero, Esq.

     (v)  If to the Holder:   c/o Robert T. Tucker, Esq.
                              61 Purchase Street
                              Suite 2R
                              Rye, New York 10580

Notice so mailed shall be deemed to have been given upon receipt if delivered
personally or on the fifth business day next following the date of the returned
receipt.  Any notice delivered to the party to whom it is addressed shall be
deemed to have been given and received on the day it is delivered.  Any party
may from time to time notify the others in the manner provided herein of any
change of address which thereafter, until changed by like notice, shall be the
address of such party for all purposes hereof.

     11.  Governing Law; Choice Of Forum; Certain Consents; Waiver Of Jury
          ----------------------------------------------------------------
Trial, Counterclaim, Setoff. This Agreement has been executed and delivered at
---------------------------
and shall be deemed to have been made in New York, New York.  This Agreement and
the rights granted herein shall be governed by and construed and enforced under
the laws of the State of New York (without giving effect to any conflicts of law
rules or principles).  Any judicial proceeding brought by or against the Company
with respect to this Agreement or any related Agreement shall be brought in any
court of competent jurisdiction in the United States of America in the Southern
District of New York, and, by execution and delivery of this Agreement, the
Company accepts the exclusive jurisdiction of the aforesaid courts and
irrevocably agrees to be bound by any judgment rendered thereby in connection
with this Agreement.  If any action is commenced in any other jurisdiction the
parties hereto hereby consent to the removal of such action to the United States
District Court for the Southern District of New York.  The Company hereby
irrevocably designates Latham & Watkins-New York as the designee, appointee and
agent of the Company to receive, for and on behalf of the Company, service of
process in the above described
<PAGE>

jurisdiction in any legal action or proceeding with respect to this Agreement or
any other Transaction Document or the rights and obligations hereunder or
thereunder and such service shall be deemed completed upon delivery thereof to
such agent. It is understood that a copy of such process served on such agent
will be promptly forwarded by mail to the Company at its address set forth in
Section 10 hereof, but the failure of the Company to receive such copy shall not
affect in any way the service of such process. The Company further irrevocably
consents to the service of process out of any of the aforementioned courts in
any such action or proceeding by the mailing of copies thereof by registered or
certified mail, postage prepaid, to the Company at its address, such service to
become effective 10 days after such mailing. Nothing herein shall affect the
right of the Purchaser to serve process in any other manner permitted by law or
commence legal proceedings in or otherwise proceed against the Company in any
other jurisdiction. The Company waives in each such action and other legal
proceeding the right to trial by jury and the right to assert any counterclaim
or setoff.

     12.  Replacement Note. This Note amends and restates, is in substitution
          ----------------
of and supersedes, the Senior Secured Note Due April 14, 2002, dated as of April
14, 1999, which was issued pursuant to the Purchase Agreement.

                        [signature appears on next page]
<PAGE>

     IN WITNESS WHEREOF, the Corporation has caused this Note to be executed and
delivered as of the day and year and at the place first above written.


                              SENETEK PLC


                              By:_______________________________
                                 Name:
                                 Title: