<PAGE>

                                                                   Exhibit 10.33

NEITHER THIS WARRANT NOR ANY OF THE SECURITIES ISSUABLE HEREUNDER NOR ANY
AMERICAN DEPOSITARY SHARES REPRESENTING THE SECURITIES ISSUABLE HEREUNDER HAVE
BEEN REGISTERED UNDER THE SECURITIES ACT OF 1933, AS AMENDED (THE "SECURITIES
ACT"), AND NONE OF THEM MAY BE OFFERED, SOLD, TRANSFERRED, ASSIGNED NOR
HYPOTHECATED IN THE ABSENCE OF A REGISTRATION STATEMENT IN EFFECT WITH RESPECT
TO SUCH SECURITIES UNDER THE SECURITIES ACT AND APPLICABLE STATE SECURITIES LAW
OR AN OPINION OF COUNSEL REASONABLY SATISFACTORY TO THE COMPANY THAT SUCH
REGISTRATION IS NOT REQUIRED.


                                AMENDED WARRANT
                 to Purchase [___________] Ordinary Shares of
                                  SENETEK PLC

                            Issued:  April 14, 1999
Series B                    Expires: April 14, 2009
NO. [__]

     This Warrant amends and restates in its entirety the Warrant issued to
Holder (as defined below) to purchase the same number of Ordinary Shares (as
defined below) set forth above issued on April 14, 1999.  This Warrant certifies
that [___________________] or its registered and permitted successors or assigns
("[______]" or the "Holder"), is entitled to, subject to the terms set forth
below, purchase from SENETEK PLC, a corporation organized under the laws of
England (the "Company"), from time and time up to [___________________]
([________]) duly authorized, validly issued, fully paid and nonassessable
Ordinary Shares (as such number may be adjusted pursuant to Section 4(a) and
Section 5 herein) which may be exchanged for American Depositary Shares ("ADS")
represented by American Depositary Receipts ("ADR") (the Ordinary Shares of the
Company, including any shares into which it may be changed, reclassified, or
converted, are herein referred to as the "Ordinary Shares").  This Warrant is
one of the Series A Warrants (the "Warrants") issued pursuant to Section 2 of
the Securities Purchase Agreement (the "Securities Purchase Agreement"), dated
as of April 14, 1999, by and between the Company, Silver Creek Investments,
Ltd., Bomoseen Investments, Ltd., Dandelion Investments, Ltd. and Elstree
Holdings, Ltd.  The Ordinary Shares issuable upon exercise of the Warrants (and
any other or additional shares, securities or property that may hereafter be
issuable upon exercise of the Warrants) are sometimes referred to herein as the
"Warrant Shares," and the maximum number of shares so issuable under this
Warrant is sometimes  referred to as the "Aggregate Number" (as such number may
be increased or decreased as more fully set forth herein).
<PAGE>

     This Warrant is subject to the following provisions, terms and conditions:

Section 1.  Exercise of Warrant.
            -------------------

     (a)  To exercise this Warrant in whole or in part, the Holder shall deliver
to the Company at its principal office located at 620 Airpark Road, Napa,
California 94558, (A) a written notice, in substantially the form of the
Exercise Notice attached hereto as Exhibit 1, of the Holder's election to
                                   ---------
exercise this Warrant, which notice shall specify the number of Warrant Shares
to be purchased, (B) (i) cash, money order, certified check or wire transfer of
immediately available funds payable to the Company, in an amount equal to the
Exercise Price (as defined below) multiplied by the number of Warrant Shares
                                  ----------
being purchased, or (ii) a copy of an instrument representing outstanding
principal amount of indebtedness of the Company owed to the Holder, accompanied
by a notice stating the Holder's intent to exercise this Warrant, in whole or in
part, by the reduction of the amount of indebtedness stated in the notice and
represented by the instrument in an amount equal to the Exercise Price
multiplied by the number of Warrant Shares being purchased, and (C) this
Warrant.  The Company shall as promptly as practicable, and in any event within
ten (10) Business Days thereafter, execute and deliver or cause to be executed
and delivered, in accordance with such notice, a certificate or certificates
representing the aggregate number of Warrant Shares specified in such notice.
The stock certificate or certificates so delivered shall be in such
denominations as may be specified in such notice and shall be issued in the name
of the Holder or such other name as shall be designated in such notice.  Such
certificate or certificates shall be deemed to have been issued and the Holder
or any other person so designated to be named therein shall be deemed for all
purposes to have become a Holder of record of such shares immediately prior to
the close of business on the date such notice is received by the Company as
aforesaid.  If this Warrant shall have been exercised only in part, the Company
shall, at the time of delivery of said stock certificate or certificates,
deliver to the Holder a new Warrant evidencing the rights of the Holder to
purchase the remaining Ordinary Shares called for by this Warrant, which new
Warrant shall in all other respects be identical to this Warrant, or, at the
request of the Holder, appropriate notation may be made on this Warrant and the
same returned to the Holder.  The Company shall pay all expenses, taxes (except
United Kingdom stamp tax duties) and other charges payable in connection with
the preparation, issue and delivery of such certificates and new Warrants,
except that in case such stock certificates or new Warrants shall be registered
in a name or names other than the name of the Holder, funds sufficient to pay
all stock transfer taxes that are payable upon the issuance of such stock
certificates or new Warrants shall be paid by the Holder at the time of
delivering the notice of exercise mentioned above.

     (b)  All Ordinary Shares issued upon the exercise of this Warrant shall be
validly issued, fully paid and nonassessable and free from all preemptive rights
of any stockholder, and from all taxes, liens and charges with respect to the
issue thereof (other than United Kingdom stamp duty taxes and any other transfer
taxes and, if any Ordinary Shares are then listed on a national securities
exchange (as defined in the Securities Exchange Act of 1934, as amended) or
quoted on an automated quotation system, shall be listed or quoted thereon, as
the case may be, to the extent permissible under the rules of such exchange and
not prohibited by law, it being understood that such listing does not bear upon
the transferability of such shares under the Act

                                       2
<PAGE>

and the other provisions of this Agreement.

     (c)  The Company shall not be required upon any exercise of this Warrant to
issue a certificate representing any fraction of an Ordinary Share, but, in lieu
thereof, shall pay to the Holder cash in an amount equal to a corresponding
fraction (calculated to the nearest 1/100 of a share) of the Fair Market Value
(as defined below) of one Ordinary Share on the Business Day immediately prior
to the date of receipt by the Company of notice of exercise of this Warrant.

     (d)  The Company shall pay all depositary fees payable to the depositary in
respect of the issuance of American Depositary Shares or American Depositary
Receipts in respect of Ordinary Shares issued upon exercise of the Warrant.

Section 2.  Terms and Conditions of Warrants.
            --------------------------------

     (a)  Exercise.  Warrants to purchase 991,379 (as adjusted in accordance
with the principles of Section 4(a) or Section 5 hereof) Ordinary Shares shall
be exercisable at any time, and from time to time, on or after the date hereof
(the "Exercise Date"), and shall expire at 11:59 p.m., New York City time, on
April 14, 2009 (the "Expiration Date").

     (b)  Purchase Price.  Subject to the provisions of Sections 5 and 6 hereof,
the purchase price per Ordinary Share shall be $1.50 (the "Exercise Price").

     (c)  Restrictions on Transfer and Registration Rights.

          (i)   Each certificate for any Warrant Shares issued upon the exercise
of this Warrant, and each certificate issued upon the transfer of any such
Warrant Shares and each American Depositary Receipt representing American
Depositary Shares (except as otherwise permitted by this Section 2(c)) shall be
stamped or otherwise imprinted with a legend in substantially the following
form:

     THE SECURITIES REPRESENTED BY THIS CERTIFICATE HAVE NOT BEEN REGISTERED
     UNDER THE SECURITIES ACT OF 1933, AS AMENDED (THE "ACT"), AND MAY NOT BE
     OFFERED, SOLD, TRANSFERRED, ASSIGNED OR HYPOTHECATED IN THE ABSENCE OF A
     REGISTRATION STATEMENT IN EFFECT WITH RESPECT TO SUCH SECURITIES UNDER THE
     ACT AND REGISTRATION OR QUALIFICATION UNDER APPLICABLE STATE SECURITIES LAW
     OR AN OPINION OF COUNSEL REASONABLY SATISFACTORY TO THE COMPANY THAT SUCH
     REGISTRATION AND QUALIFICATION IS NOT REQUIRED.

          (ii)  The restrictions imposed by this Section 2(c) upon the
transferability of Warrants and Warrant Shares and related American Depositary
Shares shall cease and terminate as to any particular Warrants, Warrant Shares
or related American Depositary Shares, (a) when such securities shall have been
effectively registered under the Securities Act and disposed of in accordance
with the registration statement covering such securities, or (b) when in the
reasonable

                                       3
<PAGE>

opinion of counsel for the Company such restrictions are no longer required in
order to comply with the Securities Act. Whenever such restrictions shall
terminate as to any Warrants, Warrant Shares or related American Depositary
Shares, the Holder thereof shall be entitled to receive from the Company,
without expense, new certificates of like tenor not bearing the restrictive
legend set forth in Section 2(c)(i).

     (d)  Investment Representation. The Holder, by acceptance hereof,
represents as of the date hereof, as follows:

          (i)   The Warrant Shares issuable upon exercise of the Warrants
(collectively, the "Acquired Securities") will be acquired for investment for
the Holder's own account, not as a nominee or agent, and not with a view to the
resale or distribution of any part of the Acquired Securities in contravention
of applicable law, and that the Holder has no present intention of selling,
granting any participation in, or otherwise distributing the same.  The Holder
does not have any contract, undertaking, agreement or arrangement with any
person to sell, transfer or grant participations to such person or to any third
person in or with respect to any of the Acquired Securities.

          (ii)  The Holder is and upon the acquisition of Acquired Securities
upon exercise of the Warrants will be an "accredited investor" within the
meaning of Rule 501 of Regulation D of the Rules and Regulations of the
Securities and Exchange Commission under the Securities Act. The Holder has not
been organized for the purposes of acquiring the Acquired Securities.

          (iii) The Holder understands that the Acquired Securities it may
acquire as contemplated by this Warrant are "restricted securities" within the
meaning of Rule 144 under the Securities Act ("Rule 144") inasmuch as they will
be acquired from the Company in a transaction not involving a public offering
and that under the federal securities laws and applicable regulations such
Acquired Securities may be resold without registration under the Securities Act
only in certain limited circumstances.  In this connection, the Holder
represents that it is familiar with Rule 144 and understands the resale
limitations imposed thereby and by the Securities Act.  The Holder acknowledges
that its investment in the Acquired Securities may be an illiquid investment
requiring the Holder to bear the economic risk of the investment for an
indefinite period; and

          (iv)  Without in any way limiting the representations set forth in
this Section 2(d), the Holder agrees not to make any disposition of all or any
portion of the Acquired Securities unless and until the transferee has agreed in
writing for the benefit of the Company to be bound by the terms of this Warrant
(provided that such Holder is making such disposition in a transaction other
than pursuant to Rule 144 or under an effective registration statement under the
Securities Act and in accordance with any applicable state securities laws), and
(A) the Holder shall have notified the Company of the proposed disposition, and
(B) if requested by the Company, the Holder shall have furnished the Company
with an opinion of counsel, in form and substance reasonably satisfactory to the
Company, rendered by a law firm experienced in matters involving the sale of
securities under federal and state securities laws, that such disposition will

                                       4
<PAGE>

not require registration of the Acquired Securities under the Securities Act or
registration or qualification under any state securities or "blue sky" law.

     In the event certificates for Ordinary Shares are delivered upon the
exercise of this Warrant, the Company may cause a legend or legends to be placed
on such certificates to make appropriate reference to such foregoing
representations and to restrict transfer in the absence of compliance with
applicable federal or state securities laws.

Section 3.  Transfer, Division and Combination.  The Company agrees to maintain
            ----------------------------------
at its offices in Napa, California, books for the registration and transfer of
this Warrant and, subject to the provisions of Section 2 hereof, this Warrant
and all rights hereunder are transferable, in whole or in part, on such books at
such office, upon surrender of this Warrant at such office, together with a
written assignment of this Warrant duly executed by the Holder or his agent or
attorney and funds sufficient to pay any stock transfer taxes payable upon the
making of such transfer.  Upon such surrender and payment, the Company shall
execute and deliver a new Warrant or Warrants in the name of the assignee or
assignees and in the denominations specified in such instrument of assignment,
and this Warrant shall promptly be canceled.  Notwithstanding the foregoing, a
Warrant may be exercised by a new Holder for the purchase of Ordinary Shares
without having a new Warrant issued if Holder shall otherwise have complied with
the foregoing provisions of this Section 3 and the applicable provisions of
Section 2 hereof.  All of the provisions of this Section 3 are subject to the
provisions of Sections 2 above.  This Warrant may be divided or combined with
other Warrants upon surrender hereof and of any Warrant or Warrants with which
this Warrant is to be combined, together with a written notice specifying the
names and denominations in which the new Warrant or Warrants are to be issued,
signed by the holders thereof or their respective duly authorized agents or
attorneys.  The Company shall execute and deliver a new Warrant or Warrants
exchangeable for the Warrant or Warrants to be divided or combined in accordance
with such notice.

Section 4.  Successor; Taxes.
            ----------------

     (a)  Successor Company.  The obligations of the Company under this Warrant
shall be binding upon any successor company or organization resulting from the
merger, consolidation or other reorganization of the Company, or upon any
successor company or organization succeeding to substantially all of the assets
and business of the Company. The Company agrees that it will make appropriate
provision for the preservation of Holder's rights under this Warrant in any
agreement or plan which it may enter into or adopt to effect any such merger,
consolidation, reorganization or transfer of assets.

     (b)  Taxes on Conversion.  The issuance of certificates for Warrant Shares
upon the exercise of this Warrant shall be made without charge to the Holder
exercising this Warrant for any issue or stamp tax in respect of the issuance of
such certificates, and such certificates shall be issued in the respective names
of, or in such names as may be directed by, the holder; provided, however, that
                                                        --------  -------
the Company shall not be required to pay any tax that may be payable in respect
of any transfer involved in the issuance and delivery of any such certificate in
a name other than that of the Holder, and the Company shall not be required to
issue or deliver such certificates

                                       5
<PAGE>

unless or until the person or persons requesting the issuance thereof shall have
paid to the Company the amount of such tax or shall have established to the
satisfaction of the Company that such tax has been paid.

     (c)  Withholding Taxes.

          (i)   Except to the extent otherwise required by law, the Company will
not withhold United States or United Kingdom withholding taxes from payments to
be made to holders of Warrants if such holders (a) are corporations organized
under the laws of a jurisdiction outside the United States or United Kingdom or
are otherwise persons not resident in the United States or United Kingdom for
U.S. federal income tax purposes or United Kingdom tax purposes, and (b) provide
the Company, upon the Company's reasonable request, with one or more of Internal
Revenue Service Form W-8, Form 4224 or other applicable form, certificate or
document prescribed by the Internal Revenue Service of the United States or
Inland Revenue of the United Kingdom certifying as to such holders' entitlement
to an exemption from any such withholding requirements.

          (ii)  Except to the extent otherwise required by law, the Company will
not withhold United States or United Kingdom withholding taxes from payments to
be made to holders of Warrants in excess of an applicable treaty rate if such
holders (a) are corporations organized under the laws of a jurisdiction outside
the United States or United Kingdom or are otherwise persons not resident in the
United States or United Kingdom for U.S. federal income tax purposes or United
Kingdom tax purposes, and (b) provide the Company upon the Company's reasonable
request, with one or more of certification of their residence address, Internal
Revenue Service Form 1001 or other applicable form, certificates or documents
certifying as to such holders' entitlement to a reduced rate of withholding
under any such withholding requirements.

          (iii) Except to the extent otherwise required by law, neither Section
4(c)(1) nor Section 4(c)(ii) hereof shall require the Company to apply an
exemption or reduced rate of withholding during any period when it shall have
received notice or has knowledge that (a) the residence or other information
previously provided on any applicable form, certificate or document is incorrect
and no corrected form, certificate or document as applicable has been provided
to the Company, or (b) of any other information which would render such
exemption or reduced rate inapplicable.

          (iv)  Notwithstanding the preceding Sections 4(c)(i) and 4(c)(ii), if
the Company is required by law to withhold from amounts otherwise payable to a
holder of Warrants, whether by reason of a change in law or applicable treaty,
or because the applicable treaty withholding rate is greater than zero or by
reason of the failure of a holder of Warrants to provide a valid certification
or form, the Company shall withhold the amounts required to be withheld.
Amounts so withheld with respect to a holder in accordance with this Section 4
shall be treated as distributed to such holder for all purposes of this Warrant.

                                       6
<PAGE>

Section 5.  Adjustments to Aggregate Number. The Aggregate Number shall be
            -------------------------------
subject to adjustment from time to time as follows and thereafter as adjusted
shall be deemed to be the Aggregate Number hereunder.

     (a)  Reorganization, Reclassification, Consolidation, Merger or Sale.  If
any capital reorganization or reclassification of the Company, or any
consolidation or merger of the Company with another person, or the sale,
transfer or lease of all or substantially all of its assets to another person
shall be effected in such a way that holders of Ordinary Shares shall be
entitled to receive stock, securities or assets with respect to or in exchange
for their shares, then provision shall be made, in accordance with this Section
5, whereby the Holder hereof shall thereafter have the right to purchase and
receive, upon the basis and upon the terms and conditions specified in this
Warrant and in addition to or in exchange for, as applicable, the Warrant Shares
subject to this Warrant immediately theretofore purchasable and receivable upon
the exercise of the rights represented hereby, such securities or assets as
would have been issued or payable with respect to or in exchange for the
Aggregate Number immediately theretofore purchasable and receivable upon the
exercise of the rights represented hereby if exercise of the Warrant has
occurred immediately prior to such reorganization, reclassification,
consolidation, merger or sale.  The Company will not effect any such
consolidation, merger, sale, transfer or lease unless prior to the consummation
thereof the successor entity (if other than the Company) resulting from such
consolidation or merger or the entity purchasing or leasing such assets shall
assume by written instrument (1) the obligation to deliver to such Holder such
securities or assets as, in accordance with the foregoing provisions, such
Holder may be entitled to purchase, and (2) all other obligations of the Company
under this Warrant.  The provisions of this Section 5(a) shall similarly apply
to successive consolidations, mergers, exchanges, sales, transfers or leases.

     (b)  Distributions.  If at any time or from time to time the Company shall
take a record of the holders of its Ordinary Shares for the purpose of entitling
them to receive or pays any dividend or other distribution to holders of
Ordinary Shares (collectively, a "Distribution") of:

          (i)   cash,

          (ii)  any evidences of its indebtedness (other than securities
     convertible into Ordinary Shares ("Convertible Securities")), any shares of
     its capital stock (other than additional Ordinary Shares or Convertible
     Securities) or any other securities or property of any nature whatsoever
     (other than cash) , or

          (iii) any options or warrants or other rights to subscribe for or
     purchase any of the following:  any evidences of its indebtedness (other
     than Convertible Securities), any shares of its capital stock (other than
     additional Ordinary Shares or Convertible Securities) or any other
     securities or property of any nature whatsoever,

then the holder of this Warrant shall be entitled to receive upon the exercise
hereof at any time on or after the taking of such record the number of Ordinary
Shares to be received upon exercise of such Warrant determined as stated herein
and, in addition and without further payment, the cash, stock, securities, other
property, options, warrants and/or other rights to which such holder or

                                       7
<PAGE>

holders would have been entitled by way of the Distribution and subsequent
dividends and distributions if such Holder (x) had exercised such Warrants
immediately prior to such Distribution, and (y) had retained the Distribution in
respect of the Ordinary Shares and all subsequent dividends and distributions of
any nature whatsoever in respect of any stock or securities paid as dividends
and distributions and originating directly or indirectly from such Ordinary
Shares. A reclassification of the Ordinary Shares into any other class of stock
shall be deemed a distribution by the Company to the holders of its Ordinary
Shares or such shares of such other class of stock within the meaning of
paragraph (c) of this Section 5 and, if the outstanding Ordinary Shares shall be
changed into a larger or smaller number of Ordinary Shares as a part of such
reclassification, such event shall be deemed a subdivision or combination, as
the case may be, of the outstanding Ordinary Shares within the meaning of
paragraph (c) of this Section 5. If the securities to be distributed by the
Company involve rights, warrants, options or any other form of Convertible
Securities and the right to exercise or convert such securities would expire in
accordance with its terms prior to the exercise of this Warrant, then the terms
of such securities shall provide that such exercise or convertibility right
shall remain in effect until 30 days after the date the Holder of this Warrant
receives such securities pursuant to the exercise hereof.

     (c)  In addition to those adjustments set forth in Sections 5(a) and 5(b),
but without duplication of the adjustments to be made under such Sections 5(a)
and 5(b) and Section 6, if the Company:

          (i)   takes a record of the holders of its Ordinary Shares for the
     purpose of entitling them to receive or pays a dividend payable in, or
     other distribution of, Ordinary Shares;

          (ii)  subdivides its outstanding shares of Ordinary Shares into a
     greater number of Ordinary Shares;

          (iii) combines its outstanding Ordinary Shares into a lesser number
     of shares of Ordinary Shares; and/or

          (iv)  makes a distribution on its Ordinary Shares in shares of its
     capital stock other than Ordinary Shares,

then (A) the Aggregate Number in effect immediately prior thereto shall be
adjusted so that the holder or holders of this Warrant shall thereafter be
entitled to receive, upon exercise hereof, the number of Ordinary Shares or
other securities of the Company (such other securities thereafter enjoying the
rights of Warrant Shares under this Warrant) that such Holder would have owned
or have been entitled to receive after the occurrence of such event had such
Warrants been exercised immediately prior to the occurrence of such event or the
record date with respect thereto, and (B) the Exercise Price shall (until
another such event) be adjusted to equal (calculated to the nearest full cent)
the quotient derived by dividing (x) the Aggregate Number in effect immediately
prior to such adjustment multiplied by the Exercise Price in effect immediately
prior to such

                                       8
<PAGE>

adjustment, divided by (y) the Aggregate Number in effect after adjustment
pursuant to this Section 5(c).

Section 6.  Adjustment to Exercise Price.
            ----------------------------

     (a)  If the Company shall issue or sell any Ordinary Shares at a price
which is less than the Exercise Price, then the Exercise Price in effect
immediately prior thereto shall be adjusted immediately so that the Exercise
Price thereafter shall equal the price per Ordinary Share at which such Ordinary
Shares described in this Section 6(a) were issued. The provisions of this
paragraph (a) shall not apply to any issuance of additional Ordinary Shares for
which an adjustment is provided under Sections 5(a), (b) or (c).

     (b)  If the Company shall take a record of the holders of its Ordinary
Shares for the purpose of entitling them to receive a distribution of, or shall
in any manner issue or sell, any warrants or other rights to subscribe for or
purchase (x) any shares of Ordinary Shares or (y) any Convertible Securities,
whether or not the rights to subscribe, purchase, exchange or convert thereunder
are immediately exercisable, at a purchase price per Ordinary Share which is
less than the Exercise Price, then the Exercise Price in effect immediately
prior thereto shall be adjusted immediately so that the Exercise Price
thereafter shall equal the consideration for which such Ordinary Shares or
Ordinary Shares subject to Convertible Securities described in this Section 6(b)
were issued. For purposes of this Section 6(b), the consideration for any
additional Ordinary Shares issuable pursuant to any warrants or other rights to
subscribe for or purchase the same or for any additional Ordinary Shares
issuable pursuant to Convertible Securities subject to any warrants or other
rights shall be the consideration received or receivable by the Company for
issuing such warrants or other rights, plus the additional consideration payable
to the Company upon the exercise of such warrants or other rights and upon the
exercise of the Convertible Securities, as the case may be.

     (c)  If the Company shall take a record of the holders of its Ordinary
Shares for the purpose of entitling them to receive a distribution of or shall
in any manner issue or sell Convertible Securities, whether or not the rights to
exchange or convert thereunder are immediately exercisable, at a purchase price
per Ordinary Share which is less than the Exercise Price, then the Exercise
Price in effect immediately prior thereto shall be adjusted immediately so that
the Exercise Price thereafter shall equal the purchase price per Ordinary Share
issuable pursuant to the terms of any Convertible Securities. For purposes of
this Section 6(c), the purchase price per Ordinary Share issuable pursuant to
the terms of any Convertible Security shall be the consideration received or
receivable by the Company for issuing the Convertible Security, plus the
additional consideration, if any, payable to the Company upon the purchase of
the Ordinary Share pursuant to the Convertible Security.

                                       9
<PAGE>

Section 7.  General Provisions Regarding Adjustments to Aggregate Number or
            ---------------------------------------------------------------
            Exercise Price.
            --------------

     (a)  The following provisions shall be applicable to the making of
adjustments of (i) the Aggregate Number as provided in Section 5 or (ii) the
Exercise Price as provided in Section 6:

          (i)    The sale or other disposition of any issued Ordinary Shares
     owned or held by or for the account of the Company shall be deemed an
     issuance thereof for the purposes of Sections 5 and 6.

          (ii)   The adjustments required by Sections 5 and 6 shall be made
     whenever and as often as any specified event requiring an adjustment shall
     occur, except as expressly provided herein.  For the purpose of any
     adjustment, any specified event shall be deemed to have occurred at the
     close of business on the date of its occurrence.

          (iii)  In computing adjustments under Sections 5 and 6, fractional
     interests in Ordinary Shares shall be taken into account to the nearest
     one-thousandth (.001) of a share and shall be aggregated until they equal
     one whole share.

          (iv)   If the Company shall take a record of the holders of its
     Ordinary Shares for an action described in Sections 5 or 6 hereof, but
     abandons its plan to take such action prior to effecting such action, then
     no adjustment shall be required by reason of the taking of such record.

          (v)    Notwithstanding anything herein to the contrary, no adjustment
     shall be made to the Aggregate Number or Exercise Price as a result of
     adjustments to the Aggregate Number or Exercise Price as defined in any
     Warrants issued to the Holder on the date hereof.

          (vi)   Upon the expiration or termination of any of the warrants or
     other rights or options referred to in Section 6(b) above or the
     Convertible Securities referred to in Section 6(b) or 6(c) above, the
     Exercise Price after the expiration or termination of any such warrants,
     rights, options or Convertible Securities without any exercise or
     conversion thereof, the issuance of which caused an adjustment to the
     Exercise Price, shall be readjusted to such Exercise Price prior to the
     adjustment made upon the issuance of such warrants, rights, options or
     Convertible Securities.

          (vii)  In case of the issuance at any time of any additional Ordinary
     Shares or Convertible Securities in payment or satisfaction of any dividend
     upon any class of stock other than Ordinary Shares, the Company shall be
     deemed to have received for such additional Ordinary Shares or Convertible
     Securities a consideration equal to the amount of such dividend so paid or
     satisfied.

          (viii) No adjustment to the Aggregate Number or Exercise Price shall
     be made for issuances of (A) Options granted under the Company's No. 1
     Executive Share Option

                                       10
<PAGE>

     Scheme or No. 2 Executive Share Option Scheme or any other employee, non-
     executive director or consultant share option scheme approved by the
     Company's directors, and Ordinary Shares issuable or issued upon exercise
     of such options, (B) Ordinary Shares issued or issuable upon (x) the
     exercise of options, warrants or rights to subscribe for or purchase
     Ordinary Shares, or (y) the conversion or exchange of securities
     convertible into or exchangeable for Ordinary Shares or options, warrants
     or rights to subscribe for or purchase Ordinary Shares, in each case only
     to the extent outstanding on the date of issuance of this Warrant and (C)
     Ordinary Shares issued pursuant to a transaction described in Section 5(a)
     or (b) hereof.

          (ix)   No adjustment of the Exercise Price shall be made in an amount
     less than one cent per share, provided that any adjustments which are not
     required to be made by reason of this sentence shall be carried forward and
     shall be taken into account in any subsequent adjustment made.

     (b)  If any event occurs as to which the provisions of Section 5 or Section
6 are not strictly applicable but the lack of any provision for the exercise of
the rights of a holder or holders of Warrants would not fairly protect the
purchase rights of such holder or holders of Warrants in accordance with the
essential intent and principles of such provisions, then the Company shall
appoint a firm of independent certified public accountants in the United States
(which may be the regular outside auditors of the Company) of recognized
national standing in the United States satisfactory to the Holder, which shall
give its opinion as to the adjustments, if any, necessary to preserve, without
dilution, on a basis consistent with the essential intent and principles
established in the provisions of Section 5 or Section 6, the exercise rights of
the holders of Warrants.  Upon receipt of such opinion, the Company shall
forthwith make the adjustments described therein.

     (c)  Within 45 days after the end of each fiscal quarter during which an
event occurred that resulted in an adjustment pursuant to Section 5 or Section
6, the Company shall cause to be promptly mailed to each holder of Warrants (and
upon the exercise of any Warrants to the exercising holder) by first-class mail,
postage prepaid, notice of each adjustment or adjustments to the Aggregate
Number or Exercise Price, as the case may be, effected since the date of the
last such notice and a certificate of the Company's Chief Financial Officer or,
in the case of any such notice delivered within 45 days after the end of a
fiscal year, a firm of independent public accountants in the United States
selected by the Company and acceptable to a majority in interest of the holders
of the Warrants (who may be the regular outside auditors employed by the
Company), in each case, setting forth the Aggregate Number or Exercise Price, as
the case may be, after such adjustment, a brief statement of the facts requiring
such adjustment and the computation by which such adjustment was made.  The fees
and expenses of such accountants shall be paid by the Company.

Section 8.  Covenant to Reserve Shares of Ordinary Shares.  The Company
            ---------------------------------------------
covenants and agrees that it will at all times reserve and set apart and have,
free from preemptive rights, a number of shares of authorized but unissued
Ordinary Shares sufficient to enable it at any time to fulfill all its
obligations hereunder.  The issuance of such shares has been duly and validly

                                       11
<PAGE>

authorized, and when issued and sold in accordance with the Warrants, such
shares will be duly and validly issued, fully paid and nonassessable.

Section 9.  Intentionally Omitted.

Section 10. Notices.  In the event that:
            -------

            (A)  the Company proposes to pay any dividend payable in stock (of
     any class or classes) or any obligations or stock convertible into or
     exchangeable for shares of Ordinary Shares upon its Ordinary Shares or make
     any distribution (other than ordinary cash dividends) to the holders of its
     Ordinary Shares;

            (B)  the Company proposes to grant to the holders of its Ordinary
     Shares generally any rights or warrants (excluding any warrants granted to
     any employee, director, officer, contractor or consultant of the Company
     pursuant to any plan approved by the Board of Directors of the Company);

            (C)  the Company proposes to effect any capital reorganization or
     reclassification of capital stock of the Company;

            (D)  the Company proposes to consolidate with, or merge into, any
     other Company or to transfer its property as an entirety or substantially
     as an entirety; or

            (E)  the Company proposes to effect the liquidation, dissolution or
     winding up of the Company,

then the Company shall cause notice of any such intended action to be given to
the Holder of this Warrant not less than 30 days before the date on which the
transfer books of the Company shall close or a record shall be taken for such
stock dividend, distribution or granting of rights or Warrants, or the date when
such capital reorganization, reclassification, consolidation, merger, transfer,
liquidation, dissolution or winding up shall be effective, as the case may be.

     Any notice or other document required or permitted to be given or delivered
to the Holder of this Warrant shall be delivered in accordance with Section 15
herein.

Section 11.  Limitation of Liability; Not Shareholders.  No provision of this
             -----------------------------------------
Warrant shall be construed as conferring upon the Holder the right to vote or to
consent or to receive dividends or to receive notice as a shareholder in respect
of meetings of shareholders for the election of directors of the Company or any
other matter whatsoever as shareholders of the Company.  No provision hereof, in
the absence of affirmative action by the Holder to purchase shares of Ordinary
Shares, and no mere enumeration herein of the rights or privileges of the
Holder, shall give rise to any liability of Holder for the purchase price or as
a shareholder of the Company, whether such liability is asserted by the Company,
creditors of the Company or others.

                                       12
<PAGE>

Section 12.  Loss, Destruction of Warrant.  Upon receipt of evidence
             ----------------------------
satisfactory to the Company of the loss, theft, mutilation or destruction of
this Warrant, 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 Warrantholder's indemnity being
satisfactory indemnity in the event of loss, theft or destruction of any Warrant
owned by such holder), or in the event of such mutilation upon surrender and
cancellation of this Warrant, the Company will make and deliver a new Warrant,
of like tenor and representing the right to purchase the same Aggregate Number
of Ordinary Shares, as adjusted in Section 5, as provided for in such lost,
stolen, destroyed or mutilated Warrant, in lieu of such lost, stolen, destroyed
or mutilated Warrant.  Any Warrant issued under the provisions of this Section
12 in lieu of any Warrant alleged to be lost, destroyed or stolen, or of any
mutilated Warrant, shall constitute an original contractual obligation on the
part of the Company.

Section 13.  Amendments.  Neither this Warrant nor any term hereof may be
             ----------
changed, waived, discharged or terminated orally or in writing, provided that
any term of this Warrant 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 Warrants that are exercisable for a number of Ordinary Shares
that represent in the aggregate at least a majority of the total number of
Ordinary Shares for which all of the Warrants are then exercisable (whether or
not the Holder of this Warrant consents).

Section 14.  Severability.  If in any jurisdiction, any provision of this
             ------------
Agreement or its 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.

Section 15.  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 Airpark Road
                              Napa, California 94558
                              Attention: President

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

                                       13
<PAGE>

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

          copy to:            Pryor Cashman Sherman & Flynn LLP
                              410 Park Avenue
                              New York, New York 10022
                              Attention: Selig D. Sacks, Esq.

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.

Section 16.  Governing Law; Choice Of Forum; Certain Consents; Waiver Of Jury
             ----------------------------------------------------------------
             Trial, Counterclaim, Setoff.
             ----------------------------

     THIS WARRANT SHALL BE DEEMED TO HAVE BEEN EXECUTED AND DELIVERED AT AND
SHALL BE DEEMED TO HAVE BEEN MADE IN NEW YORK, NEW YORK.  THIS WARRANT, AND THE
RIGHTS AND OBLIGATIONS OF THE PARTIES HEREUNDER SHALL BE CONSTRUED IN ACCORDANCE
WITH AND BE GOVERNED BY THE SUBSTANTIVE LAWS OF THE STATE OF NEW YORK (WITHOUT
GIVING EFFECT TO ANY OF SUCH STATE'S CONFLICT OF LAWS RULES OR PRINCIPLES).  ANY
LEGAL ACTION OR PROCEEDING WITH RESPECT HERETO AND THERETO SHALL ONLY BE BROUGHT
IN ANY STATE OR FEDERAL COURT IN THE BOROUGH OF MANHATTAN, NEW YORK CITY, NEW
YORK, AND, BY EXECUTION, ACCEPTANCE AND DELIVERY OF THIS WARRANT, THE COMPANY
HEREBY IRRE-VOCABLY ACCEPTS FOR ITSELF AND IN RESPECT OF ITS PROPERTY, GENERALLY
AND UNCONDITIONALLY, THE JURISDICTION OF THE AFORESAID COURTS AND IRREVOCABLY
WAIVES ANY OBJECTION, DEFENSE OR CLAIM TO SUCH JURIS-DICTION WHICH MAY BE BASED,
DIRECTLY OR INDIRECTLY, ON THE GROUNDS OF FORUM NON CONVENIENS THAT IT MAY NOW
OR HEREAFTER HAVE TO THE BRINGING OF ANY ACTION OR PROCEEDING IN SUCH
JURISDICTION IN RESPECT OF THIS WARRANT.  IF ANY ACTION IS COMMENCED IN ANY
OTHER JURISDICTION, THE PARTIES HERETO HEREBY CONSENT TO THE REMOVAL OF SUCH
ACTION TO THE AFOREMENTIONED COURTS.  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 30 DAYS AFTER SUCH MAILING.  NOTHING HEREIN SHALL AFFECT THE RIGHT OF
THE HOLDERS OF ANY OF THE WARRANTS OR WARRANT SHARES TO SERVE PROCESS IN ANY
OTHER MANNER PERMITTED BY LAW OR COMMENCE

                                       14
<PAGE>

LEGAL PROCEEDINGS 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.


     [signature page follows; remainder of page left intentionally blank]

                                       15
<PAGE>

     IN WITNESS WHEREOF, the Company has caused this Amended Warrant to be
signed in its name by its duly authorized officer.


Dated:  _________________, 2001


                                  SENETEK PLC


                                  By:___________________________
                                     Name:
                                     Title:

                                       16
<PAGE>

                                                                       Exhibit 1

                                EXERCISE NOTICE

     The undersigned Holder hereby elects to exercise purchase rights
represented by such Warrant for, and to purchase thereunder ________ Ordinary
Shares covered by such Warrant and herewith makes payment in full therefor of
$_________ cash and/or by cancellation of $__________ of indebtedness of the
Company to the Holder hereof and requests that, subject to the terms and
conditions of the Warrant, certificates for such shares (and any securities or
property deliverable upon such exercise) be issued in the name of and delivered
to ______________________ whose address is____________________________________,
and whose social security or employer identification number is ____________.

     The undersigned agrees that, in the absence of an effective registration
statement with respect to Ordinary Shares issued upon this exercise, the
undersigned is acquiring such Ordinary Shares for the Holder's own account and
not as a nominee for any other party, for investment and not with a view to
distribution thereof and that the certificate or certificates representing such
Ordinary Shares may bear a legend substantially as follows:

     THESE SHARES HAVE NOT BEEN REGISTERED UNDER THE SECURITIES ACT OF
     1933, AS AMENDED, AND MAY NOT BE OFFERED, SOLD, TRANSFERRED,
     ASSIGNED OR HYPOTHECATED IN THE ABSENCE OF A REGISTRATION STATEMENT
     IN EFFECT WITH RESPECT TO SUCH SECURITIES UNDER THE ACT AND
     APPLICABLE STATE SECURITIES LAW OR AN OPINION OF COUNSEL REASONABLY
     SATISFACTORY TO THE COMPANY THAT SUCH REGISTRATION IS NOT REQUIRED.

     In addition, the undersigned agrees that, in the absence of an effective
registration statement with respect to Ordinary Shares issued upon this
exercise, stop transfer instructions will be entered on the Company's stock
transfer records with respect to Ordinary Shares issued upon this exercise.


Dated:                             __________________________
                                   Signature guaranteed:

                                       17
<PAGE>

                              FORM OF ASSIGNMENT

     FOR VALUE RECEIVED the undersigned registered Holder of the within Warrant
hereby sells, assigns, and transfers unto the Assignee(s) named below (including
the undersigned with respect to any Warrants constituting a part of the Warrants
evidenced by the within Warrant not being assigned hereby) all of the right of
the undersigned under the within Warrant, with respect to the number of Warrants
set forth below:

<TABLE>
<CAPTION>
                                               Social security or
                                               other identifying
    Name of Assignees             Address         number of          Number of Warrants
    -----------------             -------         ---------          ------------------
                                                 Assignee(s)
                                                 -----------
    <S>                           <C>          <C>                   <C>
</TABLE>

and does hereby irrevocably constitute and appoint ______________ the
undersigned's attorney to make such transfer on the books of _____________
maintained for that purpose, with full power of substitution in the premises.


Dated: ______________

                                __________________(1)
                                (Signature of Owner)

                                __________________
                                (Street Address)

                                __________________
                                (City)(State)(Zip Code)


_________

(1)  The signature must correspond with the name as written upon the face of the
     within Warrant in every particular, without alteration or enlargement or
     any change whatsoever.

                                       18