Exhibit 10.1

FIRST AMENDMENT TO CREDIT AGREEMENT

FIRST AMENDMENT TO CREDIT AGREEMENT (this “First Amendment”), dated as of
June 3, 2008, among WYETH, a Delaware corporation (the “Company”), various
lenders from time to time party to the Credit Agreement referred to below (the
“Lenders”), and JPMORGAN CHASE BANK, N.A., as Administrative Agent (in such
capacity, the “Administrative Agent”). Unless otherwise indicated, all
capitalized terms used herein and not otherwise defined shall have the
respective meanings provided such terms in the Credit Agreement referred to
below.

W I T N E S S E T H:

WHEREAS, the Company, the Lenders, J.P. Morgan Securities Inc. and Citigroup
Global Markets Inc., as Co-Lead Arrangers and Joint Book Managers, Citicorp USA,
Inc., as Syndication Agent, Bank of America, N.A., The Bank of Nova Scotia and
UBS Securities LLC, as Co-Documentation Agents, and the Administrative Agent are
parties to a Credit Agreement, dated as of August 2, 2007 (the “Credit
Agreement”); and

WHEREAS, subject to the terms and conditions of this First Amendment, the
parties hereto wish to amend the Credit Agreement as herein provided;

NOW, THEREFORE, it is agreed:

I. Amendments to Credit Agreement.

1. Subsection 1.1 of the Credit Agreement is hereby amended by (i) deleting the
definition of “Extension Date” appearing in said subsection in its entirety and
(ii) inserting the following new definitions in appropriate alphabetical order
in said subsection:

“Concurrent Extension Requests”: as defined in the definition of “Extension
Date”.

“Extension Date”: (i) with respect to the first extension request that the
Company may make pursuant to subsection 2.20, a single date (which shall be
notified in writing by the Company to the Administrative Agent on a Business Day
occurring at least 60 days but no more than 90 days prior to such specified
date) occurring during the period commencing on the one-year anniversary of the
Effective Date and ending on (and including) the two-year anniversary of the
Effective Date and (ii) with respect to the second extension request that the
Company may make pursuant to subsection 2.20 (which, for avoidance of doubt, may
be the first such request actually made if the Company does not elect to make
the request described in preceding clause (i)), a single date (which shall be
notified in writing by the Company to the Administrative Agent on a Business Day
occurring at least 60 days but no more than 90 days prior to such specified
date) occurring during the period commencing on (and including) the two-year
anniversary of the Effective Date and ending on (and including) the three-year
anniversary of the Effective Date; provided that, unless both the first and
second extension requests are delivered by the Company on the same date and each
specify the

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

“Extension Date” as the two-year anniversary of the Effective Date (any such
requests, the “Concurrent Extension Requests”), the “Extension Date” notified by
the Company pursuant to preceding clause (ii) shall be at least 60 days after
the “Extension Date”, if any, notified by the Company pursuant to preceding
clause (i).

2. Subsection 2.20 of the Credit Agreement is hereby amended by inserting the
following text immediately prior to the period (“.”) appearing at the end of
each of the first and third sentences of said subsection:

“(or, if Concurrent Extension Requests are delivered, the date occurring
twenty-four (24) months after such then existing Final Termination Date)”.

3. Notwithstanding anything to the contrary contained in subsection 2.20 of the
Credit Agreement, the Company and the Lenders hereby agree that, upon the
occurrence of the First Amendment Effective Date (as defined below), the written
extension request, dated June 3, 2008, furnished by the Company to the
Administrative Agent and the Lenders pursuant to subsection 2.20 of the Credit
Agreement shall be deemed rescinded, shall cease to have any force or effect for
purposes of subsection 2.20 of the Credit Agreement (on the same basis as if
such request had never been furnished), and shall not be construed to be one of
the notices permitted under subsection 2.20 of the Credit Agreement (as amended
by Section 1 of Part I of this First Amendment).

II. Miscellaneous Provisions.

1. In order to induce the Lenders to enter into this First Amendment, the
Company hereby represents and warrants that (i) no Default or Event of Default
exists as of the First Amendment Effective Date, both before and after giving
effect to this First Amendment and (ii) all of the representations and
warranties contained in the Credit Agreement are true and correct in all
material respects on the First Amendment Effective Date, both before and after
giving effect to this First Amendment, with the same effect as though such
representations and warranties had been made on and as of the First Amendment
Effective Date (it being understood that any representation or warranty made as
of a specific date shall be true and correct in all material respects as of such
specific date).

2. This First Amendment is limited as specified and shall not constitute a
modification, acceptance or waiver of any other provision of the Credit
Agreement.

3. This First Amendment may be executed in any number of counterparts and by the
different parties hereto on separate counterparts, each of which counterparts
when executed and delivered shall be an original, but all of which shall
together constitute one and the same instrument. A complete set of counterparts
shall be lodged with the Company and the Administrative Agent.

4. THIS FIRST AMENDMENT AND THE RIGHTS AND OBLIGATIONS OF THE PARTIES HEREUNDER
SHALL BE CONSTRUED IN ACCORDANCE WITH AND GOVERNED BY THE LAW OF THE STATE OF
NEW YORK.

 

-2-

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

5. This First Amendment shall become effective on the date (the “First Amendment
Effective Date”) when the Company and the Lenders constituting the Majority
Lenders shall have signed a counterpart hereof (whether the same or different
counterparts) and shall have delivered (including by way of facsimile
transmission) the same to White & Case LLP, 1155 Avenue of the Americas, New
York, NY 10036 Attention: May Yip (facsimile number 212-354-8113). The
Administrative Agent will provide notice of the First Amendment Effective Date
to the Lenders promptly upon the occurrence thereof.

6. From and after the First Amendment Effective Date, all references in the
Credit Agreement shall be deemed to be references to the Credit Agreement as
modified hereby.

*    *    *

 

-3-

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

IN WITNESS WHEREOF, the parties hereto have caused their duly authorized
officers to execute and deliver this First Amendment as of the date first above
written.

 

WYETH By:   /s/ Robert E. Landry   Title:   Treasurer

 

JPMORGAN CHASE BANK, N.A.,   Individually and as Administrative Agent By:   /s/
Dawn Lee Lum   Title:   Executive Director

 

CITIBANK NORTH AMERICA, INC., By:   /s/ William E. Clark   Title:   Vice
President

 

BANK OF AMERICA, N.A.,   Individually and as Co-Documentation Agent By:   /s/
Jill J. Hogan   Title:   Vice President

 

THE BANK OF NOVA SCOTIA,   Individually and as Co-Documentation Agent By:   /s/
P. M. Brown   Title:   Managing Director

 

UBS LOAN FINANCE LLC   as Co-Documentation Agent By:   /s/ Iria R. Otsa   Title:
  Associate Director

 

By:   /s/ Mary E. Evans   Title:   Associate Director

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

 

SIGNATURE PAGE TO THE FIRST AMENDMENT, DATED AS OF THE DATE FIRST WRITTEN ABOVE,
TO THE CREDIT AGREEMENT, DATED AS OF AUGUST 2, 2007, AMONG WYETH, THE LENDERS
FROM TIME TO THERETO, J.P. MORGAN SECURITIES INC. AND CITIGROUP GLOBAL MARKETS
INC., AS CO-LEAD ARRANGERS AND JOINT BOOK MANAGERS, CITICORP USA, INC., AS
SYNDICATION AGENT, BANK OF AMERICA, N.A., THE BANK OF NOVA SCOTIA AND UBS
SECURITIES LLC, AS CO-DOCUMENTATION AGENTS, AND JPMORGAN CHASE BANK, N.A. AS
ADMINISTRATIVE AGENT. ABN AMRO BANK N.V. By:   /s/ Michael Costello   Title:  
Director By:   /s/ Tim Khisameyev   Title:   Associate

 

BANCO POPULAR DE PUERTO RICO,   New York Branch By:   /s/ Hector J. Gonzalez  
Title:   Vice President

 

BANK OF NEW YORK By:   /s/ Richard Fronapfel, Jr.   Title:   Vice President

 

BANK OF TOKYO-MITSUBISHI UFJ TRUST COMPANY By:   /s/ George Stoecklein   Title:
  Vice President

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

BARCLAYS BANK PLC By:   /s/ Nicholas A. Bell   Title:   Director

 

BNP PARIBAS By:   /s/ Angela Bentley Arnold   Title:   Director By:   /s/
Benjamin Sileo   Title:   Vice President

 

COMMERZBANK AG, NEW YORK AND GRAND CAYMAN BRANCHES By:   /s/ Robert S. Taylor  
Title:   Senior Vice President By:   /s/ Barbara Peters   Title:   Assistant
Vice President WILLIAM STREET COMMITMENT CORPORATION (Recourse only to the
assets of William Street Commitment Corporation)

 

By:   /s/ Mark Walton   Title:   Assistant Vice President

 

INTESA SANPAOLO S.P.A. By:   /s/ Luca Sacchi   Title:   Vice President By:   /s/
Francesco DiMario   Title:   First Vice President, Credit Manager

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

LEHMAN BROTHERS COMMERCIAL BANK By:   /s/ Darren S. Lane   Title:   Operations
Officer

 

 

MORGAN STANLEY BANK By:   /s/ Daniel Twenge   Title:   Authorized Signatory

 

THE NORTHERN TRUST COMPANY By:   /s/ Thomas Hausnauer   Title:   Vice President

 

UBS LOAN FINANCE LLC By:   /s/ Irja R. Otsa   Title:   Associate Director By:  
/s/ Mary E. Evans   Title:   Associate Director

 

U.S. BANK, N.A. By:   /s/ Christopher T. Kordes   Title:   Vice President

 

WACHOVIA BANK, NATIONAL ASSOCIATION By:   /s/ Andrew S. Chen   Title:   Vice
President