<PAGE>
                                                                   EXHIBIT 10(W)




                                  AMENDMENT TO
                        UNITED HEALTHCARE SERVICES, INC.
                                      AND
                          UNITEDHEALTH NETWORKS, INC.
                     PHARMACY BENEFIT MANAGEMENT AGREEMENT



         This Amendment is made to the agreement ("Agreement") between United
HealthCare Services, Inc. and UnitedHealth Networks, Inc., collectively
referred to as "United", and the entity named below ("MMMC"). The Agreement
currently sets forth the terms and conditions under which MMMC or an affiliate
shall provide or arrange for the provision of health care services to
individuals covered by a United's affiliated Health Plan pursuant to its
Medicare contract with the Health Care Financing Administration ("HCFA"). The
parties understand and agree that the Balanced Budget Act of 1997 ("BBA")
established a new program known as Medicare+Choice, which replaced Health
Plan's existing Medicare risk program. The purpose of this Amendment is to
incorporate all provisions necessary to meet the HCFA requirements for
Medicare+Choice. This Amendment is effective on August 1, 1999.

1.       The Agreement shall be amended by the addition of the attached
         Health Plan Medicare+Choice Requirements Addendum.

2.       All other provisions of the Agreement shall remain in full force and
         effect.


UNITED HEALTHCARE SERVICES, INC.             MERCK MEDCO MANAGED CARE, L.L.C.


Signature  Illegible                         Signature  Illegible
          --------------------                         ------------------------

Title  President                             Title  Senior Vice President-
       -----------------------                      Regulatory and Managed Care
                                                    Programs
                                                    ---------------------------

Date  1/29/01                                Date  1/24/01
      ------------------------                     ----------------------------

UNITEDHEALTH NETWORKS, INC.


Signature  /s/ Illegible
          --------------------

Title Secretary
      ------------------------

Date  1/26/01
      ------------------------

<PAGE>
                                   HEALTH PLAN
                     MEDICARE+CHOICE REQUIREMENTS ADDENDUM

In addition to PBM's obligations under the Agreement, PBM agrees, and shall
require PBM Contracting Providers to agree, as participating providers under a
United affiliated Health Plan's contract with HCFA to be a Medicare+Choice
managed care organization (hereafter the "M divided by C Contract"), to abide by
all applicable provisions of the M+C Contract and to fulfill PBM's and PBM
Contracting Provider's obligations under the Agreement in a manner consistent
with a United affiliated Health Plan's (hereafter the "Health Plan") obligations
under the M divided by C Contract. For purposes of this Addendum, "Medicare
Member" means a Health Plan's Member who is enrolled in a Medicare+Choice plan
through Health Plan. PBM and PBM Contracting Provider compliance with the M+C
Contract specifically includes, but is not limited to, the following
requirements:

1.       Prompt Payment. Health Plan shall pay "clean" claims for Covered
         Services within forty-five (45) days of receipt and approve or deny all
         claims that are not "clean" claims within sixty (60) days from the date
         of the request.

2.       Medicare Compliance. PBM shall, and shall require PBM Contracting
         Providers to, comply with all applicable Medicare laws and regulations
         and HCFA instructions.

3.       Audits and Information. In addition to PBM's and PBM Contracting
         Provider's obligations under Section 5.3.2, PBM shall, and shall
         require PBM Contracting Providers to, permit audits and inspection by
         HCFA and/or its designees, and cooperate, assist and provide
         information to HCFA and/or its designees as requested from time to
         time. This provision shall survive termination of the Agreement.

4.       Maintenance of Records. In addition to PBM's and PBM Contracting
         Providers' obligations under Section 5.3.2, PBM shall, and shall
         require PBM Contracting Providers to, retain books, contracts,
         documents, papers and records, including without limitation, medical
         records, patient care documentation, and other records that pertain to
         any aspect of services performed, financial solvency, reconciliation of
         benefit liabilities and determination of amounts payable under Health
         Plan's M divided by C Contract for a minimum of six (6) years from the
         end of the applicable one-year contract period in the M divided by C
         Contract or the completion of an audit, or in certain instances
         described in applicable Medicare+Choice regulations, for periods in
         excess of six (6) years, if appropriate. PBM shall, and shall require
         PBM Contracting Providers to, maintain such records accurately and
         update them on a regular basis. PBM and PBM's employees and agents
         shall, and shall require PBM Contracting Providers to, maintain the
         confidentiality of all Medicare Member records in accordance with the
         applicable laws and regulations, and shall safeguard Medicare Members'
         privacy. This provision shall survive termination of the Agreement.

5.       Data Collection. PBM shall submit to Health Plan, upon request, all
         data necessary for Health Plan to fulfill its reporting obligations
         pursuant to 42 C.F.R.SS.422.516. PBM must submit to Health Plan all
         data, including medical records, necessary to characterize the content
         and purpose of each encounter with a Medicare Member. PBM must certify
         (based



                                       1
<PAGE>
    on best knowledge, information and belief) the accuracy, completeness and
    truthfulness of such data on certification forms provided by Health Plan.
    PBM shall hold harmless and indemnify Health Plan for any fines or penalties
    it may incur due to PBM's submission of inaccurate or incomplete data.

6.  Accountability.  PBM acknowledges, and shall require PBM Contracting
    Providers to acknowledge, that Health Plan oversees and is responsible to
    HCFA for any functions or responsibilities provided or performed by PBM or
    PBM Contracting Providers pursuant to the M+C Contract, as applicable.

7.  Delegation.  If any service or activity to be performed by PBM under this
    Agreement is delegated, to the extent permitted by and in accordance with
    this Agreement, to a downstream entity, such entity shall enter into a
    contract with PBM obligating such entity to perform such service or activity
    consistent with and in compliance with the terms of this Agreement and the
    M+C Contract.

8.  Continued Care.  In addition to PBM's and PBM Contracting Providers'
    obligations pursuant to Section 3.8 of the Agreement, PBM shall, and shall
    require PBM Contracting Providers to, provide Covered Services to Medicare
    Members (i) for all Medicare Members, for the duration of the M+C Contract
    period for which HCFA payments have been made; and (ii) for Medicare Members
    who are hospitalized on the date the M+C Contract terminates or in the event
    of Health Plan's or PBM's insolvency, through discharge.  This provision
    shall survive termination of the Agreement.

9.  Compliance with Pharmacy Services Manual.  PBM shall require PBM Contracting
    Providers to comply with PMB's Pharmacy Services Manual, including, without
    limitation, the Medicare Plus Choice Requirements addendum (the "Pharmacy
    Attachment").  PBM shall comply with those requirements of the Pharmacy
    Attachment applicable to the performance of PBM's obligations under this
    Agreement, including, without limitation, where an obligation is placed upon
    PBM Contracting Providers but such obligation may be performed or could be
    violated by PBM.  In the event of a conflict between any provision in this
    ADDENDUM and the Pharmacy Attachment, this ADDENDUM shall govern.





                                       2

<PAGE>
                                  AMENDMENT TO
                        UNITED HEALTHCARE SERVICES, INC.
                     PHARMACY BENEFIT MANAGEMENT AGREEMENT



         This Amendment is made to the Pharmacy Benefit Management Agreement
("Agreement") between United HealthCare Services, Inc., UnitedHealth Networks,
Inc. (collectively "United") and Merck-Medco Managed Care, L.L.C. ("PBM") dated
November 11, 1998.

WHEREAS, the Agreement sets forth the obligations of the parties in order for
United to make available pharmacy benefit management and related services to
Health Plans and other non-Health Plan business and PBM agreed to provide such
services; and

WHEREAS, the parties desire to amend the Agreement in order to add PAID
Prescriptions, L.L.C. ("PAID") as a signatory to the Agreement.

NOW THEREFORE, in consideration of the terms and conditions set forth in this
Addendum, the parties agree as follows:

1.       PAID is a subsidiary of PBM and acts as a Third Party Administrator
         ("TPA") for PBM on behalf of United. PAID is licensed in certain states
         as a TPA as required by applicable law.

2.       The parties agree that PAID is added as a signatory to the Agreement
         shall perform the TPA functions in the Agreement.

3.       All other provisions of the Agreement shall remain in full force and
         effect.



United HealthCare Services, Inc.            Marck-Medco Managed Care, L.L.C.

Signature:  Illegible                       Signature:  Illegible
          --------------------                        --------------------

Title:  COO                                 Title: Vice President
      ------------------------                     -----------------------

Date:  3/28/01                              Date:  4/12/01
     -------------------------                     -----------------------

United HealthNetworks, Inc.                 PAID Prescriptions, L.L.C.

Signature: Illegible                        Signature:  Illegible
          --------------------                        --------------------

Title: Vice President                       Title: Vice President
      ------------------------                     -----------------------

Date:  3/28/01                              Date:  4/12/01
     -------------------------                     -----------------------
<PAGE>

                                   AMENDMENT
                                       TO
                 PHARMACY BENEFIT MANAGEMENT AGREEMENT BETWEEN
       UNITED HEALTHCARE SERVICES, INC. AND MERCK-MEDCO MANAGED CARE, LLC,
excerpted from Letter Agreement dated June 29, 2001, between United HealthCare
Services, Inc. and Merck-Medco Managed Care, LLC



Rebate Contracting

(a) PBM agrees to work with United Healthcare to negotiate new or amended rebate
agreements with drug manufacturers by June 30, 2002 that will result in United
HealthCare earning ***









***   Represents text deleted pursuant to a confidentiality treatment request
      filed with the Securities and Exchange Commission pursuant to Rule 24b-2
      under the Securities Exchange Act of 1934, as amended.


<PAGE>
                                   AMENDMENT


United HealthCare Services, Inc., on behalf of itself and its affiliates from
time to time (collectively, "United HealthCare") and Merck-Medco Managed Care,
LLC ("PBM") hereby agree to make the following changes to the Pharmacy Benefit
Management Agreement between United HealthCare and PBM that was executed by
United HealthCare on November 11, 1998 (the "Agreement"):

1. Section 4.6 of the Agreement is hereby revised to read as follows:

         "4.6 MINIMUM PDL ENROLLMENT. Effective as of December 11, 2001 and
         continuing throughout the term of this Agreement, United HealthCare
         agrees that it shall maintain a minimum of *** Covered Persons
         (including, as a subset thereof, at least *** non-Health Plan
         Covered Persons) receiving services under this Agreement including
         participating in United HealthCare's PDL.***

2. Section 3.15 is hereby deleted from the Agreement.

3. Except as otherwise defined in this Amendment, capitalized terms shall have
   the meanings set forth in the Agreement. Except as specifically modified by
   this Amendment, the Agreement as heretofore amended shall remain in effect.

ACCEPTED AND AGREED as of the 19th day of December 2001.


United HealthCare Services, Inc.             Merck-Medco Managed Care, LLC

By: /s/ William A. Munsell                   By: /s/ Glenn Taylor
    -----------------------                      ------------------------
Name: William A. Munsell                     Name: Glenn Taylor
      ---------------------                        ----------------------
Title: Vice President                        Title: Sr. Vice President
       --------------------                         ---------------------



***   Represents text deleted pursuant to a confidentiality treatment request
      filed with the Securities and Exchange Commission pursuant to Rule 24b-2
      under the Securities Exchange Act of 1934, as amended.