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                                                                Exhibit 10.9
                                                                ------------




                                     FORM OF

                      PATIENT ASSISTANCE PROGRAM AGREEMENT

                                     BETWEEN

                             MERCK & CO., INC.

                                       AND

                      MERCK-MEDCO MANAGED CARE, L.L.C.


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                      PATIENT ASSISTANCE PROGRAM AGREEMENT

     THIS PATIENT ASSISTANCE PROGRAM AGREEMENT (this "Agreement"), dated as of
_______, 2002, between Merck & Co., Inc., a New Jersey corporation ("Merck"),
and Merck-Medco Managed Care, L.L.C., a Delaware limited liability company
("Medco"; Merck and Medco each being referenced herein individually as a
"Party," and collectively as the "Parties"). Capitalized terms used herein but
not otherwise defined herein shall have the meaning ascribed to such terms in
the Master Separation and Distribution Agreement to be entered into between the
Parties.

          WHEREAS, the Board of Directors of Merck has determined that it is
appropriate and desirable for Merck to separate the Medco Group from the Merck
Group (the "Separation");

          WHEREAS, in connection with the foregoing, Merck and Medco intend to
enter into a Master Separation Agreement, which will provide, among other
things, for the conversion of Medco to a Delaware corporation named MedcoHealth
Solution, Inc. (the "Conversion"), the Separation, the IPO of Medco Common
Stock, the declaration of the Merck Dividend immediately after the IPO Closing
Date, the subsequent Distribution of all the Medco Common Stock then owned by
Merck to the holders of Merck common stock, and the execution and delivery of
certain other agreements in order to facilitate and provide for the foregoing;

          WHEREAS, Merck has instituted a Patient Assistance Program (the
"General Program") to help provide access to Merck Products (other than
Crixivan(R)), and a separate Patient Assistance Program (the "Crixivan(R)
Program," together with the General Program, the "Programs") to help provide
access to Crixivan(R), for patients with medical needs who lack prescription
coverage and cannot afford drug treatment;

          WHEREAS, Merck desires that Medco, dispense, through one or more of
its pharmacies, as provided herein, Merck Products, including Crixivan(R), by
mail in connection with the Programs;

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          WHEREAS, Medco and Merck have developed an electronic feed between the
Nominated Agent (defined below) for the General Program and Medco pursuant to
which such Nominated Agent may electronically transmit to Medco eligibility
information with respect to patients under the General Program (the "Eligibility
Electronic Feed"); and

          WHEREAS, also as part of the foregoing, the parties further desire to
enter into this Agreement to set forth Medco's obligation with respect to the
Programs.

          NOW, THEREFORE, in consideration of the foregoing and the covenants
and agreements set forth below, the parties hereto agree as follows:

                                    ARTICLE I

                                   DEFINITIONS

     For the purpose of this Agreement, the following capitalized terms shall
have the following meanings:

     1.1 Ancillary Agreements. "Ancillary Agreements" shall have the
meaning set forth in the Master Separation and Distribution Agreement.

     1.2 Confidential Disclosure Agreement. "Confidential Disclosure
Agreement" shall mean that certain Confidential Disclosure Agreement to be
entered into between the Parties.

     1.3 "Dispensing Pharmacies" shall mean mail order pharmacies of Medco
located in the U.S. from which the Merck Products shall be dispensed in
accordance with Article II.

     1.4 Effective Date. "Effective Date" shall mean the date hereof.

     1.5 Expiration Date. "Expiration Date" shall have the meaning set
forth in Article 10.

     1.6 Master Separation Agreement. "Master Separation Agreement" shall
mean that certain Master Separation and Distribution Agreement dated as of
the date hereof, between the Parties.

     1.7 Merck Products. "Merck Products" means pharmaceutical products
(including Crixivan(R)), other than injectables and vaccines, that (w) are
manufactured by Merck or any of its Subsidiaries, (x) have been approved or
recommended by the U.S. Food and Drug Administration, (y) may be dispensed only
pursuant to a Prescription under applicable law and (z) are subject to an
effective patent granted by the U.S. Patent and Trademark Office.

     1.8 Nominated Agent. "Nominated Agent" shall mean one or more third
party vendor from time to time employed by Merck to administer the initial
application receipt, application review, general program eligibility
determination, and patient enrollment functions of the Programs. The Nominated
Agent for the General Program is currently TeleRx Marketing Inc. The Nominated
Agent for the Crixivan(R) Program is currently the Lash Group. Merck shall have
the right to replace Nominated Agents or appoint additional Nominated Agents for
all or any portion of either of the Programs. Merck shall provide Medco with
reasonable advance notice of any anticipated appointed of a new Nominated Agent
to allow Medco to develop appropriate operational links with such Nominate Agent
to insure continuous service for the Programs.

     1.9 Person. "Person" means any individual, corporation, association,

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partnership (general or limited), joint venture, trust, estate, limited
liability company, or other legal entity or organization.

     1.10 Prescription. "Prescription" means a valid and legal order to
dispense a Merck Product.

     1.11 Programs. "Programs" shall have the meaning set forth in the
Recitals.

     1.12 Subsidiary. "Subsidiary" of either Party means a corporation or other
organization whether incorporated or unincorporated, of which at least a
majority of the securities or interests having by the terms thereof ordinary
voting power to elect at least a majority of the board of directors or others
performing similar functions with respect to such corporation or other
organization is directly or indirectly owned or controlled by such Party or by
any one or more of its Subsidiaries, or by such Party and one or more of its
Subsidiaries. For purposes of this Agreement, neither Medco nor any of its
Subsidiaries shall be deemed to be a Subsidiary of Merck.

     1.13 "Term" shall have the meaning set forth in Section 2.6.

                                   ARTICLE II

                                    SERVICES

     During the Term, Medco shall provide, the following services with respect
to the Programs:

     2.1 Patient Enrollment. Receipt of the initial applications with respect to
each of the Programs, and application review, general program eligibility
determination and enrollment functions with respect to each Program, shall be
the responsibility of the applicable Nominated Agent.

     2.2 Prescriptions For the General Program. (a) The Nominated Agent for the
General Program will be responsible for sending to Medco eligibility and
Prescription information with respect to patients eligible to participate in the
General Program. Eligibility information with respect to the General Program
shall be sent to Medco by the Nominating Agent through the Eligibility
Electronic Feed. On the day that any eligibility information is sent through the
Eligibility Electronic Feed, the Nominated Agent shall either (1) send the
original prescription form via Federal Express (or other comparable overnight
courier providing a traceable, secure method of shipment) for receipt by Medco
at a Dispensing Pharmacy (the address of which shall be provided to the
Nominated Agent by Medco) on the following day or (2) send a copy of the
original prescription form to Medco pursuant to the Faxable Application Process
(as defined in Section 2.5 below). Refill requests under the General Program may
be made by the patient or prescribing physician using a toll free number
established by Medco or by mail (it being understood that patients and
physicians will be discouraged from making refill requests by mail). When Medco
has received all eligibility and Prescription information with respect to a
Prescription or any request for a refill in accordance with the foregoing, Medco
shall cause a Dispensing Pharmacy to dispense the Merck Product covered by such
Prescription (or refill) as written (subject to the next sentence) from such
pharmacy's stock of such Merck Product, by mailing such Merck Products via
Federal Express (or other comparable courier providing a traceable, secure
method of shipment), two (2) day ground, directly to the patient or, at the
physician's request (as set forth in the applicable application form), directly
to the patient's physician's office. Prescriptions under the General Program may
provide for up to a 90-day supply at a time with up to three refills each with
up to a 90-day supply.

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     (b) In addition to providing services with respect to the General Program
as otherwise provided in this Agreement, Medco shall continue to provide
services with respect to the General Program in accordance with the Memorandum
of Understanding between the Parties, effective April 1, 1996, relating to the
General Program from the date hereof until June 30, 2002; provided that the fees
and reimbursement amounts payable to Medco for providing such services shall be
determined in accordance with Article 3 of this Agreement.

     2.3 Prescriptions for the Crixivan(R) Program. The Nominated Agent for the
Crixivan(R) Program will be responsible for sending to Medco hard-copy paper
eligibility and Prescription information with respect to patients eligible to
participate in the Crixivan(R) Program. The parties shall cooperate to maintain
a 24-hour turn-around time for this transfer of such information. Such
information shall be sent via any traceable, secure method to a Dispensing
Pharmacy (the address of which shall be provided to the Nominated Agent by
Medco). Refill requests under the Crixivan(R) Program may be made by
transmitting a refill request, including the patients' name and ID (and Social
Security number and Prescription number, if available), to Medco by facsimile
(to a facsimile number specified by Medco. When Medco has received all
eligibility and Prescription information (including the original Prescription
form) with respect to a Prescription or any request for a refill for Crixivan(R)
in accordance with the foregoing, Medco shall cause a Dispensing Pharmacy to
dispense the Crixivan(R) covered by such Prescription (or refill) as written
(subject to the next sentence) from such pharmacy's stock of Crixivan(R), by
mailing such Merck Products via Federal Express (or other comparable courier
providing a traceable, secure method of shipment), two (2) day ground, directly
to the patient or, at the physician's request (as set forth in the applicable
application form), directly to the patient's physician's office. Prescriptions
under the Crixivan(R) Program may provide for up to a 90-day supply at a time
with up to three refills each with up to a 90-day supply.

     2.4 Prescription Volume; Design Changes. (a) Merck shall use
commercially reasonable efforts to provide to Medco monthly Merck's good
faith estimate of anticipated Prescription volume under the General Program
and the Crixivan(R) Program for the following six-month period. If any such
estimate provided by Merck anticipates that the compounded volume growth of
the General Program and the Crixivan(R) Program will exceed the compounded
volume growth for such Programs estimated as of the date hereof by the Parties,
Medco will provide to Merck Medco's good faith estimate of any capital
expenditures Medco will be required to make for the purpose of providing
services hereunder with respect to the Programs. After Medco's delivery of such
estimate to Merck, the parties shall negotiate in good faith with the goal of
agreeing on the specific amount of capital expenditures Medco will be required
to make that is allocable to that portion of the anticipated compounded volume
growth for the General Program and the Crixivan(R) Program that exceeds the
compounded volume growth for such Programs estimated as of the date hereof by
the Parties (the "Anticipated Excess Volume"). Merck agrees to reimburse Medco
for the capital expenditures incurred by Medco in accordance with a budget
approved by Merck setting forth the amounts of capital expenditures allocable to
the Anticipated Excess Volume.

     (b) In the event that at any time during the Term, Merck proposes to
implement material changes to the design of the Programs (other than increases
in volume under the Programs, which shall be subject to Section 2.4(a)), Merck
shall provide to Medco a written notice describing such proposed design changes
in reasonable detail. Within 20 days after its receipt of such notice, Medco
will provide to Merck Medco's good faith estimate of any of the out-of-pocket
expenses Medco will be required to incur to implement the proposed design
changes. After Medco delivers such

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estimate to Merck, the parties shall negotiate in good faith with the goal of
agreeing on a budget for the out-of-pocket expenses to be incurred by Medco to
implement the proposed design changes (a "Design Change Budget"). Medco shall
implement the proposed design changes in accordance with a Design Change Budget
agreed by the parties as promptly as practicable after Merck and Medco reach
agreement thereon. Merck shall reimburse Medco for the out-of-pocket expenses
incurred by Medco in connection with the implementation of the proposed design
changes in accordance with the agreed-upon Design Change Budget.

     (c) Each party shall designate one or more representatives to communicate
with the designated representatives of the other with respect to the subject
matter of this Section 2.4. The parties shall provide each other with the names
and contact information of their designated representatives.

     2.5 Additional Services. In relation to the General Program (but not
the Crixivan Program), Medco shall:

     o    provide a data entry function for each Prescription verifying such
          Prescription against eligibility information received from the
          Nominated Agent through the Electronic Feed;

     o    engage in ongoing support interactions with physicians in respect of
          the General Program to ensure that the Merck Products subject to the
          General Program can be dispensed;

     o    capture all information on Prescriptions that have been fulfilled on a
          claims file using Medco's standard record layout and electronically
          provide such data to the Nominated Agent according to Medco's standard
          bi-weekly billing cycle;

     o    in the period between Medco receiving each electronic eligibility
          file and Prescription from the Nominated Agent and Medco supplying the
          Nominated Agent with a claims file tape, maintain a status inquiry
          support capability (or receive transferred calls from patients
          directly from the Nominated Agent to check actual prescription
          dispensing status) so that the Nominated Agent can access information
          with respect to any application;

     o    maintain an automated Prescription refill service allowing
          patients and prescribing physicians to order permissible refills
          using a toll free number established for that purpose (the
          "Automated Refill Service"). The Automated Refill Service shall
          provide for a refill process agreed upon by the parties; provided
          that such process shall employ the use of all applicable
          technologies available to Medco (to the extent technologically
          feasible), and Medco shall use commercially reasonable efforts to
          ensure that such process maximizes time efficiencies and savings
          for Merck; and

     o    develop and incorporate technology to enable Medco to support a
          process for receipt by facsimile from the Nominated Agent of
          Prescription information (the "Faxable Application Process"), as
          promptly as practicable (but in any event within 90 days) of the
          Nominated Agent and Medco reaching agreement with respect to the
          detailed design and technical architecture for the Faxable
          Application Process. Medco shall use commercially reasonable
          efforts to reach such agreement with the Nominated Agent as
          promptly as practicable after the date of this Agreement.

     2.6 Term. This Agreement shall remain in effect from the Effective Date
through the Expiration Date (the "Term"). The "Expiration Date" shall

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be December 31, 2006; provided that in the event of the early termination of
this Agreement in accordance with Article V, the date of such early termination
shall be "Expiration Date".

                                   ARTICLE III

                                  COMPENSATION

     3.1 Charges. For the services provided by Medco to Merck hereunder,
Merck shall pay Medco the fees, and reimburse Medco for its expenses, as
set forth on Schedule 3.1

     3.2 Payment Terms. Merck shall pay and reimburse Medco in accordance with
Section 3.1 for the services provided hereunder during each fiscal month of
Medco during the Term, within thirty (30) days after a receipt of an invoice
therefor (accompanied by such documentation verifying the charges reflected
thereon as shall be reasonably requested by Merck).

                                   ARTICLE IV

                               GENERAL PROVISIONS

     4.1 Parameters. Medco shall, and shall cause to be provided, the services
under this Agreement in the manner in which such services were provided prior to
the date of this Agreement (or in a manner that is more technologically
advanced, or efficient).

     4.2 Good Faith Cooperation; Consents. The Parties will use good faith
efforts to cooperate with each other in all matters relating to the provision
and receipt of the services to be provided hereunder. Such cooperation shall
include exchanging information, and obtaining all third party consents,
authorizations, licenses, sublicenses or approvals necessary to permit each
Party to perform its obligations hereunder (including by way of example, not by
way of limitation, rights to use third party software needed for the performance
of services hereunder). Each Party will maintain, in accordance with its
standard document retention procedures, documentation supporting the information
relevant to cost calculations and cooperate with each other in making such
information available as needed in the event of a tax or regulatory audit,
whether in the United States or any other country.

     4.3 Promotional Materials. Merck shall have sole responsibility for
preparing and distributing all promotional materials relating to the Programs,
and the cost of preparing and distributing such materials shall be borne by
Merck. No Medco Party may prepare or distribute any promotional materials
relating to any Program without Merck's consent. Merck shall provide Medco with
an opportunity to review and comment on promotional materials with respect to
the Programs to be disseminated by Merck prior to the public dissemination
thereof. Merck shall use commercially reasonable efforts to provide a draft of
any such promotional materials to Medco at lease 30 days prior to the public
dissemination thereof.

     4.4 Medco Participation. The Parties acknowledge Medco has not participated
in, and shall not participate in the design of the Program relative to financial
criteria, patient selection, etc. Medco has assisted in the design of dispensing
technology and automated process design to administer the Patient Assistance
Program.

     4.5 Information. Any information or data generated by any Medco Party in
connection with its services hereunder ("Program Information") shall be the
property of Merck and shall not be disclosed or shared by any Medco Party with
any Person except as permitted by Merck, provided that information concerning
the dispensing of prescription drugs customarily

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maintained by Medco shall be maintained by Medco and may be disclosed by Medco
to regulatory agencies having jurisdiction or as otherwise required under
applicable laws or regulations. Medco shall disclose Program Information to
third-parties to the extent requested by Merck. No Medco Party shall use Program
Information for purposes other than patient care in connection with the
Programs.

                                    ARTICLE V

                                EARLY TERMINATION

     5.1 Early Termination. Merck may terminate this Agreement any time upon
sixty- (60) days prior written notice to Medco. Either party may terminate this
Agreement if the other breaches in any material respect any of its obligations
hereunder and does not cure such breach hereunder within thirty (30) days after
being notified of such breach.

     5.2 Survival. Those Sections of this Agreement that, by their nature, are
intended to survive termination will survive in accordance with their terms.

                                   ARTICLE VI

                                 CONFIDENTIALITY

     Without limiting the obligations of the Parties under this Agreement, the
terms of the Confidential Disclosure Agreement shall apply to any Confidential
Information (as defined in that Agreement) of either Party provided to the other
Party for the purpose of providing services under this Agreement.

                                   ARTICLE VII

                                 PATIENT PRIVACY

     7.1 Medco Obligations. Medco represents and warrants and agrees that it
will perform all of its duties under this Agreement in compliance with all
applicable federal, state, local and foreign laws and regulations and licensing
requirements, including but not limited to those related to patient
notification, authorization and consent, privacy of medical records and medical
information. By way of example, Medco is required under the Standards adopted
pursuant to the Health Insurance Portability and Accountability Act of 1996,
either directly as a covered entity or in its role as a business associate of
its health plan clients, to assure that protected health information (all as
defined in such Standards) is used or disclosed only in accordance with such
Standards. If at any time during the Term, Medco concludes that it cannot
perform one or more obligations under this Agreement because of legal or
regulatory restrictions imposed upon it, Medco shall promptly notify Merck,
explain why it believes it cannot legally perform the obligation, and provide
Merck with an estimate of the impact of the restriction on its performance of
this Agreement as a whole. Nothing in this Agreement is intended to allow Medco
to create by contract an impediment to performance of this Agreement that
differs from any restriction to which Medco is subject as to either drug
manufacturers generally or any broader category of third parties.

     7.2 Merck Obligations. Merck represents, warrants and agrees that the data
provided by Merck to Medco pursuant to this Agreement shall not violate the
privacy and/or security rights of any third party or individual and that such
data shall be provided by Merck in compliance with the applicable rules and
regulations governing the use of data, including but not limited to, rules and
regulations governing the use of patient medical information. Merck further
represents, warrants and agrees that prior to

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providing any such data to Medco it will have obtained any and all necessary
consents or authorizations required for Merck to provide the data to Medco.

                                  ARTICLE VIII

                        RELATIONSHIP BETWEEN THE PARTIES

     The relationship between the Parties established under this Agreement is
that of independent contractors and neither Party is an employee, agent,
partner, or joint venture of or with the other.

                                   ARTICLE IX

                               DISPUTE RESOLUTION

     ANY DISPUTE, CONTROVERSY OR CLAIM BETWEEN THE PARTIES HERETO ARISING OUT OF
OR RELATING TO THIS AGREEMENT, INCLUDING, WITHOUT LIMITATION, DISPUTES
CONCERNING THE VALIDITY, INTERPRETATION OR PERFORMANCE OF OR UNDER THIS
AGREEMENT OR ANY TERM OR PROVISION HEREOF, SHALL BE EXCLUSIVELY GOVERNED BY AND
SETTLED IN ACCORDANCE WITH THE PROVISIONS OF ARTICLE III OF THE INDEMNIFICATION
AGREEMENT.

                                    ARTICLE X

                                  MISCELLANEOUS

     10.1 Press Releases. Merck shall use commercially reasonable efforts to
provide Medco with notice of, and an opportunity to review, any press release
relating to any of the Programs that Merck prior to the release thereof. Medco
shall not make any public statement with respect to any of the Programs without
the prior approval of Merck.

     10.2 Entire Agreement. This Agreement, the Separation Agreement and the
other Ancillary Agreements and the Exhibits, Annexes and Schedules referenced or
attached hereto and thereto constitute the entire agreement between the Parties
with respect to the subject matter hereof and thereof and shall supersede all
prior written and oral and all contemporaneous oral agreements and
understandings with respect to the subject matter hereof and thereof.

     10.3 Governing Law; Forum. This Agreement shall be construed in accordance
with, and all Disputes hereunder shall be governed by, the procedural (except to
the extent inconsistent with the procedures set forth in Article III of the
Indemnification Agreement) and substantive laws of the State of New York as to
all matters regardless of the laws that might otherwise govern under principles
of conflicts of laws applicable thereto. Under no circumstances may any party
seek or be awarded punitive damages under this Agreement. Any state court
sitting in New York county, New York and/or the United States District Court for
the Southern District of New York shall have exclusive jurisdiction and venue,
and each party hereto hereby submits to such jurisdiction and venue and
irrevocably waives, to the fullest extent permitted by applicable law, any
objection it may now or hereafter have to such jurisdiction or the laying of
such venue over any Disputes between the parties that are permitted to be
brought in a court, or the enforcement of any decision of an arbitrator,
pursuant to Article III of the Indemnification Agreement. Each of the parties
hereby irrevocably waives any right to a jury trial with respect to a Dispute.

     10.4 Notices. Except as expressly provided herein, all notices and other
communications required or permitted to be given by either Party pursuant to the
terms of this Agreement shall be in writing to and shall be deemed to have been
duly given when delivered in person, by express or

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overnight mail delivery by a nationally recognized courier (delivery charges
prepaid), or by registered or certified mail (postage prepaid, return receipt
requested), as follows:

               if to Merck:

                                     Merck & Co., Inc.
                                     One Merck Drive
                                     P.O. Box 100
                                     Whitehouse Station, New Jersey 08889
                                     Attention: General Counsel

               if to Medco:

                                     MedcoHealth Solutions, Inc.
                                     100 Parsons Pond Road
                                     Franklin Lakes, New Jersey  07417
                                     Attention: General Counsel

or to such other address as the Party to whom notice is given may have
previously furnished to the other in writing in the manner set forth above. All
notices and other communication shall be deemed to have been given and received
on the date of actual delivery.

     10.5 Binding Effect; Assignment; Third-Party Beneficiaries. Medco may not,
directly or indirectly, in whole or in part, whether by operation of law or
otherwise, assign or transfer this Agreement or its rights or obligations
hereunder, without Merck's prior written consent and, except as otherwise
permitted hereby, any attempted assignment, transfer or delegation without such
prior written consent shall be voidable at the sole option of Merck. Nothing in
this Agreement shall restrict any transfer of this Agreement by Merck, whether
by operation of law or otherwise. Without limiting the foregoing, this Agreement
shall be binding upon Merck and the other members of the Merck Group and Medco
and the other members of the Medco Group and their respective legal
representatives, successors and permitted assigns, and nothing in this
Agreement, express or implied, is intended to confer upon any other Person any
rights or remedies of any nature whatsoever under or by reason of this
Agreement.

     10.6 Offset. In addition to, and not in limitation of, any other remedies
any member of the Merck Group or any Merck Indemnitee (as defined in the
Indemnification Agreement) may be entitled to under the Separation Agreement,
any Ancillary Agreement (including this Agreement) or any Intercompany Agreement
(as defined in the Indemnification Agreement) , any member of the Merck Group or
any Merck Indemnitee may satisfy any amounts owed to such member of the Merck
Group or Merck Indemnitee by any member of the Medco Group by means of an offset
against any amounts any member of the Merck Group may from time to time owe to
any member of the Medco Group or an Medco Indemnitee, whether under the
Separation Agreement, any Ancillary Agreement (including this Agreement), any
Intercompany Agreement, any other agreement or arrangement existing between any
member of the Merck Group and any member of the Medco Group, or otherwise.

     10.7 Severability. If any term or other provision of this Agreement or any
Annexes, Schedules or Exhibits attached hereto is determined by a court,
administrative agency or arbitrator to be invalid, illegal or incapable of being
enforced by any rule of law or public policy, all other conditions and
provisions of this Agreement will nevertheless remain in full force and effect
so long as the economic or legal substance of the transactions contemplated
hereby is not affected in any manner materially adverse to any party hereto.
Upon such determination that any term or other provision is invalid, illegal or
incapable of being enforced, the parties hereto shall negotiate in good faith to
modify this Agreement so as to

<PAGE>

effect the original intent of the parties hereto as closely as possible in an
acceptable manner to the end that transactions contemplated hereby are fulfilled
to the fullest extent possible. If the parties are unable to reach an agreement
on any such modification, the arbitrator selected in accordance with Article III
of the Indemnification Agreement shall have the authority to determine such
modification.

     10.8 Failure or Indulgence Not Waiver. No failure or delay on the part of
any party hereto in the exercise of any right hereunder shall impair such right
or be construed to be a waiver of, or acquiescence in, any breach of any
representation, warranty or agreement herein, nor shall any single or partial
exercise of any such right preclude other or further exercise thereof or of any
other right.

     10.9 Amendment. No change or amendment will be made to this Agreement
except by an instrument in writing signed on behalf of each of the parties to
this Agreement.

     10.10 Interpretation. The headings contained in this Agreement, in any
Annex, Exhibit or Schedule hereto and in the table or contents to this Agreement
are for reference purposes only and shall not affect in any way the meaning or
interpretation of this Agreement. Any capitalized term used in any Annex,
Schedule or Exhibit but not otherwise defined therein, shall have the meaning
assigned to such term in this Agreement. When a reference is made in this
Agreement to an Article or Section, or an Annex, Exhibit or Schedule, such
reference shall be to an Article or Section of, or an Annex, Exhibit or Schedule
to, this Agreement unless otherwise indicated.

     10.11 Counterparts. This Agreement, including any Annexes, Schedules and
Exhibits hereto, and the other documents referred to herein, may be executed in
counterparts, each of which shall be deemed to be an original but all of which
shall constitute one and the same agreement.

     10.12 Reexecution. Medco shall reexecute and deliver this Agreement
after the Conversion and prior to the consummation of the IPO.

     10.13 Memoranda of Understandings. The Parties agree and acknowledge that,
subject to Section 2.2(b) this Agreement, shall supercede and replace in its
entirety the Memoranda of Understandings between the Parties regarding the
Programs.

     10.14 Indemnification Agreement. The indemnification obligation of the
Parties with respect to this Agreement shall be as set forth in the
Indemnification Agreement to be entered into between the Parties in connection
with the IPO.


     IN WITNESS WHEREOF, each of the Parties has caused this Agreement to be
executed in duplicate originals by its duly authorized representatives.

MERCK & CO., INC.                       MERCK-MEDCO MANAGED CARE, L.L.C


By:                                     By:
      ------------------------------         ----------------------------
Name:                                   Name:
Title:                                  Title: