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                                                                    EXHIBIT 10.4

                                                                  EXECUTION COPY


                 INDEMNIFICATION AND INSURANCE MATTERS AGREEMENT

                                 BY AND BETWEEN

                               MERCK & CO., INC.,

                                       AND

                          MEDCO HEALTH SOLUTIONS, INC.


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                                Table of Contents
                                -----------------

                                                                            Page
                                                                            ----

ARTICLE I      INDEMNIFICATION.................................................1
   Section 1.1   Indemnification by Medco......................................1
   Section 1.2   Indemnification by Merck......................................2
   Section 1.3   Procedures for Defense, Settlement and
                 Indemnification of Third Party Claims.........................3
   Section 1.4   Additional Matters............................................5
   Section 1.5   Survival of Indemnities.......................................6
ARTICLE II     INSURANCE MATTERS...............................................6
   Section 2.1   Medco Insurance Coverage......................................6
   Section 2.2   Cooperation and Agreement Not to Release Carriers.............6
   Section 2.3   No Liability..................................................6
   Section 2.4   No Restrictions...............................................7
   Section 2.5   Further Agreements............................................7
ARTICLE III    DISPUTE RESOLUTION..............................................7
   Section 3.1   Negotiation...................................................7
   Section 3.2   Binding Arbitration...........................................7
   Section 3.3   Specific Performance..........................................9
ARTICLE IV     PRIVILEGED INFORMATION..........................................9
   Section 4.1   Privileged Information........................................9
ARTICLE V      MISCELLANEOUS..................................................10
   Section 5.1   Entire Agreement.............................................10
   Section 5.2   Governing Law; Forum.........................................10
   Section 5.3   Notices......................................................11
   Section 5.4   Binding Effect; Assignment; Third-Party Beneficiaries........11
   Section 5.5   Offset.......................................................12
   Section 5.6   Other Agreements Evidencing Indemnification Obligations......12
   Section 5.7   Counterparts.................................................12
   Section 5.8   Severability.................................................12
   Section 5.9   Failure or Indulgence Not Waiver.............................12
   Section 5.10  Amendment....................................................13
   Section 5.11  Interpretation...............................................13
ARTICLE VI     DEFINITIONS....................................................13
   Section 6.1   Action.......................................................13
   Section 6.2   Dispute......................................................13
   Section 6.3   Indemnitee...................................................13
   Section 6.4   Indemnifying Party...........................................13
   Section 6.5   Insurance Policies...........................................13
   Section 6.6   Intercompany Agreements......................................13

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                                Table of Contents
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   Section 6.7   Liabilities..................................................13
   Section 6.8   Material Adverse Effect......................................14
   Section 6.9   Medco Assets.................................................14
   Section 6.10  Medco Balance Sheets.........................................14
   Section 6.11  Medco Business...............................................14
   Section 6.12  Medco Indemnitees............................................14
   Section 6.13  Medco Liabilities............................................14
   Section 6.14  Merck Indemnitees............................................17
   Section 6.15  Merck Insurance Policy.......................................17
   Section 6.16  Merck Liabilities............................................17
   Section 6.17  Merck Share of the Shared Liability Actions..................17
   Section 6.18  Privileged Information.......................................17
   Section 6.19  Securities Liabilities.......................................17
   Section 6.20  Distribution Agreement.......................................18
   Section 6.21  Shared Liability Actions.....................................18
   Section 6.22  Subsidiary...................................................18
   Section 6.23  Taxes........................................................18
   Section 6.24  Third Party Claim............................................18
   Section 6.25  Other Definitions............................................18

                                       ii

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                 INDEMNIFICATION AND INSURANCE MATTERS AGREEMENT

     THIS INDEMNIFICATION AND INSURANCE MATTERS AGREEMENT (this "Agreement") is
entered into as of August __, 2003, by and between Merck & Co., Inc., a New
Jersey corporation ("Merck"), and Medco Health Solutions, Inc., a Delaware
corporation ("Medco"). Certain capitalized terms used herein are defined in
Article VI. Capitalized terms used herein and not otherwise defined herein shall
have the meanings ascribed to such terms in the Distribution Agreement (defined
below).

                                    RECITALS

     WHEREAS, the Merck Board has determined that it is appropriate and
desirable for Merck to separate the Medco Group from the Merck Group; and

     WHEREAS, as part of the foregoing, Merck and Medco have entered into the
Master Separation and Distribution Agreement, dated as of August __, 2003 (the
"Distribution Agreement"), which provides, among other things, for the
declaration of the Merck Dividend prior to the Distribution Date, the pro-rata
distribution by Merck of all of its shares of Medco Common Stock 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; and

     WHEREAS, in connection therewith, the parties desire to set forth certain
agreements regarding indemnification and insurance.

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

                                    ARTICLE I

                                 INDEMNIFICATION

     Section 1.1  Indemnification by Medco.

     (a)  Indemnification. Except as otherwise provided in this Agreement, Medco
shall, for itself and as agent for each member of the Medco Group, indemnify,
defend and hold harmless the Merck Indemnitees from and against any and all
Liabilities that any third party seeks to impose upon any of the Merck
Indemnitees, or which are imposed upon any of the Merck Indemnitees, if and to
the extent such Liabilities relate to, arise out of or result from any of the
following items (without duplication):

                  (i)  any breach by Medco or any member of the Medco Group of
          the Distribution Agreement or any of the Ancillary Agreements
          (including this Agreement), other than breaches of the Amended and
          Restated Managed Care Agreement between Merck and Medco, dated as of
          May 28, 2003 (the "Restated Agreement"), as further amended from time
          to time, or the original Managed Care Agreement between Merck and
          Medco, dated as of June 28, 2002 (the "Original Agreement" together
          with the Restated Agreement, the "Managed Care Agreement"), which
          shall be covered by the provisions thereof; or

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                  (ii) any Medco Liability.

     (b)  Reduction of Liability. In the event that any member of the Medco
Group makes a payment to any Merck Indemnitee hereunder, and the Liabilities on
account of which such payment was made are subsequently diminished or reduced,
either directly or through a third-party recovery (other than as a result of a
recovery under a Merck Insurance Policy, unless such recovery is pursuant to the
Credit Support Insurance Coverage, if any), Merck will promptly repay (or will
procure the relevant Merck Indemnitee promptly to repay) such member of the
Medco Group the amount by which the payment made by such member of the Medco
Group exceeds the actual cost of the associated indemnified Liabilities.

     (c)  Joint and Several Liability; No Modification to Other Agreements. The
liability of the members of the Medco Group under this Section 1.1 shall be
joint and several. Nothing in this Section 1.1 shall modify or limit the rights
and remedies of Merck under the Distribution Agreement or any of the Ancillary
Agreements (other than this Agreement) relating to, arising out of or resulting
from any breach by Medco or any member of the Medco Group of the Distribution
Agreement or any of the Ancillary Agreements (other than this Agreement),
including without limitation, any provisions relating to the measure of damages,
consequential damages, liquidated damages, limitation of damages and/or specific
performance.

     Section 1.2  Indemnification by Merck.

     (a)  Indemnification. Except as otherwise provided in this Agreement, Merck
shall, for itself and as agent for each member of the Merck Group, indemnify,
defend and hold harmless the Medco Indemnitees from and against any and all
Liabilities that any third party seeks to impose upon any of the Medco
Indemnitees, or which are imposed upon any of the Medco Indemnitees, if and to
the extent such Liabilities relate to, arise out of or result from (without
duplication):

                  (i)  any breach by Merck or any member of the Merck Group of
          the Distribution Agreement or any of the Ancillary Agreements
          (including this Agreement), other than breaches of the Managed Care
          Agreement, which shall be covered by the provisions thereof; or

                  (ii) any Merck Liability;

provided, however, that notwithstanding anything to the contrary herein, in no
event shall Merck or any member of the Merck Group be obligated to indemnify,
defend or hold harmless the Medco Indemnitees from, against or in respect of any
Medco Liability.

     (b)  Reduction of Liability. In the event that any member of the Merck
Group makes a payment to any Medco Indemnitee hereunder, and the Liabilities on
account of which such payment was made are subsequently diminished or reduced,
either directly or through a third-party recovery, Medco will promptly repay (or
will procure a Medco Indemnitee to promptly repay) such member of the Merck
Group the amount by which the payment made by such member of the Merck Group
exceeds the actual cost of the associated indemnified Liabilities.

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     (c)  Joint and Several Liability; No Modification to Other Agreements. The
liability of the members of the Merck Group under this Section 1.2 shall be
joint and several. Nothing in this Section 1.2 shall modify or limit the rights
and remedies of Medco under the Distribution Agreement or any of the Ancillary
Agreements (other than this Agreement) relating to, arising out of or resulting
from any breach by Merck or any member of the Merck Group of the Distribution
Agreement or any of the Ancillary Agreements (other than this Agreement),
including without limitation, any provisions relating to the measure of damages,
consequential damages, liquidated damages, limitation of damages and/or specific
performance.

     Section 1.3  Procedures for Defense, Settlement and Indemnification of
Third Party Claims.

          (a)     Notice of Claims. If an Indemnitee shall receive notice or
otherwise learn of the assertion of any Third Party Claim with respect to which
a party may be obligated to provide indemnification to such Indemnitee pursuant
to Section 1.1 or 1.2, Merck or Medco (as applicable) shall ensure that such
Indemnitee shall give the potential Indemnifying Party written notice thereof
(including any pleadings relating thereto) within twenty (20) days after
becoming aware of such Third Party Claim. Any such notice shall describe the
Third Party Claim in reasonable detail. Notwithstanding the foregoing, any delay
or failure of any Indemnitee to give notice as provided in this Section 1.3(a)
shall not relieve the Indemnifying Party of its obligations under this Article
I, except to the extent that the Indemnifying Party is actually and
substantially prejudiced by such delay or failure to give notice.

          (b)     Defense by Indemnifying Party. For any Third Party Claim
concerning which notice is required to be given under Section 1.3(a), the
Indemnifying Party may elect to defend and, subject to Section 1.3(f), may
settle or compromise the Third Party Claim using counsel appointed by the
Indemnifying Party, which counsel shall be reasonably satisfactory to the
Indemnitee. An Indemnifying Party electing to defend a Third Party Claim must
(i) notify the Indemnitee of its election to defend within twenty (20) days of
receipt of notice of such claim pursuant to Section 1.3(a) or sooner if the
nature of the Third Party Claim so requires and (ii) subject to Section 1.3(c),
acknowledge and agree in writing that if such Third Party Claim is adversely
determined, such Indemnifying Party will have an obligation to indemnify the
Indemnitee in respect of all Liabilities relating to, arising out of or
resulting from such Third Party Claim and that such Indemnifying Party
irrevocably waives in full all defenses it may have to contest such obligation.

          (c)     Defense by Merck. Notwithstanding Section 1.3(b), Merck, in
its sole discretion, upon written notice to Medco, may elect to defend (or may
at any time assume the defense of) and, subject to Section 1.3(f), may settle or
compromise, any Third Party Claim or series of related Third Party Claims,
regardless of whether Merck is obligated to indemnify any member of the Medco
Group in respect of such Third Party Claim or series of related Third Party
Claims or whether Merck acknowledges any obligation to indemnify any Medco
Indemnitee if:

                  (i)  any member of the Merck Group is named as a party to any
          of such Third Party Claims; or

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                  (ii) both Merck and Medco may be Indemnifying Parties with
          respect to such Third Party Claim(s).

     Except as otherwise provided in the definition of "Merck Share of the
Shared Liability Actions," if Merck elects to defend against a Third Party Claim
pursuant to this Section 1.3(c) all costs and expenses incurred by members of
the Merck Group in connection with such defense shall be paid by Merck and Medco
pro rata based on their respective proportionate liability for any Liabilities
relating to, arising out of or resulting from such Third Party Claim (after
taking into account the parties' respective indemnification obligations under
this Agreement, other than with respect to payment of defense costs).

          (d)     Defense By Non-Electing Party. If the party having the right
to elect to defend a Third Party Claim pursuant to Section 1.3(b) or 1.3(c)
elects not to defend, or does not within any time frame required thereunder
elect to defend, a particular claim, the other party shall defend such Third
Party Claim. In such case, (i) the other party shall have the right, subject to
Sections 1.3(c) and 1.3(f) and the provisions contained in the definition of
"Merck Share of the Shared Liability Actions," to compromise, settle or consent
to the entry of any judgment with respect to such Third Party Claim (but such
compromise, settlement or judgment shall not necessarily be determinative of
which party hereunder is entitled to indemnification) and (ii) the Indemnifying
Party shall bear all costs and expenses of defending such Third Party Claim;
provided, however, that if both parties may be Indemnifying Parties with respect
to such Third Party Claim, except as otherwise provided in the definition of
"Merck Share of the Shared Liability Actions," the Non-Defending Party (defined
below) shall reimburse the Defending Party for the Non-Defending Party's pro
rata share of all costs and expenses incurred by the Defending Party in
connection with its defense of such Third Party Claim, based on the
Non-Defending Party's proportionate liability for any Liabilities relating to,
arising out of or resulting from such Third Party Claim (after taking into
account the parties' indemnification obligations under this Agreement, other
than with respect to payment of defense costs).

          (e)     Participation by Non-Defending Party. In the event that a
party (a "Defending Party") elects or is required to defend a particular Third
Party Claim pursuant to Section 1.3(b), 1.3(c) or 1.3(d), the other party (the
"Non-Defending Party") shall have the right to participate in the defense of
such Third Party Claim; provided, however, that (i) the Defending Party shall
control, manage and direct the defense of such Third Party Claim; and (ii) the
costs and expenses of participating in such defense by the Non-Defending Party
shall be the sole responsibility of the Non-Defending Party. Nothing in this
Section 1.3(e) shall affect the rights of Merck under Section 1.3(c) at any time
to assume the defense of any Third Party Claim and to be indemnified for costs
and expenses of such defense in accordance with Section 1.3(c).

          (f)     No Settlement, Compromise or Consent to Judgments.

                  (i)  No Non-Defending Party may compromise or settle or
          consent to the entry of judgment or determination of liability with
          respect to any Third Party Claim without the consent of the Defending
          Party.

                  (ii) Notwithstanding anything to the contrary herein (but
          subject to the provisions contained in the definition of "Merck Share
          of the Shared Liability

                                        4

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          Actions"), no Defending Party shall compromise, settle or consent to
          the entry of judgment or determination of liability concerning any
          Third Party Claim without providing at least 10 days' prior written
          notice of such compromise, settlement or consent to the Indemnitor (if
          the Indemnitor is other than the Defending Party) and without the
          consent of the Non-Defending Party (such approval not to be
          unreasonably withheld) if the terms or conditions of such compromise,
          settlement or consent would have a Material Adverse Effect on the
          Non-Defending Party's Group.

     Section 1.4  Additional Matters.

          (a)     Other Claims for Indemnification. Any claim in respect of a
Liability which does not relate to, arise out of or result from a Third Party
Claim shall be asserted by written notice from the Indemnitee to the
Indemnifying Party stating the specific provisions of this Agreement or any
Ancillary Agreement upon which such claim is based. Such Indemnifying Party
shall have a period of twenty (20) days from actual receipt of the notice within
which to respond thereto. If such Indemnifying Party does not respond within
such 20-day period, then such Indemnifying Party shall be deemed to have denied
responsibility for such claim.

          (b)     Contribution. If with respect to any Securities Liabilities an
Indemnitee's right to indemnification therefor contained in this Article I is
for any reason held by a court or other tribunal to be unavailable on policy
grounds or otherwise, the Indemnifying Party shall contribute to any amount
payable by the Indemnitee as a result of such Securities Liabilities in such
proportion as to reflect the relative benefit received by the members of the
Indemnifying Party's Group and such Indemnitee from the transaction or
disclosure giving rise to such Securities Liability. If the contribution
provided above is not permitted by applicable law, the Indemnifying Party shall
contribute to any amount payable by the Indemnitee as a result of such
Securities Liabilities in such proportion as to reflect the relative benefit
received by the members of the Indemnifying Party's Group and such Indemnitee
from the transaction and the statements and omissions giving rise to such
Securities Liability, and the relative fault of such members and the Indemnitee
in connection with such statements or omissions. The relative fault of the
members of the Indemnifying Party's Group and such Indemnitee shall be
determined by reference to, among other things, their relative intent,
knowledge, access to information and opportunity to prevent or correct the
statements or omissions giving rise to such Securities Liability.

          (c)     Subrogation. In the event of payment by or on behalf of any
Indemnifying Party to or on behalf of any Indemnitee in connection with any
Third Party Claim, such Indemnifying Party shall be subrogated to and shall
stand in the place of such Indemnitee, in whole or in part based upon whether
the Indemnifying Party has paid all or only part of the Indemnitee's Liability,
as to any events or circumstances in respect of which such Indemnitee may have
any right, defense or claim relating to such Third Party Claim against any
claimant or plaintiff asserting such Third Party Claim or against any other
Person. Such Indemnitee shall cooperate with such Indemnifying Party in a
reasonable manner, and at the cost and expense of such Indemnifying Party, in
prosecuting any subrogated right, defense or claim.

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          (d)     Effect of Insurance on Indemnification/Contribution
Obligations. No Indemnitee shall be required to pursue any claim under any
Insurance Policies of which it is a beneficiary in connection with any Liability
for which such Indemnitee is entitled to indemnification hereunder. The amount
of indemnification or contribution to which such Indemnitee may be entitled
hereunder shall not be reduced as a result of any claim such Indemnitee may
pursue, or have the right to pursue, under any Insurance Policy in respect of
the Liability to which such right to indemnification or contribution relates,
unless the Indemnitee shall have actually recovered any portion of such
Liability from its insurance carrier(s), in which case, whether or not the
amount of indemnification or contribution to such Indemnitee shall be reduced
shall be determined in accordance with Sections 1.1(b) and 1.2(b), as
applicable.

          (e)     Not Applicable to Taxes. Notwithstanding anything to the
contrary contained herein, this Agreement shall not apply to Taxes (which are
covered by the Tax Agreement).

     Section 1.5  Survival of Indemnities. Subject to Section 5.4, the rights
and obligations of the members of the Merck Group and the Medco Group under this
Article I shall survive the sale or other transfer by any party of any assets or
businesses or the assignment by it of any Liabilities or the sale by any member
of the Merck Group or the Medco Group of the capital stock or other equity
interests of any Subsidiary to any Person.

                                   ARTICLE II

                                INSURANCE MATTERS

     Section 2.1  Medco Insurance Coverage. Medco, and Medco alone, shall be
responsible for obtaining and maintaining insurance programs for its risk of
loss and such insurance arrangements shall be separate and apart from Merck's
insurance programs. Merck shall not be required to maintain any insurance
coverage for the benefit of the members of the Medco Group or the directors,
officers or employees of any member of the Medco Group for any period prior to
or after the Distribution.

     Section 2.2  Cooperation and Agreement Not to Release Carriers. Each of
Merck and Medco will share such information as is reasonably necessary in order
to permit the other to manage and conduct its insurance matters in an orderly
fashion. Medco, at the request of Merck, shall cooperate with and use
commercially reasonable efforts to assist Merck in recoveries for claims made
under any Merck Insurance Policy for the benefit of members of the Merck Group.
Neither Medco nor any of its Subsidiaries shall take any action which would
intentionally jeopardize or otherwise interfere with the ability of any member
of the Merck Group to collect any proceeds payable pursuant to any insurance
policy. Nothing in this Agreement shall be interpreted to require Merck to
maintain any insurance coverage for any Member of the Medco Group or any of
their officers, directors or employees.

     Section 2.3  No Liability. Medco does hereby, for itself and as agent for
each other member of the Medco Group, agree that no member of the Merck Group or
any Merck Indemnitee shall have any Liability whatsoever as a result of the
insurance policies and practices

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of Merck and its Subsidiaries as in effect at any time prior to the Distribution
Date, including as a result of the level or scope of any such insurance, the
creditworthiness of any insurance carrier, the terms and conditions of any
policy, the adequacy or timeliness of any notice to any insurance carrier with
respect to any claim or potential claim or otherwise.

     Section 2.4  No Restrictions. Nothing in this Agreement shall be deemed to
restrict any member of the Medco Group from acquiring at its own expense any
other insurance policy in respect of any Liabilities or covering any period.

     Section 2.5  Further Agreements. Medco, the members of the Medco Group, and
the directors, officers and employees of any member of the Medco Group, shall
not make any claims under Merck Insurance Policies, including in respect of
events that occurred when Medco and the members of the Medco Group were
subsidiaries of Merck.

                                   ARTICLE III

                               DISPUTE RESOLUTION

     EXCEPT AS OTHERWISE SET FORTH IN THE DISTRIBUTION AGREEMENT OR ANY
ANCILLARY AGREEMENT, ANY DISPUTES ARISING OUT OF OR RELATING TO THE DISTRIBUTION
AGREEMENT OR ANY ANCILLARY AGREEMENT (INCLUDING THIS AGREEMENT BUT EXPRESSLY
EXCLUDING THE MANAGED CARE AGREEMENT), INCLUDING, WITHOUT LIMITATION, DISPUTES
CONCERNING THE VALIDITY, INTERPRETATION AND PERFORMANCE OF OR UNDER ANY SUCH
AGREEMENT, SHALL BE EXCLUSIVELY GOVERNED BY AND SETTLED IN ACCORDANCE WITH THE
PROVISIONS OF THIS ARTICLE III.

     Section 3.1  Negotiation. The parties shall make a good faith attempt to
resolve any Dispute through negotiation. Within fifteen (15) days after notice
of a Dispute is given by either party to the other party, each party shall
select one or more representatives who are vice presidents, senior vice
presidents or executive vice presidents of such party and shall notify the other
party in writing of the names and contact details of its representatives, which
representatives shall meet and make a good faith attempt to resolve such Dispute
and shall continue to negotiate in good faith in an effort to resolve the
Dispute without the necessity of any formal proceedings. The specific format for
such negotiations will be left to the discretion of the designated
representatives but may include the preparation of agreed upon statements of
fact or written statements of position furnished to the other party.

     Section 3.2  Binding Arbitration.

          (a)     If such representatives fail to resolve a Dispute within ten
(10) days after the date of delivery of the later of the notices of selection of
the representatives, unless otherwise mutually agreed, either party shall have
the right to submit such Dispute to final and binding arbitration. It is the
intent of the parties that any such arbitration be structured in such a way as
to result in a resolution of such Dispute as promptly as practicable in
accordance herewith. Except as otherwise provided in this Article III, any
arbitration shall be conducted pursuant to

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the then current Rules for Non-Administered Arbitration of the Center for Public
Resources ("CPR Rules") and the site of the arbitration shall be in New York
County, New York.

          (b)     A party (a "Disputing Party") shall institute any arbitration
proceeding hereunder by providing written notice thereof to the other party (the
"Arbitration Demand") which shall describe in reasonable detail the nature of
the Dispute, the claims of the Disputing Party and the requested relief and, if
the Disputing Party is Merck, setting forth a list of at least five potential
independent and impartial arbitrators selected by Merck, each of whom shall not
have a personal or financial interest in the result of the arbitration or the
parties to the arbitration (provided that the ownership of shares in a mutual
fund that owns securities of either of the parties shall not be considered a
personal or financial interest for this purpose) and shall be experienced in
representing clients in commercial arbitration. Within thirty (30) days after
the other party's receipt of the Arbitration Demand, such other party shall
furnish the Disputing Party with a written statement (a "Response Statement")
(1) answering the claims set forth in the Arbitration Demand, (2) asserting any
counterclaim, describing in reasonable detail the nature of the Dispute relating
to such counterclaim and the requested relief for such counterclaims, and (3) if
such other party is Medco, selecting as the sole arbitrator for the proceeding
one of the potential arbitrators listed in the Arbitration Demand or if such
other party is Merck setting forth a list of at least five potential impartial
arbitrators selected by Merck, each of whom shall not have a personal or
financial interest in the result of the arbitration or the parties to the
arbitration (provided that the ownership of shares in a mutual fund that owns
securities of either of the parties shall not be considered a personal or
financial interest for this purpose) and shall be experienced in representing
clients in commercial arbitration. If the Disputing Party is Medco, Medco shall
notify Merck within ten (10) days of Medco's receipt of the Response Statement
of Medco's selection as the sole arbitrator for the proceeding from the
potential arbitrators listed in the Arbitration Demand. If Medco fails within
the applicable time period to select an arbitrator from the list of potential
arbitrators included in Merck's Arbitration Demand or Response Statement, as
applicable, an arbitrator shall be selected in accordance with the CPR Rules
from such list of potential arbitrators.

          (c)     The arbitrator shall be instructed to use best efforts to
complete all arbitration hearings no later than three (3) months from the date
of the arbitrator's appointment and use best efforts to render a decision within
four (4) months from such date.

          (d)     With respect to discovery in an arbitration proceeding, the
arbitrator must allow either party to make discovery requests for documents of
the other party where the information sought is reasonably calculated to lead to
the discovery of admissible evidence, and each party agrees to respond to such
discovery request within a reasonable time. The arbitrator is obligated to
construe the term "document" literally to encompass data compilations in any
form.

          (e)     The prevailing party in any arbitration as determined by the
arbitrator shall be entitled to expenses, including costs and reasonable
attorneys' and other professional fees, incurred in connection with the
arbitration.

          (f)     In connection with any Dispute, the arbitrator shall be
obligated to apply solely principles of law.

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          (g)  The decision of the arbitrator shall be final and non-appealable
and may be enforced in any court of competent jurisdiction.

          (h)  The use of any alternative dispute resolution procedures will not
be construed under the doctrine of laches, waiver or estoppel to adversely
affect the rights of either party.

     Section 3.3  Specific Performance. The parties agree and acknowledge that
each would suffer irreparable harm in the event that the other fails to perform
any of its obligations under Article IV hereunder in accordance with its
specific terms or otherwise breaches any of such obligations. Each of the
parties further agrees and acknowledges that money damages may be an inadequate
remedy for such failure to perform or breach of Article IV by it. Accordingly,
notwithstanding anything herein to the contrary, and without waiving any remedy
hereunder, each of the parties shall be entitled to seek specific performance by
the other of its obligations under Article IV hereunder and/or injunctive or
other equitable relief to prevent or cure breaches of Article IV hereunder in an
arbitration proceeding (without first complying with the negotiation provision
of Section 3.1) or in court (subject to Section 5.2).

                                   ARTICLE IV

                             PRIVILEGED INFORMATION

     Section 4.1  Privileged Information. In furtherance of the rights and
obligations of the parties set forth in the Distribution Agreement and the
Ancillary Agreements:

          (a)  Each party hereto acknowledges that (i) each of the Merck Group
on the one hand, and the Medco Group on the other hand, has or may obtain
Information regarding a member of the other Group, or any of its operations,
employees, assets or liabilities (whether in documents or stored in any other
form or known to its employees or agents), as applicable, that is or may be
protected from disclosure pursuant to the attorney-client privilege, the work
product doctrine or other applicable privileges ("Privileged Information"); (ii)
there are a number of actual, threatened or future litigations, investigations,
proceedings (including arbitration proceedings), claims or other legal matters
that have been or may be asserted by or against, or otherwise affect, each or
both of Merck and Medco (or members of either Group) ("Litigation Matters");
(iii) Merck and Medco have a common legal interest in Litigation Matters, in the
Privileged Information, and in the preservation of the confidential status of
the Privileged Information, in each case relating to the Merck Business or the
Medco Business or any former businesses or the assets or liabilities of each
party as it or they existed prior to the Distribution Date or relating to or
arising in connection with the relationship between the constituent elements of
the Groups on or prior to the Distribution Date; and (iv) Merck and Medco intend
that the transactions contemplated by the Related Agreements and any transfer of
Privileged Information in connection herewith or therewith shall not operate as
a waiver of any potentially applicable privilege.

          (b)  Each of Merck and Medco agrees, on behalf of itself and each
member of the Group of which it is a member, not to disclose or otherwise waive
any privilege attaching to any Privileged Information relating to the Merck
Business or the Medco Business or any former

                                        9

<PAGE>

businesses or the assets or liabilities of either party as it or they existed
prior to the Distribution Date or relating to or arising in connection with the
relationship between the Groups on or prior to the Distribution Date, without
providing prompt written notice to and obtaining the prior written consent of
the other, which consent shall not be unreasonably withheld and shall not be
withheld if the other party certifies that such disclosure is to be made in
response to a likely threat of suspension, debarment, criminal indictment or
similar action; provided, however, that Merck may make such disclosure or waiver
with respect to Privileged Information if such Privileged Information relates
solely to the Merck Business, its former businesses (other than the Medco
Business), its assets or liabilities (other than assets or liabilities of the
Medco Business), and Medco may make such disclosure or waiver with respect to
Privileged Information if such Privileged Information relates solely to the
Medco Business, or assets or liabilities exclusively of the Medco Business. The
parties will use commercially reasonable efforts to limit any such disclosure or
waiver to the maximum extent possible and shall seek the execution of a
confidentiality agreement by the party or parties to which such disclosure or
waiver is made.

          (c)  Upon any member of the Merck Group or any member of the Medco
Group receiving any subpoena or other compulsory disclosure notice from any
Governmental Authority or otherwise which requests disclosure of Privileged
Information, in the case of the Medco Group, relating to the Merck Business, its
former businesses (other than the Medco Business), its assets or liabilities
(other than assets or liabilities of the Medco Business), or, in the case of the
Merck Group, relating to the Medco Business, or assets or liabilities
exclusively of the Medco Business, as it or they existed prior to the
Distribution Date or, in either case, relating to or arising in connection with
the relationship between the constituent elements of the Groups on or prior to
the Distribution Date, the recipient of the notice shall promptly provide to
Merck, in the case of receipt by a member of the Medco Group, or to Medco, in
the case of receipt by a member of the Merck Group, a copy of such notice, the
intended response, and all materials or information relating to the other Group
that might be disclosed. In the event of a disagreement as to the intended
response or disclosure, unless and until the disagreement is resolved as
provided in Article III, Merck and Medco shall cooperate to assert all defenses
to disclosure claimed by either Group, at the cost and expense of the Group
claiming such defense to disclosure, and shall not disclose any disputed
documents or information until all legal defenses and claims of privilege have
been finally determined.

                                    ARTICLE V

                                  MISCELLANEOUS

     Section 5.1  Entire Agreement. This Agreement, the Distribution Agreement,
the other Ancillary Agreements and any Annexes, Exhibits and Schedules attached
hereto and thereto, constitutes the entire agreement among 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.

     Section 5.2  Governing Law; Forum. This Agreement, the Distribution
Agreement and all other Ancillary Agreements 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

                                       10

<PAGE>

forth in Article III of this 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, the
Distribution Agreement or any other Ancillary 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 arbitrators, pursuant to Article III above. Each
of the parties hereby irrevocably waives any right to a jury trial with respect
to a Dispute.

     Section 5.3  Notices. All notices and other communications required or
permitted to be given by any 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 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:

               Medco Health Solutions, Inc.
               100 Parsons Pond Drive
               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.

     Section 5.4  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 inure solely to the benefit of the
Medco Indemnitees and the Merck

                                       11

<PAGE>

Indemnitees 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.

     Section 5.5  Offset. In addition to, and not in limitation of, any other
remedies any member of the Merck Group or any Merck Indemnitee may be entitled
to under the Distribution Agreement, any Ancillary Agreement (including this
Agreement) or any Intercompany 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
Distribution 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.

     Section 5.6  Other Agreements Evidencing Indemnification Obligations. Merck
hereby agrees to execute, for the benefit of any Medco Indemnitee, such
documents as may be reasonably requested by such Medco Indemnitee, evidencing
Merck's agreement that the indemnification obligations of Merck set forth in
this Agreement inure to the benefit of and are enforceable by such Medco
Indemnitee. Medco hereby agrees to execute, for the benefit of any Merck
Indemnitee, such documents as may be reasonably requested by such Merck
Indemnitee, evidencing Medco's agreement that the indemnification obligations of
Medco set forth in this Agreement inure to the benefit of and are enforceable by
such Merck Indemnitee.

     Section 5.7  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.

     Section 5.8  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 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 this Agreement shall have the
authority to determine such modification.

     Section 5.9  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.

                                       12

<PAGE>

     Section 5.10 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.

     Section 5.11 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.

                                   ARTICLE VI

                                   DEFINITIONS

     Section 6.1  Action. "Action" means any claim, demand, action, suit,
countersuit, arbitration, inquiry, proceeding or investigation by or before any
federal, state, local, foreign or international governmental authority or any
arbitration or mediation tribunal.

     Section 6.2  Dispute. "Dispute" means a dispute arising from or in
connection with the Distribution Agreement, this Agreement or any other
Ancillary Agreement, whether based on contract, tort, or otherwise.

     Section 6.3  Indemnitee. "Indemnitee" means a Merck Indemnitee or a Medco
Indemnitee.

     Section 6.4  Indemnifying Party. "Indemnifying Party" means any party who
is required to indemnify any other Person pursuant to this Agreement.

     Section 6.5  Insurance Policies. "Insurance Policies" means insurance
policies pursuant to which a Person makes a true risk transfer to an insurer.

     Section 6.6  Intercompany Agreements. "Intercompany Agreements" means any
written agreement, arrangement or understanding between any member of the Merck
Group and any member of the Medco Group which is in effect prior to, as of or
after the Distribution Date.

     Section 6.7  Liabilities. "Liabilities" means all debts, liabilities,
guarantees, assurances, commitments and obligations, whether fixed, contingent
or absolute, asserted or unasserted, matured or unmatured, liquidated or
unliquidated, accrued or not accrued, known or unknown, due or to become due,
whenever or however arising (including, without limitation, whether arising out
of any contract or tort based on negligence or strict liability) and whether or
not the same would be required by generally accepted principles and accounting
policies to be reflected in financial statements or disclosed in the notes
thereto. For purposes of any indemnification hereunder, "Liabilities" shall be
deemed also to include any and all damages, claims, suits, judgments, fines,
penalties, costs and expenses of any kind or character, including attorney's
fees and expenses, costs of investigation and preparation, expert witness costs
and any

                                       13

<PAGE>

other fees and expenses associated with the defense of any Action
whether relating to Third Party Claims or Actions against the other party
hereto.

     Section 6.8  Material Adverse Effect. "Material Adverse Effect" means, with
respect to either Group, a material adverse effect on the business, results of
operations or financial conditions of the members of such Group, taken as a
whole, provided that, without limiting the events, circumstances or conditions
which may constitute or result in a Material Adverse Effect on the Merck Group,
any compromise, settlement or consent affecting the Merck Group that, if applied
to Medco or any member of the Medco Group, would result in a Material Adverse
Effect on the Medco Group, shall be deemed to result in a Material Adverse
Effect on the Merck Group.

     Section 6.9  Medco Assets. "Medco Assets" means all assets of the Medco
Group following the consummation of the Distribution.

     Section 6.10 Medco Balance Sheets. "Medco Balance Sheets" means the
consolidated balance sheets of Medco and its Subsidiaries included in the Form
10.

     Section 6.11 Medco Business. "Medco Business" means (a) the business and
operations of Medco, Merck-Medco LLC and its Subsidiaries and Affiliates (other
than members of the Merck Group), and (b) except as otherwise expressly provided
herein, any terminated, divested or discontinued businesses or operations that
at the time of termination, divestiture or discontinuation primarily related to
the Medco Business as then conducted; provided, that the Medco Business shall
not include the business or operations of Merck Capital Ventures LLC, Merck
Liability Management Company or Merck Medco Holdings II Corp.

     Section 6.12 Medco Indemnitees. "Medco Indemnitees" means Medco, each
member of the Medco Group and each of their respective directors, officers,
employees, agents or representatives.

     Section 6.13 Medco Liabilities. "Medco Liabilities" means, collectively,
all of the Liabilities of Medco and each of the other members of the Medco
Group, including without limitation:

                  (i)    all of the Liabilities reflected on the Medco Balance
             Sheet;

                  (ii)   all Liabilities relating to, arising out of or
             resulting from any of the Credit Support Arrangements, including,
             without limitation, any payment required to be made by a member of
             the Merck Group under any of the Credit Support Arrangements;

                  (iii)  all Liabilities which are incurred or arise, or which
             accrue or exist or are accrued at any time on, prior to or after
             the date of the Medco Balance Sheets and which arise or arose out
             of, or in connection with, or otherwise relate to or result from,
             the Medco Assets or the Medco Business;

                                       14

<PAGE>

                  (iv)   all Liabilities of each member of the Medco Group
             under, allocated to or to be retained or assumed by Medco or any of
             the other members of the Medco Group pursuant to the Distribution
             Agreement, this Agreement or any Ancillary Agreements, or
             Intercompany Agreements; provided that nothing in this Agreement
             shall adversely affect the rights and remedies of Merck or Medco
             under the Managed Care Agreement relating to, arising out of or
             resulting from a breach of the Managed Care Agreement, or any
             Liability of either party to the other relating to, arising out of
             or resulting from such breach;

                  (v)    all of the Liabilities of any member of the Merck Group
             or Medco Group (whenever arising whether prior to, on or following
             the Distribution Date) arising out of or in connection with or
             otherwise relating to the management or conduct prior to, on or
             following the Distribution Date of the Medco Business or the Medco
             Assets; provided that nothing in this Agreement shall adversely
             affect the rights and remedies of Merck or Medco under the Managed
             Care Agreement relating to, arising out of or resulting from a
             breach of the Managed Care Agreement, or any Liability of either
             party to the other relating to, arising out of or resulting from
             such breach;

                  (vi)   Subject to the proviso set forth after clause (x) of
             this Section 6.13, all Liabilities relating to, arising out of or
             resulting from (a) the Shared Liability Actions, any Actions in
             respect of which as of the date of this Agreement any member of the
             Medco Group has been named as a defendant (including, without
             limitation, the Actions captioned U.S.A. ex rel. Hunt and Gauger v.
             Medco and U.S.A. ex rel. v. Piacentile v. Medco) or any amendments
             to such Actions (the "Existing Actions"), (b) any of the facts,
             circumstances and events giving rise to Shared Liability Actions or
             any of the Existing Actions, and (c) any Actions involving similar
             claims or which are based upon similar facts, circumstances or
             events, whether involving the same parties or other parties, in
             each case whether relating to, arising out of or resulting from
             facts, circumstances or events prior to, on or after the
             Distribution Date;

                  (vii)  all Liabilities relating to, arising out of or
             resulting from, any Third Party Claim relating to, arising out of
             or resulting from (1) the Managed Care Agreement or (2) any
             infringement or alleged infringement by the Patents or the Patent
             License (or the use thereof) on any intellectual property or other
             rights of any Person;

                  (viii) all Liabilities relating to, arising out of or
             resulting from the Actions, Third Party Claims, the examinations,
             notices, letters, reviews and investigations by Governmental
             Authorities, referred to in the Form 10 under "Business - Legal
             Proceedings and Government Investigations", and "Management -
             Retirement Benefits - Cash Balance Plan" and Liabilities relating
             to, arising out of, or resulting from the facts, circumstances or
             events giving rise to any of such Actions, Third Party Claims,
             examinations, notices, letters, reviews

                                       15

<PAGE>

             or investigations (subject to the proviso set forth after clause
             (x) of this Section 6.13);

                  (ix)   all Securities Liabilities relating to, arising out of
             or resulting from (A) the Notes Offering, the Distribution and any
             documents, information or data (financial or otherwise) furnished
             or provided, orally or in writing, to purchasers or transferees or
             potential purchasers and transferees (or any of their respective
             representatives), in connection therewith or filed or furnished in
             connection therewith with or to any Governmental Authority or any
             securities exchange or securities market, including, without
             limitation, the Registration Statements, (B) any other offer,
             issuance, sale, exchange or other transfer of securities of or by
             Medco or any member of the Medco Group prior to, on or after the
             Distribution Date, or any documents, information or data (financial
             or otherwise) furnished or provided, orally or in writing, to
             transferees or purchasers or potential transferees or purchasers
             (or any of their respective representatives) of such securities or
             filed or furnished in connection therewith with or to any
             Governmental Authority or securities exchange or securities market,
             including, without limitation, any registration statement, (C) any
             oral or written disclosure made, whether or not included in
             documents filed with or furnished to any Governmental Authority or
             securities exchange or securities market, by Medco or any member of
             the Medco Group, or on behalf of Medco or any Member of the Medco
             Group, prior to, on or after the Distribution Date or any
             disclosure made (other than by a member of the Merck Group), orally
             or in writing, of information or data (financial or otherwise)
             relating to or concerning Medco or any other member of the Medco
             Group, the business, operations and management of the Medco
             Business and/or Medco or any other member of the Medco Group, and
             (D) any oral or written disclosure made, whether or not included in
             documents filed with or furnished to any Governmental Authority or
             securities exchange or securities market, by Merck or any member of
             the Merck Group prior to, on or after the Distribution Date based
             on any information or data (financial or otherwise) provided by or
             on behalf of Medco or any member of the Medco Group; and

                  (x)    all other Liabilities arising out of, relating to or
             resulting from any Action or Third Party Claim by any Governmental
             Authority or any other Person that is based on (A) any violations
             or alleged violations by Medco, its Subsidiaries and/or any of
             their respective directors, officers, employees, agents or
             representatives of any of the provisions of the Securities Act,
             Exchange Act, or the rules and regulations of the Commission
             promulgated thereunder, any other securities or similar law or any
             other law, rule or regulation, including, without limitation, the
             federal False Claims Act and state False Claims Acts, or (B) any
             breach or alleged breach of fiduciary duty by the Medco Board or
             any Committee of the Medco Board (or any member of the Medco Board
             or any Committee thereof) or the board of directors or similar body
             or any Committee of the board of directors or similar body (or any
             member of any such board or similar body or any Committee thereof)
             of any other member of the Medco Group, or by any officer or
             employee of any member of the Medco Group.

                                       16

<PAGE>

provided, however, that (i) Medco Liabilities shall not include the Merck
Defendant Robinson-Patman Act Liabilities and the Specified Litigation
Liabilities (both as defined in Section 6.16), and (ii) Merck shall be
responsible for the Merck Share of the Shared Liability Actions.

     Section 6.14 Merck Indemnitees. "Merck Indemnitees" means Merck, each
member of the Merck Group and each of their respective directors, officers,
employees, agents and representatives.

     Section 6.15 Merck Insurance Policy. "Merck Insurance Policy" shall mean
each Insurance Policy owned or maintained by a member of the Merck Group.

     Section 6.16 Merck Liabilities. "Merck Liabilities" means

                  (i)    all Liabilities of any member of the Merck Group under,
             allocated to or to be retained or assumed by Merck or any of the
             other members of the Merck Group pursuant to the Distribution
             Agreement, this Agreement or any other Ancillary Agreement (other
             than Liabilities resulting from a breach of the Managed Care
             Agreement, which shall be subject to the terms thereof);

                  (ii)   all Liabilities incurred by members of the Merck Group
             in connection with the management or conduct prior to, on or
             following the Distribution Date of the Merck Business (other than
             Liabilities resulting from a breach of the Managed Care Agreement,
             which shall be subject to the terms thereof);

                  (iii)  all monetary Liabilities arising out of those Actions
             set forth on Schedule 6.16(a) (but not including any lost sales or
             profits resulting from any of such Actions) (the "Merck Defendant
             Robinson-Patman Act Liabilities"); and

                  (iv)   all monetary Liabilities arising out of claims made
             prior to the date of this Agreement in the Action set forth on
             Schedule 6.16(b) (but not including any lost sales or profits
             resulting from such Action ) ("Specified Litigation Liabilities");

provided, however, that Merck Liabilities shall not include any Liability that
constitutes a Medco Liability.

     Section 6.17 Merck Share of the Shared Liability Actions. "Merck Share of
the Shared Liability Actions" shall have the meaning set forth on Schedule 6.17.

     Section 6.18 Privileged Information. "Privileged Information" has the
meaning set forth in Section 4.1(a).

     Section 6.19 Securities Liabilities. "Securities Liabilities" means any and
all losses, liabilities, penalties, claims, damages, demands, costs or expenses
or other Liabilities whatsoever that are assessed, imposed, awarded against,
incurred or accrued by a Person arising out of or relating in whole or in part
to any Action, any potential or threatened Action, any Third Party

                                       17

<PAGE>

Claim or any potential or threatened Third Party Claim by any Governmental
Authority or any other Person that is based on any violations or alleged
violations of the Securities Act, the Exchange Act, and any of the rules or
regulations of the Commission promulgated under the Securities Act or Exchange
Act, or any other securities or other similar laws, rules or regulations,
including, without limitation, state securities or "blue sky" laws, rules or
regulations, foreign securities laws, rules or regulations and rules or
regulations of any securities exchange or market.

     Section 6.20 Distribution Agreement. "Distribution Agreement" has the
meaning set forth in the Recitals hereof.

     Section 6.21 Shared Liability Actions. "Shared Liability Actions" has the
meaning set forth on Schedule 6.21.

     Section 6.22 Subsidiary. "Subsidiary" has the meaning set forth in the
Distribution Agreement.

     Section 6.23 Taxes. "Taxes" has the meaning set forth in the Tax Agreement.

     Section 6.24 Third Party Claim. "Third Party Claim" means an Action
brought, asserted, commenced or pursued by a Person (including any Governmental
Authority) other than a member of the Merck Group or the Medco Group.

     Section 6.25 Other Definitions. Any capitalized terms used but not defined
herein shall have the meanings assigned to them in the Distribution Agreement.


                         [SIGNATURES ON FOLLOWING PAGE]


                                       18

<PAGE>

     IN WITNESS WHEREOF, each of the parties has caused this Indemnification and
Insurance Matters Agreement to be executed on its behalf by its officers
thereunto duly authorized on the day and year first above written.

                                        MERCK & CO., INC.


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

                                        MEDCO HEALTH SOLUTIONS, INC.


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

                                       19

<PAGE>

                                Schedule 6.16(a)

                           Robinson-Patman Act Actions
                           ---------------------------

The Actions in which Merck was named as defendant that were consolidated for
pre-trial proceedings in the United States District Court for the Northern
District of Illinois into the Action captioned In Re Brand Name Prescription
Drug Antitrust Litigation.


<PAGE>

                                Schedule 6.16(b)

                           Specified Litigation Action
                           ---------------------------

The Action filed in the United States District Court For the District of New
Jersey (No. 03 CV 2631 (SRC)) captioned Ellen Fagin and Judith Fagin,
derivatively and on behalf of Merck & Co., Inc. and Medco Health Solutions,
Inc., v. Raymond V. Gilmartin, Judy C. Lewent, William B. Harrison, Jr., Heidi
G. Miller, Thomas E. Shenk, Samuel O. Their, Richard T. Clark, Joan A. Reed,
Richard J. Rubino, Lawrence A. Bossidy, Jeanetta B. Cole, William N. Kelly,
William G. Bowen, Niall Fitzgerald, Anne M. Tatlock, Edward M. Skolnick and
Arthur Andersen, LLP and Merck & Co., Inc.


                                        2

<PAGE>

                                  Schedule 6.17

     "Merck Share of the Shared Liability Actions" means (x) 10% of amounts
payable in settlement of, and/or pursuant to judgments rendered in, the ERISA
Shared Liability Actions (as defined on Schedule 6.21) ("Merck's Share of the
ERISA Shared Liability Actions"); provided that Merck's Share of the ERISA
Shared Liability Actions shall not exceed $25 million, in the aggregate, and
notwithstanding anything to the contrary contained in this Agreement, Merck
shall not be responsible for any, and Medco shall be responsible for all,
amounts incurred defending against the ERISA Shared Liability Actions and (y)
80% of amounts payable in settlement of, and/or pursuant to judgments rendered
in, the Revenue Recognition Actions (as defined on Schedule 6.21), and
notwithstanding anything to the contrary contained in this Agreement, Medco
shall not be responsible for any, and Merck shall be responsible for all,
amounts incurred defending against the Revenue Recognition Actions, it being
understood that Medco shall be responsible for 20% (but not more than 20%) of
amounts payable in settlement of, and/or pursuant to judgments rendered in, the
Revenue Recognition Actions. Under no circumstances shall Merck be responsible
for any lost sales and profits of members of the Medco Group resulting from, or
relating to, the Shared Liability Actions. Merck shall have the sole right to
compromise, settle, or consent to the entry of a judgment or determination of
liability concerning any Revenue Recognition Actions, it being understood that
Merck shall be under no obligation to provide prior notice to, or obtain consent
from, Medco in connection with any such compromise, settlement or consent. Medco
shall have the sole right to compromise, settle, or consent to the entry of a
judgment or determination of liability concerning any ERISA Shared Liability
Actions, it being understood that Medco shall be under no obligation to obtain
consent from Merck in connection with any such compromise, settlement or
consent.

                                       3

<PAGE>

                                  Schedule 6.21

     "ERISA Shared Liability Actions" means the Action captioned Gruer v.
Merck-Medco Managed Care, L.L.C. filed in the United States District Court for
the Southern District of New York (the "Gruer Action") and all other Actions
that prior to the date of this Agreement were transferred and consolidated with
the Gruer Action in the District Court for the Southern District of New York
into the Action captioned In re Medco Health Solutions, Inc. Pharmacy Benefit
Management Litigation and other Actions naming Merck as a defendant that are
commenced prior to the first anniversary of the Distribution Date, in each case
to the extent such Actions include, or are amended to include, (a) claims that a
member of the Medco Group should be treated as a fiduciary under the Employment
Retirement Income Security Act of 1974, as amended ("ERISA"), and that a member
of the Medco Group breached its fiduciary obligations under such Act in
connection with the development and implementation prior to the Distribution
Date of formularies, preferred drug listings and intervention programs by
members of the Medco Group and (b) state or federal claims alleging antitrust
violations based on or arising from conduct occurring prior to the Distribution
Date alleged to be violative of ERISA in the Actions captioned above or in
similar Actions. ERISA Shared Liability Actions shall not include: (a) any
Action or Third Party Claim of, brought by or on behalf of, or in which there is
intervention by, any Governmental Authority, including without limitation the
office of the U.S. Attorney for the Eastern District of Pennsylvania, (b) any
Action or Third Party Claim of, or brought by or on behalf of, any other Person
as a result of, or alleging, facts, circumstances or events discovered as a
result of, any review or investigation made by any Governmental Authority,
including without limitation the office of the U.S. Attorney for the Eastern
District of Pennsylvania, or (c) any Action or Third Party Claim alleging
violations of the federal False Claims Act or state False Claims Acts,
including, without limitation, the Actions captioned U.S.A. ex rel. Hunt and
Gauger v. Medco and U.S.A. ex rel. v. Piacentile v. Medco. Without limiting
Medco's responsibilities and obligations under this Agreement, it is understood
that any Action or Third Party Claim that would constitute an ERISA Shared
Liability Action but for the immediately preceding sentence and all Liabilities
resulting therefrom shall be the sole responsibility of Medco.

     "Revenue Recognition Actions" means the Actions in which Merck and Medco
and their officers and directors were named as defendants (relating to Merck and
Medco's revenue recognition practices, for retail co-payments and rebates
received by Medco and Medco's independent status) that were consolidated in the
United States District Court for the District of New Jersey into the Action
captioned In re Merck & Co. Securities Litigation.

     "Shared Liability Actions" means the Revenue Recognition Actions and the
ERISA Shared Liability Actions.

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