Exhibit 4.1

EIGHTH SUPPLEMENTAL INDENTURE

The Eighth Supplemental Indenture (this “ Eighth Supplemental Indenture ”), dated as of April 2, 2012, among Express Scripts Holding Company (formerly Aristotle Holding, Inc.), a corporation duly organized and existing under the laws of the State of Delaware (the “ Company ”), the Guarantors listed as signatories hereto (each, an “ Existing Guarantor ” and collectively, the “ Existing Guarantors ”), Medco Health Solutions, Inc., a Delaware corporation, and its subsidiaries listed as signatories hereto (each, an “ Additional Guarantor ,” and, collectively, the “ Additional Guarantors ”) and Wells Fargo Bank, National Association, as trustee under the indenture referred to below (the “ Trustee ”).

W I T N E S S E T H

WHEREAS, the Company, the Existing Guarantors and the Trustee are parties to the indenture, dated as of November 21, 2011 (the “ Base Indenture ”), as supplemented by the First Supplemental Indenture thereto, dated as of November 21, 2011 (the “ First Supplemental Indenture ”), relating to the Company’s 2.750% Notes due 2014 (the “ 2014 Notes ”), the Second Supplemental Indenture thereto, dated as of November 21, 2011 (the “ Second Supplemental Indenture ”), relating to the Company’s 3.500% Notes due 2016 (the “ 2016 Notes ”), the Third Supplemental Indenture thereto, dated as of November 21, 2011 (the “ Third Supplemental Indenture ”), relating to the Company’s 4.750% Notes due 2021 (the “ 2021 Notes ”), the Fourth Supplemental Indenture thereto, dated as of November 21, 2011 (the “ Fourth Supplemental Indenture ”), relating to the Company’s 6.125% Notes due 2041 (the “ 2041 Notes ”), the Fifth Supplemental Indenture thereto, dated as of February 9, 2012 (the “ Fifth Supplemental Indenture ”), relating to the Company’s 2.100% Notes due 2015 (the “ 2015 Notes ”), the Sixth Supplemental Indenture thereto, dated as of February 9, 2012 (the “ Sixth Supplemental Indenture ”), relating to the Company’s 2.650% Notes due 2017 (the “ 2017 Notes ”) and the Seventh Supplemental Indenture thereto, dated as of February 9, 2012 (together with the First Supplemental Indenture, the Second Supplemental Indenture, the Third Supplemental Indenture, the Fourth Supplemental Indenture, the Fifth Supplemental Indenture and the Sixth Supplemental Indenture, the “ Supplemental Indentures ” and the Base Indenture as so supplemented, the “ Indenture ”), relating to the 3.900% Notes due 2022 (together with the 2014 Notes, the 2016 Notes, the 2021 Notes, the 2041 Notes, the 2015 Notes and the 2017 Notes, the “ Notes ”);

WHEREAS, each Additional Guarantor desires to provide a full and unconditional guarantee (the “ Guarantee ”) of the obligations of the Company under the Notes, the Securities (as defined in the Indenture) and the Indenture on the terms and conditions set forth herein;

WHEREAS, the Company has complied with all conditions precedent provided for in the Indenture and each Supplemental Indenture relating to this Eighth Supplemental Indenture; and

WHEREAS, pursuant to Section 9.1 of the Base Indenture and Section 7.1 of each Supplemental Indenture, the Company, the Trustee and the Additional Guarantors are authorized to execute and deliver this Eighth Supplemental Indenture.

NOW, THEREFORE, for good and valuable consideration, the receipt of which is acknowledged, each Additional Guarantor guarantees the Company’s obligations under the Securities as follows:

1. Capitalized Terms . Capitalized terms used herein without definition shall have the meanings assigned to them in the Indenture.

2. Guarantee, Etc. Each Additional Guarantor hereby agrees that from and after the date hereof it shall be a Guarantor under the Indenture and be bound by its terms thereof applicable to Guarantors and shall be entitled to all of the rights and subject to all of the obligations of a Guarantor thereunder.

3. Ratification of Indenture; Supplemental Indenture Part of Indenture . The Indenture is in all respects ratified and confirmed, and all terms, conditions and provisions thereof shall remain in full force and effect. This Eighth Supplemental Indenture shall form a part of the Indenture for all purposes, and every Holder of Securities heretofore or hereafter authenticated and delivered shall be bound hereby.

4. Representations and Warranties . Each Additional Guarantor hereby represents that (a) it is duly organized, validly existing and in good standing under the laws of the jurisdiction of its organization, (b) it

has full power, authority and legal rights to execute and deliver this Eighth Supplemental Indenture and to perform its obligations hereunder and under the Indenture, (c) the execution, delivery and performance by it of this Eighth Supplemental Indenture has been duly authorized by all necessary corporate action, and no other proceedings or actions on the part of such Additional Guarantor are necessary therefor and (d) this Eighth Supplemental Indenture has been duly and validly executed and delivered by such Additional Guarantor and constitutes a legal, valid and binding obligation of such Additional Guarantor, enforceable against such Additional Guarantor in accordance with its terms (subject to applicable bankruptcy, insolvency, receivership, reorganization, moratorium and other similar laws of general applicability relating to or affecting creditors’ rights and to general equity principles).

5. No Personal Liability of Directors, Officers, Employees or Stockholders . No director, officer, employee, member or stockholder of any Additional Guarantor, as such, will have any liability for any obligations of the Company, any Existing Guarantor or any other Additional Guarantor under the Securities, the Indenture or the Guarantees, or for any claim based on, in respect of, or by reason of, such obligations or their creation. Each Holder of Securities, by accepting a Security, waives and releases the Company, each Existing Guarantor and each Additional Guarantor from all such liability. The waiver and release are part of the consideration for issuance of the Guarantee by the Additional Guarantors.

6. GOVERNING LAW . THIS EIGHTH SUPPLEMENTAL INDENTURE AND THE GUARANTEES HEREUNDER SHALL BE GOVERNED BY, AND CONSTRUED IN ACCORDANCE WITH, THE LAWS OF THE STATE OF NEW YORK.

7. Counterparts . This Eighth Supplemental Indenture may be executed in any number of counterparts, each of which shall be deemed an original; but all such counterparts shall together constitute but one and the same instrument.

8. Effect of Headings . The Section headings herein are for convenience only and shall not affect the construction hereof.

9. Trustee . The Trustee shall not be responsible in any manner whatsoever for or in respect of the validity or sufficiency of this Eighth Supplemental Indenture or for or in respect of the recitals contained herein, all of which recitals are made solely by the Additional Guarantors, the Existing Guarantors and the Company.

IN WITNESS WHEREOF, the parties hereto have caused this Eighth Supplemental Indenture to be duly executed, all as of the day and year first above written.

EXISTING GUARANTORS

[Signature Page to Express Scripts Holding Company Eighth Supplemental Indenture]

[Signature Page to Express Scripts Holding Company Eighth Supplemental Indenture]

[Signature Page to Express Scripts Holding Company Eighth Supplemental Indenture]

ADDITIONAL GUARANTORS

[Signature Page to Express Scripts Holding Company Eighth Supplemental Indenture]

[Signature Page to Express Scripts Holding Company Eighth Supplemental Indenture]

Exhibit 4.2

EIGHTH SUPPLEMENTAL INDENTURE

The Eighth Supplemental Indenture (this “ Eighth Supplemental Indenture ”), dated as of April 2, 2012, among Express Scripts, Inc., a corporation duly organized and existing under the laws of the State of Delaware (the “ Company ”), the Guarantors listed as signatories hereto (each, an “ Existing Guarantor ” and collectively, the “ Existing Guarantors ”), Medco Health Solutions, Inc., a Delaware corporation, and its subsidiaries listed as signatories hereto (each, an “ Additional Guarantor ,” and, collectively, the “ Additional Guarantors ”) and Union Bank, N.A., a national association, as trustee under the indenture referred to below (the “ Trustee ”).

W I T N E S S E T H

WHEREAS, the Company, the Existing Guarantors and the Trustee are parties to the indenture, dated as of June 9, 2009 (the “ Base Indenture ”), as supplemented by the First Supplemental Indenture thereto, dated as of June 9, 2009 (the “ First Supplemental Indenture ”), relating to the Company’s 5.250% Notes due 2012 (the “ 2012 Notes ”), the Second Supplemental Indenture thereto, dated as of June 9, 2009 (the “ Second Supplemental Indenture ”), relating to the Company’s 6.250% Notes due 2014 (the “ 2014 Notes ”), the Third Supplemental Indenture thereto, dated as of June 9, 2009 (the “ Third Supplemental Indenture ”), relating to the Company’s 7.250% Notes due 2019 (the “ 2019 Notes ”), the Fourth Supplemental Indenture thereto, dated as of December 1, 2009 (the “ Fourth Supplemental Indenture ”), to add subsidiary guarantees, the Fifth Supplemental Indenture thereto, dated as of April 26, 2011 (the “ Fifth Supplemental Indenture ”), to add subsidiary guarantees, the Sixth Supplemental Indenture thereto, dated as of May 2, 2011 (the “ Sixth Supplemental Indenture ”), relating to the Company’s 3.125% Notes due 2016 (together with the 2012 Notes, the 2014 Notes and the 2019 Notes, the “ Notes ”), and the Seventh Supplemental Indenture thereto, dated as of November 21, 2011 (together with the First Supplemental Indenture, the Second Supplemental Indenture, the Third Supplemental Indenture, the Fourth Supplemental Indenture, the Fifth Supplemental Indenture and the Sixth Supplemental Indenture, the “ Supplemental Indentures ” and the Base Indenture as so supplemented, the “ Indenture ”), to add subsidiary guarantees;

WHEREAS, each Additional Guarantor desires to provide a full and unconditional guarantee (the “ Guarantee ”) of the obligations of the Company under the Notes, the Securities (as defined in the Indenture) and the Indenture on the terms and conditions set forth herein;

WHEREAS, the Company has complied with all conditions precedent provided for in the Base Indenture and each Supplemental Indenture relating to this Eighth Supplemental Indenture; and

WHEREAS, pursuant to Section 901 of the Base Indenture and Section 7.1 of each of the First Supplemental Indenture, the Second Supplemental Indenture, the Third Supplemental Indenture and the Sixth Supplemental Indenture, the Company, the Trustee and the Additional Guarantors are authorized to execute and deliver this Eighth Supplemental Indenture.

NOW, THEREFORE, for good and valuable consideration, the receipt of which is acknowledged, each Additional Guarantor hereby guarantees the Company’s obligations under the Securities as follows:

1. Capitalized Terms . Capitalized terms used herein without definition shall have the meanings assigned to them in the Indenture.

2. Guarantee, Etc. Each Additional Guarantor hereby agrees that from and after the date hereof it shall be a Guarantor under the Indenture and be bound by its terms thereof applicable to Guarantors and shall be entitled to all of the rights and subject to all of the obligations of a Guarantor thereunder.

3. Ratification of Indenture; Supplemental Indenture Part of Indenture . The Indenture is in all respects ratified and confirmed, and all terms, conditions and provisions thereof shall remain in full force and effect. This Eighth Supplemental Indenture shall form a part of the Indenture for all purposes, and every Holder of Securities heretofore or hereafter authenticated and delivered shall be bound hereby.

4. Representations and Warranties . Each Additional Guarantor hereby represents that (a) it is duly organized, validly existing and in good standing under the laws of the jurisdiction of its organization, (b) it has full power, authority and legal rights to execute and deliver this Eighth Supplemental Indenture and to perform

its obligations hereunder and under the Indenture, (c) the execution, delivery and performance by it of this Eighth Supplemental Indenture has been duly authorized by all necessary corporate action, and no other proceedings or actions on the part of such Additional Guarantor are necessary therefor and (d) this Eighth Supplemental Indenture has been duly and validly executed and delivered by such Additional Guarantor and constitutes a legal, valid and binding obligation of such Additional Guarantor, enforceable against such Additional Guarantor in accordance with its terms (subject to applicable bankruptcy, insolvency, receivership, reorganization, moratorium and other similar laws of general applicability relating to or affecting creditors’ rights and to general equity principles).

5. No Personal Liability of Directors, Officers, Employees or Stockholders . No director, officer, employee, member or stockholder of any Additional Guarantor, as such, will have any liability for any obligations of the Company, any Existing Guarantor or any other Additional Guarantor under the Securities, the Indenture or the Guarantees, or for any claim based on, in respect of, or by reason of, such obligations or their creation. Each Holder of Securities, by accepting a Security, waives and releases the Company, each Existing Guarantor and each Additional Guarantor from all such liability. The waiver and release are part of the consideration for issuance of the Guarantee by the Additional Guarantors.

6. GOVERNING LAW . THIS EIGHTH SUPPLEMENTAL INDENTURE AND THE GUARANTEES HEREUNDER SHALL BE GOVERNED BY, AND CONSTRUED IN ACCORDANCE WITH, THE LAWS OF THE STATE OF NEW YORK.

7. Counterparts . This Eighth Supplemental Indenture may be executed in any number of counterparts, each of which shall be deemed an original; but all such counterparts shall together constitute but one and the same instrument.

8. Effect of Headings . The Section headings herein are for convenience only and shall not affect the construction hereof.

9. Trustee . The Trustee shall not be responsible in any manner whatsoever for or in respect of the validity or sufficiency of this Eighth Supplemental Indenture or for or in respect of the recitals contained herein, all of which recitals are made solely by the Additional Guarantors, the Existing Guarantors and the Company.

IN WITNESS WHEREOF, the parties hereto have caused this Eighth Supplemental Indenture to be duly executed, all as of the day and year first above written.

EXISTING GUARANTORS

[Signature Page to Express Scripts, Inc. Eighth Supplemental Indenture]

[Signature Page to Express Scripts, Inc. Eighth Supplemental Indenture]

[Signature Page to Express Scripts, Inc. Eighth Supplemental Indenture]

ADDITIONAL GUARANTORS

[Signature Page to Express Scripts, Inc. Eighth Supplemental Indenture]

[Signature Page to Express Scripts, Inc. Eighth Supplemental Indenture]

Exhibit 4.3

FIRST SUPPLEMENTAL INDENTURE

The Supplemental Indenture (this “ First Supplemental Indenture ”), dated as of April 2, 2012, among Medco Health Solutions, Inc., a corporation duly organized and existing under the laws of the State of Delaware (the “ Company ”), Express Scripts Holding Company (formerly Aristotle Holding, Inc.), a Delaware corporation, its subsidiaries listed as signatories hereto and the Company subsidiaries listed as signatories hereto (each, a “ Guarantor ,” and, collectively, the “ Guarantors ”) and U.S. Bank Trust National Association, as trustee under the indenture referred to below (the “ Trustee ”).

W I T N E S S E T H

WHEREAS, the Company and the Trustee are parties to the indenture, dated as of March 18, 2008 (the “ Base Indenture ”), relating to the Company’s 6.125% Notes due 2013, its 7.125% Notes due 2018, its 2.750% Notes due 2015 and its 4.125% Notes due 2020 (collectively, the “ Notes ”);

WHEREAS, each Guarantor desires to provide a full and unconditional guarantee (the “ Guarantee ”) of the obligations of the Company under the Notes, the Securities (as defined in the Base Indenture) and the Base Indenture on the terms and conditions set forth herein;

WHEREAS, the Company has complied with all conditions precedent provided for in the Base Indenture relating to this First Supplemental Indenture; and

WHEREAS, pursuant to Section 901 of the Base Indenture, the Company is permitted to amend the Base Indenture to make any provision with respect to matters or questions arising under the Base Indenture, provided such action does not adversely affect the interest of the Holders.

NOW, THEREFORE, for good and valuable consideration, the receipt of which is acknowledged, each Guarantor hereby guarantees the Company’s obligations under the Securities as follows:

1. Capitalized Terms . Capitalized terms used herein without definition shall have the meanings assigned to them in the Base Indenture.

2. Unconditional Guarantee . (1) For value received, each of the Guarantors hereby jointly and severally and fully and unconditionally guarantee, to each Holder of a Security authenticated and delivered by the Trustee (including the Notes) and to the Trustee and its successors and assigns, irrespective of the validity and enforceability of the Indenture or the Securities or the obligations of the Company or any other Guarantor to the Holders or the Trustee hereunder or thereunder, that: (a) the principal of, premium, if any, and interest on the Securities will be duly and promptly paid in full when due, whether at Stated Maturity, upon redemption, by acceleration or otherwise, and interest on the overdue principal and (to the extent permitted by law) interest, if any, on the Securities and all other obligations of the Company or the Guarantor to the Holders of or the Trustee hereunder or thereunder (including fees, expenses or others) (collectively, the “ Obligations ”) will be promptly paid in full or performed, all in accordance with the terms hereof and thereof; and (b) in case of any extension of time of payment or renewal of any Obligations (with or without notice to such Guarantor), the same will be promptly paid in full when due or performed in accordance with the terms of the extension or renewal, whether at Stated Maturity, by acceleration or otherwise. If the Company shall fail to pay when due, or to perform, any Obligations, for whatever reason, each Guarantor shall be jointly and severally obligated to pay in cash, or to perform or cause the performance of, the same promptly. An Event of Default under the Indenture or the Securities of a particular series shall entitle the Holders of the Securities of such series to accelerate the Obligations of the Guarantor hereunder in the same manner and to the same extent as the Obligations of the Company.

(2) Each Guarantor hereby agrees that its obligations hereunder shall be unconditional, irrespective of the validity, regularity or enforceability of the Securities or the Indenture, the absence of any action to enforce the same, any waiver or consent by any Holder of the Securities with respect to any provisions of the Indenture or the Securities, any release of any other Guarantor, the recovery of any judgment against the Company, any action to enforce the same, whether or not a Guarantee is affixed to any particular Security, or any other circumstance which might otherwise constitute a legal or equitable discharge or defense of a Guarantor.

(3) Each Guarantor further agrees that, as between it, on the one hand, and the Holders of the Securities and the Trustee, on the other hand, (a) the maturity of the Obligations guaranteed hereby may be

accelerated as provided in Article Five of the Base Indenture for the purposes of the Guarantee, notwithstanding any stay, injunction or other prohibition preventing such acceleration in respect of the Obligations and (b) in the event of any acceleration of such Obligations as provided in Article Five of the Base Indenture, such Obligations (whether or not due and payable) shall forthwith become due and payable by the Guarantor for the purposes of its Guarantee.

3. Waiver . To the fullest extent permitted by applicable law, each of the Guarantors waives diligence, presentment, demand of, payment, filing of claims with a court in the event of insolvency or bankruptcy of the Company, any right to require a proceeding first against the Company, protest, notice and all demands whatsoever and covenants that the Guarantee will not be discharged except by complete performance of the Obligations contained in the Securities and the Indenture.

4. Guarantee of Payment . Each of the Guarantors further agrees that its Guarantee constitutes a guarantee of payment, performance and compliance when due and not a guarantee of collection, and waives any right to require that any resort be had by the Trustee or any Holder of the Securities to the security, if any, held for payment of the Obligations.

5. No Discharge or Diminishment of Guarantee . Subject to Section 11 hereof, the obligations of each of the Guarantors hereunder shall not be subject to any reduction, limitation, termination, impairment or for any reason (other than the payment in full in cash of the Obligations), including any claim of waiver, release, surrender, alteration or compromise of any of the Obligations, and shall not be subject to any defense or setoff, counterclaim, recoupment or termination whatsoever by reason of the invalidity, illegality or unenforceability of the Obligations or otherwise. Without limiting the generality of the foregoing, the obligations of each of the Guarantors hereunder shall not be discharged or impaired or otherwise affected by the failure of the Trustee or any Holder of the Securities to assert any claim or demand or to enforce any remedy under the Indenture or the Securities, any other guarantee or any other agreement, by any waiver or modification of any provision thereof, by any default, failure or delay, willful or otherwise, in the performance of the Obligations, or by any other act or omission or delay to do any other act that may or might in any manner or to any extent vary the risk of any Guarantor or that would otherwise operate as a discharge of any Guarantor as a matter of law or equity (other than the payment in full in cash of all the Obligations).

6. Defenses of Company Waived . To the extent permitted by applicable law, each of the Guarantors waives any defense based on or arising out of any defense of the Company or any other Guarantor or the unenforceability of the Obligations or any part thereof from any cause, or the cessation from any cause of the liability of the Company, other than final payment in full in cash of the Obligations. Each of the Guarantors waives any defense arising out of any such election even though such election operates to impair or to extinguish any right of reimbursement or subrogation or other right or remedy of each of the Guarantors against the Company or any security.

7. Continued Effectiveness . Subject to Section 11 hereof, each of the Guarantors further agrees that its Guarantee hereunder shall continue to be effective or be reinstated, as the case may be, if at any time payment, or any part thereof, of principal of or interest on any Obligation is rescinded or must otherwise be restored by the Trustee or any Holder of the Securities upon the bankruptcy or reorganization of the Company or otherwise.

8. Subrogation . In furtherance of the foregoing and not in limitation of any other right of each of the Guarantors by virtue hereof, upon the failure of the Company to pay any Obligation when and as the same shall become due, whether at maturity, by acceleration, after notice of prepayment or otherwise, each of the Guarantors hereby promises to and will, upon receipt of written demand by the Trustee or any Holder of the Securities, forthwith pay, or cause to be paid, to the Holders in cash the amount of such unpaid Obligations, and thereupon the Holders shall assign (except to the extent that such assignment would render a Guarantor a “creditor” of the Company within the meaning of Section 547 of Title 11 of the United States Code as now in effect or hereafter amended or any comparable provision of any successor statute) the amount of the Obligations owed to it and paid by such Guarantor pursuant to this Guarantee to such Guarantor, such assignment to be pro rata to the extent the Obligations in question were discharged by such Guarantor, or make such other disposition thereof as such Guarantor shall direct (all without recourse to the Holders, and without any representation or warranty by the Holders). If (a) a Guarantor shall make payment to the Holders of all or any part of the Obligations and (b) all the Obligations and all other amounts payable under the Indenture shall be paid in full, the Trustee will, at such

Guarantor’s request, execute and deliver to such Guarantor appropriate documents, without recourse and without representation or warranty, necessary to evidence the transfer by subrogation to such Guarantor of an interest in the Obligations resulting from such payment by such Guarantor.

9. Information . Each of the Guarantors assumes all responsibility for being and keeping itself informed of the Company’s financial condition and assets, and of all other circumstances bearing upon the risk of nonpayment of the Obligations and the nature, scope and extent of the risks that each of the Guarantors assumes and incurs hereunder, and agrees that the Trustee and the Holders of the Securities will have no duty to advise the Guarantors of information known to it or any of them regarding such circumstances or risks.

10. Subordination . Upon payment by any Guarantor of any sums to the Holders, as provided above, all rights of such Guarantor against the Company, arising as a result thereof by way of right of subrogation or otherwise, shall in all respects be subordinated and junior in right of payment to the prior payment in full in cash of all the Obligations to the Trustee; provided , however , that any right of subrogation that such Guarantor may have pursuant to the Indenture is subject to Section 8 hereof.

11. Release of Guarantor . (1) A Guarantor shall, upon notice by the Company to the Trustee, be automatically and unconditionally released and discharged from all obligations under the Indenture and its Guarantee without any action required on the part of the Trustee or any Holder.

(2) The Trustee shall deliver an appropriate instrument evidencing such release upon receipt of a request of the Company. Any Guarantor not so released will remain liable for the full amount of the principal of, premium, if any, and interest on the Securities provided in the Indenture and its Guarantee.

12. Limitation of Guarantor’s Liability . (1) Each Guarantor, and by its acceptance hereof each Holder, hereby confirms that it is the intention of all such parties that the Guarantee by such Guarantor not constitute a fraudulent transfer or conveyance for purposes of Title 11 of the United States Code, the Uniform Fraudulent Conveyance Act, the Uniform Fraudulent Transfer Act or any similar federal or state law to the extent applicable to any Guarantor. To effectuate the foregoing intention, the Holders and such Guarantor hereby irrevocably agree that the obligations of such Guarantor under the Indenture and its Guarantee shall be limited to the maximum aggregate amount which, after giving effect to all other contingent and fixed liabilities of such Guarantor, and after giving effect to any collections from or payments made by or on behalf of any other Guarantor in respect of the obligations of such Guarantor under its Guarantee or pursuant to its contribution obligations under the Indenture, will result in the obligations of such Guarantor under its Guarantee not constituting such fraudulent transfer or conveyance.

(2) The Guarantee is expressly limited so that in no event, including the acceleration of the maturity of the Securities, shall the amount paid or agreed to be paid in respect of interest on the Securities (or fees or other amounts deemed payment for the use of funds) exceed the maximum permissible amount under applicable law, as in effect on the date hereof and as subsequently amended or modified to allow a greater amount of interest (or fees or other amounts deemed payment for the use of funds) to be paid under the Guarantee. If for any reason the amount in respect of interest (or fees or other amounts deemed payment for the use of funds) required by the Guarantee exceeds such maximum permissible amount, the obligation to pay interest under the Guarantee (or fees or other amounts deemed payment for the use of funds) shall be automatically reduced to such maximum permissible amount and any amounts collected by any holder of any Security in excess of the permissible amount shall be automatically applied to reduce the outstanding principal on such Security.

13. Contribution from Other Guarantors . Each Guarantor that makes a payment or distribution under its Guarantee shall be entitled to seek contribution from each other non-paying Guarantor in a pro rata amount based on the net assets of each Guarantor, determined in accordance with generally accepted accounting principles in effect in the United States of America as of the date hereof so long as the exercise of such right does not impair the rights of the Holders under the Guarantee.

14. No Obligation to Take Action Against the Company . Neither the Trustee, any Holder nor any other Person shall have any obligation to enforce or exhaust any rights or remedies or take any other steps under any security for the Obligations or against the Company or any other Person or any Property of the Company or any other Person before the Trustee, such Holder or such other Person is entitled to demand payment and performance by any or all Guarantors of their liabilities and obligations under their Guarantee.

15. Execution and Delivery of the Guarantee . (1) To further evidence the Guarantee set forth in this First Supplemental Indenture, each Guarantor hereby agrees that a notation of such Guarantee shall be endorsed on each Security authenticated and delivered by the Trustee and executed by either manual or facsimile signature of an officer, manager or member, as applicable, of each Guarantor.

(2) Each of the Guarantors hereby agrees that its Guarantee set forth in this First Supplemental Indenture shall remain in full force and effect notwithstanding any failure to endorse on each Security a notation of such Guarantee.

(3) If an officer of a Guarantor whose signature is on the Indenture or a Guarantee no longer holds that office or is no longer a manager or member, as applicable, at the time the Trustee authenticates such Guarantee or at any time thereafter, such Guarantor’s Guarantee of such Security shall be valid nevertheless.

(4) The delivery of any Security by the Trustee, after the authentication thereof under the Indenture, shall constitute due delivery of any Guarantee set forth in the Indenture on behalf of each Guarantor.

16. Successor Guarantor . Unless otherwise released and discharged from its obligations in accordance with the Indenture, upon any consolidation or merger by any Guarantor with or into any other Person, the successor Person formed by such consolidation or merger shall sign a supplemental indenture and guarantee and succeed to, and be substituted for, and may exercise every right and power of, the Guarantor under the Indenture with the same effect as if such successor Person has been named as a Guarantor herein, and thereafter the predecessor Person shall be relieved of all obligations and covenants under the Indenture and the Securities (to the extent the Guarantor was the predecessor Person).

17. Ratification of Base Indenture; Supplemental Indenture Part of Indenture . The Base Indenture is in all respects ratified and confirmed, and all terms, conditions and provisions thereof shall remain in full force and effect. This First Supplemental Indenture shall form a part of the Base Indenture for all purposes, and every Holder of Securities heretofore or hereafter authenticated and delivered shall be bound hereby.

18. Representations and Warranties . Each Guarantor hereby represents that (a) it is duly organized, validly existing and in good standing under the laws of the jurisdiction of its organization, (b) it has full power, authority and legal rights to execute and deliver this First Supplemental Indenture and to perform its obligations hereunder and under the Base Indenture, (c) the execution, delivery and performance by it of this First Supplemental Indenture has been duly authorized by all necessary corporate action, and no other proceedings or actions on the part of such Guarantor are necessary therefor and (d) this First Supplemental Indenture has been duly and validly executed and delivered by such Guarantor and constitutes a legal, valid and binding obligation of such Guarantor, enforceable against such Guarantor in accordance with its terms (subject to applicable bankruptcy, insolvency, receivership, reorganization, moratorium and other similar laws of general applicability relating to or affecting creditors’ rights and to general equity principles).

19. No Personal Liability of Directors, Officers, Employees or Stockholders . No director, officer, employee, member or stockholder of any Guarantor, as such, will have any liability for any obligations of the Company or any other Guarantor under the Securities, the Base Indenture or the Guarantees, or for any claim based on, in respect of, or by reason of, such obligations or their creation. Each Holder of Securities, by accepting a Security, waives and releases the Company and each Guarantor from all such liability. The waiver and release are part of the consideration for issuance of the Guarantee by the Guarantors.

20. GOVERNING LAW . THIS FIRST SUPPLEMENTAL INDENTURE AND THE GUARANTEES HEREUNDER SHALL BE GOVERNED BY, AND CONSTRUED IN ACCORDANCE WITH, THE LAWS OF THE STATE OF NEW YORK.

21. Counterparts . This First Supplemental Indenture may be executed in any number of counterparts, each of which shall be deemed an original; but all such counterparts shall together constitute but one and the same instrument.

22. Effect of Headings . The Section headings herein are for convenience only and shall not affect the construction hereof.

23. Trustee . The Trustee shall not be responsible in any manner whatsoever for or in respect of the validity or sufficiency of this First Supplemental Indenture or for or in respect of the recitals contained herein, all of which recitals are made solely by the Guarantors and the Company.

IN WITNESS WHEREOF, the parties hereto have caused this First Supplemental Indenture to be duly executed, all as of the day and year first above written.

GUARANTORS

[Signature Page to 2008 Medco First Supplemental Indenture]

[Signature Page to 2008 Medco First Supplemental Indenture]

[Signature Page to 2008 Medco First Supplemental Indenture]

[Signature Page to 2008 Medco First Supplemental Indenture]

Exhibit 4.4

FIRST SUPPLEMENTAL INDENTURE

FIRST SUPPLEMENTAL INDENTURE (this “First Supplemental Indenture”), dated as of April 2, 2012, among Medco Health Solutions, Inc., a Delaware corporation (the “Company”), the entities listed on Schedule I hereto, each a subsidiary of the Company (each, a “Subsidiary Guarantor” and, collectively, the “Subsidiary Guarantors”), and U.S. Bank Trust National Association, as trustee under the indenture referred to below (the “Trustee”).

W I T N E S S E T H

WHEREAS, the Company has heretofore executed and delivered to the Trustee an indenture (the “Indenture”), dated as of August 12, 2003 providing for the issuance of $500.0 million aggregate principal amount of the Company’s 7.25% Senior Notes due 2013 (the “Notes”);

WHEREAS, the Indenture provides that the Company may cause any of its direct or indirect Restricted Subsidiaries to become a Subsidiary Guarantor by executing and delivering to the Trustee a supplemental indenture pursuant to which the Subsidiary Guarantor shall unconditionally guarantee all of the Company’s Obligations under the Notes and the Indenture on the terms and conditions set forth herein (the “Subsidiary Guarantee”); and

WHEREAS, pursuant to Section 9.01 of the Indenture, the Trustee is authorized to execute and deliver this First Supplemental Indenture.

NOW THEREFORE, in consideration of the foregoing and for other good and valuable consideration, the receipt of which is hereby acknowledged, each Subsidiary Guarantor and the Trustee mutually covenant and agree for the equal and ratable benefit of the Holders of the Notes as follows:

1. Capitalized Terms. Capitalized terms used herein without definition shall have the meanings assigned to them in the Indenture.

2. Agreement to Guarantee. Each Subsidiary Guarantor hereby agrees as follows:

(a) To guarantee, jointly and severally with each other Subsidiary Guarantor heretofore or hereafter designated as such by the Company, and with any other guarantor hereafter designated as such by the Company, to each Holder

of a Note authenticated and delivered by the Trustee and to the Trustee and its successors and assigns, irrespective of the validity and enforceability of the Indenture, the Notes or the obligations of the Company hereunder or thereunder, that:

(i) the principal of, and any premium and interest on, the Notes will be promptly paid in full when due, whether at maturity, by acceleration, redemption or otherwise, and interest on the overdue principal of and interest on the Notes, if any, if lawful, and all other obligations of the Company to the Holders or the Trustee hereunder or thereunder will be promptly paid in full or performed, all in accordance with the terms hereof and under the Indenture; and

(ii) in case of any extension of time of payment or renewal of any Notes or any of such other obligations, that same will be promptly paid in full when due or performed in accordance with the terms of the extension or renewal, whether at the date scheduled to be paid, by acceleration or otherwise.

Failing payment when due of any amount so guaranteed or any performance so guaranteed for whatever reason, each Subsidiary Guarantor shall be obligated to pay the same immediately. Each Subsidiary Guarantor hereby agrees that this is a guarantee of payment and not a guarantee of collection.

(b) The obligations hereunder shall be unconditional, irrespective of the validity, regularity or enforceability of the Notes or the Indenture, the absence of any action to enforce the same, any waiver or consent by any Holder of the Notes with respect to any provisions hereof or thereof, the recovery of any judgment against the Company, any action to enforce the same or any other circumstance which might otherwise constitute a legal or equitable discharge or defense of any Subsidiary Guarantor.

(c) The Subsidiary Guarantors hereby waive diligence, presentment, demand of payment, filing of claims with a court in the event of insolvency or bankruptcy of the Company, any right to require a proceeding first against the Company, protest, notice and all demands whatsoever.

(d) This Subsidiary Guarantee shall not be discharged except by complete performance of the obligations contained in the Notes and the Indenture or release in accordance with the Indenture, and each Subsidiary Guarantor accepts all obligations of a Subsidiary Guarantor under the Indenture.

(e) If any Holder or the Trustee is required by any court or otherwise to return to the Company, any Subsidiary Guarantor, or any custodian, trustee, liquidator or other similar official acting in relation to either the Company or any Subsidiary Guarantor, any amount paid by any of them to the Trustee or such Holder, this Subsidiary Guarantee, to the extent theretofore discharged, shall be reinstated in full force and effect.

(f) The Subsidiary Guarantors shall not be entitled to any right of subrogation in relation to the Holders in respect of any obligations guaranteed hereby until payment in full of all obligations guaranteed hereby.

(g) As between the Subsidiary Guarantors, on the one hand, and the Holders and the Trustee, on the other hand, (x) the maturity of the obligations guaranteed hereby may be accelerated as provided in Article 6 of the Indenture for the purposes of this Subsidiary Guarantee, notwithstanding any stay, injunction or other prohibition preventing such acceleration in respect of the obligations guaranteed hereby, and (y) in the event of any declaration of acceleration of such obligations as provided in Article 6 of the Indenture, such obligations (whether or not due and payable) shall forthwith become due and payable by the Subsidiary Guarantors for the purpose of this Subsidiary Guarantee.

(h) Pursuant to Section 10.02 of the Indenture, after giving effect to any maximum amount and all other contingent and fixed liabilities that are relevant under any applicable Bankruptcy or fraudulent conveyance laws, this Subsidiary Guarantee shall be limited to the maximum amount permissible such that the obligations of the Subsidiary Guarantors under this Subsidiary Guarantee will not constitute a fraudulent transfer or conveyance.

3. Execution and Delivery. Each Subsidiary Guarantor agrees that the Subsidiary Guarantee shall remain in full force and effect notwithstanding any failure to endorse such Subsidiary Guarantee.

4. Subsidiary Guarantors May Consolidate, Etc. On Certain Terms.

(a) Except as otherwise provided in Section 5 hereof, no Subsidiary Guarantor shall sell or otherwise dispose of all or substantially all of its assets to, or consolidate with or merge with or into, any Person that is (either before or after giving effect to such transaction) an Affiliate of the Company, unless that Affiliate unconditionally assumes all of the obligations of such Subsidiary Guarantor pursuant to a supplemental indenture in form and substance reasonably satisfactory to the Trustee, under the Notes, the Indenture and the Subsidiary Guarantee on the terms set forth therein.

(b) Except as otherwise provided in Section 5 hereof, no Subsidiary Guarantor shall sell or otherwise dispose of all or substantially all of its assets to, or consolidate with or merge with or into, any Person that is not an Affiliate of the Company (whether or not such Subsidiary Guarantor is the surviving Person) other than the Company unless:

(i) immediately after giving effect to such transaction, no Default or Event of Default exists; and

(ii) the Net Proceeds of such sale or other disposition are applied in accordance with the applicable provisions of the Indenture, including without limitation, Section 4.10 of the Indenture.

In case of any such consolidation, merger, sale or conveyance and upon the assumption by the successor Affiliate, by supplemental indenture, executed and delivered to the Trustee and satisfactory in form to the Trustee, of the Subsidiary Guarantee and the due and punctual performance of all of the covenants and conditions of the Indenture to be performed by the Subsidiary Guarantor, such successor Affiliate will succeed to and be substituted for such Subsidiary Guarantor with the same effect as if it had been named therein as the Subsidiary Guarantor. Such successor Affiliate thereupon may cause to be signed the Subsidiary Guarantee of the Notes issuable hereunder which theretofore shall not have been signed by the Company and delivered to the Trustee. The Subsidiary Guarantee so issued will in all respects have the same legal rank and benefit under the Indenture as the Subsidiary Guarantees theretofore and thereafter issued in accordance with the terms of the Indenture as though the Subsidiary Guarantee had been issued at the date of the execution of the Indenture.

Except as set forth in Articles 4 and 5 of the Indenture, and notwithstanding Section 4(b)(ii) hereof, nothing contained in the Indenture or in any of the Notes will prevent any consolidation or merger of such Subsidiary Guarantor with or into the Company, or will prevent any sale or conveyance of the property of such Subsidiary Guarantor as an entirety or substantially as an entirety to the Company.

(c) For purposes of this Section 4, beneficial ownership of 35% or more of the Voting Stock of a Person will be deemed to be control.

5. Releases.

(a) Notwithstanding the provisions of Section 4 hereof, any Subsidiary Guarantor will be released automatically and relieved of any obligations under its Subsidiary Guarantee:

(i) upon the sale or other disposition of all or substantially all of the assets of such Subsidiary Guarantor (including by way of merger or consolidation) to a Person that is not (either before or after giving effect to such transaction) the Company or an Affiliate of the Company, if the sale or other disposition complies with Sections 3.08 and 4.10 of the Indenture and the Subsidiary Guarantor either no longer has an Indebtedness (other than the Subsidiary Guarantee) after compliance with such Sections or it would be permitted at the time of such release to incur all of its then outstanding Indebtedness in compliance with Section 4.09 of the Indenture,

(ii) upon the sale of all of the Capital Stock of such Subsidiary Guarantor to a Person that is not (either before or after giving effect to such transaction) an Affiliate of the Company, if the sale complies with Sections 3.08 and 4.10 of the Indenture;

(iii) upon the legal defeasance of the Notes as described in Article 8 of the Indenture;

(iv) upon (a) the merger of such Subsidiary Guarantor into the Company or another Subsidiary Guarantor; (b) the dissolution of such Subsidiary Guarantor into the Company or another Subsidiary Guarantor; or (c) the transfer of all or substantially all of the assets of such Subsidiary Guarantor to the Company or another Subsidiary Guarantor; or

(v) at the option of the Company, if at any time the Subsidiary Guarantor has no Indebtedness outstanding other than the Subsidiary Guarantee or, assuming it ceased to be a Subsidiary Guarantor but continued to be a Restricted Subsidiary of the Company following such release, it would be permitted at the time of such release to incur all of its then outstanding Indebtedness in compliance with Section 4.09 of the Indenture.

Upon delivery by the Company to the Trustee of an Officers’ Certificate and an Opinion of Counsel to the effect that one of the events described in this Section 5 has occurred in accordance with the provisions

of the Indenture, the Trustee will execute any documents reasonably required in order to evidence the release of such Subsidiary Guarantor from its obligations under its Subsidiary Guarantee.

6. No Recourse Against Others. No past, present or future director, officer, employee, incorporator, stockholder or agent of any Subsidiary Guarantor, as such, shall have any liability for any obligations of the Company or any Subsidiary Guarantor under the Notes, the Subsidiary Guarantee, the Indenture or this First Supplemental Indenture or for any claim based on, in respect of, or by reason of, such obligations or their creation. Each Holder of the Notes by accepting a Note waives and releases all such liability. The waiver and release are part of the consideration for issuance of the Notes.

7. Successors and Assigns. All covenants agreements of any Subsidiary Guarantor in this Indenture supplemental will bind its successors and assigned, whether so expressed or not, except as otherwise provided in Section 5 hereof.

8. Separability. In case any provision in this First Supplemental Indenture or in the Subsidiary Guarantee is invalid, illegal or unenforceable, the validity, legality and enforceability of the remaining provisions will not in any way be affected or impaired thereby.

9. Governing Law. This First Supplemental Indenture and the Subsidiary Guarantee shall be governed by and construed in accordance with the laws of the State of New York.

10. Counterparts. The parties may sign any number of copies of this First Supplemental Indenture. Each signed copy shall be an original, but all of them together represent the same agreement.

11. Effect of Headings. The Section headings herein are for convenience of reference only, are not to be considered part of this First Supplemental Indenture and will in no way modify or restrict any of the terms or provisions hereof.

12. The Trustee. The Trustee shall not be responsible in any manner whatsoever for or in respect of the validity or sufficiency of this First Supplemental Indenture or for or in respect of any statement or recital herein or in the Subsidiary Guarantee, all of which statements and recitals are made solely by the Subsidiary Guarantors and the Company.

IN WITNESS WHEREOF, the parties hereto have caused this First Supplemental Indenture to be duly executed and attested, all as of the date first above written.

Dated: April 2, 2012

                Subsidiary Guarantors

[Signature Page to 2003 Medco First Supplemental Indenture]

[Signature Page to 2003 Medco First Supplemental Indenture]

Exhibit 4.5

SECOND SUPPLEMENTAL INDENTURE

SECOND SUPPLEMENTAL INDENTURE (this “Second Supplemental Indenture”), dated as of April 2, 2012, among Medco Health Solutions, Inc., a Delaware corporation (the “Company”), the existing subsidiary guarantors listed as signatories hereto (each, an “Existing Guarantor” and collectively, the “Existing Guarantors”), the entities listed on Schedule I hereto (each, a “Guarantor” and, collectively, the “Guarantors”), and U.S. Bank Trust National Association, as trustee under the indenture referred to below (the “Trustee”).

W I T N E S S E T H

WHEREAS, the Company has heretofore executed and delivered to the Trustee an indenture (as amended, the “Indenture”), dated as of August 12, 2003 providing for the issuance of $500.0 million aggregate principal amount of the Company’s 7.25% Senior Notes due 2013 (the “Notes”);

WHEREAS, pursuant to Section 9.01 of the Indenture, the Company is permitted to amend the Indenture to add guarantees with respect to the Notes, as defined in the Indenture and this Second Supplemental Indenture (the “Guarantees”); and

WHEREAS, pursuant to Section 9.01 of the Indenture, the Trustee is authorized to execute and deliver this Second Supplemental Indenture.

NOW THEREFORE, in consideration of the foregoing and for other good and valuable consideration, the receipt of which is hereby acknowledged, each Guarantor and the Trustee mutually covenant and agree for the equal and ratable benefit of the Holders of the Notes as follows:

1. Capitalized Terms. Capitalized terms used herein without definition shall have the meanings assigned to them in the Indenture.

2. Agreement to Guarantee. Each Guarantor hereby agrees as follows:

(a) To guarantee, jointly and severally with each other Guarantor, each Existing Guarantor and with any other guarantor hereafter designated as such by the Company, to each Holder of a Note authenticated and delivered by the Trustee and to the Trustee and its successors and assigns, irrespective of the validity and enforceability of the Indenture, the Notes or the obligations of the Company hereunder or thereunder, that:

(i) the principal of, and any premium and interest on, the Notes will be promptly paid in full when due, whether at maturity, by acceleration, redemption or otherwise, and interest on the overdue principal of and interest on the Notes, if any, if lawful, and all other obligations of the Company to the Holders or the Trustee hereunder or thereunder will be promptly paid in full or performed, all in accordance with the terms hereof and under the Indenture; and

(ii) in case of any extension of time of payment or renewal of any Notes or any of such other obligations, that same will be promptly paid in full when due or performed in accordance with the terms of the extension or renewal, whether at the date scheduled to be paid, by acceleration or otherwise.

Failing payment when due of any amount so guaranteed or any performance so guaranteed for whatever reason, each Guarantor shall be obligated to pay the same immediately. Each Guarantor hereby agrees that this is a guarantee of payment and not a guarantee of collection.

(b) The obligations hereunder shall be unconditional, irrespective of the validity, regularity or enforceability of the Notes or the Indenture, the absence of any action to enforce the same, any waiver or consent by any Holder of the Notes with respect to any provisions hereof or thereof, the recovery of any judgment against the Company, any action to enforce the same or any other circumstance which might otherwise constitute a legal or equitable discharge or defense of any Guarantor.

(c) The Guarantors hereby waive diligence, presentment, demand of payment, filing of claims with a court in the event of insolvency or bankruptcy of the Company, any right to require a proceeding first against the Company, protest, notice and all demands whatsoever.

(d) This Guarantee shall not be discharged except by complete performance of the obligations contained in the Notes and the Indenture or release in accordance with the Indenture, and each Guarantor accepts all obligations of a Guarantor under the Indenture.

(e) If any Holder or the Trustee is required by any court or otherwise to return to the Company, any Guarantor, or any custodian, trustee, liquidator or other similar official acting in relation to either the Company or any Guarantor, any amount paid by any of them to the Trustee or such Holder, this Guarantee, to the extent theretofore discharged, shall be reinstated in full force and effect.

(f) The Guarantors shall not be entitled to any right of subrogation in relation to the Holders in respect of any obligations guaranteed hereby until payment in full of all obligations guaranteed hereby.

(g) As between the Guarantors, on the one hand, and the Holders and the Trustee, on the other hand, (x) the maturity of the obligations guaranteed hereby may be accelerated as provided in Article 6 of the Indenture for the purposes of this Guarantee, notwithstanding any stay, injunction or other prohibition preventing such acceleration in respect of the obligations guaranteed hereby, and (y) in the event of any declaration of acceleration of such obligations as provided in Article 6 of the Indenture, such obligations (whether or not due and payable) shall forthwith become due and payable by the Guarantors for the purpose of this Guarantee.

(h) After giving effect to any maximum amount and all other contingent and fixed liabilities that are relevant under any applicable Bankruptcy or fraudulent conveyance laws, this Guarantee shall be limited to the maximum amount permissible such that the obligations of the Guarantors under this Guarantee will not constitute a fraudulent transfer or conveyance.

3. Execution and Delivery. Each Guarantor agrees that the Guarantee shall remain in full force and effect notwithstanding any failure to endorse such Guarantee.

4. [Reserved.]

5. Releases. Any Guarantor will be, upon action by the Company to the Trustee, released automatically and relieved of any obligations under its Guarantee. The Trustee will execute any documents reasonably required in order to evidence the release of such Guarantor from its obligations under its Guarantee.

6. No Recourse Against Others. No past, present or future director, officer, employee, incorporator, stockholder or agent of any Guarantor, as such, shall have any liability for any obligations of the Company or any Guarantor under the Notes, the Guarantee, the Indenture or this Second Supplemental Indenture or for any claim based on, in respect of, or by reason of, such obligations or their creation. Each Holder of the Notes by accepting a Note waives and releases all such liability. The waiver and release are part of the consideration for issuance of the Notes.

7. [Reserved.]

8. Separability. In case any provision in this Second Supplemental Indenture or in the Guarantee is invalid, illegal or unenforceable, the validity, legality and enforceability of the remaining provisions will not in any way be affected or impaired thereby.

9. Governing Law. This Second Supplemental Indenture and the Guarantee shall be governed by and construed in accordance with the laws of the State of New York.

10. Counterparts. The parties may sign any number of copies of this Second Supplemental Indenture. Each signed copy shall be an original, but all of them together represent the same agreement.

11. Effect of Headings. The Section headings herein are for convenience of reference only, are not to be considered part of this Second Supplemental Indenture and will in no way modify or restrict any of the terms or provisions hereof.

12. The Trustee. The Trustee shall not be responsible in any manner whatsoever for or in respect of the validity or sufficiency of this Second Supplemental Indenture or for or in respect of any statement or recital herein or in the Guarantee, all of which statements and recitals are made solely by the Guarantors and the Company.

IN WITNESS WHEREOF, the parties hereto have caused this Second Supplemental Indenture to be duly executed and attested, all as of the date first above written.

Dated: April 2, 2012

[Signature Page to 2003 Medco Second Supplemental Indenture]

[Signature Page to 2003 Medco Second Supplemental Indenture]

[Signature Page to 2003 Medco Second Supplemental Indenture]

[Signature Page to 2003 Medco Second Supplemental Indenture]

Exhibit 4.6

EXECUTION COPY

SUBSIDIARY GUARANTY

This SUBSIDIARY GUARANTY is entered into as of April 2, 2012, by and among THE UNDERSIGNED (each a “ Guarantor ”, and, together with any Additional Guarantors (as hereinafter defined), collectively the “ Guarantors ”) in favor of and for the benefit of Credit Suisse AG, Cayman Islands Branch, as agent for and representative of (in such capacity herein called “ Guarantied Party ”) the financial institutions party to the Credit Agreement (as hereinafter defined) (the “ Lenders ”) referred to below, and, subject to subsection 3.12, for the benefit of the other Beneficiaries (as hereinafter defined).

RECITALS

A. Aristotle Holding, Inc. (to be renamed Express Scripts Holding Company), a Delaware corporation, has entered into that certain Credit Agreement dated as of August 29, 2011, with Express Scripts, Inc., a Delaware corporation, the financial institutions from time to time party thereto as Lenders and Credit Suisse AG, Cayman Islands Branch, as Administrative Agent (as amended, supplemented or otherwise modified from time to time, the “ Credit Agreement ”; capitalized terms defined therein and not otherwise defined herein being used herein as therein defined).

B. Each Guarantor is an Affiliate of Company and will derive substantial benefits from the extension of credit to Company pursuant to the Credit Agreement.

C. It is a condition precedent to the making of the Loans under the Credit Agreement that Company’s obligations thereunder be guarantied by Guarantors.

D. Guarantors are willing irrevocably and unconditionally to guaranty such obligations of Company.

NOW , THEREFORE , based upon the foregoing and other good and valuable consideration, the receipt and sufficiency of which are hereby acknowledged, and in order to induce Lenders and Guarantied Party to enter into the Credit Agreement and to make Loans and other extensions of credit thereunder, Guarantors hereby agree as follows:

SECTION 1. DEFINITIONS

1.1 Certain Defined Terms . As used in this Guaranty, the following terms shall have the following meanings unless the context otherwise requires:

“ Beneficiaries ” means Guarantied Party and Lenders.

“ Guarantied Obligations ” has the meaning assigned to that term in subsection 2.1.

“ Guaranty ” means this Subsidiary Guaranty, as it may be amended, supplemented or otherwise modified from time to time.

“ payment in full ”, “ paid in full ” or any similar term means payment in full of the Guarantied Obligations, including all principal, interest, costs, fees and expenses (including reasonable legal fees and expenses) of Beneficiaries as required under the Loan Documents.

1.2 Interpretation .

(a) References to “Sections” and “subsections” shall be to Sections and subsections, respectively, of this Guaranty unless otherwise specifically provided.

(b) In the event of any conflict or inconsistency between the terms, conditions and provisions of this Guaranty and the terms, conditions and provisions of the Credit Agreement, the terms, conditions and provisions of this Guaranty shall prevail.

SECTION 2. THE GUARANTY

2.1 Guaranty of the Guarantied Obligations . Subject to the provisions of subsection 2.2(a), Guarantors jointly and severally hereby irrevocably and unconditionally guaranty, as primary obligors and not merely as sureties, the due and punctual payment in full of all Guarantied Obligations when the same shall become due, whether at stated maturity, by required prepayment, declaration, acceleration, demand or otherwise (including amounts that would become due but for the operation of the automatic stay under Section 362(a) of the Bankruptcy Code, 11 U.S.C. § 362(a)). The term “ Guarantied Obligations ” is used herein in its most comprehensive sense and includes:

(a) any and all Obligations of Company, in each case now or hereafter made, incurred or created, whether absolute or contingent, liquidated or unliquidated, whether due or not due, and however arising under or in connection with the Credit Agreement and the other Loan Documents, including those arising under successive borrowing transactions under the Credit Agreement which shall either continue the Obligations of Company or from time to time renew them after they have been satisfied and including interest which, but for the filing of a petition in bankruptcy with respect to Company, would have accrued on any Guarantied Obligations, whether or not a claim is allowed against Company for such interest in the related bankruptcy proceeding; and

(b) those expenses set forth in subsection 2.8.

2.2 Limitation on Amount Guarantied; Contribution by Guarantors . (a) Anything contained in this Guaranty to the contrary notwithstanding, if any Fraudulent Transfer Law (as hereinafter defined) is determined by a court of competent jurisdiction to be applicable to the obligations of any Guarantor under this Guaranty, such obligations of such Guarantor hereunder shall be limited to a maximum aggregate amount equal to the largest amount that would not render its obligations hereunder subject to

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avoidance as a fraudulent transfer or conveyance under Section 548 of Title 11 of the United States Code or any applicable provisions of comparable state law (collectively, the “ Fraudulent Transfer Laws ”), in each case after giving effect to all other liabilities of such Guarantor, contingent or otherwise, that are relevant under the Fraudulent Transfer Laws (specifically excluding, however, any liabilities of such Guarantor (x) in respect of intercompany indebtedness to Company or other affiliates of Company to the extent that such indebtedness would be discharged in an amount equal to the amount paid by such Guarantor hereunder and (y) under any guaranty of Indebtedness of Company or its Subsidiaries subordinated or junior in right of payment to the Guarantied Obligations which guaranty contains a limitation as to maximum amount similar to that set forth in this subsection 2.2(a), pursuant to which the liability of such Guarantor hereunder is included in the liabilities taken into account in determining such maximum amount) and after giving effect as assets to the value (as determined under the applicable provisions of the Fraudulent Transfer Laws) of any rights to subrogation, reimbursement, indemnification or contribution of such Guarantor pursuant to applicable law or pursuant to the terms of any agreement (including any such right of contribution under subsection 2.2(b).

(b) Guarantors under this Guaranty together desire to allocate among themselves in a fair and equitable manner, their obligations arising under this Guaranty. Accordingly, in the event any payment or distribution is made on any date by any Guarantor under this Guaranty (a “ Funding Guarantor ”) that exceeds its Fair Share (as defined below) as of such date, that Funding Guarantor shall be entitled to a contribution from each of the other Guarantors in the amount of such other Guarantor’s Fair Share Shortfall (as defined below) as of such date, with the result that all such contributions will cause each Guarantor’s Aggregate Payments (as defined below) to equal its Fair Share as of such date. “ Fair Share ” means, with respect to a Guarantor as of any date of determination, an amount equal to (i) the ratio of (x) the Adjusted Maximum Amount (as defined below) with respect to such Guarantor to (y) the aggregate of the Adjusted Maximum Amounts with respect to all Guarantors multiplied by (ii) the aggregate amount paid or distributed on or before such date by all Funding Guarantors under this Guaranty in respect of the obligations guarantied. “ Fair Share Shortfall ” means, with respect to a Guarantor as of any date of determination, the excess, if any, of the Fair Share of such Guarantor over the Aggregate Payments of such Guarantor. “ Adjusted Maximum Amount ” means, with respect to a Guarantor as of any date of determination, the maximum aggregate amount of the obligations of such Guarantor under this Guaranty determined as of such date, in the case of any Guarantor, in accordance with subsection 2.2(a); provided that, solely for purposes of calculating the “Adjusted Maximum Amount” with respect to any Guarantor for purposes of this subsection 2.2(b), any assets or liabilities of such Guarantor arising by virtue of any rights to subrogation, reimbursement or indemnification or any rights to or obligations of contribution hereunder shall not be considered as assets or liabilities of such Guarantor. “ Aggregate Payments ” means, with respect to a Guarantor as of any date of determination, an amount equal to (i) the aggregate amount of all payments and distributions made on or before such date by such Guarantor in respect of this Guaranty (including in respect of this subsection 2.2(b)) minus (ii) the aggregate amount of all payments received on or before such date by such Guarantor from the other Guarantors as contributions under this

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subsection 2.2(b). The amounts payable as contributions hereunder shall be determined as of the date on which the related payment or distribution is made by the applicable Funding Guarantor. The allocation among Guarantors of their obligations as set forth in this subsection 2.2(b) shall not be construed in any way to limit the liability of any Guarantor hereunder.

2.3 Payment by Guarantors; Application of Payments . Subject to the provisions of subsection 2.2(a), Guarantors hereby jointly and severally agree, in furtherance of the foregoing and not in limitation of any other right which any Beneficiary may have at law or in equity against any Guarantor by virtue hereof, that upon the failure of Company to pay any of the Guarantied Obligations when and as the same shall become due, whether at stated maturity, by required prepayment, declaration, acceleration, demand or otherwise (including amounts that would become due but for the operation of the automatic stay under Section 362(a) of the Bankruptcy Code, 11 U.S.C. § 362(a)), Guarantors will upon demand pay, or cause to be paid, in cash, to Guarantied Party for the ratable benefit of Beneficiaries, an amount equal to the sum of the unpaid principal amount of all Guarantied Obligations then due as aforesaid, accrued and unpaid interest on such Guarantied Obligations (including interest which, but for the filing of a petition in bankruptcy with respect to Company, would have accrued on such Guarantied Obligations, whether or not a claim is allowed against Company for such interest in the related bankruptcy proceeding) and all other Guarantied Obligations then owed to Beneficiaries as aforesaid. All such payments shall be applied promptly from time to time by Guarantied Party as provided in subsection 2.4C of the Credit Agreement.

2.4 Liability of Guarantors Absolute . Each Guarantor agrees that its obligations hereunder are irrevocable, absolute, independent and unconditional and shall not be affected by any circumstance which constitutes a legal or equitable discharge of a guarantor or surety other than payment in full of the Guarantied Obligations. In furtherance of the foregoing and without limiting the generality thereof, each Guarantor agrees as follows:

(a) This Guaranty is a guaranty of payment when due and not of collectibility.

(b) Guarantied Party may enforce this Guaranty upon the occurrence of an Event of Default under the Credit Agreement notwithstanding the existence of any dispute between Company and any Beneficiary with respect to the existence of such Event of Default.

(c) The obligations of each Guarantor hereunder are independent of the obligations of Company under the Loan Documents and the obligations of any other guarantor (including any other Guarantor) of the obligations of Company under the Loan Documents, and a separate action or actions may be brought and prosecuted against such Guarantor whether or not any action is brought against Company or any of such other guarantors and whether or not Company is joined in any such action or actions.

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(d) Payment by any Guarantor of a portion, but not all, of the Guarantied Obligations shall in no way limit, affect, modify or abridge any Guarantor’s liability for any portion of the Guarantied Obligations which has not been paid. Without limiting the generality of the foregoing, if Guarantied Party is awarded a judgment in any suit brought to enforce any Guarantor’s covenant to pay a portion of the Guarantied Obligations, such judgment shall not be deemed to release such Guarantor from its covenant to pay the portion of the Guarantied Obligations that is not the subject of such suit, and such judgment shall not, except to the extent satisfied by such Guarantor, limit, affect, modify or abridge any other Guarantor’s liability hereunder in respect of the Guarantied Obligations.

(e) Any Beneficiary, upon such terms as it deems appropriate, without notice or demand and without affecting the validity or enforceability of this Guaranty or giving rise to any reduction, limitation, impairment, discharge or termination of any Guarantor’s liability hereunder, from time to time may (i) renew, extend, accelerate, increase the rate of interest on, or otherwise change the time, place, manner or terms of payment of the Guarantied Obligations, (ii) settle, compromise, release or discharge, or accept or refuse any offer of performance with respect to, or substitutions for, the Guarantied Obligations or any agreement relating thereto and/or subordinate the payment of the same to the payment of any other obligations; (iii) request and accept other guaranties of the Guarantied Obligations and take and hold security for the payment of this Guaranty or the Guarantied Obligations; (iv) release, surrender, exchange, substitute, compromise, settle, rescind, waive, alter, subordinate or modify, with or without consideration, any security for payment of the Guarantied Obligations, any other guaranties of the Guarantied Obligations, or any other obligation of any Person (including any other Guarantor) with respect to the Guarantied Obligations; (v) enforce and apply any security now or hereafter held by or for the benefit of such Beneficiary in respect of this Guaranty or the Guarantied Obligations and direct the order or manner of sale thereof, or exercise any other right or remedy that such Beneficiary may have against any such security, in each case as such Beneficiary in its discretion may determine consistent with the Credit Agreement and any applicable security agreement, including foreclosure on any such security pursuant to one or more judicial or nonjudicial sales, whether or not every aspect of any such sale is commercially reasonable, and even though such action operates to impair or extinguish any right of reimbursement or subrogation or other right or remedy of any Guarantor against Company or any security for the Guarantied Obligations; and (vi) exercise any other rights available to it under the Loan Documents.

(f) This Guaranty and the obligations of Guarantors hereunder shall be valid and enforceable and shall not be subject to any reduction, limitation, impairment, discharge or termination for any reason (other than payment in full of the Guarantied Obligations), including the occurrence of any of the following, whether or not any Guarantor shall have had notice or knowledge of any of them: (i) any failure or omission to assert or enforce or agreement or election not to assert or enforce, or the stay or enjoining, by order of court, by operation of law

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or otherwise, of the exercise or enforcement of, any claim or demand or any right, power or remedy (whether arising under the Loan Documents, at law, in equity or otherwise) with respect to the Guarantied Obligations or any agreement relating thereto, or with respect to any other guaranty of or security for the payment of the Guarantied Obligations; (ii) any rescission, waiver, amendment or modification of, or any consent to departure from, any of the terms or provisions (including provisions relating to events of default) of the Credit Agreement, any of the other Loan Documents or any agreement or instrument executed pursuant thereto, or of any other guaranty or security for the Guarantied Obligations, in each case whether or not in accordance with the terms of the Credit Agreement or such Loan Document or any agreement relating to such other guaranty or security; (iii) the Guarantied Obligations, or any agreement relating thereto, at any time being found to be illegal, invalid or unenforceable in any respect; (iv) the application of payments received from any source (other than payments received pursuant to the other Loan Documents or from the proceeds of any security for the Guarantied Obligations) to the payment of indebtedness other than the Guarantied Obligations, even though any Beneficiary might have elected to apply such payment to any part or all of the Guarantied Obligations; (v) any Beneficiary’s consent to the change, reorganization or termination of the corporate structure or existence of Company or any of its Subsidiaries and to any corresponding restructuring of the Guarantied Obligations; (vi) any failure to perfect or continue perfection of a security interest in any collateral which secures any of the Guarantied Obligations; (vii) any defenses, set-offs or counterclaims which Company may allege or assert against any Beneficiary in respect of the Guarantied Obligations, including failure of consideration, breach of warranty, payment, statute of frauds, statute of limitations, accord and satisfaction and usury; and (viii) any other act or thing or omission, or delay to do any other act or thing, which may or might in any manner or to any extent vary the risk of any Guarantor as an obligor in respect of the Guarantied Obligations.

2.5 Waivers by Guarantors . Each Guarantor hereby waives, for the benefit of Beneficiaries:

(a) any right to require any Beneficiary, as a condition of payment or performance by such Guarantor, to (i) proceed against Company, any other guarantor (including any other Guarantor) of the Guarantied Obligations or any other Person, (ii) proceed against or exhaust any security held from Company, any such other guarantor or any other Person, (iii) proceed against or have resort to any balance of any deposit account or credit on the books of any Beneficiary in favor of Company or any other Person, or (iv) pursue any other remedy in the power of any Beneficiary whatsoever;

(b) any defense arising by reason of the incapacity, lack of authority or any disability or other defense of Company including any defense based on or arising out of the lack of validity or the unenforceability of the Guarantied Obligations or any agreement or instrument relating thereto or by reason of the cessation of the liability of Company from any cause other than payment in full of the Guarantied Obligations;

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(c) any defense based upon any statute or rule of law which provides that the obligation of a surety must be neither larger in amount nor in other respects more burdensome than that of the principal;

(d) any defense based upon any Beneficiary’s errors or omissions in the administration of the Guarantied Obligations, except behavior which amounts to bad faith;

(e) (i) any principles or provisions of law, statutory or otherwise, which are or might be in conflict with the terms of this Guaranty and any legal or equitable discharge of such Guarantor’s obligations hereunder, (ii) the benefit of any statute of limitations affecting such Guarantor’s liability hereunder or the enforcement hereof, (iii) any rights to set-offs, recoupments and counterclaims, and (iv) promptness, diligence and any requirement that any Beneficiary protect, secure, perfect or insure any security interest or lien or any property subject thereto;

(f) notices, demands, presentments, protests, notices of protest, notices of dishonor and notices of any action or inaction, including acceptance of this Guaranty, notices of default under the Credit Agreement or any agreement or instrument related thereto, notices of any renewal, extension or modification of the Guarantied Obligations or any agreement related thereto, notices of any extension of credit to Company and notices of any of the matters referred to in subsection 2.4 and any right to consent to any thereof; and

(g) any defenses or benefits that may be derived from or afforded by law which limit the liability of or exonerate guarantors or sureties, or which may conflict with the terms of this Guaranty.

2.6 Guarantors’ Rights of Subrogation, Contribution, Etc . Each Guarantor hereby waives, until the Guarantied Obligations shall have been indefeasibly paid in full and the Commitments shall have terminated and all Letters of Credit shall have expired or been cancelled, any claim, right or remedy, direct or indirect, that such Guarantor now has or may hereafter have against Company or any of its assets in connection with this Guaranty or the performance by such Guarantor of its obligations hereunder, in each case whether such claim, right or remedy arises in equity, under contract, by statute under common law or otherwise and including (a) any right of subrogation, reimbursement or indemnification that such Guarantor now has or may hereafter have against Company, (b) any right to enforce, or to participate in, any claim, right or remedy that any Beneficiary now has or may hereafter have against Company, and (c) any benefit of, and any right to participate in, any collateral or security now or hereafter held by any Beneficiary. In addition, until the Guarantied Obligations shall have been indefeasibly paid in full and the Commitments shall have terminated and all Letters of Credit shall have expired or been cancelled, each Guarantor shall withhold

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exercise of any right of contribution such Guarantor may have against any other guarantor (including any other Guarantor) of the Guarantied Obligations (including any such right of contribution under subsection 2.2(b)). Each Guarantor further agrees that, to the extent the waiver or agreement to withhold the exercise of its rights of subrogation, reimbursement, indemnification and contribution as set forth herein is found by a court of competent jurisdiction to be void or voidable for any reason, any rights of subrogation, reimbursement or indemnification such Guarantor may have against Company or against any collateral or security, and any rights of contribution such Guarantor may have against any such other guarantor, shall be junior and subordinate to any rights any Beneficiary may have against Company, to all right, title and interest any Beneficiary may have in any such collateral or security, and to any right any Beneficiary may have against such other guarantor. If any amount shall be paid to any Guarantor on account of any such subrogation, reimbursement, indemnification or contribution rights at any time when all Guarantied Obligations shall not have been paid in full, such amount shall be held in trust for Guarantied Party on behalf of Beneficiaries and shall forthwith be paid over to Guarantied Party for the benefit of Beneficiaries to be credited and applied against the Guarantied Obligations, whether matured or unmatured, in accordance with the terms hereof.

2.7 Subordination of Other Obligations . Any indebtedness of Company or any Guarantor now or hereafter held by any Guarantor (the “ Obligee Guarantor ”) is hereby subordinated in right of payment to the Guarantied Obligations, and any such indebtedness collected or received by the Obligee Guarantor after an Event of Default has occurred and is continuing shall be held in trust for Guarantied Party on behalf of Beneficiaries and shall forthwith be paid over to Guarantied Party for the benefit of Beneficiaries to be credited and applied against the Guarantied Obligations but without affecting, impairing or limiting in any manner the liability of the Obligee Guarantor under any other provision of this Guaranty.

2.8 Expenses . Guarantors jointly and severally agree to pay, or cause to be paid, on demand, and to save Beneficiaries harmless against liability for, any and all costs and expenses (including reasonable fees and disbursements of counsel and reasonable allocated costs of internal counsel) incurred or expended by any Beneficiary in connection with the enforcement of or preservation of any rights under this Guaranty.

2.9 Continuing Guaranty . This Guaranty is a continuing guaranty and shall remain in effect until all of the Guarantied Obligations shall have been paid in full and the Commitments shall have terminated and all Letters of Credit shall have expired or been cancelled. Each Guarantor hereby irrevocably waives any right to revoke this Guaranty as to future transactions giving rise to any Guarantied Obligations.

2.10 Rights Cumulative . The rights, powers and remedies given to Beneficiaries by this Guaranty are cumulative and shall be in addition to and independent of all rights, powers and remedies given to Beneficiaries by virtue of any statute or rule of law or in any of the other Loan Documents or any agreement between any Guarantor and any Beneficiary or Beneficiaries or between Company and any Beneficiary or Beneficiaries. Any forbearance or failure to exercise, and any delay by any Beneficiary in exercising, any right, power or remedy hereunder shall not impair any such right, power or remedy or be construed to be a waiver thereof, nor shall it preclude the further exercise of any such right, power or remedy.

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2.11 Bankruptcy; Post-Petition Interest; Reinstatement of Guaranty . (a) So long as any Guarantied Obligations remain outstanding, no Guarantor shall, without the prior written consent of Guarantied Party acting pursuant to the instructions of Requisite Lenders, commence or join with any other Person in commencing any bankruptcy, reorganization or insolvency proceedings of or against Company. The obligations of Guarantors under this Guaranty shall not be reduced, limited, impaired, discharged, deferred, suspended or terminated by any proceeding, voluntary or involuntary, involving the bankruptcy, insolvency, receivership, reorganization, liquidation or arrangement of Company or by any defense which Company may have by reason of the order, decree or decision of any court or administrative body resulting from any such proceeding.

(b) Each Guarantor acknowledges and agrees that any interest on any portion of the Guarantied Obligations which accrues after the commencement of any proceeding referred to in clause (a) above (or, if interest on any portion of the Guarantied Obligations ceases to accrue by operation of law by reason of the commencement of said proceeding, such interest as would have accrued on such portion of the Guarantied Obligations if said proceedings had not been commenced) shall be included in the Guarantied Obligations because it is the intention of Guarantors and Beneficiaries that the Guarantied Obligations which are guarantied by Guarantors pursuant to this Guaranty should be determined without regard to any rule of law or order which may relieve Company of any portion of such Guarantied Obligations. Guarantors will permit any trustee in bankruptcy, receiver, debtor in possession, assignee for the benefit of creditors or similar person to pay Guarantied Party, or allow the claim of Guarantied Party in respect of, any such interest accruing after the date on which such proceeding is commenced.

(c) In the event that all or any portion of the Guarantied Obligations are paid by Company, the obligations of Guarantors hereunder shall continue and remain in full force and effect or be reinstated, as the case may be, in the event that all or any part of such payment(s) are rescinded or recovered directly or indirectly from any Beneficiary as a preference, fraudulent transfer or otherwise, and any such payments which are so rescinded or recovered shall constitute Guarantied Obligations for all purposes under this Guaranty.

2.12 Notice of Events . As soon as Guarantor obtains knowledge thereof, Guarantor shall give Guarantied Party written notice of any condition or event which has resulted in (a) a material adverse change in the financial condition of Guarantor or Company or (b) any Event of Default or Potential Event of Default.

2.13 Set Off . In addition to any other rights any Beneficiary may have under law or under this Guaranty, such Beneficiary is authorized at any time or from time to time while an Event of Default has occurred and is continuing, without notice (any such

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notice being hereby expressly waived), to set off and to appropriate and to apply any and all deposits (general or special, including indebtedness evidenced by certificates of deposit, whether matured or unmatured) and any other indebtedness of such Beneficiary owing to Guarantor and any other property of Guarantor held by any Beneficiary to or for the credit or the account of Guarantor against and on account of the Guarantied Obligations and liabilities of Guarantor to any Beneficiary under this Guaranty.

2.14 Representations and Warranties . Each Guarantor represents and warrants as to itself, on the date that it becomes a party hereto, on the Term Loan Funding Date, on each Funding Date (other than, in the case of Funding Dates occurring after the Term Loan Funding Date, subsections 5.4 and 5.6 of the Credit Agreement) and on the date of the issuance of each Letter of Credit (other than, in the case of Funding Dates occurring after the Term Loan Funding Date, subsections 5.4 and 5.6 of the Credit Agreement) that all representations and warranties relating to it contained in the Loan Documents are true, correct and complete in all material respects, except to the extent such representations and warranties specifically relate to an earlier date, in which case such representations and warranties were true, correct and complete in all material respects on and as of such earlier date.

2.15 Covenants . Each Guarantor covenants and agrees that such Guarantor will perform and observe, and cause each of its Subsidiaries to perform and observe, all of the terms, covenants and agreements set forth in the Loan Documents that are required to be, or that Company has agreed to cause to be, performed or observed by such Guarantor or Subsidiary.

2.16 Information . Each Guarantor assumes all responsibility for being and keeping itself informed of the Company’s and each other Loan Party’s financial condition and assets and of all other circumstances bearing upon the risk of nonpayment of the Guaranteed Obligations and the nature, scope and extent of the risks that such Guarantor assumes and incurs hereunder, and agrees that neither the Guarantied Party nor any other Beneficiary will have any duty to advise such Guarantor of information known to it or any of them regarding such circumstances or risks.

SECTION 3. MISCELLANEOUS

3.1 Survival of Warranties . All agreements, representations and warranties made herein shall survive the execution and delivery of this Guaranty and the other Loan Documents and any increase in the Commitments under the Credit Agreement.

3.2 Notices . Any communications between Guarantied Party and any Guarantor and any notices or requests provided herein to be given may be given by mailing the same, postage prepaid, or by telex, facsimile transmission or cable to each such party at its address set forth in the Credit Agreement, on the signature pages hereof or to such other addresses as each such party may in writing hereafter indicate. Any notice, request or demand to or upon Guarantied Party or any Guarantor shall not be effective until received.

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3.3 Severability . In case any provision in or obligation under this Guaranty shall be invalid, illegal or unenforceable in any jurisdiction, the validity, legality and enforceability of the remaining provisions or obligations, or of such provision or obligation in any other jurisdiction, shall not in any way be affected or impaired thereby.

3.4 Amendments and Waivers . (a) No failure or delay by the Guarantied Party or any other Beneficiary in exercising any right or power hereunder or under any other Loan Document shall operate as a waiver hereof or thereof, nor shall any single or partial exercise of any such right or power, or any abandonment or discontinuance of steps to enforce such a right or power, preclude any other or further exercise thereof or the exercise of any other right or power. The rights and remedies of the Guarantied Party and the other Beneficiaries hereunder and under the other Loan Documents are cumulative and are not exclusive of any rights or remedies that they would otherwise have. No waiver of any provision of any Loan Document or consent to any departure by any Loan Party therefrom shall in any event be effective unless the same shall be permitted by paragraph (b) of this Section 3.4 and then such waiver or consent shall be effective only in the specific instance and for the purpose for which given. No notice or demand on any Loan Party in any case shall entitle any Loan Party to any other or further notice or demand in similar or other circumstances.

(b) No amendment, modification, termination or waiver of any provision of this Guaranty, and no consent to any departure by any Guarantor therefrom, shall in any event be effective without the written concurrence of Guarantied Party and, in the case of any such amendment or modification, each Guarantor against whom enforcement of such amendment or modification is sought. Any such waiver or consent shall be effective only in the specific instance and for the specific purpose for which it was given. Any amendment, modification, termination, waiver or consent effected in accordance with this subsection 3.4(b) shall be binding upon each Beneficiary.

3.5 Headings . Section and subsection headings in this Guaranty are included herein for convenience of reference only and shall not constitute a part of this Guaranty for any other purpose or be given any substantive effect.

3.6 Applicable Law; Rules of Construction . THIS GUARANTY AND THE RIGHTS AND OBLIGATIONS OF GUARANTORS AND BENEFICIARIES HEREUNDER SHALL BE GOVERNED BY, AND SHALL BE CONSTRUED AND ENFORCED IN ACCORDANCE WITH, THE INTERNAL LAWS OF THE STATE OF NEW YORK. The rules of construction set forth in subsection 1.3 of the Credit Agreement shall be applicable to this Guaranty mutatis mutandis .

3.7 Successors and Assigns . This Guaranty is a continuing guaranty and shall be binding upon each Guarantor and its respective successors and assigns. This Guaranty shall inure to the benefit of Beneficiaries and their respective successors and assigns. No Guarantor shall assign this Guaranty or any of the rights or obligations of such Guarantor hereunder without the prior written consent of all Lenders. Any

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Beneficiary may, without notice or consent, assign its interest in this Guaranty in whole or in part. The terms and provisions of this Guaranty shall inure to the benefit of any transferee or assignee of any Loan, and in the event of such transfer or assignment the rights and privileges herein conferred upon such Beneficiary shall automatically extend to and be vested in such transferee or assignee, all subject to the terms and conditions hereof.

3.8 Consent to Jurisdiction and Service of Process . ALL JUDICIAL PROCEEDINGS BROUGHT AGAINST ANY GUARANTOR ARISING OUT OF OR RELATING TO THIS GUARANTY, OR ANY OBLIGATIONS HEREUNDER, MAY BE BROUGHT IN ANY STATE OR FEDERAL COURT OF COMPETENT JURISDICTION IN THE STATE, COUNTY AND CITY OF NEW YORK. BY EXECUTING AND DELIVERING THIS AGREEMENT, EACH GUARANTOR, FOR ITSELF AND IN CONNECTION WITH ITS PROPERTIES, IRREVOCABLY

(I) ACCEPTS GENERALLY AND UNCONDITIONALLY THE NONEXCLUSIVE JURISDICTION AND VENUE OF SUCH COURTS;

(II) WAIVES ANY DEFENSE OF FORUM NON CONVENIENS WITH RESPECT TO ANY STATE OR FEDERAL COURT OF COMPETENT JURISDICTION IN THE STATE, COUNTY AND CITY OF NEW YORK;

(III) AGREES THAT SERVICE OF ALL PROCESS IN ANY SUCH PROCEEDING IN ANY SUCH COURT MAY BE MADE BY REGISTERED OR CERTIFIED MAIL, RETURN RECEIPT REQUESTED, TO SUCH GUARANTOR AT ITS ADDRESS PROVIDED IN ACCORDANCE WITH SUBSECTION 3.2;

(IV) AGREES THAT SERVICE AS PROVIDED IN CLAUSE (III) ABOVE IS SUFFICIENT TO CONFER PERSONAL JURISDICTION OVER SUCH GUARANTOR IN ANY SUCH PROCEEDING IN ANY SUCH COURT, AND OTHERWISE CONSTITUTES EFFECTIVE AND BINDING SERVICE IN EVERY RESPECT;

(V) AGREES THAT BENEFICIARIES RETAIN THE RIGHT TO SERVE PROCESS IN ANY OTHER MANNER PERMITTED BY LAW OR TO BRING PROCEEDINGS AGAINST SUCH GUARANTOR IN THE COURTS OF ANY OTHER JURISDICTION; AND

(VI) AGREES THAT THE PROVISIONS OF THIS SUBSECTION 3.8 RELATING TO JURISDICTION AND VENUE SHALL BE BINDING AND ENFORCEABLE TO THE FULLEST EXTENT PERMISSIBLE UNDER NEW YORK GENERAL OBLIGATIONS LAW SECTION 5-1402 OR OTHERWISE.

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3.9 Waiver of Trial by Jury . EACH GUARANTOR AND, BY ITS ACCEPTANCE OF THE BENEFITS HEREOF, EACH BENEFICIARY HEREBY AGREES TO WAIVE ITS RESPECTIVE RIGHTS TO A JURY TRIAL OF ANY CLAIM OR CAUSE OF ACTION BASED UPON OR ARISING OUT OF THIS GUARANTY. The scope of this waiver is intended to be all encompassing of any and all disputes that may be filed in any court and that relate to the subject matter of this transaction, including contract claims, tort claims, breach of duty claims and all other common law and statutory claims. Each Guarantor and, by its acceptance of the benefits hereof, each Beneficiary, each (i) acknowledges that this waiver is a material inducement for such Guarantor and Beneficiaries to enter into a business relationship, that such Guarantor and Beneficiaries have already relied on this waiver in entering into this Guaranty or accepting the benefits thereof, as the case may be, and that each will continue to rely on this waiver in their related future dealings and (ii) further warrants and represents that each has reviewed this waiver with its legal counsel, and that each knowingly and voluntarily waives its jury trial rights following consultation with legal counsel. THIS WAIVER IS IRREVOCABLE, MEANING THAT IT MAY NOT BE MODIFIED EITHER ORALLY OR IN WRITING (OTHER THAN BY A MUTUAL WRITTEN WAIVER SPECIFICALLY REFERRING TO THIS SUBSECTION 3.9 AND EXECUTED BY GUARANTIED PARTY AND EACH GUARANTOR), AND THIS WAIVER SHALL APPLY TO ANY SUBSEQUENT AMENDMENTS, RENEWALS, SUPPLEMENTS OR MODIFICATIONS TO THIS GUARANTY. In the event of litigation, this Guaranty may be filed as a written consent to a trial by the court.

3.10 No Other Writing . This writing is intended by Guarantors and Beneficiaries as the final expression of this Guaranty and is also intended as a complete and exclusive statement of the terms of their agreement with respect to the matters covered hereby. No course of dealing, course of performance or trade usage, and no parol evidence of any nature, shall be used to supplement or modify any terms of this Guaranty. There are no conditions to the full effectiveness of this Guaranty.

3.11 Further Assurances . At any time or from time to time, upon the request of Guarantied Party, Guarantors shall execute and deliver such further documents and do such other acts and things as Guarantied Party may reasonably request in order to effect fully the purposes of this Guaranty.

3.12 Additional Guarantors . The initial Guarantors hereunder shall be such of the Domestic Subsidiaries of Company as are signatories hereto on the date hereof. From time to time subsequent to the date hereof, additional Domestic Subsidiaries of Company may become parties hereto, as additional Guarantors (each an “ Additional Guarantor ”), by executing a counterpart of this Guaranty. Upon delivery of any such counterpart to Administrative Agent, notice of which is hereby waived by Guarantors, each such Additional Guarantor shall be a Guarantor and shall be as fully a party hereto as if such Additional Guarantor were an original signatory hereof. Each Guarantor expressly agrees that its obligations arising hereunder shall not be affected or diminished by the addition or release of any other Guarantor hereunder, nor by any election of Administrative Agent not to cause any Subsidiary of Company to become an Additional Guarantor hereunder. This Guaranty shall be fully effective as to any Guarantor that is or becomes a party hereto regardless of whether any other Person becomes or fails to become or ceases to be a Guarantor hereunder.

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3.13 Counterparts; Effectiveness . This Guaranty may be executed in any number of counterparts and by the different parties hereto in separate counterparts, each of which when so executed and delivered shall be deemed to be an original for all purposes; but all such counterparts together shall constitute but one and the same instrument. This Guaranty shall become effective as to each Guarantor upon the execution of a counterpart hereof by such Guarantor (whether or not a counterpart hereof shall have been executed by any other Guarantor) and receipt by Guarantied Party of written or telephonic notification of such execution and authorization of delivery thereof. Delivery of an executed counterpart of a signature page of this Guaranty by telefacsimile or electronic transmission (in PDF format) shall be effective as delivery of a manually executed counterpart of this Guaranty.

3.14 Guarantied Party as Agent .

(a) Guarantied Party has been appointed to act as Guarantied Party hereunder by Lenders. Guarantied Party shall be obligated, and shall have the right hereunder, to make demands, to give notices, to exercise or refrain from exercising any rights, and to take or refrain from taking any action, solely in accordance with this Guaranty and the Credit Agreement; provided that Guarantied Party shall exercise, or refrain from exercising, any remedies hereunder in accordance with the instructions of Requisite Lenders.

(b) Guarantied Party shall at all times be the same Person that is Administrative Agent under the Credit Agreement. Written notice of resignation by Administrative Agent pursuant to subsection 9.5 of the Credit Agreement shall also constitute notice of resignation as Guarantied Party under this Guaranty; removal of Administrative Agent under the Credit Agreement shall also constitute removal as Guarantied Party under this Guaranty; and appointment of a successor Agent pursuant to subsection 9.5 of the Credit Agreement shall also constitute appointment of a successor Guarantied Party under this Guaranty. Upon the acceptance of any appointment as Administrative Agent under subsection 9.5 of the Credit Agreement by a successor Administrative Agent, that successor Administrative Agent shall thereupon succeed to and become vested with all the rights, powers, privileges and duties of the resigning or removed Guarantied Party under this Guaranty, and the resigning or removed Guarantied Party under this Guaranty shall promptly (i) transfer to such successor Guarantied Party all sums held hereunder, together with all records and other documents necessary or appropriate in connection with the performance of the duties of the successor Guarantied Party under this Guaranty, and (ii) take such other actions as may be necessary or appropriate in connection with the assignment to such successor Guarantied Party of the rights created hereunder, whereupon such retiring or removed Guarantied Party shall be discharged from its duties and obligations under this Guaranty. After any retiring or removed Guarantied Party’s resignation or removal hereunder as Guarantied Party, the provisions of this Guaranty shall inure to its benefit as to any actions taken or omitted to be taken by it under this Guaranty while it was Guarantied Party hereunder.

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3.15 Release of Guarantors . A Guarantor shall automatically be released from its Guarantied Obligations upon the consummation of any transaction permitted by the Credit Agreement as a result of which such Guarantor ceases to be a Domestic Subsidiary; provided that, if so required by the Credit Agreement, the Requisite Lenders shall have consented to such transaction and the terms of such consent shall not have provided otherwise.

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IN WITNESS WHEREOF , each of the undersigned Guarantors has caused this Guaranty to be duly executed and delivered by its officer thereunto duly authorized as of the date first written above.

[ Subsidiary Guaranty ]

[ Subsidiary Guaranty ]

BYFIELD DRUG, INC.

CARE CONTINUUM, INC.

CFI OF NEW JERSEY, INC.

CHESAPEAKE INFUSION, INC.

CONNECTYOURCARE COMPANY LLC

CONNECTYOURCARE, LLC

CURASCRIPT PBM SERVICES, INC.

DIVERSIFIED PHARMACEUTICAL SERVICES, INC.

ESI ACQUISITION, INC.

ESI CLAIMS, INC.

ESI ENTERPRISES, LLC

ESI MAIL ORDER PROCESSING, INC.

EXPRESS SCRIPTS CANADA HOLDING CO.

EXPRESS SCRIPTS CANADA HOLDING, LLC

EXPRESS SCRIPTS, INC.

EXPRESS SCRIPTS PHARMACEUTICAL PROCUREMENT, LLC

EXPRESS SCRIPTS SERVICES COMPANY FRECO, INC.

FREEDOM SERVICE COMPANY, LLC

HEALTHBRIDGE, INC.

HEALTHBRIDGE REIMBURSEMENT AND PRODUCT SUPPORT, INC.

IBIOLOGIC, INC.

IVTX, INC.

LYNNFIELD COMPOUNDING CENTER, INC.

LYNNFIELD DRUG, INC.

MATRIX GPO LLC

NATIONAL PRESCRIPTION ADMINISTRATORS, INC.

PRIORITYHEALTHCARE.COM, INC.

IN WITNESS WHEREOF, the undersigned Additional Guarantor has caused this Guaranty to be duly executed and delivered by its officer thereunto duly authorized as of                     ,             .