Change in ControlAgreement

EXHIBIT 10.3

Change in Control Agreement

This Change in Control Agreement is entered into this 21st day of July, 2005 (“Effective Date”) between Pony Acquisition Corporation (“MergerSub”), Priority Healthcare Corporation and its affiliated and subsidiary companies, with its primary offices at 250 Technology Park, Suite 124, Lake Mary, Florida 32746 (the “Company”) and Robert L. Myers (“Executive”).

WITNESSETH:

WHEREAS, the Company and Express Scripts, Inc. have entered into negotiations concerning the merger of MergerSub, a wholly owned, indirect subsidiary of Express Scripts, Inc. (“ESI”) with and into the Company, resulting in the Company surviving as a wholly owned, indirect subsidiary of ESI (the “Merger”);

WHEREAS, Executive acknowledges that as a result of the Merger, Executive shall be entitled to receive certain payments and benefits, pursuant to the Merger Agreement and otherwise, that Executive would not otherwise be entitled to receive;

WHEREAS, as a precondition for ESI and MergerSub to enter into that certain Agreement and Plan of Merger by and among ESI, MergerSub and the Company, dated as of the Effective Date (the “Merger Agreement”), that certain Termination Benefits Agreement entered into as of July 1, 1996 by and between the Company and Executive (the “Termination Benefits Agreement”) and that certain Agreement made and entered into as of June 30, 2004 by and between the Company and Executive (the “Supplemental Agreement” together with the Termination Benefits Agreement, the “Prior Agreements”) shall terminate.

NOW THEREFORE, for and in consideration of the payments set forth in this Agreement and other good and valuable consideration, the receipt and sufficiency of which is affirmed by the parties by their execution of this Agreement, the parties agree and covenant to the following terms and conditions:

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Except for the termination of the Prior Agreements, this Agreement shall not terminate, modify or amend any other written agreement plans, benefits, or stock options, including but not limited to the Supplemental Agreement, the Company’s 1997 Stock Option and Incentive Plan, as amended, the Company’s Non-qualified Deferred Compensation Plan, and the Company’s 401k Excess Plan, which shall remain unchanged. Any rights or interest of Executive in any equity or equity-based awards shall continue to be subject to the terms provided for in the applicable equity or equity-based award plans, documents and agreements. This Section 4 shall survive any termination of this Agreement.

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Should any clause, portion or section of this Agreement be unenforceable or invalid for any reason, such unenforceability or invalidity shall not affect the enforceability or validity of the remainder of this Agreement. Should any particular covenant in this Agreement be held unreasonable or unenforceable for any reason, including without limitation, the time period, geographical area and scope of activity covered by such covenant, then the covenant shall be given effect and enforced to whatever extent would be reasonable and enforceable.

For the avoidance of doubt, in the event of any conflicts between that certain Indemnification Agreement entered into by and between the Company and Executive dated June     , 2003 (the “Indemnification Agreement”) and the provisions of Section 5.10 of the Merger Agreement, the parties hereto acknowledge and agree that to the extent the Company satisfies its obligations to Executive pursuant to Section 5.10 of the Merger Agreement, the Company shall be deemed to have satisfied its obligations to provide Director’s and Officer’s liability coverage under the Indemnification Agreement. This Section 7 shall survive any termination of this Agreement.

In the event of Executive’s resignation or termination of Executive’s employment hereunder, Executive shall have no obligation to seek other employment or otherwise mitigate damages and there shall be no offset for any remuneration attributable to any subsequent employment that the Executive may obtain. This Section 8 shall survive any termination of this Agreement.

All notices which are required or may be given pursuant to the terms of this Agreement shall be in writing and shall be sufficiently delivered if provided in writing, delivered personally, by certified or registered mail, return receipt requested, by a nationally recognized overnight courier or via facsimile confirmed in writing to the recipient. Delivery shall be to Company at Company’s principal place of business, to MergerSub at MergerSub’s principal place of business and to Executive at Executive’s most recently filed home address.

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This Agreement is governed by the laws of the State of Florida.

Failure to insist upon strict compliance with any of the terms, conditions or provisions of this Agreement shall not be deemed a waiver hereof, nor shall any waiver or relinquishment of any right or power hereunder at any one or more times be deemed a waiver or relinquishment of any right or power at any other time.

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This Agreement may be executed in two or more counterparts, each of which shall be deemed an original but all of which together shall constitute the same instrument.

[Signatures on next page.]

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IN WITNESS WHEREOF, MergerSub, the Company and Executive have executed this Agreement on the date first stated above.

EXECUTIVE:

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Schedule I

[See attached]

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Exhibit A

RELEASE

Section 1. Release

For and in consideration of the payment of the amounts described in that certain Change in Control Agreement dated as of the 21^st day of July, 2005 by and between Robert L. Myers (“Executive”), Pony Acquisition Corporation and Priority Healthcare Corporation (the “Agreement”), Executive hereby agrees on behalf of himself, his agents, assignees, attorneys, successors, assigns, heirs and executors, to, and Executive does hereby, fully and completely forever release Priority Healthcare Corporation (together with its successors, subsidiaries, officers, and any parent company by which it may be or hereinafter become wholly owned (whether directly or indirectly) (collectively, “Priority”)) and each of its respective past, current and future affiliates, predecessors and successors and all of their respective past and/or present officers, directors, partners, members, managing members, managers, employees, agents, representatives, administrators, attorneys, insurers and fiduciaries, in their individual and/or representative capacities (hereinafter collectively referred to as the “Company Releasees”), from any and all causes of action, suits, agreements, promises, damages, disputes, controversies, contentions, differences, judgments, claims, debts, dues, sums of money, accounts, reckonings, bonds, bills, specialities, covenants, contracts, variances, trespasses, extents, executions and demands of any kind whatsoever, which Executive or his agents, assignees, attorneys, successors, assigns, heirs and executors ever had, now have or may have against Company Releasees or any of them, in law, admiralty or equity, whether known or unknown to Executive, for, upon, or by reason of, any matter, action, omission, course or thing whatsoever occurring up to the date this Release is signed by Executive, including, without limitation, in connection with or in relationship to Executive’s employment or other service relationship with Priority, the termination of any such employment or service relationship and any applicable employment, compensatory or termination arrangement with Priority (including, without limitation, the Prior Agreements (as such term is defined in the Agreement)), any exhibits attached thereto, and any amendments thereto, any claims of breach of contract, wrongful termination, retaliation, fraud, defamation, infliction of emotional distress or national origin, race, age, sex, sexual orientation, disability, medical condition or other discrimination or harassment, (such released claims are collectively referred to herein as the “Released Claims”); provided that such Released Claims shall not include any claims to enforce Executive’s rights or obligations under, or with respect to, the Agreement, the Indemnification Agreement or Section 5.10 of the Merger Agreement (as such terms are defined in the Agreement), nor shall the Released Claims include any claims to enforce any rights Executive may have (i) under the Merger Agreement to receive payments thereunder as a shareholder of the Company or a holder of options to purchase stock of the Company held under stock option plans maintained by the Company and (ii) with respect to vested rights of Executive under any welfare, insurance, pension, supplemental pension, thrift, employee stock ownership, or stock option plans sponsored or made available by the Company including, without limitation, the Company 1997 Stock Option and Incentive Plan, as amended, Company Non-Qualified Deferred Compensation Plan and Company Excess Benefit Plan (all such claims referenced in clause (i) and (ii) above, collectively, the “Protected Claims”).

Section 2. Waiver

Notwithstanding the generality of Section 1 above, the Released Claims include, without limitation: (i) any and all claims relating to payments or benefits pursuant to the Prior Agreements; (ii) any and all released claims under Title VII of the Civil Rights Act of 1964, the Age Discrimination in Employment Act of 1967, the Civil Rights Act of 1971, the Civil Rights Act of 1991, the Fair Labor Standards Act, Employee Retirement Income Security Act of 1974, the Americans with Disabilities Act, the Family and Medical Leave Act of 1993, the Fair Employment and Housing Act, and any and all other

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federal, state or local laws, statutes, rules and regulations pertaining to employment or otherwise; and (iii) any claims for wrongful discharge, breach of contract, fraud, misrepresentation or any compensation claims, or any other claims under any statute, rule or regulation or under the common law, including compensatory damages, punitive damages, attorney’s fees, costs, expenses and all claims for any other type of damage or relief.

Section 3. Executive’s Representations and Warranties

Executive represents that he has read carefully and fully understands the terms of this General Release, and that Executive has been advised to consult with an attorney and has availed himself of the opportunity to consult with an attorney prior to signing this General Release. Executive acknowledges and agrees that he is executing this General Release willingly, voluntarily and knowingly, of his own free will, in exchange for the payments provided in the Agreement, and that he has not relied on any representations, promises or agreements of any kind made to him in connection with his decision to accept the terms of the Agreement or the General Release, other than those set forth in the Agreement. Executive further acknowledges, understands, and agrees that the provisions of the Agreement are in lieu of any and all payments and benefits to which Executive may otherwise be entitled to receive pursuant to the Prior Agreements. Executive acknowledges that he has been advised that he is entitled to take at least twenty-one (21) days to consider whether he wants to sign this General Release and that the Age Discrimination in Employment Act gives him the right to revoke this General Release within seven (7) days (the “Seven-Day Period”) after it is signed, and Executive understands that he will not receive any payments under the Agreement until such Seven-Day Period has passed and then, only if he has not revoked this General Release. To the extent Executive has executed this General Release within less than twenty-one (21) days after its delivery to him, Executive hereby acknowledges that his decision to execute this General Release prior to the expiration of such twenty-one (21) day period was entirely voluntary, and taken after consultation with and upon the advice of his attorney.

Executive fully understands that this General Release is a legally binding document and that by signing this General Release Executive is prevented from filing, commencing or maintaining any action against any of the Company Releasees, other than to enforce his rights under the Agreement, the Indemnification Agreement or Section 5.10 of the Merger Agreement, nor shall the Released Claims include any Protected Claims.

This General Release is final and binding and may not be changed or modified.

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