Document:

<PAGE>   1

                                                                   EXHIBIT 4.3.4

                                     FORM OF
                                  AMENDMENT TO
                             STOCK OPTION AGREEMENT
                       J.B. HUNT TRANSPORT SERVICES, INC.

     This Amendment is made this ____ day of ______________, 20 ___, (the
"Amendment") by and between J.B. Hunt Transport Services, Inc. ("the Company")
and ________________________________ (the "Optionee") and amends that certain
Stock Option Agreement between the Company and the Optionee dated
_______________________, (the "Agreement").

     For good and valuable consideration, the receipt and sufficiency of which
are hereby acknowledged, Optionee and the Company amend the Agreement as follows
(check those which apply):

[ ] The remaining unexercised portions of this Option shall be exercisable as
    follows:

[ ] This Option shall terminate as follows:

All other terms and conditions of the Agreement continue in full force and
effect.

                                         J.B. HUNT TRANSPORT SERVICES, INC.

                                         By:
                                            --------------------------------

                                         -----------------------------, Optionee<PAGE>   1
                                                                    EXHIBIT 10.1

                               AMENDMENT NO. 2 TO
                              THE CREDIT AGREEMENT

                                                       Dated as of June 22, 2001

                  AMENDMENT NO. 2 TO THE CREDIT AGREEMENT dated as of October 2,
2000 among AdvancePCS, f/k/a Advance Paradigm, Inc., a Delaware corporation, as
Borrower, the Subsidiary Guarantors party thereto, the Lenders party thereto,
Bank One, N.A., ("BANK ONE") as Documentation Agent, Bank of America, N.A.,
("BANK OF AMERICA") as Collateral Agent and as Administrative Agent for the
Lender Parties, Merrill Lynch, Pierce, Fenner & Smith Incorporated, as
Book-Runner, Lead Arranger and Syndication Agent, and Banc of America Securities
LLC as Joint Book-Runner and Joint Lead Arranger for the Lenders, as amended by
the Amendment No. 1 to the Credit Agreement dated as of November 3, 2000 (as so
amended and as otherwise amended, restated and modified from time to time, the
"CREDIT AGREEMENT"). Capitalized terms not otherwise defined in this Amendment
No. 2 (the "AMENDMENT") have the same meanings as specified in the Credit
Agreement.

                  PRELIMINARY STATEMENTS:

                  WHEREAS, the Borrower, the Subsidiary Guarantors, the Lenders
and the Agents have entered into the Credit Agreement and the Lenders have made
Advances to the Borrower thereunder;

                  WHEREAS, the Borrower intends to enter into a joint venture
with Priority Healthcare Corp., and in connection therewith to form
AdvancePrioritySpecialtyRx, LLC. The Borrower will make capital contributions in
an aggregate amount of up to $10 million to AdvancePrioritySpecialtyRx, LLC, and
will become the owner of 51% of the equity interests of
AdvancePrioritySpecialtyRx, LLC.

                  NOW, THEREFORE, in consideration of the mutual promises and
obligations contained herein and other good and valuable consideration, the
receipt and sufficiency of which are hereby acknowledged, the Borrower, the
Subsidiary Guarantors and the Required Lenders have agreed to amend the Credit
Agreement as hereinafter set forth.

                  SECTION 1. Amendment. The Credit Agreement is, effective as of
the date first above written and subject to the satisfaction of the conditions
precedent set forth in Section 2 hereof, hereby amended as follows:

                  (a) The definition of "Subsidiary" in Section 1.01 of the
Credit Agreement is amended to insert after the words "or by one or more of such
Person's other Subsidiaries" and before the period immediately following, the
phrase, "; provided, however, that AdvancePrioritySpecialtyRx, LLC shall not be
deemed to be a Subsidiary of any Loan Party".

<PAGE>   2

                  (b) The Credit Agreement is amended to add Section 4.01(aa)
thereto, which shall read as follows:

         "(aa) the capital contributions to be made by the Borrower in
AdvancePrioritySpecialtyRx, LLC are Investments made under Section 5.02(f)(xvi)
of the Credit Agreement."

                  (c) Section 5.01(j)(iv) of the Credit Agreement is amended to
insert after the words "(whether considered in a proceeding in equity or at
law))," the phrase, "except that following the formation of
AdvancePrioritySpecialtyRx, LLC, the Borrower will pledge all of the equity
interests in AdvancePrioritySpecialtyRx, LLC that it owns in favor of the
Collateral Agent within five business days of such formation, pursuant to the
terms of the Security Agreement, and on terms and conditions satisfactory to the
Administrative Agent,".

                  (d) Section 5.02(e)(viii) of the Credit Agreement is deleted
in its entirety and is replaced with the following:

         "the sale, lease, transfer or other disposition by any Loan Party of
         any or all of its assets (upon voluntary liquidation or otherwise) to
         any other Loan Party;"

                  (e) Section 5.02(e)(iv) is deleted in its entirety and is
replaced with the following:

         "[Intentionally left blank.]"

                  (f) Schedule I to the Credit Agreement is amended by
increasing the Letter of Credit Commitment of Bank of America under the Credit
Agreement from $20,000,000 to $50,000,000. In connection therewith, Bank of
America has issued a $25,000,000 standby letter of credit for the account of the
Borrower and in favor of Bergen Brunswig Drug Company which shall be deemed to
be a Letter of Credit that has been issued under the Credit Agreement.

                  SECTION 2. Conditions of Effectiveness. This Amendment shall
become effective as of the date first above written when, and only when, the
Administrative Agent shall have received counterparts of this Amendment executed
by the Borrower, the Subsidiary Guarantors and the Required Lenders or, as to
any of the Required Lenders, advice satisfactory to the Administrative Agent
that such Required Lender has executed this amendment. This amendment is subject
to the provisions of Section 9.01 of the Credit Agreement.

                  SECTION 3. Representations and Warranties of the Borrower. The
Borrower represents and warrants as follows:

                  (a) the representations and warranties contained in each Loan
Document are correct in all material respects on and as of the date hereof,
before and after giving effect to this Amendment, as though made on and as of
the date hereof, other than any such representations or warranties that by their
terms, refer to a specific date, in which case, as of such specific date; and

                  (b) no Default has occurred and is continuing under the Credit
Agreement, as amended hereby, or would result from this Amendment.

<PAGE>   3

                  SECTION 4. Reference to and Effect on the Loan Documents. (a)
On and after the effectiveness of this Amendment, each reference in the Credit
Agreement to "this Agreement", "hereunder", "hereof" or words of like import
referring to the Credit Agreement, and each reference in the Notes and each of
the other Loan Documents to "the Credit Agreement", "thereunder", "thereof" or
words of like import referring to the Credit Agreement, shall mean and be a
reference to the Credit Agreement as amended by this Amendment.

                  (b) The Credit Agreement, the Notes and each of the other Loan
Documents, as specifically amended by this Amendment, are and shall continue to
be in full force and effect and are hereby in all respects ratified and
confirmed.

                  (c) The execution, delivery and effectiveness of this
Amendment shall not, except as expressly provided herein, operate as a waiver of
any right, power or remedy of any Lender or the Administrative Agent under any
of the Loan Documents, nor constitute a waiver of any provision of any of the
Loan Documents.

                  SECTION 5. Costs, Expenses; Taxes. The Borrower agrees to pay
on demand all reasonable costs and expenses of the Administrative Agent in
connection with the preparation, execution, delivery and administration of this
Amendment (including, without limitation, the reasonable fees and expenses of
counsel for the Administrative Agent) in accordance with the terms of Section
9.04 of the Credit Agreement.

                  SECTION 6. Execution in Counterparts. This Amendment may be
executed in any number of counterparts and by different parties hereto in
separate counterparts, each of which when so executed shall be deemed to be an
original and all of which taken together shall constitute but one and the same
agreement. Delivery of an executed counterpart of a signature page to this
Amendment by telecopier shall be effective as delivery of a manually executed
counterpart of this Amendment.

                  SECTION 7. Governing Law. This Amendment shall be governed by,
and construed in accordance with, the laws of the State of New York.

              [The rest of this page is intentionally left blank.]
<PAGE>   4

                  IN WITNESS WHEREOF, the parties hereto have caused this
Amendment to be executed by their respective officers thereunto duly authorized,
as of the date first above written.

                            ADVANCEPCS

                            By:
                                ----------------------------------------
                            Name: Laura I. Johansen
                            Title: Sr. Vice President, Corporate Affairs
                            and Secretary

                      SUBSIDIARY GUARANTORS

                            ADVANCEPCS, L.P.
                            By ADVANCEPCS, its General Partner

                            By:
                                ----------------------------------------
                            Name: Laura I. Johansen
                            Title: Sr. Vice President, Corporate Affairs
                            and Secretary

                            ADVANCEPCS RESEARCH, L.L.C.

                            By:
                                ----------------------------------------
                            Name: Laura I. Johansen
                            Title: Vice President and Secretary

                            ADVANCERX.COM, L.P.
                            By ADVANCEPCS, its General Partner

                            By:
                                ----------------------------------------
                            Name: Laura I. Johansen
                            Title: Sr. Vice President, Corporate Affairs
                            and Secretary

                            ADVP CONSOLIDATION, L.L.C.

                            By:
                                ----------------------------------------
                            Name: Susan S. DeMars
                            Title: Vice President and Secretary

<PAGE>   5

                            ADVP MANAGEMENT, L.P.,
                            By ADVANCEPCS, its General Partner

                            By:
                                ----------------------------------------
                            Name: Laura I. Johansen
                            Title: Sr. Vice President, Corporate Affairs
                            and Secretary

                            AMBULATORY CARE REVIEW SERVICES, INC.

                            By:
                                ----------------------------------------
                            Name: Laura I. Johansen
                            Title: Vice President

                            BAUMEL-EISNER NEUROMEDICAL INSTITUTE, INC.

                            By:
                                ----------------------------------------
                            Name: Laura I. Johansen
                            Title: Vice President

                            FFI RX MANAGED CARE, INC.

                            By:
                                ----------------------------------------
                            Name: Laura I. Johansen
                            Title: Vice President

                            FIRST FLORIDA INTERNATIONAL HOLDINGS, INC.

                            By:
                                ----------------------------------------
                            Name: Laura I. Johansen
                            Title: Vice President

<PAGE>   6

                            FOUNDATION HEALTH PHARMACEUTICAL SERVICES
                            INC.

                            By:
                                ----------------------------------------
                            Name: Laura I. Johansen
                            Title: Vice President

                            HMN HEALTH SERVICES, INC.

                            By:
                                ----------------------------------------
                            Name: Laura I. Johansen
                            Title: Vice President

                            PCS HEALTH SYSTEMS, INC.

                            By:
                                ----------------------------------------
                            Name: Laura I. Johansen
                            Title: Vice President

                            PCS HOLDING CORPORATION

                            By:
                                ----------------------------------------
                            Name: Laura I. Johansen
                            Title: Vice President

                            PCS MAIL SERVICES, INC.

                            By:
                                ----------------------------------------
                            Name: Laura I. Johansen
                            Title: Vice President

<PAGE>   7

                            PCS MAIL SERVICES OF BIRMINGHAM, INC.

                            By:
                                ----------------------------------------
                            Name: Laura I. Johansen
                            Title: Vice President

                            PCS MAIL SERVICES OF FT. WORTH, INC.

                            By:
                                ----------------------------------------
                            Name: Laura I. Johansen
                            Title: Vice President

                            PCS MAIL SERVICES OF SCOTTSDALE, INC.

                            By:
                                ----------------------------------------
                            Name: Laura I. Johansen
                            Title: Vice President

                            PCS SERVICES, INC.

                            By:
                                ----------------------------------------
                            Name: Laura I. Johansen
                            Title: Vice President

<PAGE>   8

THE AGENTS

BANK OF AMERICA, N. A.,
as Administrative Agent, Collateral Agent,
Initial Lender and Initial Issuing Bank and Lender Party

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

BANK ONE, N.A., as Documentation Agent and Lender Party

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

MERRILL LYNCH, PIERCE, FENNER & SMITH INCORPORATED,
as Syndication Agent and Lender Party

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

<PAGE>   9

LENDERS

MERRILL LYNCH CAPITAL CORPORATION

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

BANK ONE, N.A.

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

CREDIT SUISSE FIRST BOSTON

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

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

GENERAL ELECTRIC CAPITAL CORPORATION

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

FIRST UNION NATIONAL BANK

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

BANK OF CHINA, NEW YORK BRANCH

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

<PAGE>   10

RAYMOND JAMES BANK, FSB

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

CIBC INC.

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

THE BANK OF NOVA SCOTIA

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

ERSTE BANK DER OESTERREICHISCHEN SPARKASSEN AG - NEW YORK

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

ABBEY NATIONAL TREASURY SERVICES PLC, LONDON

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

NORTHWOODS CAPITAL II, LIMITED
By: Angelo, Gordon & Co., L.P., as Collateral Manager

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

CANADIAN IMPERIAL BANK OF COMMERCE

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

<PAGE>   11

ARES LEVERAGED INVESTMENT FUND, L.P.

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

ARES LEVERAGED INVESTMENT FUND II, L.P

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

PROMETHEUS INVESTMENT FUNDING NO. 1 LTD.
By: CPF Asset Advisory L.P., as Investment Manager

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

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

CARLYLE HIGH YIELD FUND, L.P

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

CARLYLE HIGH YIELD PARTNER II, LTD.

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

<PAGE>   12

BAVARIA TRR CORPORATION

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

CARAVELLE INVESTMENT FUND, L.L.C.

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

SIERRA CLO I, LTD.

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

CITADEL HILL 2000 LTD.

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

FIVE FINANCE CORPORATION
Citibank, N.A. as Additional Investment Manager for and
on behalf of Five Finance Corporation

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

TYLER TRADING, INC.

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

FLEET NATIONAL BANK FOR THE ACCOUNT OF FLAGSHIP CLO

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

<PAGE>   13

FOOTHILL INCOME TRUST, L.P.
By FIT GP, LLC, its General Partner

By
    ----------------------------------------------------
Title: Managing Member

FRANKLIN CLO I, LIMITED

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

FRANKLIN FLOATING RATE MASTER SERIES

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

FRANKLIN FLOATING RATE TRUST

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

HELLER FINANCIAL, INC.

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

KATONAH I, LTD.

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

NOMURA BOND & LOAN FUND

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

<PAGE>   14

NUVEEN FLOATING RATE FUND
By: Nuveen Senior Loan Asset Management Inc.

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

NUVEEN SENIOR INCOME FUND
By: Nuveen Senior Loan Asset Management Inc.

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

ML CLO XII PILGRIM AMERICA (CAYMAN) LTD.
By: Pilgrim Investments, Inc., as its investment manager

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

ML CLO XV PILGRIM AMERICA (CAYMAN) LTD.
By: Pilgrim Investments, Inc., as its investment manager

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

ML CLO XX PILGRIM AMERICA (CAYMAN) LTD.
By: Pilgrim Investments, Inc., as its investment manager

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

PILGRIM PRIME RATE TRUST
By: Pilgrim Investments, Inc., as its investment manager

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

<PAGE>   15

PILGRIM CLO 1999-1 LTD.
By:  Pilgrim Investments, Inc., as its investment manager

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

SEQUILS-PILGRIM I, LTD.
By: Pilgrim Investments, Inc., as its investment manager

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

OPPENHEIMER SENIOR FLOATING RATE FUND

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

HARBOURVIEW CDO II, LTD

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

KZH SHOSHONE LLC

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

APEX (IDM) CDO I. LTD.

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

ELC (CAYMAN) LTD. CDO SERIES 1999-1

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

<PAGE>   16

ELC (CAYMAN) LTD. 2000-1

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

KZH WATERSIDE LLC

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

KZH ING-1 LLC

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

KZH ING-2 LLC

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

KZH ING-3 LLC

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

ARCHIMEDES FUNDING IV, LTD
By: ING Capital Advisors LLC, as Collateral Manager

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

NEMEAN CLO, LTD
By: ING Capital Advisors LLC, as Investment Manager

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

<PAGE>   17

THE ING CAPITAL SENIOR SECURED HIGH INCOME FUND HOLDINGS, LTD.
By: ING Capital Advisors LLC, as Investment Manager

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

SWISS LIFE US RAINBOW LIMITED
By: ING Capital Advisors LLC, as Investment Manager

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

MAPLEWOOD (CAYMAN) LIMITED MASSMUTUAL INVESTMENT ADVISOR

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

MASSACHUSETTS MUTUAL LIFE INSURANCE COMPANY

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

MASSMUTUAL HIGH YIELD PARTNERS II, LLC

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

SIMSBURY CLO, LIMITED

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

SUFFIELD CLO, LIMITED

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

<PAGE>   18

WILBRAHAM CBO, LIMITED

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

STEIN, ROE & FARNHAM, as agent for KEYPORT LIFE INSURANCE COMPANY

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

LIBERTY-STEIN ROE ADVISOR FLOATING RATE ADVANTAGE FUND
By: Stein Roe & Farnham Incorporated, as Advisor

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

SRF 2000 LLC

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

SRF TRADING, INC.

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

STEIN ROE FLOATING RATE LIMITED LIABILITY COMPANY

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

VAN KAMPEN SENIOR INCOME TRUST

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

<PAGE>   19

VAN KAMPEN CLO I, LIMITED

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

VAN KAMPEN CLO II, LIMITED

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

MONY LIFE INSURANCE COMPANY

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

AIMCO CDO SERIES 2000-A

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

ALLSTATE LIFE INSURANCE COMPANY

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

ARES III CLO LTD.
By: ARES CLO Management LLC

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

TRYON CLO LTD. 2000-1

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

<PAGE>   20

MORGAN STANLEY DEAN WITTER PRIME INCOME TRUST

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

CAPTIVA III FINANCE LTD.
as advised by Pacific Investment Management Company LLC

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

WINDSOR LOAN FUNDING, LIMITED
By:  Stanfield Capital Partners LLC, as its Investment Manager

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

STANFIELD/RMF TRANSATLANTIC CDO, LTD.
By:  Stanfield Capital Partners LLC, as its Collateral Manager

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

SENIOR DEBT PORTFOLIO
By: Boston Management and Research, as Investment Advisor

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

EATON VANCE CDO III, LTD.
By: Eaton Vance Management as Investment Advisor

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

<PAGE>   21

EATON VANCE INSTITUTIONAL SENIOR LOAN FUND
By: Eaton Vance Management, as Investment Advisor

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

OXFORD STRATEGIC INCOME FUND
By: Eaton Vance Management, as Investment Advisor

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

EATON VANCE SENIOR INCOME TRUST
By: Eaton Vance Management, as Investment Advisor

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

FIRST DOMINION FUNDING II

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

FIRST DOMINION FUNDING III

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

SANKATY HIGH YIELD PARTNERS II, L.P.

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

BRANT POINT II CBO 2000-1-LTD.

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

<PAGE>   22

GREAT POINT CLO 1999-1 LTD.

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

FLEET NATIONAL BANK AS TRUST ADMINISTRATOR FOR LONG LANE MASTER TRUST IV

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

CENTURION CDO II, LTD.
By American Express Asset Management
Group Inc., as Collateral Manager

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

ELF FUNDING TRUST I
By Highland Capital Management, L.P.,
as Collateral Manager

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

SAWGRASS TRADING LLC

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

SRV - HIGHLAND, INC.

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

<PAGE>   23

SEABOARD CLO 2000 LTD

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

TEXTRON FINANCIAL CORPORATION

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

GRAYSON & CO
By: Boston Management and Research, as Investment Advisor

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

CAPTIVA FINANCE LTD.

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

BLUE SQUARE FUNDING LIMITED SERIES 3

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

CARAVELLE INVESTMENT FUND II, L.L.C.

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

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