EXHIBIT 4.1(c)


                       Amendment No. 3 to Credit Agreement



<PAGE>

                             AMENDMENT NO. 3 TO THE
                                CREDIT AGREEMENT


                                                      Dated as of August 8, 1997

         AMENDMENT NO. 3 TO THE CREDIT AGREEMENT, among MEDIQ/PRN LIFE SUPPORT
SERVICES, INC., a Delaware corporation (the "Borrower"), MEDIQ INCORPORATED, a
Delaware corporation ("MEDIQ"), PRN HOLDINGS, INC., a Delaware corporation
(together with MEDIQ, the "Parent Guarantors"), the banks, financial
institutions and other institutional lenders parties to the Credit Agreement
referred to below (collectively, the "Lenders") and Banque Nationale de Paris as
administrative agent (the "Administrative Agent") for the Lenders and
NationsBank N.A., as documentation agent (the "Documentation Agent").

         PRELIMINARY STATEMENTS:

         (1) The Borrower, the Parent Guarantors, the Lenders, the
Administrative Agent and the Documentation Agent have entered into a Credit
Agreement dated as of October 1, 1996, as amended by Amendment No. 1 dated as of
January 24, 1997 and as further amended by Amendment No. 2 and Waiver dated as
of April 1, 1997 (as so amended, the "Credit Agreement"). Capitalized terms not
otherwise defined in this Amendment have the same meanings as specified in the
Credit Agreement.

         (2) The Borrower has requested that the Required Lenders amend
certain provisions of the Credit Agreement to increase the amount of Capital
Expenditures permitted during Fiscal Year 1997.

         (3) The Required Lenders are, on the terms and conditions stated below,
willing to grant the request of the Borrower and the Borrower and such Lenders
have agreed to amend the Credit Agreement as hereinafter set forth.



<PAGE>


         SECTION 1. Amendments to the Credit Agreement. Section 5.04(f) of the
Credit Agreement is, effective as of the date hereof and subject to the
satisfaction of the conditions precedent set forth in Section 2 hereof, hereby
amended by deleting the phrase "in any Fiscal Year to exceed $14,000,000"
contained therein and substituting for such phrase the phrase "in Fiscal Year
1997 to exceed $17,000,000 and in any Fiscal Year thereafter to exceed
$14,000,000".

         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 and the Required Lenders, or, as to any of the Lenders, advice
satisfactory to the Administrative Agent that such Lender has executed this
Amendment. The effectiveness of this Amendment is conditioned upon the accuracy
of the factual matters described herein. 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 Borrower is a corporation duly organized, validly existing and
in good standing under the laws of the jurisdiction indicated in the recital of
the parties to this Amendment.

         (b) The execution, delivery and performance by each Loan Party of this
Amendment and the Loan Documents, as amended hereby, to which it is or is to be
a party, and the consummation of the transactions contemplated hereby, are
within such Loan Party's corporate powers, have been duly authorized by all
necessary corporate action and do not (i) contravene each such Loan Party's
charter or by-laws, (ii) violate any law (including, without limitation, the
Securities Exchange Act of 1934, as amended, and the Racketeer Influenced and
Corrupt Organizations Chapter of the Organized Crime Control Act of 1970), rule
or regulation (including, without limitation, Regulation X of the Board of
Governors of the Federal Reserve System), or any order, writ, judgment,
injunction, decree, determination or award, binding on or affecting any Loan
Party or any of its Subsidiaries or any of their properties, (iii) conflict with
or result in the breach of, or constitute a default under, any contract, loan
agreement, indenture, mortgage, deed of trust, lease or other instrument binding
on or affecting any Loan Party, any of their Subsidiaries or any of their
properties or (iv) except for the Liens created under the Collateral Documents,
as amended hereby, or any amendments or supplements thereto contemplated hereby,
result in or require the creation or imposition of any Lien upon or with respect
to any of the properties of any Loan Party or any of its Subsidiaries.

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<PAGE>


         (c) No authorization or approval or other action by, and no notice to
or filing with, any governmental authority or regulatory body or any other third
party is required for the due execution, delivery, recordation, filing or
performance by any Loan Party of this Amendment, any of the Collateral Documents
or any amendments or supplements thereto contemplated hereby to which each such
Loan Party is or is to be a party, or any of the Loan Documents, as amended
hereby, to which it is or is to be a party.

         (d) This Amendment and each of the Collateral Documents and amendments
and supplements thereto contemplated hereby to which each Loan Party is a party
have been duly executed and delivered by each such Loan Party. This Amendment
and each of the other Loan Documents, as amended hereby, to which each Loan
Party is a party are, and each of the other Collateral Documents and amendments
and supplements thereto contemplated hereby to which each such Loan Party is or
is to be a party, when delivered hereunder, will be, legal, valid and binding
obligations of each such Loan Party, enforceable against each such Loan Party in
accordance with their respective terms.

         (e) There is no action, suit, investigation, litigation or proceeding
affecting any Loan Party or any of their Subsidiaries (including, without
limitation, any Environmental Action) pending or threatened before any court,
governmental agency or arbitrator that (i) would be reasonably likely to have a
Material Adverse Effect or (ii) purports to affect the legality, validity or
enforceability of this Amendment, the Collateral Documents, any amendments or
supplements thereto contemplated hereby or any of the other Loan Documents, as
amended hereby, or the consummation of any of the transactions contemplated
hereby.

         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. Without limiting the generality of the foregoing, the Collateral
Documents and all of the Collateral described therein do and shall continue to
secure the payment of all Obligations of the Loan Parties under the Loan
Documents, in each case as amended by this Amendment.

         (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 Agent under any of the Loan Documents, nor
constitute a waiver of any provision of any of the Loan Documents.

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<PAGE>

         SECTION 5. Costs, Expenses. The Borrower agrees to pay on demand all
costs and expenses of the Agent in connection with the preparation, execution,
delivery and administration, modification and amendment of this Amendment, and
the other instruments and documents to be delivered hereunder (including,
without limitation, the reasonable fees and expenses of counsel for the 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.

         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.

                                       MEDIQ/PRN LIFE SUPPORT
                                         SERVICES, INC.

                                       By /s/ Thomas E. Carroll
                                          --------------------------------------
                                          Title: President


                                       MEDIQ INCORPORATED

                                       By /s/ Thomas E. Carroll
                                          --------------------------------------
                                          Title: President


                                       PRN HOLDINGS, INC.

                                       By /s/ Thomas E. Carroll
                                          --------------------------------------
                                          Title: President

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<PAGE>



                                       BANQUE NATIONALE DE PARIS,
                                          as Administrative Agent and as Lender

                                       By /s/ Alan Mustacchi
                                          --------------------------------------
                                          Title: Vice President

                                       By /s/ Steve Kovacs
                                          --------------------------------------
                                          Title: Assistant Vice President



                                       NATIONSBANK, N.A., as
                                         Documentation Agent and as Lender

                                       By /s/ Ashley M. Crabtree
                                          --------------------------------------
                                          Title: Senior Vice President


                                       AMARA-1 FINANCE LTD.

                                       By /s/
                                          --------------------------------------
                                          Title: Director


                                       AMARA-2 FINANCE LTD.

                                       By /s/
                                          --------------------------------------
                                          Title: Director

                                       BANKBOSTON, N.A.

                                       By /s/ Kimberly F. Harris
                                          --------------------------------------
                                          Title: Vice President


                                       CAISSE NATIONALE DE CREDIT AGRICOLE

                                       By /s/ Craig Welsh
                                          --------------------------------------
                                          Title: First Vice President



                                       5
<PAGE>

                                       CAPTIVA FINANCE LTD.

                                       By /s/ John H. Cullinane
                                          --------------------------------------
                                          Title: Director


                                       CERES FINANCE LTD.

                                       By /s/ John H. Cullinane
                                          --------------------------------------
                                          Title: Director


                                       CREDITANSTALT CORPORATE FINANCE, INC.

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

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


                                       FIRST SOURCE FINANCIAL, LLP
                                       By: First Source Financial, Inc.
                                       as Agent/Manager

                                       By /s/
                                          --------------------------------------
                                          Title: Vice President


                                       METROPOLITAN LIFE INSURANCE COMPANY

                                       By /s/ James R. Dingler
                                          --------------------------------------
                                          Title: Assistant Vice President


                                       6
<PAGE>



                                       LASALLE NATIONAL BANK

                                       By /s/ F. Ward Nixon
                                          --------------------------------------
                                          Title: Senior Vice President


                                       MASSACHUSETTS MUTUAL LIFE INSURANCE 
                                         COMPANY

                                       By /s/ John B. Wheeler
                                          --------------------------------------
                                          Title: Managing Director


                                       MELLON BANK, N.A.

                                       By /s/ Mark Avallone
                                          --------------------------------------
                                          Title: Vice President


                                       MERRILL LYNCH SENIOR FLOATING RATE FUND,
                                          INC.

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


                                       PILGRIM AMERICA PRIME RATE TRUST

                                       By /s/ Michael J. Bacevich
                                          --------------------------------------
                                          Title: Vice President


                                       SUMMIT BANK

                                       By /s/ Gail L. Powers
                                          --------------------------------------
                                          Title: Vice President


                                       USTRUST

                                       By /s/ Thomas Macina
                                          --------------------------------------
                                          Title: Vice President


                                        7
<PAGE>


                                       VAN KAMPEN AMERICAN CAPITAL PRIME RATE
                                          INCOME TRUST

                                       By /s/ Jeffrey W. Maillet
                                         ---------------------------------------
                                         Title: Senior Vice President & Director


                                       RESTRUCTURED OBLIGATIONS BACKED BY
                                         SENIOR ASSETS B.V.

                                       By its Managing Director, ABN
                                       TRUSTCOMPANY (NEDERLAND) B.V.


                                       By /s/ Christopher E. Jensen
                                          --------------------------------------
                                          Title: Managing Director

                           By /s/ Chancellor LGT Senior Secured Management, Inc.
                              --------------------------------------------------
                              Title:


                                       MERRILL LYNCH PRIME RATE PORTFOLIO

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


                                       SENIOR DEBT PORTFOLIO

                                       By Boston Management and Research, as 
                                         Investment Advisor

                                       By /s/ Payson F. Swaffield
                                          --------------------------------------
                                          Title: Vice President




                                       8
<PAGE>


                                       MERRILL LYNCH PRIME RATE PORTFOLIO
                                       By Merrill Lynch Asset Management, L.P.
                                       as Investment Advisor

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


 

                                      9


<PAGE>

                                     CONSENT

                                                      Dated as of August 8, 1997


         Reference is made to Amendment No. 3 dated as of August 8, 1997 (the
"Amendment"), to the Credit Agreement dated as of October 1, 1996, as amended by
Amendment No. 1 dated as of January 24, 1997 and Amendment No. 2 and Waiver
dated as of April 1, 1997 (as so amended, the "Credit Agreement"; unless
otherwise defined herein, capitalized terms being used herein as therein
defined) among MEDIQ/PRN Life Support Services, Inc., a Delaware corporation, as
Borrower, PRN Holdings, Inc. a Delaware corporation and MEDIQ Incorporated, as
Parent Guarantors, Banque Nationale de Paris, as Administrative Agent, and
certain other Lender Parties party thereto.

         Each of the undersigned, as a Loan Party party to certain of the Loan
Documents, hereby consents to the Amendment and hereby confirms and agrees that
(a) notwithstanding the effectiveness of such Amendment, each Loan Document to
which it is a party is, and shall continue to be, in full force and effect and
is hereby ratified and confirmed in all respects, except that, on and after the
effectiveness of such Amendment, each reference in such Loan Document to the
"Credit Agreement", "thereunder", "thereof" or words of like import shall mean
and be a reference to the Credit Agreement, as amended by such Amendment, and
(b) the Collateral Documents to which such Loan Party is a party and all of the
Collateral described therein do, and shall continue to, secure the payment of
all of the Secured Obligations (in each case, as defined therein).


                                      MEDIQ INVESTMENT SERVICES, INC.

                                      By  /s/ Thomas E. Carroll
                                          --------------------------------------
                                          Name: Thomas E. Carroll
                                          Title: President


                                      MEDIQ MANAGEMENT SERVICES, INC.

                                      By  /s/ Michael F. Sandler
                                          --------------------------------------
                                          Name: Michael F. Sandler
                                          Title: Vice President & CFO


                                       10
<PAGE>



                                      MEDIQ SURGICAL EQUIPMENT SERVICES, INC.

                                      By  /s/ Thomas E. Carroll
                                          --------------------------------------
                                          Name: Thomas E. Carroll
                                          Title: President


                                      VALUE-MED PRODUCTS, INC.

                                      By  /s/ Thomas E. Carroll
                                          --------------------------------------
                                          Name: Thomas E. Carroll
                                          Title: President


                                      MEDIQ MOBILE X-RAY SERVICES, INC.

                                      By  /s/ Michael F. Sandler
                                          --------------------------------------
                                          Name: Michael F. Sandler
                                          Title: Vice President & CFO


                                      THERA-KINETICS ACQUISITION CORPORATION

                                      By  /s/ Michael F. Sandler
                                          --------------------------------------
                                          Name: Michael F. Sandler
                                          Title: Vice President & CFO


                                      MDTC HADDON, INC.

                                      By  /s/ Michael F. Sandler
                                          --------------------------------------
                                          Name: Michael F. Sandler
                                          Title: Vice President & CFO


                                      MEDIQ DIAGNOSTIC CENTERS, INC.

                                      By  /s/ Michael F. Sandler
                                          --------------------------------------
                                          Name: Michael F. Sandler
                                          Title: Vice President & CFO



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<PAGE>


                                      MEDIQ DIAGNOSTICS CENTERS-I INC.

                                      By  /s/ Michael F. Sandler
                                          --------------------------------------
                                          Name: Michael F. Sandler
                                          Title: Vice President & CFO


                                      MEDIQ IMAGING SERVICES, INC.

                                      By  /s/ Michael F. Sandler
                                          --------------------------------------
                                          Name: Michael F. Sandler
                                          Title: Vice President & CFO


                                      AMERICAN CARDIOVASCULAR IMAGING LABS, INC.

                                      By  /s/ Michael F. Sandler
                                          --------------------------------------
                                          Name: Michael F. Sandler
                                          Title: Vice President & CFO


                                      ALPHA HEALTH CONSULTANTS, INC.

                                      By  /s/ Michael F. Sandler
                                          --------------------------------------
                                          Name: Michael F. Sandler
                                          Title: Vice President & CFO


                                      P.I. CORPORATION

                                      By  /s/ Michael F. Sandler
                                          --------------------------------------
                                          Name: Michael F. Sandler
                                          Title: Vice President & CFO


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<PAGE>


                                      MEDIQ SERVICES, INC.

                                      By  /s/ Michael F. Sandler
                                          --------------------------------------
                                          Name: Michael F. Sandler
                                          Title: Vice President & CFO



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