<PAGE>   1
                                                                    Exhibit 10.5





                          CONFIDENTIALITY AGREEMENT,

                            DATED AS OF ___, 2001,

                                 BY AND BETWEEN

                          ICN PHARMACEUTICALS, INC.

                                       AND

                                RIBAPHARM INC.
<PAGE>   2
                            CONFIDENTIALITY AGREEMENT

This CONFIDENTIALITY AGREEMENT is made and entered into as of _______, 2001,
by and between ICN Pharmaceuticals, Inc., a Delaware corporation ("ICN"), and
Ribapharm Inc., a Delaware corporation and a wholly owned subsidiary of ICN
("Ribapharm").

                                    RECITALS

         WHEREAS, the Board of Directors of ICN has determined that it would be
in the best interests of ICN and its stockholders to separate certain assets and
businesses from ICN;

         WHEREAS, ICN has caused Ribapharm to be incorporated in order to
effect such separation;

         WHEREAS, ICN has, pursuant to resolutions of its Board of Directors
adopted on August 7, 2000, contributed to Ribapharm, certain assets, including
its nucleoside analog library, subject to certain consents, the Exclusive
License and Supply Agreement between ICN and Schering-Plough Ltd. dated July 28,
1995, as amended, and ICN's corporate headquarters in Costa Mesa, California;

         WHEREAS, Ribapharm has previously filed the IPO Registration Statement
(as herein defined) with the Securities and Exchange Commission but it has not
yet become effective; and

         WHEREAS, ICN and Ribapharm desire to enter into this Agreement
concerning the obligations of the parties with respect to confidential or
proprietary information, intellectual property, and other matters that are set
forth below.

         NOW, THEREFORE, in consideration of the premises and the
representations, warranties, covenants and agreements herein contained, and for
other good and valuable consideration, the receipt and sufficiency of which are
hereby acknowledged, and intending to be legally bound hereby, the parties
hereby agree as follows:

DEFINITIONS:

        For all purposes of this Agreement, and except as otherwise expressly
provided, capitalized terms used herein shall have the following meanings:

        "AFFILIATE" means a Ribapharm Affiliate or an ICN Affiliate, as the case
may be.

        "BUSINESS DAY" means any day other than a Saturday, a Sunday, or a day
on which banking institutions located in the State of California are authorized
or obligated by law or executive order to close.

        "CONFIDENTIAL INFORMATION" means Ribapharm Confidential Information or
ICN Confidential Information, as the case may be.


                                      -2-
<PAGE>   3
        "CONTRIBUTION DATE" means August 7, 2000.

        "CONTROL" means the possession, direct or indirect, of the power to
direct or cause the direction of the management of the policies of a Person,
whether through the ownership of voting securities, by contract or otherwise.

        "CONTROLLED" has the meaning correlative to the definition of "CONTROL."

        "COPYRIGHTS" means all registered and unregistered copyrights and
applications therefor.

        "DISPUTES" has the meaning ascribed thereto in Section 3.1.

        "ICN" has the meaning ascribed in the preamble hereto.

        "ICN AFFILIATE" means a Person that, directly or indirectly through one
or more intermediaries, is Controlled by ICN (other than Ribapharm and any
Subsidiary of Ribapharm).

        "ICN BUSINESSES" means the businesses conducted by ICN and/or any ICN
Affiliate at any time on or before the Contribution Date, but excluding the
Ribapharm Business.

        "ICN CONFIDENTIAL INFORMATION" means confidential or proprietary
information relating to the ICN Businesses, including, but not limited to, any
unpublished Technology, unpublished patent applications, and other confidential
or proprietary technical and business information relating to the ICN
Businesses.

        "IPO REGISTRATION STATEMENT" means the Registration Statement on Form
S-1, Registration No. 333-39350, of Ribapharm, as supplemented and amended from
time to time.

        "PATENTS" means all patents and patent applications (including any
divisions, continuations, continuations-in-part, reexaminations, extensions,
renewals or reissues thereof), design registrations, utility models and similar
rights and applications therefor.

        "PERSON" means an individual, partnership, limited liability company,
joint venture, corporation, trust, unincorporated association, any other entity,
or any government or any department or agency or other unit thereof.

        "RIBAPHARM" has the meaning ascribed in the preamble hereto.

        "RIBAPHARM AFFILIATE" means a Person that, directly or indirectly
through one or more intermediaries, is Controlled by, or is under common Control
with Ribapharm (other than any ICN Affiliate).

        "RIBAPHARM BUSINESS" means the business associated with the assets
contributed to Ribapharm by ICN by resolution of ICN's board of directors,
including, but not limited to, (i)


                                      -3-
<PAGE>   4
all information and research and development relating to all of the chemical
compounds included among the assets contributed to Ribapharm by ICN, (ii) all
business operations whose financial performance is reflected in the financial
statements (including the notes thereto) for the period December 31, 2000, as
set forth in the Registration Statement on Form S-1, Reg. No. 333-39350, as it
may be amended (the "Ribapharm Financial Statements") and (iii) all related
business operations initiated by Ribapharm after the date of the Ribapharm
Financial Statements.

        "RIBAPHARM CONFIDENTIAL INFORMATION" means confidential or proprietary
information relating exclusively to the Ribapharm Business, including, but not
limited to, any unpublished Technology, unpublished patent applications, and
other confidential or proprietary technical and business information relating
exclusively to the Ribapharm Business.

        "SERVICE AGENT" means (i) for ICN, The Corporation Trust Company, with
offices on the date hereof at 1209 Orange Street, Wilmington, County of New
Castle, Delaware 19801; and (ii) for Ribapharm, The Corporation Trust Company,
with offices on the date hereof at 1209 Orange Street, Wilmington, County of New
Castle, Delaware 19801.

        "SUBSIDIARY" means with respect to any specified Person, any corporation
or other legal entity of which such Person or any of its Subsidiaries Controls
or owns, directly or indirectly, more than 50% of the stock or other equity
interest entitled to vote with respect to the election of members to the board
of directors or similar governing body; provided, however, that for the purposes
of this Agreement, neither Ribapharm nor any of the Subsidiaries of Ribapharm
shall be deemed to be Subsidiaries of ICN or of any of the Subsidiaries of ICN.

        "TECHNOLOGY" means all technology and know-how, including without
limitation, technical information, trade secrets and knowledge, design rights
(other than statutory registrations), whether included in or derived from
specifications, manuals, notebooks, reports, documents, blue prints, inventions,
drawings, formulae, procedures, processes, devices, software and source code and
documentation therefor, flow charts, recording media, and other intangible,
tangible and electronic embodiments of information.

1.      CONFIDENTIALITY

        1.1 ICN agrees to keep confidential and not disclose, and shall cause
each ICN Affiliate to keep confidential and not disclose, to any third party and
not to use for any purpose not authorized by Ribapharm, in whole or in part, any
Ribapharm Confidential Information.

        1.2 Ribapharm agrees to keep confidential and not disclose, and to cause
each Ribapharm Affiliate to keep confidential and not disclose, to any third
party and not to use for any purpose not authorized by ICN, in whole or in part,
any ICN Confidential Information.

        1.3 For purposes of this Agreement, ICN Confidential Information and
Ribapharm Confidential Information do not include, and a party and a party's
Affiliates (a party and Affiliates of the party being referred to as the
"receiving party") will have no obligations under this Agreement, with respect
to any information of the other party or any Affiliate of the other party (the
other party and Affiliates of the other


                                      -4-
<PAGE>   5
party being referred to as the "disclosing party") which:

        (i) in the case of ICN, is known to ICN from a source other than the
Ribapharm Business or Ribapharm, as evidenced by competent proof thereof; or

        (ii) in the case of Ribapharm, is known to Ribapharm from a source other
than the ICN Businesses, as evidenced by competent proof thereof; or

        (iii) is or becomes publicly known through no wrongful act of the
receiving party (in which event the receiving party's obligations under this
Agreement in respect thereto shall terminate on the date such information enters
the public domain); or

        (iv) is or was rightfully received by the receiving party from a third
party without violation of any obligations of confidentiality and/or use
restrictions owed by the third party to the disclosing party or any other party;
or

        (v) is independently developed by employees or consultants of the
receiving party without use of or reference to the disclosing party's
proprietary information; or

        (vi) is approved for release by the prior written authorization of
the disclosing party.

        In addition, if the receiving party is requested or required (by oral
questions, interrogatories, request for information or documents, subpoena,
civil investigative demand, similar process or otherwise) to disclose any
Confidential Information of the disclosing party, such receiving party will
provide prompt notice to the disclosing party on such request(s) so that such
disclosing party may seek any appropriate protective order and/or waive
compliance with the provisions of this Agreement. Failing the entry of a
protective order or the receipt of a waiver hereunder, if the receiving party is
in the opinion of its attorneys legally required to disclose any of the
disclosing party's Confidential Information under pain of liability for contempt
or other material censure or material penalty, the receiving party may disclose
such Confidential Information without liability hereunder upon notice to the
disclosing party. Notwithstanding the foregoing, ICN is permitted to disclose
Ribapharm Confidential Information as required in litigation that is pending as
of the Contribution Date, but shall use its reasonable best efforts to obtain
confidential treatment of any such information disclosed.

2.      COOPERATION

        2.1 The parties will do everything that is necessary or appropriate to
conform to the purpose and spirit of this Agreement, including, without
limitation, cooperating with the other party in connection with the maintenance,
enforcement and protection of the Copyrights, Patents and Technology, and
executing any and all documents or instruments, or obtaining any consents, in
order to assign, transfer, perfect, record, maintain, enforce or otherwise carry
out the intent of the terms of this Agreement.


                                      -5-
<PAGE>   6
        2.2 Each party will take appropriate measures to assure the
confidentiality and non-use obligations and other applicable obligations of a
party pursuant to this Agreement are met by its legal representatives, members
of supervisory bodies, management, employees or other agents.

3.      MISCELLANEOUS

        3.1 AUTHORITY. Each of the parties hereto represents and warrants to the
other that (a) it has the corporate power and authority to execute, deliver and
perform this Agreement, (b) the execution, delivery and performance of this
Agreement by it has been duly authorized by all necessary corporate action, (c)
it has duly and validly executed and delivered this Agreement, and (d) this
Agreement is a legal, valid and binding obligation, enforceable against it in
accordance with its terms subject to applicable bankruptcy, insolvency,
reorganization, moratorium or other similar laws affecting creditors' rights
generally and general equity principles. The representations and warranties
contained in this Section 3.2 shall survive the execution and delivery hereof
until the expiration of all applicable statutes of limitations.

        3.2 COMPLETE AGREEMENT. This Agreement constitutes the entire agreement
between the parties hereto with respect to the subject matter hereof and shall
supersede all prior agreements and understandings, whether written or oral,
between the parties with respect to such subject matter.

         3.3 GOVERNING LAW. This Agreement shall be governed by and construed in
accordance with the laws of the State of California (without giving effect to
the conflict of laws principals thereof) as to all matters, including matters of
validity, construction, effect, performance and remedies.

        3.4 NOTICES. All notices and other communications hereunder shall be in
writing and shall be delivered in person, by telecopy, by express or overnight
mail delivered by a nationally recognized air courier (delivery charges
prepaid), or by registered or certified mail (postage prepaid, return receipt
requested) to the respective parties as follows:

         (a) If to ICN, to:

             ICN Pharmaceuticals, Inc.
             3300 Hyland Avenue
             Costa Mesa, CA  92626
             Attention:  David Watt, Esq.

         (b) If to Ribapharm, to:

             Ribapharm Inc.
             3300 Hyland Avenue
             Costa Mesa, CA  92626
             Attention:  Harry Roosje, Esq.


                                      -6-
<PAGE>   7
or to such other address as the party to whom notice is given may have
previously furnished to the others in writing in the manner set forth above. Any
notice or communication delivered in person shall be deemed effective on
delivery or when delivery is refused. Any notice or communication sent by
telecopy or by air courier shall be deemed effective on the first Business Day
at the place at which such notice or communication is received following the day
on which such notice or communication was sent.

         3.6 AMENDMENT AND MODIFICATION. This Agreement may not be amended or
modified in any respect except by a written agreement signed by both of the
parties hereto.

         3.7 BINDING EFFECT; ASSIGNMENT. This Agreement and all of the
provisions hereof shall be binding upon the parties hereto and inure to the
benefit of the parties hereto and their respective successors and permitted
assigns. Except with respect to a merger of either party with another Person,
neither this Agreement nor any of the rights, interests or obligations hereunder
shall be assigned by either party hereto without the prior written consent of
the other party.

         3.8 THIRD PARTY BENEFICIARIES. Nothing in this Agreement, express or
implied, is intended to or shall confer upon any Person any legal or equitable
right, benefit or remedy of any nature whatsoever under or by reason of this
Agreement, and no Person (other than as provided in the previous sentence) shall
be deemed a third party beneficiary under or by reason of this Agreement.

         3.9 COUNTERPARTS. 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 one and the same instrument. The Agreement may be
executed by facsimile signature.

         3.10 WAIVER. The observance of any term of this Agreement may be waived
(either generally or in a particular instance and either retroactively or
prospectively) by the party entitled to enforce such term, but such waiver shall
be effective only if it is in writing signed by the party against which such
waiver is to be asserted. Unless otherwise expressly provided in this Agreement,
no delay or omission on the part of any party in exercising any right or
privilege under this Agreement shall operate as a waiver thereof, nor shall any
waiver on the part of any party of any right or privilege under this Agreement
operate as a waiver of any other right or privilege under this Agreement nor
shall any single or partial exercise of any right or privilege preclude any
other or further exercise thereof or the exercise of any other right or
privilege under this Agreement. No failure by either party to take any action or
assert any right or privilege hereunder shall be deemed to be a waiver of such
right or privilege in the event of the continuation or repetition of the
circumstances giving rise to such right unless expressly waived in writing by
the party against whom the existence of such waiver is asserted.

         3.11 SEVERABILITY. Any provision of this Agreement which is prohibited
or unenforceable in any jurisdiction shall, as to such jurisdiction, be
ineffective to the extent of such prohibition or unenforceability without
invalidating the remaining provisions hereof. Any such


                                      -7-
<PAGE>   8
prohibition or unenforceability in any jurisdiction shall not invalidate or
render unenforceable such provision in any other jurisdiction.

         3.12 REMEDIES. Each of ICN and Ribapharm shall be entitled to enforce
its rights under this Agreement specifically, to recover damages and costs
(including reasonable attorneys' fees) caused by any breach of any provision of
this Agreement and to exercise all other rights existing in its favor. Each of
ICN and Ribapharm acknowledges and agrees that under certain circumstances the
breach by ICN or any of its Affiliates or Ribapharm or any of its Affiliates of
a term or provision of this Agreement will materially and irreparably harm the
other party, that money damages will accordingly not be an adequate remedy for
such breach and that the non-defaulting party, in its sole discretion and in
addition to its rights under this Agreement and any other remedies it may have
at law or in equity, may apply to any court of law or equity of competent
jurisdiction (without posting any bond or deposit) for specific performance
and/or other injunctive relief in order to enforce or prevent any breach of the
provisions of this Agreement.

         3.13 PERFORMANCE. Each of the parties hereto shall use all commercially
reasonable efforts to cause to be performed all actions, agreements and
obligations set forth herein to be performed by any Affiliate of such party.

         3.14 REFERENCES; CONSTRUCTION. The section and other headings and
subheadings contained in this Agreement are solely for the purpose of reference,
are not part of the agreement of the parties hereto, and shall not in any way
affect the meaning or interpretation of this Agreement. All references to days
or months shall be deemed references to calendar days or months. Unless the
context otherwise requires, any reference to a "Section" shall be deemed to
refer to a section of this Agreement. The words "hereof," "herein" and
"hereunder" and words of similar import referring to this Agreement refer to
this Agreement as a whole and not to any particular provision of this Agreement.
Whenever the words "include," or "including" are used in this Agreement, unless
otherwise specifically provided, they shall be deemed to be followed by the
words "without limitation." This Agreement shall be construed without regard to
any presumption or rule requiring construction or interpretation against the
party drafting or causing the document to be drafted.

                               * * * * * * * *


                                      -8-
<PAGE>   9
        IN WITNESS WHEREOF, each of the parties has caused this Agreement to be
executed on its behalf by its officers thereunto duly authorized on the day and
year first above written.



                                         RIBAPHARM INC.


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


                                         ICN PHARMACEUTICALS, INC.


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


                                      -9-