<PAGE>



                                                                Exhibit 10.10(a)

         AGREEMENT, dated as of April 12, 2001, between CLAIMSNET.COM INC., a
Delaware corporation (the "Company") having its principal place of business in
Dallas, Texas, and McKESSON HBOC, INC., a Delaware corporation (the "Customer")
having its principal place of business in Dubuque, Iowa.


                               W I T N E S S E T H


         WHEREAS, as of October 27, 1999, the Company and the Customer entered
into the Claimsnet.com inc. Development and Services Agreement, dated as of such
date (the "Development Agreement"); and

         WHEREAS, simultaneously with the execution thereof, the Company and the
Customer executed and delivered the Securities Purchase Agreement, dated as of
October 27, 1999 (the "Securities Purchase Agreement"), between the Company and
the Customer; and

         WHEREAS, simultaneously with the execution thereof and pursuant to the
terms thereof, the Company executed and delivered to the Customer warrants (the
"Warrants"), representing the right to acquire up to an 819,184 shares of Common
Stock; and

         WHEREAS, simultaneously with the execution thereof, the Company and the
Customer executed and delivered the Registration Rights Agreement, dated as of
October 27, 1999 (the "Registration Rights Agreement") between the Company and
the Customer relating to the registration under the Securities Act of 1933, as
amended (the "Securities Act"), of the resale of the shares of Common Stock
issuable upon the exercise of the Warrants; and

         WHEREAS, the parties hereto and to the Development Agreement desire to
amend and/or supersede the Development Agreement, the Securities Purchase
Agreement, the Warrants, and the Registration Rights Agreement; and

         WHEREAS, the Customer desires to acquire, and the Company desires to
sell to the Customer, shares of common stock, par value $.001 per share (the
"Common Stock"), of the Company as set forth herein; and

         WHEREAS, all capitalized terms used, but not otherwise defined, herein
shall have the respective definitions assigned thereto in the Development
Agreement.

         NOW THEREFORE, in consideration of the mutual covenants contained in
this Amendment and for other good and valuable consideration, the receipt and
sufficiency of which are hereby acknowledged, and intending to be legally bound,
the parties hereby agree as follows:


<PAGE>

                                    SECTION 1

                       Amendments to Development Agreement

         1.1 Limitation on Amendments; Compliance. Except as otherwise set forth
herein, the Development Agreement shall continue in full force and effect. Each
party hereby acknowledges that all obligations of the other party under the
Development Agreement which, in accordance with the terms thereof, was required
to be performed on or prior to the date hereof, has been performed in all
respects.

         1.2 Cessation of Development Activities; Acceptance of Modifications.
At the date hereof, the Company shall discontinue all development activities by
the Company referenced in the Development Agreement, including, without
limitation, those set forth in Milestone Schedule attached to the Development
Agreement as Exhibit B and shall not be obligated under the Development
Agreement to engage in any additional development activities under the
Development Agreement, including Section 2.7 thereof. The Customer hereby agrees
that the Testing Period has ended and that Acceptance of the Modifications by
the Customer has taken place.

         1.3 License. The license set forth in Section 2.6 of the Development
Agreement (the "License") relating to the use of the Modifications shall
continue in full force and effect, provided, however, that that in lieu of the
fees set forth in Sections 4.1, 4.2, and 4.3 of the Development Agreement, the
Customer shall pay to the Company simultaneously with the execution hereof, the
amount of $200,000 by electronic wire transfer in accordance with the
instructions set forth in Schedule 1.3 hereof.

         1.4 Dedicated Server. Customer hereby waives the requirement set forth
in Exhibit A to the Development Agreement that the services described therein
shall be maintained on a dedicated server.

         1.5 Continuing Services; Support and Maintenance. The agreements set
forth in Exhibits C and D to the Development Agreement shall remain in full
force and effect. The manner of the performance of the obligations set forth in
such Exhibits, and the course of dealing between the parties with respect
thereto, to date by the parties hereto shall be deemed sufficient to satisfy
such obligations, notwithstanding such agreements.

         1.6 Termination. Section 8.2 of the Development Agreement is herby
amended to read as follows:

       This agreement may be terminated by (a) either Party for a material
       breach of this Agreement, which is not cured within 30 days after written
       notice of the breach; (b) either Party immediately in the event the other
       Party becomes insolvent in that its liabilities exceed its assets, is
       adjudicated insolvent, files for or is subject to any insolvency or
       bankruptcy proceeding, makes an assignment for the benefit of creditors
       prior to bankruptcy or is subject to receivership, conservatorship, or


<PAGE>

       liquidation; (c) Customer upon thirty (30) days prior written notice. In
       the event Company proposes to (1) sell all or substantially all of its
       assets, or (2) be acquired, merged into another entity or otherwise
       undergo a change of ownership and control such that the holders of the
       Company's voting securities prior to the transaction hold less than fifty
       percent (50%) of the total voting power represented by the voting
       securities of the surviving or successor corporation or entity
       immediately following such transaction, the Company shall promptly
       deliver to Customer a notice of such proposed transaction, which notice
       shall specify that it is a notice pursuant to this Section 8.2 and shall
       identify the purchaser or purchasers of such assets or other party or
       parties to such transaction.


                                    SECTION 2

                 Warrants and the Registration Rights Agreement

         2.1 Termination. Each of the Warrants and the Registration Rights
Agreement are hereby terminated and of no further force or effect.

                                    SECTION 3

                        Additional Business Relationship

         3.1 Additional License. The Company and the Customer shall use
commercially reasonable best efforts to enter into an agreement mutually
agreeable thereto pursuant to which the scope of the License shall be amended to
include UB-92 claims.

         3.2 Other Opportunities. The Company and the Customer hereby agree to
use commercially reasonable best efforts to discuss and pursue agreed upon
opportunities.

                                    SECTION 4

                                   Investment

         4.1 Acquisition of Shares of Common Stock. In accordance with Section
7.1 hereof, (i) the Company shall deliver to the Customer stock certificates,
registered in the name of the Customer or its designees, representing an
aggregate of 1,514,285 shares (the "Shares") of Common Stock, and (ii) the
Customer deliver to the Company, by electronic wire transfer in accordance with
the instructions set forth in Schedule 1.3 hereto, the aggregate purchase price
of $ 2,649,998.75, representing payment in full for the Shares.



<PAGE>

                                    SECTION 5

                  Representations and Warranties of the Company

         5.1 Organization and Qualification. Each of the Company, ANC Holdings,
Inc., a Texas corporation ("ANC"), and HealthExchange.com Inc., a Delaware
corporation ("HealthExchange" and, together with ANC, the "Subsidiaries") has
been duly organized and is validly existing as a corporation in good standing
under the laws of the jurisdiction of its incorporation, with full power and
authority (corporate and otherwise) to own its properties and conduct its
business as described in the SEC Materials (as hereinafter defined) and is duly
qualified or licensed to do business as a foreign corporation and is in good
standing in each other jurisdiction in which the nature of its business or the
character or location of its properties requires such qualification, except
where the failure to so qualify will not materially affect the condition
(financial or otherwise), business, properties, prospects, net worth or results
of operations of the Company and the Subsidiaries, taken as a whole. Except for
the stock of its Subsidiaries, the Company does not control, directly or
indirectly, any corporation, partnership, joint venture, association or other
business organization. For purposes of this Agreement, the term "SEC Materials"
shall mean the Company's Prospectus, dated April 6, 1999, the Annual Report on
Form 10-K for the year ended December 31, 1999, the Quarterly Report on Form
10-Q of the Company for the three months ended March 31, 2000, the Quarterly
Report on Form 10-Q of the Company for the three months ended June 30, 2000, the
Quarterly Report on Form 10-Q of the Company for the three months ended
September 30, 2000, the proxy statement of the Company, dated September 14,
2000, Current Reports on Form 8-K of the Company dated March 23, 2000 (including
amendments thereto), March 24, 2000, July 11, 2000, November 14, 2000, December
18, 2000, January 4, 2001, March 20, 2001, and April 5, 2001, collectively, all
as filed with the United States Securities and Exchange Commission.

         5.2 Capitalization. As of the date hereof, the authorized capital stock
of the Company consists of 40,000,000 shares of Common Stock, par value $.001
per share, of which 8,951,229 shares are outstanding, and 4,000,000 shares of
preferred stock, par value $.001 per share, of which 27,534 shares are
outstanding. Each of such outstanding shares of capital stock of the Company is
validly authorized, validly issued, fully paid, and nonassessable, has not been
issued and is not owned or held in violation of any preemptive or similar right
of stockholders, and is owned, to the best knowledge of the Company, free and
clear of all liens, security interests, pledges, charges, encumbrances,
stockholders' agreements, and voting trusts. Except as set forth in the SEC
Materials, there is no commitment, plan, or arrangement to issue, and no
outstanding option, warrant, or other right calling for the issuance of, any
share of capital stock of the Company or any security or other instrument
convertible into, exercisable for, or exchangeable for capital stock of the
Company. There is outstanding no security or other instrument convertible into
or exchangeable for capital stock of the Company.


<PAGE>

         5.3 Enforceability; Validity. The Shares, when issued and delivered
pursuant hereto against payment therefor will be duly authorized and issued,
fully paid, and nonassessable and free of preemptive rights of any security
holder of the Company.

         5.4 Authorization. This Agreement has been duly and validly authorized,
executed, and delivered by the Company and, assuming due execution by the other
party hereto and thereto, as applicable, constitutes the valid and binding
obligation of the Company enforceable against the Company in accordance with its
terms, except as enforceability may be limited by applicable bankruptcy,
insolvency or other laws affecting the rights of creditors generally and the
discretion of the courts in granting equitable remedies. The Company has full
power and lawful authority to authorize and issue the Shares against payment
therefor on the terms and conditions set forth herein. No consent, approval,
authorization, or order of, or any filing or declaration with, any governmental
authority is required for the consummation of the transactions contemplated by
this Agreement or in connection with the issuance of the Shares by the Company,
except such as may be required under Federal or state securities or blue sky
laws.

         5.5 Conflicts. Except as described in the SEC Materials, neither the
Company nor any Subsidiary is in violation, breach, or default (which includes
any event that has occurred which, with notice or lapse of time or both, would
constitute a default) of or under, and consummation of the transactions herein
contemplated and the fulfillment of the terms of this Agreement will not
conflict with, or result in a breach of, any of the terms or provisions of, or
constitute a default under, or result in the creation or imposition of any lien,
charge or encumbrance upon any of the property or assets of the Company or any
Subsidiary pursuant to the terms of any indenture, mortgage, deed of trust, loan
agreement, or other agreement or instrument to which the Company or any
Subsidiary is a party or by which the Company or any Subsidiary may be bound or
to which any of the property or assets of the Company or any Subsidiary is
subject, nor will such action result in any violation of the provisions of the
articles of incorporation or any order, rule, or regulation applicable to the
Company or any Subsidiary of any court or any regulatory authority or other
governmental body having jurisdiction over the Company or any Subsidiary.

         5.6 Properties. Subject to the qualifications set forth in the SEC
Materials, the Company and each Subsidiary has good and marketable title to all
properties and assets described in the SEC Materials as owned by them, free and
clear of all liens, charges, encumbrances or restrictions, except such as are
not materially significant or important in relation to its business; all of the
material leases and subleases under which the Company or any Subsidiary is the
lessor or sublessor of properties or assets or under which the Company or any
Subsidiary holds properties or assets as lessee or sublessee as described in the
SEC Materials are in full force and effect, and, except as described in the SEC
Materials, neither the Company nor any Subsidiary is in default in any material
respect with respect to any of the terms or provisions of any of such leases or
subleases, and no claim has been asserted by anyone adverse to rights of the
Company or any Subsidiary as lessor, sublessor, lessee or sublessee under any of
the leases or subleases mentioned above, or affecting or questioning the right
of the Company or the subsidiary to continued


<PAGE>

possession of the leased or subleased premises or assets under any such lease or
sublease, except as described or referred to in the SEC Materials; and each of
the Company and each Subsidiary owns or leases all such properties described in
SEC Materials as are necessary to its operations as now conducted and, except as
otherwise stated in the SEC Materials, as proposed to be conducted as set forth
in the SEC Materials.

         5.7 Financial Condition; Financial Matters.

         (a) The consolidated financial statements and the related notes of the
Company, any supplementary financial information, any related schedules and the
pro forma financial statements of the Company set forth in the SEC Materials
present fairly the consolidated financial position and results of operations and
changes in stockholder's equity and cash flows of the Company on a consistent
basis at the respective dates and for the respective periods to which they
apply. The consolidated financial statements and the related notes of Medica
Systems, Inc., any supplementary financial information and any related schedules
set forth in the SEC Materials present fairly the consolidated financial
position and results of operations and changes in stockholders' equity and cash
flows of Medica Systems, Inc. on the basis stated in the SEC Materials at the
respective dates and for the respective periods to which they apply. Said
financial statements and notes, supplementary financial information, related
schedules, and pro forma financial statements have been prepared in accordance
with generally accepted accounting principles applied on a basis which is
consistent during the periods involved. The pro forma financial information
included in the SEC Materials has been prepared in accordance with the
applicable requirements of Regulation S-X and the assumptions used in the
preparation of such pro forma information are, in the opinion of the Company,
reasonable. There has been no material adverse change in the condition
(financial or otherwise), business, properties, prospects, net worth or results
of operations of the Company and the Subsidiaries, taken as a whole, from the
latest information set forth in the SEC Materials, except as properly described
in the SEC Materials, and there is no fact known to the Company or any of its
Subsidiaries which could reasonably be expected to have a material and adverse
effect on the future prospects of the Company and the Subsidiaries (other than
political or economic matter of general applicability or as properly described
in the SEC Materials).

         (b) Subsequent to the respective dates as of which information is given
in the SEC Materials and except as described therein, the Company has not paid
or declared any dividends or other distributions of any kind on any class of its
capital stock nor has it incurred any liabilities or obligations, direct or
contingent, not in the ordinary course of business, or entered into any
transaction not in the ordinary course of business, which is material to the
business of the Company, and there has not been any change in the capital stock
of, or any material incurrence of long-term debt by the Company or any of its
Subsidiaries or any material issuance of options, warrants, or other rights to
purchase the capital stock of the Company or any of its Subsidiaries or any
material adverse change or any material development involving, so far as the
Company or any Subsidiaries can now reasonably foresee, a prospective adverse
change in the condition


<PAGE>

(financial or otherwise), net worth, results of operations, business, key
personnel, or properties of the Company or any Subsidiary which would be
material to the business or condition (financial or otherwise) of the Company
and its Subsidiaries, taken as a whole, none of the Company or any Subsidiary
has become a party to, and neither the business nor the property of the Company
or any Subsidiary has become the subject of, any material litigation or other
legal or administrative proceedings whether or not in the ordinary course of
business.

         (c) The books, records and accounts and systems of internal accounting
controls of the Company currently comply in all material respects with the
requirements of Section 13(b)(2) of the Securities Exchange Act of 1934, as
amended (the "Exchange Act"). The Company maintains a system of internal
accounting controls sufficient to provide reasonable assurance that (1)
transactions are executed in accordance with management's general or specific
authorizations; (2) transactions are recorded as necessary to permit preparation
of financial statements in conformity with generally accepted accounting
principles and to maintain asset accountability; (3) access to assets is
permitted only in accordance with management's general or specific
authorization; and (4) the recorded accountability for assets is compared with
the existing assets at reasonable intervals and appropriate action is taken with
respect to any differences.

         5.8 Litigation. Except as set forth in the SEC Materials, there is not
now pending or threatened, any action, suit, or proceeding to which the Company
or any Subsidiary is a party before or by any court or governmental agency or
body, which might result in any material adverse change in the condition
(financial or otherwise), business, properties, prospects, net worth, or results
of operations of the Company and the Subsidiaries, taken as a whole, nor are
there any actions, suits, or proceedings related to environmental matters or
related to discrimination on the basis of age, sex, religion, or race; and no
labor disputes involving the employees of the Company or any Subsidiary exist or
are threatened which might be expected to materially adversely affect the
condition (financial or otherwise), business, properties, prospects, net worth,
or results of operations of the Company and the Subsidiaries, taken as a whole.

         5.9 Permits. Except as disclosed in the SEC Materials, the Company and
each Subsidiary has sufficient licenses, permits, certificates, and other
governmental authorizations as are required for the conduct of its business or
the ownership of its property as described in the SEC Materials and are in all
material respects complying therewith. Neither the Company nor any Subsidiary
has received any notice of proceedings relating to the revocation or
modification of any such certificate, authorization, or permit nor, to the
knowledge of the Company or any Subsidiary, do any of the activities or business
of the Company or any Subsidiary cause the Company or any Subsidiary to be in
violation of, or cause the Company or any Subsidiary to violate, any law, rule,
regulation, or order of the United States, any state, county, or locality, or of
any agency or body of the United States or of any state, county, or locality,
the violation of which would have a material adverse impact upon the condition
(financial or otherwise), business, properties, prospects, net worth, or results
of operations of the Company and the Subsidiaries, taken as a whole.

         5.10 Questionable Payments. Neither the Company nor any Subsidiary has
directly or indirectly, at any time (i) made any contributions to any candidate
for political


<PAGE>

office, or failed to disclose fully any such contribution in violation of law or
(ii) made any payment to any state, federal, or foreign governmental officer or
official, or other person charged with similar public or quasi-public duties,
other than payments or contributions required or allowed by applicable law. The
Company's internal accounting controls and procedures are sufficient to cause
the Company to comply in all material respects with the Foreign Corrupt
Practices Act of 1977, as amended.

         5.11 Transfer Taxes. At the date of this Agreement, all transfer or
other taxes (including franchise, capital stock, or other tax, other than income
taxes, imposed by any jurisdiction), if any, which are required to be paid in
connection with the issuance and delivery of the Shares to the Customer
hereunder will have been fully paid or provided for by the Company and all laws
imposing such taxes will have been fully complied with in all material respects.

         5.12 Brokers; Finders. The Company has not entered into any agreement
pursuant to which any person is entitled, either directly or indirectly, to
compensation from the Company for services as a finder in connection with the
public offering referred to herein.

         5.13 Employment Matters.

         (a) The Company has entered into an employment contract with its
principal executive officer, Bo W. Lycke, and the description of such employment
agreements in the SEC Materials is true, correct, and complete in all material
respects.

         (b) No labor dispute with the employees of the Company exists or is
threatened or imminent that could result in a material adverse change in the
condition (financial or otherwise), business, properties, prospects, net worth
or results of operations of the Company or any Subsidiary, except as described
in or contemplated by the SEC Materials.

         5.14 Intellectual Property. The Company owns or possesses, or can
acquire on reasonable terms, all material patents, patent applications,
trademarks, service marks, trade names, licenses, copyrights and proprietary or
other confidential information currently employed by them in connection with its
businesses, and neither the Company nor any Subsidiary has received any notice
of infringement of or conflict with asserted rights of any third party with
respect to any of the foregoing, which, singly or in the aggregate, if the
subject of an unfavorable decision, ruling or funding, would result in a
material adverse change in the condition (financial or otherwise), business,
properties, prospects, net worth or results of operations of the Company and the
Subsidiaries, taken as a whole, except as described in or contemplated by the
SEC Materials.

         5.15 Insurance. The Company and its Subsidiaries are insured by
insurers of recognized financial responsibility against such losses and risks
and in such amount as the Company and its Subsidiaries believe are prudent and
customary in the businesses in which they are engaged; neither the Company nor
any Subsidiary has been refused any insurance coverage sought or applied for;
and neither the Company nor any Subsidiary


<PAGE>

has no reason to believe that they will not be able to renew its existing
insurance coverage as and when such coverage expires or to obtain similar
coverage from similar insurers as may be necessary to continue its business at a
cost that would not materially and adversely affect the condition (financial or
otherwise), business, properties, prospects, net worth, or results of operations
of the Company and the Subsidiaries, taken as a whole, except as described in or
contemplated by the SEC Materials.

         5.16 Investment Company. The Company is not an investment company under
the Investment Company Act of 1940, as amended. The Company will conduct its
operations in a manner that will not subject it to registration as an investment
company under such act, and this transaction will not cause the Company to
become an investment company subject to registration under such Act.

         5.17 Tax Returns. The Company and its Subsidiaries have filed all
foreign, federal, state, and local tax returns that are required to be filed or
have requested extensions thereof (except in any case in which the failure so to
file would not have a material adverse effect on the Company and the
Subsidiaries, taken as a whole) and have paid all taxes required to be paid and
any other assessment, fine, or penalty levied, to the extent that any of the
foregoing is due and payable, except for any such assessment, fine or penalty
that is currently being contested in good faith or as described in or
contemplated by the SEC Materials.

         5.18 Quotation of Common Stock. The Common Stock is currently included
for quotation on the Nasdaq SmallCap Market under the symbol "CLAI," and for
listing on the Boston Stock Exchange under the symbol "CLA."

         5.19 Filings, Taxes, and Financial Statements.

        (a) The Company has filed the SEC Materials with the Securities and
Exchange Commission, the Nasdaq SmallCap Market, Inc. and any other required
person or entity (governmental or otherwise) in a timely manner and as otherwise
required by applicable laws and regulations, including the federal securities
laws. The audited financial statements of the Company for the fiscal year ended
December 31, 1999 and the Company's unaudited balance sheet for the period
ending September 30, 2000, together with the accompanying statements of
operations and cash flows included in the SEC Materials are accurate and
complete in all material respects and fairly present the financial condition of
the Company as at the dates thereof and have been prepared in accordance with
generally accepted accounting principles applied on a consistent basis
throughout the periods indicated (except as may be otherwise indicated in such
financial statements or the notes thereto).

         (b) Except as disclosed in the SEC Materials which sets forth a true
and accurate list and description of any employee benefit plans maintained or
sponsored by the Company or to which the Company is required to make
contributions, the Company does not maintain, sponsor, and is not required to
make contributions to or otherwise to have any liability with respect to any
pension, profit sharing, thrift, or other retirement plan, employee stock
ownership plan, deferred compensation, stock ownership, stock



<PAGE>

purchase performance share, bonus or other incentive plan, severance plan,
health or group insurance plan, welfare plan, or other similar plan, agreement,
policy, or understanding (whether written or oral), whether or not such plan is
intended to be qualified under Section 401(a) of the Code, within the meaning of
Section 3(8) of the Employee Retirement Income Security Act of 1974, as amended,
which plan covers any employee or former employee of the Company.

         5.20 SEC Materials. None of the information disclosed or set forth in
any of the SEC Materials, as of the date they were filed with the Securities and
Exchange Commission and as of the date hereof, contained or contains any untrue
statement of material fact or omitted to state a material fact required to be
stated therein or necessary to make the statements therein) in light of the
circumstances under which they were made, not misleading.

                                    SECTION 6

                 Representations And Warranties Of The Customer

         6.1 Organization and Qualification. The Customer is a corporation duly
organized, validly existing and in good standing under the laws of the State of
Delaware, with all requisite power and authority (corporate and otherwise), and
all necessary consents, authorizations, approvals, orders, licenses,
certificates, and permits of and from, and declarations and filings with, all
federal, state, local, and other governmental authorities and all courts and
other tribunals, to own, lease, license, and its properties and assets and to
carry on the business in which it is now engaged. The Customer is duly qualified
to transact the respective business in which it is engaged and is in good
standing as a foreign corporation in every jurisdiction in which its ownership,
leasing, licensing, or use of property or assets or the conduct of its business
makes such qualification necessary.

         6.2 Authorization. This Agreement has been duly and validly authorized
by the Customer. This Agreement has been duly executed and delivered by the
Customer and, assuming due execution by the other party hereto and thereto, as
applicable, constitutes the valid and binding obligation of the Customer
enforceable against the Customer in accordance with its terms, except as
enforceability may be limited by applicable bankruptcy, insolvency, or other
laws affecting the rights of creditors generally and the discretion of the
courts in granting equitable remedies. No consent, approval, authorization, or
order of, or any filing or declaration with, any governmental authority is
required for the consummation of the transactions contemplated hereby, except
such as may be required under Federal or state securities or Blue Sky Laws.

         6.3 Completeness of Disclosure. No representation or warranty by the
Customer in this Agreement contains an untrue statement of material fact or
omits to state a material fact required to be stated therein or necessary to
make the statements made therein not misleading.


<PAGE>


         6.4 Accredited Investor.

        (a) The Customer is an "accredited investor" as defined in Rule 501(a)
of Regulation D under the Securities Act of 1933, as amended. The Customer is
sophisticated in transactions of this type and capable of evaluating the merits
and risks of the transactions described herein, has the capacity to protect its
own interests, has reviewed the SEC Materials, and is aware of the risk factors
relating to an investment in the Company, as disclosed in such filings. The
Customer has not been formed solely for the purpose of entering into the
transaction described here in and is acquiring the Shares for investment for its
own account, not as a nominee or agent, and not with the view to distribute or
sell any part thereof; provided, that the Customer shall be permitted to
transfer the Shares as permitted under the applicable law. The Customer has been
afforded the opportunity to ask questions of, and receive information about, the
Company and its business and prospects, from management and representatives of
the Company, and has relied on its own independent judgment in making a judgment
about an investment in the Company.

        (b) The Customer has not retained any investment banker, broker, or
finder in connection with the transaction contemplated by this Agreement.

          6.5 No Conflicts. The execution, delivery and performance by the
Customer of this Agreement, the purchase and acceptance of the Shares, and
compliance with provisions hereof by the Customer will not (a) violate any
provisions of applicable law, statute, rule, or regulation applicable to the
Customer or any ruling, writ, injunction, order, judgment, or decree of any
court, arbitration, administrative agency, or other governmental body applicable
to the Customer or any of its properties or assets or (b) conflict with or
result in any breach of any of the terms, conditions, or provisions of, or
constitute (with notice or lapse of time to both) a default (or give rise to any
right of termination, cancellation, or acceleration) under , or result in the
creation of any encumbrance upon any of the properties or assets of the Customer
under its Certificate of Incorporation or By-laws or any material contract to
which the Customer is party, except where such violation, conflict, or breach
would not, individually or in the aggregate, have a material adverse effect on
the Customer.

          6.6 Approvals. No permit, authorization, consents, or approval of or
by, or any notification of or filing with, any person or entity (governmental or
otherwise) is required in connection with the execution, delivery, or
performance of the Agreement (including the funding and acceptance thereof) by
the Customer.


<PAGE>


                                   SECTION 7

                                  The Exchange

         7.1 Terms of the Exchange. On the basis of the representations,
warranties, covenants, and agreements contained in this Agreement and subject to
the terms and conditions of this Agreement:

         (a) The Company shall simultaneously (i) issue to the Customer the
Shares and (ii) execute and deliver to the Customer this Agreement.

         (b) The Customer shall simultaneously execute shall deliver to the
Company this Agreement.

         7.2 The Closing. The closing of the transactions contemplated by
Sections 7.1 and 7.2 shall take place at the offices of Reitler Brown LLC, 800
Third Avenue, 21st Floor, New York, New York 10022, at 10:00 a.m., local time,
on the date of this Agreement or at such different place, such different time,
or such different date or a combination thereof as the Company and Customer
agrees in writing. The closing of the transactions contemplated by Sections
7.1(a) and 7.1(b) is herein called the "Closing."

         7.3 Indemnity Against Liabilities. Each party hereto agrees to
indemnify and hold harmless the other and their respective officers, directors,
employees, counsel, agents, and stockholders, in each case past, present, or as
they may exist at any time after the date of this Agreement, and each person, if
any, who controls, controlled, or will control any of them within the meaning of
Section 15 of the Securities Act or Section 20(a) of the Exchange Act (the
"Indemnitees"), against any and all losses, liabilities, damages, and expenses
whatsoever (which shall include, for all purposes of this Section 7.3, but not
be limited to, reasonable counsel fees and any reasonable expenses whatsoever
incurred in investigation, preparing, or defending against any litigation,
commenced or threatened, or any claim whatsoever, and any and all amounts paid
in settlement of any claim or litigation) as and when incurred arising out of,
based upon, or in connection with (a) any breach of any representation,
warranty, covenant, or agreement of the indemnifying party contained in this
Agreement and (b) any act, alleged act, omission, or alleged omission occurring
at or prior to the Closing (including without limitation any which arise out of
, are based upon, or are in connection with any of this Agreement or any of the
transactions contemplated hereby).

         The foregoing agreement to indemnify shall be in addition to any
liability the parties hereto may otherwise have, including liabilities arising
under this Agreement.

                                    SECTION 8

                     Covenants and Agreements of the Parties

         Each of the Company and Customer covenants and agrees as follows:



<PAGE>

         8.1 Public Statements. Before the Company or Customer shall release any
information concerning this Agreement or the transactions contemplated hereby
which is intended for or may result in public dissemination thereof, it shall
cooperate with the other party , shall furnish drafts of all documents or
proposed oral statements to the other party, for comments, and shall not release
any such information without the prior written consent of the other party.
Nothing contained herein shall prevent the Company or Customer from releasing
any information to any governmental authority if required to do so by law.

         8.2 Confidentiality. The parties hereto shall insure that all
confidential information which either party, any of its respective officers,
directors, employees, counsel, agents, investment bankers, or accountants may
now possess or may hereafter create or obtain relating to the financial
condition, results of operations, business, properties, assets, liabilities, or
future prospects of the Company, any affiliate thereof, or any customer or
supplier thereof or any such affiliate shall not be published, disclosed, or
made accessible by any of them to any other person or entity at any time or used
by any of them. Notwithstanding the foregoing, the restrictions of the
immediately preceding sentence shall not apply (a) as may otherwise be required
by law, (b) as may be necessary or appropriate in connection with the
enforcement of the Agreement, or (c) to the extent such information shall have
otherwise become publicly available. The Customer shall, and shall cause all
other such persons and entities to, deliver to the Company all tangible evidence
of such confidential information to which the restrictions of the foregoing
sentence apply at the Closing or the earlier termination of this Agreement.


                                    SECTION 9

                                  Miscellaneous

         9.1 Further Actions. At any time and from time to time, each party
agrees, at its or his expense, to take such actions and to execute and deliver
such documents as may be reasonably necessary to effectuate the purposes of this
Agreement.

         9.2 Availability of Equitable Remedies. Since a breach of the
provisions of this Agreement could not adequately be compensated by money
damages, any party shall be entitled, either before or after the Closing, in
addition to any other right or remedy available to it, to an injunction
restraining such breach or a threatened breach and to specific performance of
any such provision of this Agreement, and in either case no bond or other
security shall be required in connection therewith, and the parties hereby
consent to the issuance of such an injunction and to the ordering of specific
performance.

         9.3 Survival. The covenants, agreements, representations, and
warranties contained in or made pursuant to this Agreement shall survive the
Closing and any delivery of the Shares to the Customer, irrespective of any
investigation made by or on behalf of any party. The statements contained in any
statement, certificate, or other instrument executed by the Company and relating
hereto or delivered to the Customer in connection with the transactions
contemplated hereby or thereby shall be deemed representations and warranties,
covenants and agreements, or conditions, as the case may be, of the Company
hereunder for all purposes of this Agreement (including all statements,
certificates, or other




<PAGE>

instruments delivered pursuant hereto or thereto or delivered in connection with
the transactions contemplated hereby or thereby). The statements contained in
any statement, certificate, or other instrument executed by the Customer and
relating hereto or delivered to the Company in connection with the transactions
contemplated hereby or thereby shall be deemed representations and warranties,
covenants and agreements, or conditions, as the case may be, of the Customer
hereunder for all purposes of this Agreement (including all statements,
certificates, or other instruments delivered pursuant hereto or thereto or
delivered in connection with the transactions contemplated hereby or thereby).

         9.4 Modification. This Agreement and the Schedule hereto set forth the
entire understanding of the parties with respect to the subject matter hereof
(except as provided in Section 9.3), supersede all existing agreements among
them concerning such subject matter (except as otherwise provided herein), and
may be modified only by a written instrument duly executed by each party with
the approval of an authorized officer or partner of each party.

         9.5 Notices. Any notices required or permitted to be given to any party
hereto in connection with this Agreement shall be in writing, shall be deemed
delivered when received and sufficient if delivered personally; deemed delivered
the next Business Day if sent by Federal Express or similar overnight courier
service for next Business Day delivery; shall be effective if delivered during
the Business Day by telecopier or similar means with written confirmation of
receipt during business hours (or, otherwise, effective the next Business Day);
or deemed delivered and effective three Business Days after deposit in first
class mail, Express Mail, or registered or certified mail, postage prepaid,
addressed as follows:

If to Company:                               If to Customer:

Claimsnet.com inc.                           McKesson HBOC, Inc.
12801 N. Central Expressway                  5995 Windward Parkway
Suite 1515                                   Alpharetta, Georgia 30003
Dallas, Texas 75243                          Fax:  (404) 338-5154
Fax:  (972) 458-1737

ATTENTION:                                   ATTENTION:

Bo W. Lycke                                  J.R. Hughes
Chief Executive Officer                      President, Provider Solutions Group

With a copy (which shall not constitute      With a copy (which shall not
constitute notice) to:                       notice) to:


<PAGE>

Reitler Brown, LLC                           McKesson HBOC, Inc.
800 Third Avenue                             Law Department
21st Floor                                   One Post Street
New York, New York 10022                     San Francisco,
                                             California 94104-5296

ATTENTION:                                   ATTENTION:

Robert Steven Brown, Esq.                    General Counsel
Fax:  (212) 371-5500                         Fax:  (415) 983-8826


         9.6 Waiver. Any waiver by any party of a breach of any term of this
Agreement shall not operate as or be construed to be a waiver of any other
breach of that term or of any breach of any other term of this Agreement. The
failure of a party to insist upon strict adherence to any term of this Agreement
on one or more occasions will not be considered a waiver or deprive that party
of the right thereafter to insist upon strict adherence to that term or any
other term of this Agreement. Any waiver must be in writing.

         9.7 Binding Effect. The provisions of this Agreement shall be binding
upon and inure to the benefit of the Company and the Customer and their
respective successors and assigns.

         9.8 No Third Party Beneficiaries. This Agreement does not create, and
shall not be construed as creating, any rights enforceable by any person not a
party to this Agreement.

         9.9 Separability. If any provision of this Agreement is invalid,
illegal, or unenforceable, the balance of this Agreement shall remain in effect,
and if any provision is inapplicable to any person or circumstance, it shall
nevertheless remain applicable to all other persons and circumstances.

         9.10 Headings. The headings in this Agreement are solely for
convenience of reference and shall be given no effect in the construction or
interpretation of this Agreement.

         9.11 Counterparts; Governing Law. This Agreement may be executed in any
number of counterparts, each of which shall be deemed an original, but all of
which together shall constitute one and the same instrument. It shall be
governed by and construed in accordance with the laws of Delaware, without
giving effect to conflict of laws.


               [THE REMAINDER OF THIS PAGE IS INTENTIONALLY BLANK]











<PAGE>


         IN WITNESS WHEREOF, the parties have duly executed this Agreement as of
the date first written above.

                                CLAIMSNET.COM INC.


                                By:  /s/ Bo W. Lycke
                                     ----------------------------------------
                                     Bo W. Lycke
                                     Chairman of the Board of Directors,
                                       President, and Chief Executive Officer


                                McKESSON HBOC, INC.


                                By:  /s/ J.R. Hughes
                                     ----------------------------------------
                                     J. R. Hughes
                                     President Provider Solutions Group







<PAGE>



                                  SCHEDULE 1.3


Wire to:

         Bank: Bank of America
         ABA#: 111000025
         Account Name: Claimsnet.com
         Account#: 4770647184