Document:

<PAGE>   1
                                                                     EXHIBIT 4.2

               No.       Date of Issue: April 30, 2001        $

                            VINEYARD NATIONAL BANCORP
                             9590 Foothill Boulevard
                           Rancho Cucamonga, CA 91730

                     10% CONVERTIBLE SUBORDINATED DEBENTURE

                                   OBLIGATION

        Vineyard National Bancorp, a California corporation (the "Bancorp") for
value received, hereby promises to pay to ____ of ____ or registered assigns, at
the office or agency of the Bancorp for that purpose in the City of Rancho
Cucamonga, State of California, a principal sum of $____ on June 30, 2008, in
lawful money of the United States of America, unless the Debenture has been duly
called for redemption, and payment of the redemption price has been made or
provided for, or unless the Debenture has been converted into common stock of
the Bancorp prior to maturity or redemption, in accordance with the terms of the
offering for this Debenture.

        Bancorp further promises to pay interest on the principal sum from time
to time remaining on this Debenture at the rate of ten percent (10%) per annum
to the registered holder from the date hereof, payable quarterly on the last
business day of March, June, September and December of each year commencing on
the first interest payment date after the date on which this Debenture was
issued until payment of the principal sum has been made or duly provided for,
subject to certain terms, conditions and exceptions provided herein.

                                  AUTHORIZATION

        This Debenture is one of a duly authorized issue of Debentures of the
Bancorp, designated as its 10% Convertible Subordinated Debentures, due June 30,
2008 (the "Debentures"), limited to a minimum aggregate principal amount of
three million dollars ($3,000,000) and a maximum aggregate principal amount of
five million dollars ($5,000,000) all issued or to be issued under and pursuant
to a Trust Indenture dated April 30, 2001 (the "Indenture"), duly executed and
delivered to Union Bank of California, N.A., as Trustee (the "Trustee"), which
Indenture and all indentures supplemental thereto are hereby incorporated by
reference in and made a part of this instrument; the Indenture is hereby
referred to for a description of the rights, limitation of rights, obligations,
duties, and immunities thereunder of the Trustee, the Bancorp, and the
registered holders or designated holder ("holders" or "holder") of the
Debentures.

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                                  DENOMINATION

        This Debenture is issued without coupons, and the denomination shall be
twenty-five thousand dollars ($25,000), or any multiple of twenty-five thousand
dollars ($25,000).

                                     DEFAULT

        In case an Event of Default, as defined in the Indenture, occurs and
continues, the principal hereof may be declared due and payable, and on that
declaration shall become due and payable in the manner, with the effect, and
subject to the conditions provided in the Indenture.

                             SUPPLEMENTAL INDENTURES

        The Indenture contains provisions permitting the Bancorp and the
Trustee, with the consent of holders of not less than a majority in aggregate
principal amount of the Debentures at the time outstanding to execute
supplemental provisions to or change in any manner, the rights of the holders of
the Debentures; provided, however, that no supplemental indenture shall permit
certain modifications or amendments affecting the basic terms of this Debenture,
as described more specifically in Article IX of the Indenture, without the
consent of the holder of each Debenture so effected. It is also provided in the
Indenture that prior to any declaration accelerating the maturity of the
Debentures on account of Default, holders of a majority in aggregate principal
amount of the Debentures at the time outstanding may, on behalf of the holders
of all the Debentures, waive any past default under the Indenture and its
consequences, except a default in the payment of the principal of or interest on
any of the Debentures. Any consent or waiver of the holder of this Debenture
(unless revoked as provided in the Indenture) shall be conclusive and binding on
that holder and on all future holders and owners of this Debenture, and of any
Debenture issued in exchange or substitution therefore, irrespective whether or
not any notation of that consent or waiver is made on this Debenture.

                              PAYMENT OF DEBENTURE

        No reference to the within Indenture and no provision of this Debenture
or of the Indenture shall alter or impair the obligation of the Bancorp, which
is absolute and unconditional, to pay the principal of and interest on this
Debenture at the place, at the respective times, at the rate and in the lawful
money as herein prescribed.

                                   REDEMPTION

        The Debentures may be redeemed at the option of the Bancorp, in whole or
in part, from time to time (selected by lot) at any time on or after July 1,
2003, on notice of not less than 30 but not more than 60 days prior to the
redemption date, on the condition that for 90 days prior to the redemption date
the average closing price of the Bancorp's common stock on the Over-the-

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Counter Bulletin Board (OTCBB) equaled or exceeded $6.00 per share (adjusted as
necessary for any stock split, recapitalization, merger, reorganization or other
such event affecting the stock's price). The prices for redemption of the
Debentures are expressed as percentages of the principal amount, plus accrued
interest to the redemption date. The percentages of the principal amount,
redeemed during the twelve month periods beginning on July 1 of the years shown
below, are:

<TABLE>
               <S>                                <C>
               2003                               103%
               2004                               102%
               2005                               101%
               2006 and thereafter                100%
</TABLE>

Payment of principal and interest on the Debentures may be accelerated in the
case of certain events of default.

                              TRANSFER OF DEBENTURE

        On due presentment of this Debenture at the above-mentioned office or
agency of the Trustee in Los Angeles, California for registration of a permitted
transfer, a new Debenture or Debentures for a like aggregate principal amount,
will be issued to the transferee as provided in the Indenture. The Debenture
holder shall pay the reasonable expenses and charges of the Bancorp and Trustee
in connection therewith, together with a sum sufficient to cover any tax or
other governmental charge that may be imposed in relation thereto.

        Prior to the registration of transfer of this Debenture, the Bancorp,
the Trustee, and any paying agent may deem and treat only the registered
Debenture holder as the absolute owner for the purpose of receiving payment of
or on account of the principal of the Debenture (and premium, if any) and
interest thereon, and for all other purposes.

                                LIMITED LIABILITY

        The holder or holders of this Debenture shall not have any recourse for
the payment of the principal of (or premium, if any), or the interest on this
Debenture, or for any claim based hereon, or otherwise in respect hereof, or
based on or in respect of the Indenture or any indenture supplemental thereto,
against any incorporator, shareholder, officer or director, or attorney, past,
present or future, of the Bancorp or Trustee, or of any successor corporation,
whether by virtue of any constitution, statute, or rule of law, or by the
enforcement of any assessment or penalty or otherwise. The holder or holders of
this Debenture, as part of the consideration therefore, expressly waive all
liability and release claims against the foregoing persons in connection with
this Debenture.

                 CONVERSION OF DEBENTURE INTO EQUITY SECURITIES

        This Debenture is convertible at the option of the registered holder at
any time prior to its maturity or redemption. This Debenture will be convertible
into fully paid and non-assessable shares of Bancorp common stock at the rate of
one (1) share for each five dollars ($5.00)

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principal amount to be converted, with minimum conversion amounts of twenty-five
thousand dollars each. In order to exercise the conversion privilege granted,
the holder of this Debenture will surrender this Debenture to the Bancorp with
the election of conversion form below duly executed. If the common stock into
which this Debenture is convertible is to be issued in a name or names other
than that of the registered holder of this Debenture, the Debenture must bear or
be accompanied by proper endorsement or assignment of the Debenture.

                         NOTICE OF CONVERSION AND RIGHT

        A holder desiring to convert this Debenture into capital stock must give
written notice to the Bancorp and, simultaneously with the giving of election of
conversion, surrender this Debenture at the principal office of the Bancorp in
Rancho Cucamonga, California. The Bancorp will promptly issue to the holder the
shares of stock into which this Debenture is to be convertible. Shares of the
capital stock of the Bancorp issued on the conversion of this Debenture will not
be entitled to any dividend declared on the stock prior to the date of receipt
by the Bancorp of the notice of election to convert and this Debenture
accompanied by any instrument of assignment and transfer, and on conversion the
holder shall be entitled to any interest on this Debenture which is due and
payable at or prior to the date notice of conversion is received by the Bancorp.

                     SURRENDER OR CANCELLATION OF DEBENTURES

        This Debenture will be deemed to have been surrendered for conversion,
and to have been converted, at the close of business on the date on which the
Debenture is received by the Bancorp or a designated agent of the Bancorp with
the attached Election to Convert form duly executed, and upon receipt of the
Debenture and Election to Convert form the Bancorp will promptly issue and
deliver to the person or persons entitled a certificate or certificates of its
stock evidencing the number of shares into which this Debenture shall have been
converted. The Bancorp will then cancel this Debenture, and in the event that
less than the entire principal amount is converted, the Bancorp will issue a new
Debenture for the balance not so converted.

                                 AUTHENTICATION

        This Debenture shall not be valid or become obligatory for any purpose
until the certificate of authentication herein shall have been executed by or on
behalf of the Trustee under the Indenture referred to above.

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        IN WITNESS WHEREOF, the Bancorp has caused this Debenture to be signed
by its Chair of the Board, President, or one of its Vice-Presidents, and by its
Secretary or Chief Financial Officer, and has caused its corporate seal to be
affixed hereto or a facsimile thereof printed hereon.

       Dated:                         VINEYARD NATIONAL BANCORP
                                      A California corporation

                                      By:
                                      Norman Morales, President

                                      ATTEST:

                                      By:
                                      Sara F. Ahern, Secretary

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                          CERTIFICATE OF AUTHENTICATION

        The undersigned Trustee certifies that this is one of the Debentures in
the series described as Vineyard National Bancorp 10% Convertible Subordinated
Debentures in the aforementioned Indenture.

Dated:

                                       Trustee: Union Bank of California, N.A.

                                       By:

                                       ----------------------------------------
                                       Alison T. Braunstein, Authorized Officer

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                     ELECTION TO CONVERT DEBENTURE TO SHARES

        The undersigned holder of this Debenture surrenders $____________
aggregate principal amount of the Vineyard National Bancorp 10% Convertible
Debenture for conversion on the terms and conditions set forth in the Debenture,
and requests that the shares issuable on conversion be issued to the following
person or persons:

<TABLE>
<CAPTION>
       Name                                  Address
       ----                                  -------
<S>                                   <C>

----------------------------------    ---------------------------------

                                      ---------------------------------

Dated:

----------------------------------
Signature of Registered Owner
</TABLE>

NOTE: In the event that the aggregate principal amount of the within Debenture
which is being surrendered for conversion has not been specified, it is agreed
that the entire aggregate principal amount evidenced by the within Debenture
will be deemed to have been so surrendered for conversion into shares of common
stock of the Bancorp.

                                      -7-<PAGE>   1

                                                                     EXHIBIT 4.8

NEITHER THIS WARRANT NOR THE SECURITIES ISSUABLE UPON EXERCISE HEREOF HAVE BEEN
REGISTERED UNDER THE SECURITIES ACT OF 1933, AS AMENDED (THE "ACT"), AND SUCH
SECURITIES MAY NOT BE SOLD, TRANSFERRED OR ASSIGNED UNLESS SO REGISTERED OR AN
EXEMPTION FROM REGISTRATION UNDER SAID ACT IS AVAILABLE. THIS LEGEND SHALL BE
IMPRINTED ON ANY WARRANT ISSUED IN EXCHANGE FOR THIS WARRANT.

                                WARRANT AGREEMENT

                             FOR PREFERRED STOCK OF

                                DRKOOP.COM, INC.

WARRANT NO. PCA-01

               THIS CERTIFIES that, for value received, Commonwealth Associates,
L.P. ("Commonwealth"), or its permitted assigns (collectively, the "Holder"), is
entitled to purchase from drkoop.com, Inc., a Delaware corporation (the
"Company"), at any time, and from time to time, during the exercise period
referred to in Section 1 hereof 36,000 fully paid, validly issued and
nonassessable shares (the "Warrant Shares") of the Company's Series E 8%
Convertible Preferred Stock (the "Preferred Stock") at the exercise price of
$10.00 per share, subject to adjustment as provided herein (the "Warrant Share
Price"). Securities issuable upon exercise of this Warrant and the exercise
price payable therefor are subject to adjustment from time to time as
hereinafter set forth. As used herein, the term "Warrant" shall include any
warrant or warrants hereafter issued in consequence of the exercise of this
Warrant in part or transfer of this Warrant in whole or in part.

1. Exercise; Payment for Ownership Interest.

               (a) Upon the terms and subject to the conditions set forth
herein, this Warrant may be exercised in whole or in part by the Holder hereof
at any time, or from time to time, on or after the date hereof and prior to 5
p.m. New York time on August 20, 2008, by presentation and surrender of this
Warrant to the principal offices of the Company, or at the office of its
Transfer Agent (as hereinafter defined), if any, together with the Purchase Form
annexed hereto, duly executed, and accompanied by payment to the Company of an
amount equal to the Warrant Share Price multiplied by the number of Warrant
Shares as to which this Warrant is then being exercised; provided, however, that
in each case, the minimum number of Warrant Shares as to which this Warrant is
being exercised shall not be less than 100 Warrant Shares; provided, further,
that in the event of

<PAGE>   2

any merger, consolidation or sale of all or substantially all the assets of the
Company resulting in any distribution to the Company's stockholders, prior to
August 20, 2008, the Holder shall have the right to exercise this Warrant
commencing at such time through August 20, 2008 into the kind and amount of
shares of stock and other securities and property (including cash) receivable by
a holder of the number of shares of Preferred Stock into which this Warrant
might have been exercisable immediately prior thereto. Any transfer of Warrant
Shares obtained by the Holder in exercise of this Warrant is subject to the
requirement that such securities be registered under the Securities Act of 1933,
as amended (the "1933 Act"), and applicable state securities laws or exempt from
registration under such laws. The Holder of this Warrant shall be deemed to be a
shareholder of the Warrant Shares as to which this Warrant is exercised in
accordance herewith effective immediately after the close of business on the
date on which the Holder shall have delivered to the Company this Warrant in
proper form for exercise and payment by certified or official bank check or wire
transfer of the cash purchase price for the number of Warrant Shares as to which
the exercise is being made, notwithstanding that the stock transfer books of the
Company shall be then closed or that certificates representing such Warrant
Shares shall not then be physically delivered to the Holder.

               (b) All or any portion of the Warrant Share Price may be paid by
surrendering Warrants effected by presentation and surrender of this Warrant to
the Company, or at the office of its Transfer Agent, if any, with a Cashless
Exercise Form annexed hereto duly executed (a "Cashless Exercise"). Such
presentation and surrender shall be deemed a waiver by the Company of the
Holder's obligation to pay all or any portion of the aggregate Warrant Share
Price. In the event of a Cashless Exercise, the Holder shall exchange this
Warrant for the number of Warrant Shares equal to (i) the number of Warrant
Shares specified by the Holder in its Cashless Exercise Form (the "Total
Number") less (ii) the number of Warrant Shares equal to the quotient obtained
by dividing (A) the product of the Total Number and the existing Warrant Share
Price by (B) the current market value of the shares of common stock ("Common
Stock") issuable upon conversion of a share of Preferred Stock. For purposes of
any computation under this Section 1(b), the then current market price per share
of Common Stock at any date shall be deemed to be the average for the ten
consecutive business days immediately prior to the Cashless Exercise of the
daily closing prices of the Common Stock on the principal national securities
exchange on which the Common Stock is admitted to trading or listed, or if not
listed or admitted to trading on any such exchange, the closing prices as
reported by the Nasdaq National Market or, if applicable, the Nasdaq SmallCap
Market, or if not then included for quotation on the Nasdaq National Market or
the Nasdaq SmallCap Market, the average of the highest reported bid and lowest
reported asked prices as reported by the OTC Bulletin Board or the National
Quotations Bureau, as the case may be, or if not then publicly traded, the fair
market price, not less than book value thereof, of the Common Stock as
determined in good faith by the independent members of the Board of Directors of
the Company.

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<PAGE>   3

               (c) If this Warrant shall be exercised in part only, the Company
shall, upon surrender of this Warrant for cancellation, execute and deliver a
new Warrant evidencing the rights of the Holder thereof to purchase the balance
of the Warrant Shares purchasable hereunder as to which the Warrant has not been
exercised. If this Warrant is exercised in part, such exercise shall be for a
whole number of Warrant Shares. Upon any exercise and surrender of this Warrant,
the Company (i) will issue and deliver to the Holder a certificate or
certificates in the name of the Holder for the largest whole number of Warrant
Shares to which the Holder shall be entitled and, if this Warrant is exercised
in whole, in lieu of any fractional Warrant Share to which the Holder otherwise
might be entitled, cash in an amount equal to the fair value of such fractional
Warrant Share (determined in such reasonable and equitable manner as the Board
of Directors of the Company shall in good faith determine), and (ii) will
deliver to the Holder such other securities, properties and cash which the
Holder may be entitled to receive upon such exercise, or the proportionate part
thereof if this Warrant is exercised in part, pursuant to the provisions of this
Warrant.

2. Anti-Dilution Provisions. The Warrant Share Price in effect at any time and
the number and kind of securities issuable upon exercise of this Warrant and the
Warrant Share Price shall be subject to adjustment from time to time upon
happening of certain events as follows:

        2.1 Reorganization, Reclassification, Consolidation, Merger or Sale. If
any capital reorganization, reclassification or any other change of capital
stock of the Company, or any consolidation or merger of the Company with another
person, or the sale or transfer of all or substantially all of its assets to
another person shall be effected in such a way that holders of shares of
Preferred Stock shall be entitled to receive stock, securities or assets with
respect to or in exchange for their shares of Preferred Stock, then provision
shall be made by the Company, in accordance with this Section 2.1, whereby the
Holder hereof shall thereafter have the right to purchase and receive, upon the
basis and upon the terms and conditions specified in this Warrant and in
addition to or in exchange for, as applicable, the Warrant Shares subject to
this Warrant immediately theretofore purchasable and receivable upon the
exercise of the rights represented hereby, such securities or assets as would
have been issued or payable with respect to or in exchange for the aggregate
Warrant Shares immediately theretofore purchasable and receivable upon the
exercise of the rights represented hereby if exercise of the Warrant had
occurred immediately prior to such reorganization, reclassification,
consolidation, merger or sale. The Company will not effect any such
consolidation, merger, sale, transfer or lease unless prior to the consummation
thereof the successor entity (if other than the Company) resulting from such
consolidation or merger or the entity purchasing such assets shall assume by
written instrument (i) the obligation to deliver to the Holder such securities
or assets as, in accordance with the foregoing provisions, the Holder may be
entitled to purchase, and (ii) all other obligations of the Company under this
Warrant; provided, however, that the failure to comply with the foregoing shall
not affect the validity or legality of such consolidation, merger, sale,
transfer or lease. The provisions

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<PAGE>   4

of this Section 2.1 shall similarly apply to successive consolidations, mergers,
exchanges, sales, transfers or leases. In the event that in connection with any
such capital reorganization or reclassification, consolidation, merger, sale or
transfer, additional shares of Preferred Stock shall be issued in exchange,
conversion, substitution or payment, in whole or in part, for a security of the
Company other than Preferred Stock, any such issue shall be treated as an issue
of Preferred Stock covered by the provisions of Section 2.2 hereof.

        2.2 Stock Dividends and Securities Distributions. If, at any time or
from time to time after the date of this Warrant, the Company shall distribute
to the holders of shares of Preferred Stock (i) securities (including rights,
warrants, options or another form of convertible securities) (but other than
pursuant to the dividend provisions of Section 4 of the Certificate of
Designation of the Preferred Stock), (ii) property, other than cash, or (iii)
cash (other than pursuant to the dividend provisions of Section 4 of the
Certificate of Designation of the Preferred Stock), without fair payment
therefor, then, and in each such case, the Holder, upon the exercise of this
Warrant, shall be entitled to receive such securities, property and cash which
the Holder would hold on the date of such exercise if, on the date of the
distribution, the Holder had been the holder of record of the shares of
Preferred Stock issued upon such exercise and, during the period from the date
of this Warrant to and including the date of such exercise, had retained such
shares of Preferred Stock and the securities, property and cash receivable by
the Holder during such period, subject, however, to the Holder agreeing to any
conditions to such distribution as were required of all other holders of shares
of Preferred Stock in connection with such distribution.

        2.3 Other Adjustments. In addition to those adjustments set forth in
Sections 2.1 and 2.2, but without duplication of the adjustments to be made
under such Sections, if the Company:

                   (i) declares or pays a dividend or makes a distribution on
its Preferred Stock in shares of its Preferred Stock (other than pursuant to the
dividend provisions of Section 4 of the Certificate of Designation of the
Preferred Stock);

                   (ii) subdivides or reclassifies its outstanding shares of
Preferred Stock into a greater number of shares;

                   (iii)combines or reclassifies its outstanding shares of
Preferred Stock into a smaller number of shares;

                   (iv) makes a distribution on its Preferred Stock in shares of
its capital stock other than Preferred Stock; and/or

                   (v) issues, by reclassification of its Preferred Stock, any
shares of its capital stock;

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<PAGE>   5

then the number and kind of Warrant Shares purchasable upon exercise of this
Warrant shall be adjusted so that the Holder upon exercise hereof shall be
entitled to receive the kind and number of Warrant Shares or other securities of
the Company that the Holder would have owned or have been entitled to receive
after the happening of any of the events described above had this Warrant been
exercised immediately prior to the happening of such event or any record date
with respect thereto. An adjustment made pursuant to this Section 2.3 shall
become effective immediately after the record date in the case of a dividend or
distribution and shall become effective immediately after the effective date in
the case of a subdivision, combination or issuance. If, as a result of an
adjustment made pursuant to this Section 2.3, the Holder of this Warrant
thereafter surrendered for exercise shall become entitled to receive shares of
two or more classes of capital stock or shares of Preferred Stock and any other
class of capital stock of the Company, the Board of Directors (whose
determination shall be conclusive and shall be described in a written notice to
all holders of Warrants promptly after such adjustment) shall determine the
allocation of the adjusted Warrant Share Price between or among shares of such
classes of capital stock or shares of Preferred Stock and such other class of
capital stock.

               The adjustment to the number of Warrant Shares purchasable upon
the exercise of this Warrant described in this Section 2.3 shall be made each
time any event listed in paragraphs (i) through (v) of this Section 2.3 occurs.

               Simultaneously with all adjustments to the number and/or kind of
securities, property and cash under this Section 2.3 to be issued in connection
with the exercise of this Warrant, the Warrant Share Price will also be
appropriately and proportionately adjusted.

        In the event that at any time, as a result of an adjustment made
pursuant to this Section 2.3, the Holder of this Warrant thereafter shall become
entitled to receive any shares of the Company, other than Preferred Stock,
thereafter the number of such other shares so receivable upon exercise of this
Warrant shall be subject to adjustment from time to time in a manner and on
terms as nearly equivalent as practicable to the provisions with respect to the
Preferred Stock contained in Sections 2.1 and 2.2 above.

        2.4 Notice of Adjustments. Upon the occurrence of each adjustment or
readjustment of the Warrant Share Price pursuant to this Section 2, the Company
at its expense will promptly compute such adjustment or readjustment in
accordance with the terms of this Warrant and prepare a certificate setting
forth such adjustment or readjustment, including a statement of the adjusted
Warrant Share Price or adjusted number of shares of Preferred Stock, if any,
issuable upon exercise of each Warrant, describing the transaction giving rise
to such adjustments and showing in detail the facts upon which such adjustment
or readjustment is based. The Company will forthwith mail, by first class mail,
postage prepaid, a copy of each such certificate to the Holder of this

                                       5
<PAGE>   6

Warrant at the address of such Holder as shown on the books of the Company, and
to its Transfer Agent.

        2.5    Other Notices.  If at any time:

               (a) the Company shall (i) offer for subscription pro rata to the
holders of shares of the Common Stock or Preferred Stock any additional equity
in the Company or other rights; (ii) pay a dividend in additional shares of the
Preferred Stock or Common Stock or distribute securities or other property to
the holders of shares of the Preferred Stock or Common Stock (including, without
limitation, evidences of indebtedness and equity and debt securities); or (iii)
issue securities convertible into, or rights or warrants to purchase, securities
of the Company;

               (b) there shall be any capital reorganization or reclassification
or consolidation or merger of the Company with, or sale, transfer or lease of
all or substantially all of its assets to, another entity; or

               (c) there shall be a voluntary or involuntary dissolution,
liquidation or winding up of the Company;

then, in any one or more of said cases, the Company shall give, by first class
mail, postage prepaid, to the Holder of this Warrant at the address of such
Holder as shown on the books of the Company, (a) at least 15 days' prior written
notice of the date on which the books of the Company shall close or a record
shall be taken for such subscription rights, dividend, distribution or issuance,
and (b) in the case of any such reorganization, reclassification, consolidation,
merger, sale, dissolution, liquidation or winding up, at least 15 days' prior
written notice of the date when the same shall take place if no stockholder vote
is required and at least 15 days' prior written notice of the record date for
stockholders entitled to vote upon such matter if a stockholder vote is
required. Such notice in accordance with the foregoing clause (a) shall also
specify, in the case of any such subscription rights, the date on which the
holders of shares of Common Stock or Preferred Stock shall be entitled to
exercise their rights with respect thereto, and such notice in accordance with
the foregoing clause (b) shall also specify the date on which the holders of
shares of Preferred Stock or Common Stock, as the case may be, shall be entitled
to exchange such shares for securities or other property deliverable upon such
reorganization, reclassification, consolidation, merger, sale, dissolution,
liquidation or winding up, as the case may be. Failure to give the notice
referred to herein shall not affect the validity or legality of the action which
should have been the subject of the notice.

        2.6 No adjustment in the Warrant Share Price shall be required unless
such adjustment would require an increase or decrease of at least one cent
($0.01) in such price; provided, however, that any adjustments which by reason
of this Section 2.6 are not required to be made shall be carried forward and
taken into account in any subsequent

                                       6
<PAGE>   7

adjustment required to be made hereunder. All calculations under this Section 2
shall be made to the nearest cent or to the nearest one-hundredth of a share, as
the case may be.

3. No Voting Rights. This Warrant shall not be deemed to confer upon the Holder
any right to vote or to consent to or receive notice as a stockholder of the
Company, as such, in respect of any matters whatsoever, or any other rights or
liabilities as a stockholder, prior to the exercise hereof.

4. Warrants Transferable. This Warrant and all rights hereunder are
transferable, in whole or in part, at the principal offices of the Company by
the Holder hereof, upon surrender of this Warrant properly endorsed; provided,
however, that in each case the minimum number of Warrant Shares being
transferred by the Holder shall not be less than 100 Warrant Shares; provided,
further, that without the prior written consent of the Company, this Warrant and
all rights hereunder may be transferred only (i) to an affiliate of the initial
Holder hereof or successor in interest to any such person in a transaction
exempt from registration under the 1933 Act, provided that the Company receives
an opinion of counsel that such transfer may be effected without registration
under the 1933 Act; or (ii) pursuant to the registration of this Warrant or the
Warrant Shares under the 1933 Act or subsequent to one year from the date hereof
pursuant to an available exemption from such registration.

5. Warrants Exchangeable; Assignment; Loss, Theft, Destruction, Etc. This
Warrant is exchangeable, without expense, upon surrender hereof by the Holder
hereof at the principal offices of the Company, or at the office of its Transfer
Agent, if any, for new Warrants of like tenor representing in the aggregate the
right to subscribe for and purchase the Warrant Shares which may be subscribed
for and purchased hereunder, each such new Warrant to represent the right to
subscribe for and purchase such Warrant Shares as shall be designated by such
Holder hereof at the time of such surrender. Upon surrender of this Warrant to
the Company at its principal office, or at the office of its Transfer Agent, if
any, with an instrument of assignment duly executed and funds sufficient to pay
any transfer tax, the Company shall, without charge, execute and deliver a new
Warrant in the name of the assignee named in such instrument of assignment and
this Warrant shall promptly be cancelled. This Warrant may be divided or
combined with other warrants which carry the same rights upon presentation
hereof at the principal office of the Company, or at the office of its Transfer
Agent, if any, together with a written notice specifying the names and
denominations in which new Warrants are to be issued and signed by the Holder
hereof. The term "Warrant" as used herein includes any Warrants into which this
Warrant may be divided or exchanged. Upon receipt of evidence satisfactory to
the Company of the loss, theft, destruction or mutilation of this Warrant and,
in the case of any such loss, theft or destruction, upon delivery of a bond or
indemnity satisfactory to the Company, or, in the case of any such mutilation,
upon surrender or cancellation of this Warrant, the Company will issue to the
Holder hereof a new Warrant of like tenor, in lieu of this Warrant, representing
the right to subscribe for and purchase the Warrant Shares which may be
subscribed for and purchased hereunder.

                                       7
<PAGE>   8

Any such new Warrant executed and delivered shall constitute an additional
contractual obligation of the Company, whether or not this Warrant so lost,
stolen, destroyed, or mutilated shall be at any time enforceable by anyone.

6. Legends; Investment Representations.

               (a) Any certificate evidencing the securities issued upon
exercise of this Warrant shall bear a legend in substantially the following
form:

               THE SECURITIES REPRESENTED BY THIS CERTIFICATE HAVE NOT BEEN
        REGISTERED UNDER THE SECURITIES ACT OF 1933, AS AMENDED (THE "ACT"), AND
        SUCH SECURITIES MAY NOT BE SOLD, TRANSFERRED OR ASSIGNED UNLESS SO
        REGISTERED OR AN EXEMPTION FROM REGISTRATION UNDER SAID ACT IS
        AVAILABLE.

               (b) The Holder hereby represents that it is purchasing this
        Warrant for its own account for investment and not with the view to or
        for sale in connection with the distribution of this Warrant, nor with
        any present intention of selling or otherwise disposing of all or any
        part of this Warrant. The Holder hereby represents that it understands
        that there may not be any market for this Warrant or the Warrant Shares.
        The Holder hereby agrees that (1) the purchase of this Warrant is a
        long-term investment, (2) the Holder may have to bear the economic risk
        of investment for an indefinite period of time because neither this
        Warrant nor the Warrant Shares has been registered under the Securities
        Act and, cannot be resold, pledged, assigned or otherwise disposed of
        unless they are subsequently registered under said Securities Act and
        under applicable securities laws of certain states or an exemption of
        such registration is available and (3) the Holder is an accredited
        investor as defined in Rule 501 promulgated under the 1933 Act. The
        Holder hereby represents that it understands that the Company is under
        no obligation to register this Warrant or the Warrant Shares, and,
        except as set forth in Section 10 below, the Company is under no
        obligation to register the Common Stock issuable upon conversion of the
        Warrant Shares. The Holder shall be deemed to reaffirm the foregoing
        investment representations at such time the Holder exercises this
        Warrant.

7. Modifications and Waivers. The terms of this Warrant may be amended, modified
or waived only by the written agreement of the Company, Commonwealth and the
holders of Warrants exercisable for at least 50% of the Warrant Shares issuable
upon exercise of all then outstanding Warrants. Any amendment, modification or
waiver effected pursuant to the preceding sentence shall bind all transferees
who acquire Warrants.

                                       8
<PAGE>   9

8. Miscellaneous. The Company shall pay all expenses and other charges payable
in connection with the preparation, issuance and delivery of this Warrant and
all substitute Warrants. The Holder shall pay all taxes (other than any issuance
taxes, including, without limitation, documentary stamp taxes, transfer taxes
and other governmental charges, which shall be paid by the Company) in
connection with such issuance and delivery of this Warrant and the Warrant
Shares.

               The Company shall maintain, at the office or agency of the
Company maintained by the Company, books for the registration and transfer of
the Warrant.

9. Reservation of Shares. The Company shall at all times reserve for issuance
and/or delivery upon exercise of this Warrant such number of shares of Preferred
Stock as shall be required for issuance and delivery upon exercise of this
Warrant. In addition, the Company will at all times reserve and keep available,
free from preemptive rights, out of the aggregate of its authorized but unissued
Common Stock or its authorized and issued Common Stock held in its treasury,
solely for the purpose of enabling it to satisfy any obligation to issue shares
of Common Stock underlying the Preferred Stock issuable upon exercise of this
Warrant, the maximum number of shares of Common Stock which may then be
deliverable upon the conversion of such Preferred Stock.

               The Company or, if appointed, the transfer agent for the Common
Stock and/or Preferred Stock (the "Transfer Agent") and every subsequent
transfer agent for any shares of the Company's capital stock issuable upon the
exercise of any of the rights of purchase aforesaid, will be irrevocably
authorized and directed at all times to reserve such number and kinds of
authorized shares as shall be required for such purpose. The Company will keep a
copy of this Warrant on file with the Transfer Agent and with every subsequent
transfer agent for any shares of the Company's capital stock issuable upon the
exercise of the rights of purchase represented by this Warrant. The Company will
furnish such Transfer Agent a copy of all notices of adjustments and
certificates related thereto transmitted to the Holder pursuant to Section 2.5
hereof.

               The Company covenants that all Warrant Shares which may be issued
upon exercise of this Warrant will, upon issue, be fully paid, nonassessable,
free of preemptive rights and free from all taxes, liens, charges and security
interests with respect to the issue thereof.

10. Registration. The Holder shall be entitled to the registration rights with
respect to the Warrant Shares as set forth in that certain Annex A to the
Subscription Agreements between the Company and the respective subscribers
therein named relating to the purchase of the Preferred Stock.

11. Descriptive Headings and Governing Law. The descriptive headings of the
several paragraphs of this Warrant are inserted for convenience only and do not
constitute a part of this Warrant. This Warrant shall be construed and enforced
in accordance with

                                       9
<PAGE>   10

the laws of the State of New York, and the rights of the parties shall be
governed by, the law of such State.

                                       10
<PAGE>   11

        IN WITNESS WHEREOF, this Warrant Agreement has been executed as of the
20th day of August, 2001.

                                DRKOOP.COM, INC.

                                    By: /s/ RICHARD M. ROSENBLATT
                                        _______________________________________
                                          Name: Richard M. Rosenblatt

                                          Title: Chief Executive Officer

                                       11
<PAGE>   12

                                  PURCHASE FORM

                                                          Dated:__________, ____

               The undersigned hereby irrevocably elects to exercise the within
Warrant to the extent of purchasing _____ Warrant Shares and hereby makes
payment of $_____________ in payment of the exercise price thereof. The
undersigned further confirms that the representations and warranties contained
in Section 6(b) of the Warrant are true and correct as of the date hereof.

                                    -----------------------------------------

                                       12
<PAGE>   13

                                CASHLESS EXERCISE

                                                          Dated:__________, ____

               The undersigned irrevocably elects to exercise the within Warrant
for Warrant Shares and hereby makes payment pursuant to the Cashless Exercise
provision of the within Warrant, and directs that the payment of the Warrant
Share Price be made by cancellation as of the date of exercise of a portion of
the within Warrant in accordance with the terms and provisions of Section 1(b)
of the within Warrant.

                                    -----------------------------------------

                                       13

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