Document:

<PAGE>

                                                                   EXHIBIT 10.81

                                                                 August 18, 2000

drkoop.com, Inc.
7000 North Mopac
Austin, TX  78731
Attn.:  Donald Hackett

Gentlemen:

     The purpose of this letter is to confirm the engagement of Commonwealth
Associates, L.P., ("Commonwealth") by drkoop, Inc. (the "Company") to act as the
Company's non-exclusive financial advisor to provide financial advisory services
and other investment banking services to the Company in connection with the
possible sale of the Company, whether such transaction (a "Sale Transaction") is
in the form of a merger, sale of assets or equity securities, or joint venture
or other similar business combination.

     Section 1. Services.  Commonwealth will perform such of the following
     -------------------
financial advisory and investment banking services as the Company may reasonably
request:

     (a) Commonwealth will familiarize itself to the extent appropriate with the
business, operations, properties, financial condition and prospects of any
prospective acquiror, it being understood that Commonwealth shall, in the course
of such familiarization, rely entirely upon publicly available information and
such other information as may be supplied by the Company or such acquiror,
without independent investigation;

     (b) Commonwealth will advise and assist the Company in developing a general
strategy for accomplishing a Sale Transaction;

     (c) Commonwealth will advise and assist the Company in identifying
potential acquirors and will on behalf of the Company, contact such potential
acquirors as the Company may designate;

     (d) Commonwealth will advise and assist the Company in the course of its
negotiation of a Sale Transaction with a potential acquiror and will participate
directly in such negotiations. It is understood that you will be under no
obligation to enter into a Sale Transaction and you will be within your rights
declining any offer made in connection with a Sales Transaction; and

     (e) Commonwealth will render such other financial advisory and investment
banking services as may from time to time be agreed upon by Commonwealth and the
Company, it being
<PAGE>

understood that Commonwealth will not be requested or required to issue any
fairness opinions in connection with any Sale Transaction.

In connection with our activities on the Company's behalf, the Company will
furnish us and any potential acquiror(s) approved by the Company with all
information (the "Information") which we may reasonably request and is
reasonably acceptable to the Company and will provide us and any potential
acquiror(s) approved by the Company reasonable access to the Company's officers,
directors, accountants and counsel; provided however, that prior to the delivery
of such information, a potential acquiror shall have signed and delivered a
confidentiality agreement acceptable to the Company. The Company represents and
warrants that to the best of its knowledge the information will be true,
accurate and complete and will not contain any untrue statement of a material
fact or omit to state any material fact required to be stated therein or
necessary to make the statements therein not misleading. The Company further
represents and warrants that any projections provided to us or contained in any
materials prepared by the Company with respect to a Sale Transaction will have
been prepared in good faith. The Company acknowledges and agrees that, in
rendering our services hereunder, we will be using and relying on the
Information (and information available from public sources and other sources
which we deem to be reliable) without independent verification thereof and
without independent appraisal of any of the Company's assets. We do not assume
responsibility for the accuracy or the completeness of the Information or any
other information regarding the Company or any prospective acquiror.

          Section 2. Fees.  The Company shall pay to Commonwealth for its
          ---------------
services hereunder a fee equal to the amount calculated using the Applicable Fee
Percentage (as determined below) multiplied by the Total Consideration received
by the Company and its shareholders, such fee to be earned, due and payable upon
the consummation of a Sale Transaction and payable at the closing thereof unless
otherwise provided herein.

                                        Fee Schedule
                                        ------------
    Total Consideration Paid to Company      Fee %      Maximum Fee Amount
    -----------------------------------      -----      ------------------

             Up to $100 million                0.5%          $ 500,000
      * $100 million  ** $150 million          0.75%        $ 1,125,000
                $150 million                     1%         $ 1,500,000+

     For purposes of this Agreement, "Total Consideration" shall mean the total
value of all cash, securities, or other property paid at the closing of a Sale
Transaction to the Company or its shareholders or to be paid in the future to
them with respect to such Sale Transaction as provided below (other than
payments of interest or dividends) in respect of (i) the assets of the Company,
(ii) the capital stock of the Company (and any securities convertible into
options, warrants or other rights to acquire such capital stock) and (iii) the
assumption, directly or indirectly (by

*  Greater than sign
** Less than or equals to sign

                                       2
<PAGE>

operation of law or otherwise), of any indebtedness of the Company for borrowed
money, less all cash and cash equivalents held by the Company at closing. In the
event a Sale Transaction is consummated in one or more steps, including without
limitation, any additional consideration paid or to be paid in any subsequent
step in the Sale Transaction including payments pursuant to promissory notes
delivered to the Company in connection with a Sale Transaction in respect of (x)
the assets of the Company, (y) the capital stock of the Company (and any
securities convertible into or options, warrants or other rights to acquire,
such capital stock) and (z) the assumption, directly or indirectly (by operation
of law or otherwise), of any long-term liabilities of the Company or repayment
of indebtedness, including, without limitation indebtedness secured by assets of
the Company, shall be included in the definition of "Total Consideration".

If all or a portion of the Total Consideration paid in the Sale Transaction is
other than cash or negotiable securities then the value of such non-cash
consideration shall be the fair market value thereof on the date the Sale
Transaction is consummated as mutually agreed upon in good faith by the Company
and us.  If such non-cash consideration consists of common stock, convertible
preferred stock or other convertible security, options, warrants or other rights
for which a public trading market for such security or underlying security
existed prior to consummation of the Sale Transaction, then the value of such
securities shall be determined by the closing or last sales price of such
security or underlying security on the date of the consummation of the Sale
Transaction.  If no public market exists for the common stock, options, warrants
or rights issued in the Sale Transaction, then the value of such securities
shall be as mutually agreed upon in good faith by the Company's Board of
Directors and us.  If such non-cash consideration consists of preferred stock or
debt securities (regardless of whether a public trading market existed for such
preferred stock or debt securities prior to the consummation of the Sale
Transaction or exists thereafter), the value thereof shall be the fair market
value of such non-cash consideration.  Any amounts payable to the Company, or
any affiliate of the Company or any shareholder of the Company in connection
with a non-competition agreement or any employment, consulting, licensing,
supply or other agreement, to the extent that such amounts payable are greater
than what would customarily be paid on an arms-length basis to an employee,
consultant, licensee or supplier who had not been acquired, shall be deemed to
be part of the consideration paid in the Sale Transaction. If all or a portion
of the Total Consideration payable in connection with a Sale Transaction
includes future payments, then the Company shall pay us any additional cash fee,
determined in accordance with this section 2, when, and if such payments are
paid.

     Section 3.  Expenses.  In addition to the compensation described in Section
     --------------------
2 above, the Company agrees to promptly reimburse us, upon request from time to
time, not more than monthly, for all out-of-pocket expenses incurred (including,
without limitation, all travel and lodging expenses, and reasonable fees and
disbursements of any counsel, consultants and advisors retained by us with the
Company's consent) in connection with our services pursuant to this agreement;
provided however, that unless otherwise consented to in writing by the Company
----------------
in advance such expenses shall not exceed $10,000 in the aggregate or $1,000 on
a singular basis.

     Section 4. Indemnity. Because we will be acting on the Company's behalf, it
     --------------------
is our practice to receive indemnification. A copy of our standard
indemnification provisions (the

                                       3
<PAGE>

"Indemnification Provisions") is attached to this agreement and is incorporated
herein and made a part hereof.

     Section 5. Termination of Engagement. Commonwealth's engagement hereunder
     ------------------------------------
may be terminated by either the Company or Commonwealth at any time, with or
without cause, upon written advice to that effect to the other party; provided,
                                                                      --------
however, that notwithstanding any such termination, Commonwealth will be
-------
entitled to 100% of its full fee under Section 2 hereof in the event that at any
time prior to the expiration of 9 months after such termination, a Sale
Transaction is consummated with any party introduced to the Company by
Commonwealth, or who the Company requested that we provide any services
hereunder in connection therewith during the term of Commonwealth's engagement
hereunder ("Commonwealth Prospects"). Not more than 10 business days after
termination, Commonwealth shall provide in writing its proposed list of
Commonwealth Prospects which shall be binding unless the Company provides a
written objection within 10 days of receipt whereupon any dispute shall be
resolved in accordance with Section 7 herein. The provisions of this Section 5
and Sections 2, 3 and 4 hereof shall survive such termination. Upon termination,
Commonwealth agrees to use its reasonable best efforts to return all Information
to the Company.

     Section 6. Successors and Assigns. The benefits of this agreement shall
     ---------------------------------
inure to the respective successors and assigns of the parties hereto and of the
indemnified parties hereunder and their successors and assigns and
representatives, and the obligations and liabilities assumed in this agreement
by the parties hereto shall be binding upon their respective successors and
assigns; provided, that the rights and obligations of either party under this
agreement may not be assigned without the prior written consent of the other
party hereto and any other purported assignment shall be null and void.

     Section 7.  Miscellaneous.
     -------------------------

     (a) The validity and interpretation of this Agreement shall be governed by
the law of the State of New York applicable to agreements made and to be fully
performed therein. Commonwealth and the Company will attempt to settle any claim
or controversy arising out of this Agreement through consultation and
negotiation in good faith and a spirit of mutual cooperation. If those attempts
fail, then the dispute will be mediated by a mutually acceptable mediator to be
chosen by Commonwealth and the Company within 15 days after written notice from
either party demanding mediation. Neither party may unreasonably withhold
consent to the selection of a mediator, and the parties will share the costs of
the mediation equally. Any dispute which the parties cannot resolve through
negotiation or mediation within six months of the date of the initial demand for
it by one of the parties may then be submitted to binding arbitration under the
rules of the American Arbitration Organization of New York for resolution. The
use of mediation will not be construed under the doctrine of latches, waiver or
estoppel to affect adversely the rights of either party. Nothing in this
paragraph will prevent either party from resorting to judicial proceedings if
(a) good faith efforts to resolve the dispute under these procedures have been
unsuccessful or (b) interim relief from a court is necessary to prevent serious
and irreparable injury.

                                       4
<PAGE>

     (b) The Company expressly acknowledges that all opinions and advice
(written or oral) given by Commonwealth to the Company in connection with
Commonwealth's engagement are intended solely for the benefit and use of the
Company.

     (c) The Company is a sophisticated business enterprise that has retained
Commonwealth for the limited purposes set forth in this Agreement, and the
parties acknowledge and agree that their respective rights and obligations are
contractual in nature. Each party disclaims an intention to impose fiduciary
obligations on the other by virtue of the engagement contemplated by the
Agreement, and each party agrees that there is no fiduciary relationship between
them.

This Agreement constitutes the entire agreement of the parties with respect to
the matters herein referred and supersedes all prior agreements and
understandings, written and oral, between the parties with respect to the
subject matter hereof including that certain engagement letter dated June 5,
2000, and that certain Placement Agency Agreement dated June 23, 2000, between
the Company and Commonwealth. Neither this Agreement nor any term hereof may be
changed, waived or terminated orally, except by an instrument in writing signed
by the party against which enforcement of the change, waiver or termination is
sought.

                                       5
<PAGE>

Please confirm that the foregoing is in accordance with your understandings and
agreements with Commonwealth Associates, L.P. by signing and returning to
Commonwealth the two copies of this letter enclosed herewith.

                                        Very truly yours,

                                        COMMONWEALTH ASSOCIATES, L.P.

                                        By:  /s/ Joseph P. Wynne
                                           -------------------------------

ACCEPTED AND AGREED AS OF
THE DATE FIRST ABOVE WRITTEN:

drkoop.com, Inc.

By: /s/ Donald W. Hackett
   -------------------------------

                                       6
<PAGE>

                           INDEMNIFICATION PROVISIONS

     drkoop.com, Inc. (the "Company") agrees to indemnify and hold harmless
Commonwealth Associates, L.P. ("Commonwealth") against any and all losses,
claims, damages, obligations, penalties, judgments, awards, liabilities, costs,
expenses and disbursements (and any and all actions, suits, proceedings and
investigations in respect thereof and any and all legal and other costs,
expenses and disbursements in giving testimony or furnishing documents in
response to a subpoena or otherwise), including, without limitation, the costs,
expenses and disbursements, reasonably incurred, as and when incurred, of
investigating, preparing or defending any such action, suit, proceeding or
investigation (whether or not in connection with litigation in which
Commonwealth is a party), directly or indirectly, caused by, relating to, based
upon, arising out of, or in connection with Commonwealth's acting for the
Company in connection with the Agreement, dated July 25, 2000, between the
Company and Commonwealth to which these indemnification provisions are attached
and form a part (the "Agreement"), except to the extent primarily caused by the
gross negligence or willful misconduct of Commonwealth. The Company also agrees
that Commonwealth shall not have any liability (whether direct or indirect, in
contract or tort or otherwise) to the Company for or in connection with the
engagement of Commonwealth, except to the extent that any such liability is
found in a final judgment by a court of competent jurisdiction (not subject to
further appeal) to have resulted primarily from Commonwealth's gross negligence
or willful misconduct.

     The indemnification provisions shall be in addition to any liability which
the Company may otherwise have to Commonwealth or the persons indemnified below
in this sentence and shall extend to the following: Commonwealth, its affiliated
entities, partners, employees, legal counsel, agents and controlling persons
(within the meaning of the federal securities laws), and the officers,
directors, employees, legal counsel, agents and controlling persons of any of
them. All references to Commonwealth in these indemnification provisions shall
be understood to include any and all of the foregoing.

     If any action, suit, proceeding or investigation is commenced, as to which
Commonwealth proposes to demand indemnification, it shall notify the Company
with reasonable promptness; provided, however, that any failure by
                            --------  -------
Commonwealth to notify the Company shall not relieve the Company from its
obligations hereunder except to the extent that the Company is materially
prejudiced thereby. If the Company so elects, or is requested by Commonwealth,
the Company will assume the defense of such action, suit, proceeding or
investigation, including the employment of counsel reasonably acceptable to
Commonwealth, and the payment of the reasonable fees and disbursements of such
counsel. In the event, however, that the Company fails to promptly assume the
defense thereof with counsel reasonably acceptable to Commonwealth, or
Commonwealth determines in its reasonable judgment that it has one or more
material defenses different than or in addition to those of the Company, then
Commonwealth shall have the right to retain one counsel (in addition to any
local counsel) of its own choice to represent it, and the Company shall pay the
reasonable fees, expenses and

                                       7
<PAGE>

disbursements of such counsel; and such counsel shall, to the extent consistent
with its professional responsibilities, cooperate with the Company and any
counsel designated by the Company. The Company shall not be liable for any
settlement of any claim against Commonwealth without the Company's prior written
consent, which consent shall not be unreasonably withheld. The Company shall
not, without the prior written consent of Commonwealth, which shall not be
unreasonably withheld, settle or compromise any claim, or permit a default or
consent to the entry of any judgment in respect thereof, unless such settlement,
compromise or consent includes, as a unconditional term thereof, the giving by
the claimant to Commonwealth of an unconditional release from all liability in
respect of such claim.

     In order to provide for just and equitable contribution, if a claim for
indemnification pursuant to these indemnification provisions is made but it is
found in a final judgment by a court of competent jurisdiction (not subject to
further appeal) that such indemnification may not be enforced in such case, even
though the express provisions hereof provide for indemnification in such case,
then the Company, on the one hand, and Commonwealth, on the other hand, shall
contribute to the losses, claims, damages, obligations, penalties, judgments,
awards, liabilities, costs, expenses, and disbursements to which the indemnified
persons may be subject in accordance with the relative benefits received by the
Company, on the one hand, and Commonwealth, on the other hand, and also the
relative fault of the Company, on the one hand, and Commonwealth, on the other
hand, in connection with the statements, acts or omissions which resulted in
such losses, claims, damages, obligations, penalties, judgments, awards,
liabilities, costs, expenses or disbursements and the relevant equitable
considerations shall also be considered. No person found liable for a fraudulent
misrepresentation shall be entitled to contribution from any person who is not
also found liable for such fraudulent misrepresentation. Notwithstanding the
foregoing, Commonwealth shall not be obligated to contribute any amount
hereunder that exceeds the amount of fees previously received by Commonwealth
pursuant to this Agreement.

     Neither termination nor completion of the engagement of Commonwealth
referred to above shall affect these indemnification provisions which shall then
remain operative and in full force and effect.

                                       8<PAGE>

                                                                   EXHIBIT 10.82

                               drkoop.com, Inc.
                           7000 N. Mopac, Suite 400
                             Austin, Texas  78739

                                August 22, 2000

Prime Ventures, LLC
233 Wilshire Boulevard, Suite 800
Santa Monica CA 90401

Ladies and Gentlemen:

          This letter agreement will confirm our agreement with respect to
certain stock purchase warrants drkoop.com, Inc. (the "Company") proposes to
issue to you (or your designees) as an inducement, among other things, to your
granting permission to the Company to employ certain of your employees following
the closing of the proposed preferred stock financing described in the
Confidential Private Placement Memorandum dated July 12, 2000 and the related
Cumulative Supplement dated August 16, 2000, as corrected through the date
hereof (the "Permanent Financing").

          The Company wishes to employ Messrs. Richard M. Rosenblatt, Edward A.
Cespedes and Stephen Plutsky (collectively, the "New Employees") as officers of
the Company.  In consideration of your decision to permit the Company to employ
the New Employees, the Company will issue and deliver to you, within two
business days after the date upon which the New Employees become employed by the
Company, stock purchase warrants to purchase 3,629,000 shares of common stock of
the Company in the form attached hereto as Exhibit A  (the "Category A
                                           ---------
Warrants").

          In consideration of your assistance with evaluating and structuring
the Permanent Financing, the Company will issue and deliver to you (or your
designees, a list of which shall be provided in writing to the Company), within
two business days after the date of the final closing of the Permanent Financing
stock purchase warrants to purchase 2,700,000 shares of common stock of the
Company in the form attached hereto as Exhibit B  (the "Category B Warrants" and
                                       ---------
together with the Category A Warrants, the "Warrants").

          The Company and you make, and each of your designees shall make prior
to the issuance of any Warrants to such designee, the respective representations
and warranties with respect to the issuance of the Warrants set forth on Annex A
                                                                         -------
which constitutes a part of this letter agreement.
<PAGE>

          You agree and acknowledge that the issuance of the Warrants to you
(and your designee(s)) represents full and complete payment for your assistance
to the Company in connection with the Permanent Financing and the grant of your
permission to the Company to hire the New Employees.

          The Company agrees to reimburse you for all reasonable fees and
disbursements of your legal counsel not to exceed $75,000.00 incurred in
connection with the employment by the Company of your employees and your
assistance to the Company in connection with the Permanent Financing.  This
letter agreement shall terminate and be of no further force or effect in the
event that the Permanent Financing has not closed and the New Employees have not
become employees of the Company.

          This letter agreement contains the entire agreement between you and
the Company with respect to all matters addressed herein and will supersede and
replace all prior agreements, written or oral, between the parties relating to
the foregoing. This letter agreement will be governed by and construed in
accordance with the laws of the State of Texas without regard to conflicts of
law provisions and principles of that state.  Neither this letter agreement nor
any provisions hereof may be waived, amended, modified or supplemented except
pursuant to an agreement in writing executed by the party against whom
enforcement of such waiver, amendment, modification or supplement is being
sought.

               [Balance of Page Intentionally Left Blank]

                                       2
<PAGE>

     Please confirm that the foregoing correctly sets forth the agreement
between us by signing in the space provided below. This letter agreement may be
executed in counterpart.

                              Sincerely yours,

                              drkoop.com, Inc.

                              By:  /s/ Donald W. Hackett
                                   -----------------------------
                                   Name:   Donald W. Hackett
                                   Title:  Chief Executive Officer

The foregoing is hereby acknowledged and agreed to as
of the date first above written.

By:  /s/ Richard M. Rosenblatt
     -----------------------------
Name:  Richard M. Rosenblatt
Title: Chief Executive Officer

                                       3

Source: [{"source": "alea-institute/alea-institute/kl3m-data-edgar-agreements/train-00014-of-00352.parquet"}, [{"source": "alea-institute/alea-institute/kl3m-data-edgar-agreements/train-00014-of-00352.parquet"}]]