<PAGE>

                                                                  Exhibit 10.24

                            CHANGE IN TERMS AGREEMENT

<TABLE>
<CAPTION>

------------------ ------------ ------------- ----------- ---------- ------------- ----------- ----------- -----------
    Principal       Loan Date     Maturity     Loan No.     Call      Collateral    Account     Officer     Initials
<S>                 <C>          <C>           <C>          <C>       <C>           <C>         <C>         <C>
  $297,500,000                   11/30/2004      9002        4AO         3112       2350106       RHH
------------------ ------------ ------------- ----------- ---------- ------------- ----------- ----------- -----------
</TABLE>

-------------------------------------------------------------------------------
References in the shaded area are for Lender's use only and do not limit the
applicability of this document to any particular loan or item.
-------------------------------------------------------------------------------

BORROWER: INFORMEDIX, INC.                      LENDER: United Bank
          5920 Hubbard Drive                            2071 Chain Bridge Road
          Rockville, MD 20852                           Vienna, VA 22182

===============================================================================
                        IMPORTANT NOTICE
THIS INSTRUMENT CONTAINS A CONFESSION OF JUDGMENT PROVISION WHICH CONSTITUTES A
WAIVER OF IMPORTANT RIGHTS YOU MAY HAVE AS A DEBTOR AND ALLOWS THE CREDITOR TO
OBTAIN A JUDGMENT AGAINST YOU WITHOUT ANY FURTHER NOTICE.
===============================================================================

Principal Amount: $297,500.00                 Date of Agreement; August 1, 2001

DESCRIPTION OF EXISTING INDEBTEDNESS. All of the Indebtedness evidenced by that
certain PROMISSORY NOTE from Borrower to Lender dated May 18, 2001, in the
principal amount of $297,500.00, which is a modification for previous credit
agreements between Borrower and Lender, including but not limited to the
following: a CHANGE IN TERMS AGREEMENT dated February 6, 2000 In the principal
amount of $297,600.00, and a PROMISSORY NOTE dated July 6, 1998 In the principal
amount of $297,500.00.

DESCRIPTION OF COLLATERAL. In addition to any and all other collateral that may
be pledged either now or in the future, the Indebtedness described herein Is
secured by all of the following: (a) that certain COMMERCIAL SECURITY AGREEMENT
dated July 6, 1998, as restated by subsequent agreements of the same title and
dated respectively May 18, 2001, (b) that certain COMMERCIAL PLEDGE AND SECURITY
AGREEMENT from Leslie Z. Benet and Carol A. Benet dated May 18, 2001, (c) that
certain ASSIGNMENT OF DEPOSIT ACCOUNT from James E. Eden dated May 18, 2001, (d)
that certain ASSIGNMENT OF DEPOSIT ACCOUNT from Richard D. Gibbs, Jr. dated July
6, 1998, and (a) that certain ASSIGNMENT OF DEPOSIT ACCOUNT from Peter L.
Kreeger dated May 18,2001.

DESCRIPTION OF CHANGE IN TERMS. The maturity date, and repayment schedule have
been modified in accordance with the terms of this agreement.

PROMISE TO PAY. INFORMEDIX, INC. ("Borrower") promises to pay to United Bank
(`Lender"), or order, in lawful money of the United States of America, the
principal amount of Two Hundred Ninety Seven Thousand Five Hundred & 00/100
Dollars ($297,500.00), together with interest on the unpaid principal balance
from July 31,2001, until paid in full.

PAYMENT. Subject to any payment changes resulting from changes in the index,
Borrower will pay this loan In accordance with the following payment schedule:

         4 consecutive monthly Interest payments, beginning August 31, 2001,
         with interest calculated on the unpaid principal balances at an
         interest rate of 1.000 percentage points over the Index described
         below; 36 consecutive monthly principal payments of $8,263.89 each,
         beginning December 30, 2001, with interest calculated on the unpaid
         principal balances at an interest rate of 1.000 percentage points over
         the Index described below; and 38 consecutive monthly interest
         payments, beginning December 30, 2001, with interest calculated on the
         unpaid principal balances at an interest rate of 1.000 percentage
         points over the Index described below. Borrower's final payment of
         $8,263.89 will be due on November 30, 2004. This estimated final
         payment is based on the assumption that all payments will be made
         exactly as scheduled and that the Index does not change; the actual
         final payment will be for all principal and accrued interest not yet
         paid, together with any other unpaid amounts under this Agreement.

<PAGE>

The annual interest rate for this Agreement Is computed on a 365/360 basis; that
is, by applying the ratio of the annual interest rate over a year of 360 days,
multiplied by the outstanding principal balance, multiplied by the actual number
of days the principal balance is outstanding. Borrower will pay Lender at
Lender's address shown above or at such other place as Lender may designate in
writing. Unless otherwise agreed or required by applicable law, payments will be
applied first to accrued unpaid interest, then to principal, and any remaining
amount to any unpaid collection costs and late charges.

VARIABLE INTEREST RATE. The interest rate on this Agreement is subject to change
from time to time based on changes in an independent index which is the Prime
Lending Rate as published in the "Money Rates" section of the Wall Street
Journal (the "Index"). The Index is not necessarily the lowest rate charged by
Lender on its loans. If the Index becomes unavailable during the term of this
loan, Lender may designate a substitute Index after notice to Borrower. Lender
will tell Borrower the current index rate upon Borrower's request. Borrower
understands that Lender may make loans based on other rates as well. The
interest rate change will not occur more often than each DAY. The Index
currently is 6.760% per annum. The interest rate or rates to be applied to the
unpaid principal balance of this Agreement will be the rate or rates set forth
above in the "Payment" section. NOTICE: Under no circumstances will the interest
rate on this Agreement be more than the maximum rate allowed by applicable law.
Whenever increases occur in the interest rate, Lender, at its option, may do one
or more of the following: (a) increase Borrower's payments to ensure Borrower's
loan will pay off by its original final maturity date, (b) increase Borrower's
payments to cover accruing Interest, (c) increase the number of Borrower's
payments, and (d) continue Borrower's payments at the same amount and increase
Borrower's final payment.

PREPAYMENT. Borrower may pay without penalty all or a portion of the amount owed
earlier than it is due. Early payments will not, unless agreed to by Lender in
writing, relieve Borrower of Borrower's obligation to continue to make payments
under the payment schedule. Rather, they will reduce the principal balance due
and may result in Borrower making fewer payments.

LATE CHARGE. It a payment is 7 days or more late, Borrower will be charged
5.000% of the regularly scheduled payment.

DEFAULT. Borrower will be in default if any of the following happens: (a)
Borrower falls to make any payment when due. (b) Borrower breaks any promise
Borrower has made to Lender, or Borrower fails to comply with or to perform when
due any other term, obligation, covenant, or condition contained in this
Agreement or any agreement related to this Agreement, or in any other agreement
or loan Borrower has with Lender. (c) Borrower defaults under any loan,
extension of credit, security agreement, purchase or sales agreement, or any
other agreement, in favor of any other creditor or person that may materially
affect any of Borrower's property or Borrower's ability to repay this Note or
perform Borrower's obligations under this Note or any of the Related Documents.
(d) Any representation or statement made or furnished to Lender by Borrower or
on Borrower's behalf is false or misleading in any material respect either now
or at the time made or furnished. (e) Borrower becomes insolvent, a receiver is
appointed for any part of Borrower's property, Borrower makes an assignment for
the benefit of creditors, or any proceeding is commenced either by Borrower or
against Borrower under any bankruptcy or insolvency laws. (f) Any creditor tries
to take any of Borrower's property on or in which Lender has a lien or security
interest. This includes a garnishment of any of Borrower's accounts with Lender.
(g) Any guarantor dies or any of the other events described in this default
section occurs with respect to any guarantor of this Agreement. (h) A material
adverse change occurs in Borrower's financial condition or Lender believes the
prospect of payment or performance of the Indebtedness is impaired. (i) Lender
in good faith deems itself Insecure.

If any default, other than a default in payment, is curable and if Borrower has
not been given a notice of a breach of the same provision of this Agreement
within the preceding twelve (12) months, it may be cured (and no event of
default will have occurred) if Borrower, after receiving written notice from
Lender demanding cure of such default: (a) cures the default within fifteen (15)
days; or (b) if the cure requires more than fifteen (15) days, immediately
initiates steps which Lender deems in Lender's sole discretion to be sufficient
to cure the default and thereafter continues and completes all reasonable and
necessary steps sufficient to produce compliance as soon as reasonably
practical.


<PAGE>

LENDER'S RIGHTS. Upon default, Lender may declare the entire unpaid principal
balance on this Agreement and alt accrued unpaid interest, together with all
other applicable fees, costs and charges, if any, immediately due and payable,
without notice, and then Borrower will pay that amount. Upon default, or if this
Agreement is not paid at final maturity, Lender, at its option, may add any
unpaid accrued interest to principal and such sum will bear Interest therefrom
until paid, at the rate provided in this Agreement. Furthermore, subject to any
limits under applicable law, upon default, Borrower also agrees to pay Lender's
attorney fees equal to 15.000% of the principal balance due on the Note, and all
of Lender's other collection expenses, whether or not there is a lawsuit and
Including without limitation legal expenses for bankruptcy proceedings. This
Agreement shall be governed by, construed and enforced in accordance with the
laws of the Commonwealth of Virginia.

CONFESSION OF JUDGMENT. Upon a default in payment of the Indebtedness at
maturity, whether by acceleration or otherwise, Borrower hereby irrevocably
authorizes and empowers Neil I. Title and Julian Karpoff (either one of whom may
act alone) as Borrower's attorney-in-fact to appear in the Arlington County
clerk's office and to confess judgment against Borrower for the unpaid amount of
this Agreement as evidenced by an affidavit signed by an officer of Lender
setting forth the amount then due, plus attorneys' fees as provided in this
Agreement, plus costs of suit, and to release all errors, and waive all rights
of appeal. If a copy of this Agreement, verified by an affidavit, shall have
been filed in the proceeding, it will not be necessary to file the original as a
warrant of attorney. Borrower waives the right to any stay of execution and the
benefit of all exemption laws now or hereafter in effect. No single exercise of
the foregoing warrant and power to confess judgment will be deemed to exhaust
the power, whether or not any such exercise shall be held by any court to be
invalid, voidable, or void; but the power will continue undiminished and may be
exercised from time to time as Lender may elect until all amounts owing on this
Agreement have been paid In full.

RIGHT OF SETOFF. Borrower grants to Lender a contractual security interest in,
and hereby assigns, conveys, delivers, pledges, and transfers to Lender all
Borrower's right, title and interest in and to, Borrower's accounts with Lender
(whether checking, savings, or some other account), including without limitation
all accounts held jointly with someone else and all accounts Borrower may open
in the future, excluding however all IRA and Keogh accounts, and all trust
accounts for which the grant of a security interest would be prohibited by law.
Borrower authorizes Lender, to the extent permitted by applicable law, to charge
or setoff all sums owing on this Agreement against any and all such accounts.

CONTINUING VALIDITY. Except as expressly changed by this Agreement, the terms of
the original obligation or obligations, including all agreements evidenced or
securing the obligation(s), remain unchanged and in full force and effect.
Consent by Lender to this Agreement does not waive Lender's right to strict
performance of the obligation(s) as changed, nor obligate Lender to make any
future change in terms. Nothing in this Agreement will constitute a satisfaction
of the obligation(s). It is the intention of Lender to retain as liable parties
all makers and endorsers of the original obligation(s), including accommodation
parties, unless a party is expressly released by Lender in writing. Any maker or
endorser, including accommodation makers, will not be released by virtue of this
Agreement. If any person who signed the original obligation does not sign this
Agreement below, then all persons signing below acknowledge that this Agreement
is given conditionally, based on the representation to Lender that the
non-signing party consents to the changes and provisions of this Agreement or
otherwise will not be released by it. This waiver applies not only to any
initial extension, modification or release, but also to all such subsequent
actions.

MISCELLANEOUS PROVISIONS. Lender may delay or forgo enforcing any of its rights
or remedies under this Agreement without losing them. Borrower and any other
person who signs, guarantees or endorses this Agreement, to the extent allowed
by law, waive presentment, demand for payment, protest and notice of dishonor.
Upon any change in the terms of this Agreement, and unless otherwise expressly
stated in writing, no party who signs this Agreement, whether as maker,
guarantor, accommodation maker or endorser, shall be released from liability.
All such parties agree that Lender may renew or extend (repeatedly and for any
length of time) this loan, or release any party or guarantor or collateral; or
impair, fall to realize upon or perfect Lender's security interest in the
collateral; and take any other action deemed necessary by Lender without the
consent of or notice to anyone. All such parties also agree that Lender may
modify this loan without the consent of or notice to anyone other than the party
with whom the modification is made.


<PAGE>

PRIOR TO SIGNING THIS AGREEMENT, BORROWER READ AND UNDERSTOOD ALL THE PROVISIONS
OF THIS AGREEMENT, INCLUDING THE VARIABLE INTEREST RATE PROVISIONS. BORROWER
AGREES TO THE TERMS OF THE AGREEMENT AND ACKNOWLEDGES RECEIPT OF A COMPLETED
COPY OF THE AGREEMENT.

BORROWER:

By: /s/ Bruce Kehr
    ---------------------------
    Bruce A. Kehr, President

===============================================================================
Variable Rate. Irregular. LASER PRO, Reg. U.S. Pat. & TM. Off., Var. 3.26(c)2001
CFI ProServices, Inc. All rights reserved. [VA-D20 F3.26b INFORM.LN)


<PAGE>


                     DISBURSEMENT REQUEST AND AUTHORIZATION

<TABLE>
<CAPTION>

------------------ ------------ ------------- ----------- ---------- ------------- ----------- ----------- -----------
    Principal       Loan Date     Maturity     Loan No.     Call      Collateral    Account     Officer     Initials
<S>                 <C>          <C>           <C>          <C>       <C>           <C>         <C>         <C>
  $297,500,000                   11/30/2004      9002        4AO         3112       2350106       RHH
------------------ ------------ ------------- ----------- ---------- ------------- ----------- ----------- -----------
</TABLE>

-------------------------------------------------------------------------------
References in the shaded area are for Lender's use only and do not limit the
applicability of this document to any particular loan or item.
-------------------------------------------------------------------------------

BORROWER: INFORMEDIX, INC.                      LENDER: United Bank
          5920 Hubbard Drive                            2071 Chain Bridge Road
          Rockville, MD 20852                           Vienna, VA 22182
===============================================================================

LOAN TYPE. This is a Variable Rate (based on Prime Lending Rate as published in
the "Money Rates" section of the Wall Street Journal), Irregular Payment Loan to
a Corporation for $297,500.00 due on November 30, 2004.

PRIMARY PURPOSE OF LOAN.  The primary purpose of this loan is for:

         / / Personal, Family, or Household Purposes or Personal Investment.

         /X/ Business (Including Real Estate Investment).

SPECIFIC PURPOSE. The specific purpose of this loan is; Additional 90-days of
interest only to allow time for company to obtain additional equity financing.

DISBURSEMENT INSTRUCTIONS. Borrower understands that no loan proceeds will be
disbursed until all of Lender's conditions for making the loan have been
satisfied. Please disburse the loan proceeds of $297,500.00 as follows:

           Amount paid on Borrower's account:                       $297,500.00
           $297,500.00 Payment on Loan # 2350106--9002 Modif
                                                                    -----------
           Note Principal:                                          $297,500.00

FINANCIAL CONDITION. BY SIGNING THIS AUTHORIZATION, BORROWER REPRESENTS AND
WARRANTS TO LENDER THAT THE INFORMATION PROVIDED ABOVE IS TRUE AND CORRECT AND
THAT THERE HAS BEEN NO MATERIAL ADVERSE CHANGE IN BORROWER'S FINANCIAL CONDITION
AS DISCLOSED IN BORROWER'S MOST RECENT FINANCIAL STATEMENT TO LENDER. THIS
AUTHORIZATION IS DATED AUGUST 1,2001.



BORROWER:

By:  /s/ Bruce Kehr_________________
    Bruce A. Kehr, President

===============================================================================
Variable Rate. Irregular. LASER PRO, Reg. U.S. Pat. & TM. Off., Var. 3.26(c)2001
CFI ProServices, Inc. All rights reserved. [VA-D20 F3.26b INFORM.LN)