<PAGE>   1
                                                                   EXHIBIT 10.12

                         CONFIDENTIAL TREATMENT REQUEST

     Confidential Portions Of This Agreement Which Have Been Redacted Are Marked
With Brackets ("[***]"). The Omitted Material Has Been Filed Separately With The
Securities And Exchange Commission.

                       MANUFACTURING AND SUPPLY AGREEMENT


     THIS MANUFACTURING AND SUPPLY AGREEMENT (the "Agreement") is made and
entered into this 23rd day of April, 1999 (the "Effective Date"), by and between
HORIZON PHARMACEUTICAL CORPORATION ("Horizon") and MIKART, INC. ("Mikart").
Mikart is a Georgia corporation with its principal place of business at 1750
Chattahoochee Avenue, Atlanta, Georgia 30318. Horizon is a Delaware corporation
with its principal place of business at 660 Hembree Parkway, Suite 106, Roswell,
Georgia 30076.

                                   BACKGROUND:

     Subject to the terms and conditions contained in this Agreement, Horizon
desires to engage Mikart to manufacture the "Products" (as hereinafter defined)
for commercial distribution by Horizon, and Mikart desires to accept such
appointment.

     NOW, THEREFORE, FOR AND IN CONSIDERATION of the premise, Ten Dollars
($10.00) in hand paid, the mutual promises, covenants and agreements contained
herein, and other good and valuable consideration, the receipt and sufficiency
of which are hereby acknowledged, the parties hereto hereby agree as follows:

                                    ARTICLE 1
                                   DEFINITIONS
                                   -----------

     The following words, terms and phrases, when used herein, shall have the
following respective meanings:

     1.1 "Batch" shall mean either: (a) the quantity of [***] tablets of the
Product to be marketed and sold as "Robinul;" or (b) the quantity of [***]
tablets of the Product to be marketed and sold as "Robinul Forte."

     1.2 "Contract Year" shall mean a twelve (12) consecutive month period after
the Qualification Date and during the term of this Agreement. The first Contract
Year shall commence as of the Qualification Date, and subsequent Contract Years
shall commence on each anniversary of the Qualification Date.

     1.3 "FDA" shall mean the United States Food and Drug Administration or any
successor agency thereof.

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<PAGE>   2



     1.4 "Health Registrations" shall mean the NDA issued by the FDA with
respect to the Products and any other governmental or regulatory consents,
registrations, approvals or permits necessary to sell or manufacture the
Products in the Territory.

     1.5 "Products" shall mean Glycopyrrolate 1 mg U.S.P. tablets (regardless of
how packaged), which Product shall be marketed and sold by Horizon as "Robinul,"
and Glycopyrrolate 2 mg U.S.P. tablets (regardless of how packaged), which
Product shall be marketed and sold by Horizon as "Robinul Forte."

     1.6 "Qualification Date" shall mean the date on which Mikart satisfactorily
completes its validation and testing pursuant to Article 2 of this Agreement
such that it becomes authorized to begin manufacturing the Products under the
Health Registrations in accordance with the terms of this Agreement.

     1.7 "Specifications" shall mean the specifications for the manufacturing,
packaging and labeling of the Products described on Exhibit A attached hereto
and incorporated herein by reference.

     1.8 "Territory" shall mean the United States of America and its territories
and such other locations as may be designated by the parties hereto pursuant to
Section 2.6.

                                    ARTICLE 2
                             VALIDATION AND TESTING
                             ----------------------

     2.1 General. Mikart shall become authorized to manufacture and package the
Products under the Health Registrations as contemplated by Section 2.3. To
accomplish the same, it is the current intention of Mikart and Horizon to effect
a transfer according to the SUPAC Guidelines; provided, however, if such a
transfer cannot be accomplished, Mikart shall (with Horizon paying Mikart's
reasonable out-of-pocket expenses therefor) develop an alternative manufacturing
process and prepare and file on behalf of Horizon with the FDA and any other
applicable agency or authority supplements to the Health Registrations which,
when and if approved, would permit Mikart to manufacture the Products pursuant
to this Agreement. In any event, Mikart will use all reasonable efforts to
become authorized to manufacture the Products as soon as reasonably practicable
after the Effective Date.

     2.2 Ribbon Blender. Within sixty (60) days after the Effective Date, Mikart
will lease (for a period of five (5) years with monthly rental payments in the
amount of $405.00) and have installed a ribbon blender with a minimum working
capacity of thirty (30) cubic feet (the "Blender") for use in manufacturing the
Products. On or before the fifth (5th) day of such month during the term of such
lease, Horizon shall pay to Mikart an amount equal to $405.00, and Horizon shall
have the right, at its sole expense, to require Mikart to purchase the Blender
on Horizon's behalf.

     2.3 Validation. After its receipt of the Blender, Mikart shall begin
analytical methods development validation and process and cleaning validation

                                       2
<PAGE>   3
                                        [***] - CONFIDENTIAL TREATMENT REQUESTED

with respect to the Products. All of Mikart's costs incurred in connection
therewith (up to a maximum aggregate amount of [$***]) shall be billed to and
paid by Horizon on a quarterly basis (but based on a three (3) year amortization
schedule).

     2.4 Testing. Upon its successful completion of the validations described in
Section 2.3, Mikart will conduct stability testing on the Products as required
by federal law. All of Mikart's costs incurred in connection therewith shall be
periodically billed to and paid by Horizon on a quarterly basis (but based on a
three (3) year amortization schedule).

     2.5 Health Registrations. Horizon shall maintain the Health Registrations
in full force and effect at all times during the term of this Agreement;
provided, however, upon the reasonable request of Horizon, Mikart shall assist
Horizon in connection therewith; provided further in exchange therefor Horizon
will pay Mikart its standard fees therefor. Mikart hereby acknowledges and
agrees that the Health Registrations are owned by, in the name of and for the
benefit of Horizon and that Mikart has no rights in or to any of the Health
Registrations, except to the extent it is expressly authorized to manufacture
the Products for Horizon pursuant to this Agreement.

     2.6 Additional Locations. In the event Horizon desires to market,
distribute or sell the Products in any location not set forth in Section 1.8 (or
previously designated pursuant to this Section 2.6), then Mikart shall, at
Horizon's request, cooperate in good faith with Horizon to obtain any Health
Registrations necessary or appropriate therefor (and Horizon shall pay all of
Mikart's reasonable out-of-pocket expenses therefor); provided, however, Horizon
shall not market, distribute or sell any Products in such locations unless and
until Mikart obtains such Health Registrations.

                                    ARTICLE 3
                                   MANUFACTURE
                                   -----------

     3.1 Exclusivity. Subject to the terms and conditions contained herein,
Mikart shall manufacture, package and sell the Products exclusively to Horizon
from and after the Qualification Date and throughout the remainder of the term
of this Agreement (the "Manufacturing Period"), and Horizon shall purchase
exclusively from Mikart all of Horizon's requirements of the Products during the
Manufacturing Period. Except as otherwise permitted hereby, Mikart agrees not to
manufacture, package or sell to any other person or entity during the term of
this Agreement in any unit size or strength any other product which contains the
active ingredient Glycopyrrolate and either (a) contains no other active
ingredient, or (b) is approved for an indication for which the Products are or
become approved. Horizon hereby agrees that, in the event it desires to sell,
market or distribute any other product which contains the active ingredient
Glycopyrrolate during the term of this Agreement, it will negotiate exclusively
with Mikart regarding the manufacture thereof (which would be on commercial
terms other than price substantially similar to those contained herein) for a
period of at least ninety (90) days prior to negotiating therefor with any other
person or entity.

     3.2 Limited Warranties. Mikart hereby represents and warrants to Horizon
that the Products manufactured and sold to Horizon hereunder shall conform to

                                      3
<PAGE>   4

the Specifications and shall be free of all defects in materials and
workmanship. The Products, when manufactured, packaged and sold to Horizon shall
comply with all applicable federal, state and local laws, rules and regulations
in the Territory, including without limitation the current Good Manufacturing
Practices as published and amended from time to time by the FDA, and Mikart's
manufacturing and storage facilities shall comply with all applicable federal
state and local laws, rules and regulations in the Territory. EXCEPT AS SET
FORTH IN THIS SECTION 3.2, MILKART MAKES NO OTHER REPRESENTATIONS OR WARRANTIES,
EXPRESS OR IMPLIED, REGARDING THE PRODUCTS MANUFACTURED BY IT HEREUNDER AND
SPECIFICALLY DISCLAIMS ALL SUCH OTHER REPRESENTATIONS AND WARRANTIES, INCLUDING,
WITHOUT LIMITATION, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
PARTICULAR PURPOSE. With respect to each batch of a Product manufactured
hereunder, this Section 3.2 shall remain effective until the expiration date
noted on such Product.

     3.3 Quality Control.

          (a) Mikart will perform quality control testing on the Products in
     accordance with normal industry standards to determine whether such
     Products conform to the Specifications. Contemporaneously with each
     shipment of Product hereunder, Mikart will provide Horizon with a
     certificate of analysis with respect to such Product. In addition, Mikart
     will perform, at Horizon's expense, any and all other testing relating to
     the Products which is reasonably requested by Horizon and promptly provide
     Horizon with the results thereof; provided, however, Horizon shall not be
     responsible for the expenses associated with any such testing which shows
     that such Product does not meet the Specifications.

          (b) In addition, Mikart shall be responsible for conducting an ongoing
     stability program for the Products as required by federal law. Mikart shall
     provide the results of such testing to Horizon in a timely manner as this
     data is generated or received by Mikart. Mikart's cost therefor shall be
     billed to and paid by Horizon on a quarterly basis (but based on a three
     (3) year amortization schedule).

          (c) Mikart will, upon the reasonable request of Horizon, assay any
     Product returned to Horizon by a third party purchaser. Horizon shall
     reimburse Mikart for the costs of any such assay unless the results thereof
     prove the cause of return is as a result of Mikart's negligence or willful
     misconduct or the failure of such Product to comply with the limited
     warranties contained in Section 3.2 hereof.

          (d) In the event that any Batch is subject to a recall, Horizon, at
     its expense, shall conduct the recall, except that Mikart shall reimburse
     Horizon for the costs of such recall (including reimbursing Horizon for the
     Product at the invoice prices paid by Horizon therefor) in the Territory to
     the extent such recall results from the manufacture, packaging or storage
     of such Product by Mikart.

          (e) Each party hereto shall promptly notify the other of any recall of
     either Product which has been directed by it or by any governmental or
     regulatory entity or agency for any reason whatsoever. Such notice shall
     identify the reason for the recall and all relevant details thereof.

                                       4
<PAGE>   5

          (f) Each party hereto shall promptly deliver to the other a copy of
     all notices received by it from the FDA during the term of this Agreement
     relating to the manufacture, packaging, storage or sale of the Products.

          (g) Upon the reasonable advance request of Horizon, Mikart shall
     permit a representative of Horizon to inspect its facilities where the
     Products are manufactured, packaged and stored, provided such
     representative first executes a copy of Mikart's standard visitor
     confidentiality agreement.

     3.4 Packaging Materials. Mikart shall order from time to time, at Horizon's
request and expense, labels, package inserts and other packaging materials in
sufficient quantities to permit the packaging of the Products ordered by Horizon
from time to time hereunder.

     3.5 Trademarks. Mikart acknowledges that the trademarks "Robinul" and
"Robinul Forte" (the "Trademarks") are registered trademarks licensed to
Horizon. Mikart further agrees not to use either of such trademarks except as
specifically authorized by Horizon under this Agreement in connection with the
manufacture, packaging and sale of the Products to Horizon.

                                    ARTICLE 4
                                ORDERS AND SALES
                                ----------------

     4.1 Forecasts. Commencing on the Qualification Date, and thereafter at
least thirty (30) days prior to the commencement of each calendar quarter,
Horizon shall provide Mikart with a non-binding, rolling twelve (12) month
forecast of its requirements for the Products.

     4.2 Purchase Orders. Horizon shall place its orders for the Products no
later than ninety (90) days prior to the requested delivery date using
separately numbered, written purchase orders. Each purchase order must be for
one or more full Batches (provided Horizon shall have the right to specify the
size packaging requirements of each order from among 100 tablet bottles and any
other package sizes agreed to by the parties hereto). Purchase orders shall be
transmitted to Mikart via U.S. mail, private courier, or facsimile transmission.
Each purchase order shall include complete and accurate information with respect
to the requested Product, quantity, sizes, shipment dates, shipment method and
delivery destination. Subject to this Section 4.2, Mikart will ship Product
within five (5) days after the requested shipment date in the corresponding
purchase order. Mikart shall promptly notify Horizon upon its receipt of any
purchase orders containing shipment dates which need to be rescheduled, and
Mikart and Horizon shall work together in good faith to schedule a new shipment
date for such order (which shall not be later than thirty (30) days after the
date requested by Horizon). In addition, Horizon may postpone a requested
shipment date by providing Mikart at least sixty (60) days prior written notice
thereof.


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<PAGE>   6


                                        [***] - CONFIDENTIAL TREATMENT REQUESTED


     4.3 Minimum Purchase. During each Contract Year, Horizon shall purchase
from Mikart the following minimum number of aggregate Batches of Products:

           Contract Year                      Minimum Batches
           -------------                      ---------------
                1                                  [***]
                2                                  [***]
                3                                  [***]
                4                                  [***]
                5                                  [***]

                                    ARTICLE 5
                            PRICES, TERMS OF PAYMENT
                            ------------------------

     5.1 Price. The prices to be paid for the Products by Horizon to Mikart for
shipments made during the first year after the Effective Date shall be based on
a Glycopyrrolate price of $12,000 per kilogram and are set forth below;
provided, however, in the event Mikart's price for Glycopyrrolate changes in any
material manner, the price of the Products shall be increased or decreased (as
the case may be) to reflect such change.

         For Robinul:                 Size                       Price
         ------------                 ----                       -----
                                      100 tablet                 $[***]

         For Robinul Forte:           Size                       Price
         ------------------           ----                       -----
                                      100 tablet                 $[***]

Notwithstanding anything else contained herein to the contrary, within thirty
(30) days after the end of any Contract Year in which Horizon purchases less
than [***] Batches, Horizon shall pay to Mikart an amount equal to the product
of (a) $[***] multiplied by (b) the difference between (i) [***] and (ii) the
number of Batches actually purchased by Horizon in such Contract Year.

     5.2 Price Adjustments. Mikart shall have the right to increase the prices
charged for the Products pursuant to Section 5.1 hereof one time during each
year after the Effective Date to reflect any increase in the costs of goods and
services necessary to manufacture the Product ("Total Product Costs'); provided,
however, in the event Mikart so increases such prices in any such year and after
the effective date thereof, Mikart's cost of raw materials or components for
manufacturing the Products ("Materials Cost") further increases by more than
[***] during such year, Mikart shall have the right, by providing at least sixty
(60) days written notice to Horizon to further increase such prices in such year
by a percentage amount equal to the percentage increase in Total Product Costs
that are attributable to the percentage increase in Materials Cost in excess of
five percent (5%); provided further, that Mikart shall provide Horizon with
documented evidence of any such additional cost increases and shall use its
reasonable efforts to prevent any such cost increases from occurring. In
addition, Mikart shall reduce its prices charged hereunder to reflect any
material decrease in the prices paid by it for the active ingredient raw
materials used to manufacture the Products.

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<PAGE>   7



     5.3 Payment Terms. Mikart shall invoice Horizon for the price of the
Products sold at the time of shipment, and Horizon shall pay each such invoice
within thirty (30) days after its receipt thereof.

     5.4 Exclusivity. Horizon shall not purchase either Product from any person
or entity other than Mikart during the term hereof without the prior written
consent of Mikart, which consent must specifically state that Mikart is
consenting to waive its exclusive rights hereunder. However, in the event that
Mikart notifies Horizon in writing that it will not or cannot supply any
Products ordered by Horizon in accordance with the terms hereof, or in the event
that Mikart has failed to deliver any Products ordered by Horizon within the
period of time required under Section 4.2 (exclusive of any cure period provided
by Section 7.2(a)), then Horizon may purchase a product identical to that of
such Product in the quantity specified in the unfilled purchase order from any
available alternate source without fast obtaining the written consent required
above. In the event Horizon is permitted to purchase Product from any person or
entity other than Mikart in accordance with this Section 5.4, any amounts so
purchased by Horizon shall apply toward the minimum batch purchase obligations
set forth in Section 4.3 for such year, and, upon Horizon's request, Mikart
shall provide reasonable assistance to enable such other person or entity to
manufacture the Products under the Health Registrations (provided Mikart shall
not be required to pay any out-of-pocket costs or expenses in connection
therewith). In the event that said notice or failure occurs on two or more
occasions within a one hundred eighty (180) day period, this Section 5.4 shall
no longer be of any force or effect and Horizon shall be relieved of its
obligations pursuant to Section 4.3 hereof. Nothing in this Section 5.4 shall be
construed so as to limit or eliminate any other remedies available to Horizon in
the event of a breach of Mikart's obligations under this Agreement, including
its obligation to manufacture, package and deliver the Products ordered by
Horizon.

                                    ARTICLE 6
                            SHIPPING DEFECTS, RETURNS
                            -------------------------

     6.1 Shipping. Mikart will ship all Products ordered hereunder to Horizon
f.o.b. Mikart's manufacturing facility, at which point the risk of loss for such
Products will pass to Horizon. Title to such Products shall pass to Horizon only
upon Mikart's receipt of payment in full therefor. Mikart shall ship the
Products to the location designated by Horizon on its purchase order. The
parties agree that the method and route of shipment are at Mikart's discretion
unless Horizon furnishes Mikart explicit instructions with the purchase order.
Horizon agrees to pay all costs of shipping and any costs of freight insurance
obtained by Mikart at the request of Horizon. Mikart agrees to provide
reasonable support to assist Horizon in pursuing any claims it may have against
carriers.

     6.2 Notification of Defects. Horizon shall notify Mikart in writing as soon
as reasonably practicable after delivery to Horizon of any non-conforming
Product containing obvious defects in such Product discoverable without
affecting the integrity of such Product's packaging (but in any event within
twenty (20) days after delivery) and within thirty (30) days of the earlier of
its discovery or its notification by a third party of any latent defects.
Horizon shall be responsible for its costs to inspect all Products.

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<PAGE>   8

     6.3 Returns. Mikart shall accept for return and replacement or credit (at
invoiced cost) any Product sold to Horizon under this Agreement which does not
conform with the warranties set forth herein and for which proper notice has
been given in accordance with Section 6.2, provided Horizon obtains prior
shipping authorization from Mikart. All returns of Products with obvious defects
must be in the original manufactured condition. Mikart will pay reasonable
return freight and shipping charges, but Horizon shall assume the risk of loss
in transit associated with such returns.

                                    ARTICLE 7
                              TERM AND TERMINATION
                              --------------------

     7.1 Term. Unless earlier terminated in accordance with the provisions
hereof, the term of this Agreement shall commence on the Effective Date and
shall thereafter continue in effect until the fifth (5th) anniversary of the
Qualification Date (the "Initial Term"). At the end of the Initial Term and each
subsequent "Renewal Term" (as hereinafter defined), the term of this Agreement
shall be automatically renewed and extended for a one (1) year period (a
"Renewal Term"), unless either party delivers a written termination notice to
the other party at least six (6) months prior to the end of the Initial Term or
the then current Renewal Term, as the case may be.

     7.2 Termination. Either party may terminate this Agreement on written
notice to the other party, effective immediately if:

          (a) the other party commits a material breach of any of its
     obligations hereunder which is not cured within sixty (60) days of written
     notice from the other party specifying the breach;

          (b) the other party is dissolved or liquidated, files or has filed
     against it a petition under any bankruptcy or insolvency law, makes an
     assignment to the benefit of its creditors, has a receiver appointed for
     all or substantially all of its property, or has a petition under any
     bankruptcy or insolvency law filed against it which is not dismissed within
     sixty (60) days; or

          (c) the Qualification Date has not occurred within two (2) years after
     the Effective Date.

Such right of termination shall be in addition to any other remedy a
non-defaulting party may have at law or in equity due to the other party's
breach of is obligations hereunder.

         7.3 Post-Termination Restrictions. Upon any expiration or termination
of this Agreement (other than by Horizon pursuant to Section 7.2), Horizon shall
grant Mikart at least sixty (60) days to produce all open orders in house in
accordance with the conditions of the open orders and this Agreement. In the
event Horizon terminates this Agreement pursuant to Section 7.2: (a) Mikart
shall not manufacture, package or sell to any other person or entity for a
period of two (2) years thereafter any product Mikart is prohibited from making
during the term of this Agreement pursuant to Section 3.1; and (b) upon the

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<PAGE>   9

request of Horizon, Mikart will provide Horizon with reasonable assistance in
locating or establishing a new manufacturer for the Products.

     7.4 Changed Circumstances. In the event that the market for the Products
materially changes or either party, in good faith, believes that a material
change in such party's circumstances beyond their control has occurred which
materially affects its ability to perform its obligations pursuant to this
Agreement, the parties hereto shall, in good faith, negotiate towards mutually
acceptable revisions to this Agreement to address the impact of such material
changes; provided, however, the terms of this Agreement shall continue in full
force and effect unless and until the parties hereto agree otherwise.

     7.5 Force Majeure.

          (a) The failure of either of the parties hereto to perform any
     obligation under this Agreement solely by reason of any cause beyond its
     control (and due to no fault of its own), including, without limitation,
     acts of God, acts of government, riots, wars, strikes and accidents in
     transportation, shall not be deemed to be a breach of this Agreement;
     provided, however, that the party so prevented from complying herewith
     shall continue to take all actions within its power, including payment of
     outstanding invoices, to comply as fully as possible herewith.

          (b) If, due to force majeure, Mikart is prevented or expected to be
     prevented from supplying Horizon with the Products for a period exceeding
     one hundred twenty (120) days, then Horizon shall have the right to
     terminate this Agreement with immediate effect and upon the request of
     Horizon at Horizon's expense Mikart will provide reasonable assistance in
     establishing or locating a new manufacturer for the Products. Likewise,
     should Horizon be unable to purchase the Products for a period exceeding
     one hundred twenty (120) days, then Mikart shall have the right to
     terminate this Agreement, provided Horizon shall remain obligated to pay to
     Mikart any amounts owed hereunder.

     7.6 Special Termination. Notwithstanding anything else contained herein to
the contrary, but subject to Section 7.5, in the event Horizon fails in any
Contract Year to meet its minimum Batch purchase requirements set forth in
Section 4.3 hereof for any reason other than a breach of this Agreement by
Mikart, then Mikart shall have the right to terminate this Agreement effective
immediately by delivering written notice thereof to Horizon; provided, however,
Horizon may apply purchases in excess of the minimum Batch purchases in any
Contract Year to meet such requirements in subsequent Contract Years.

     7.7 Post-Termination Obligations. Notwithstanding anything else contained
herein to the contrary, following any termination or expiration of this
Agreement:

          (a) Mikart, at its option, shall either deliver the Blender to Horizon
     (in which case Horizon shall assume all of Mikart's remaining obligations
     under its lease therefor) or pay to Horizon amount in cash equal to the
     then-current net book value of the Blender;

                                       9
<PAGE>   10


                                        [***] - CONFIDENTIAL TREATMENT REQUESTED


          (b) Horizon shall purchase from Mikart (at Mikart's cost therefor) all
     of Mikart's remaining inventory of the active ingredient in the Products
     (but only to the extent necessary to manufacture the Products equal to
     Horizon's forecast for the subsequent four (4) month period); and

          (c) Subject to Section 7.3 hereof, Mikart shall have not further
     rights to use any of the Health Registrations.

                                    ARTICLE 8
                          INDEMNIFICATION AND INSURANCE
                          -----------------------------

     8.1 Indemnification. Mikart hereby indemnifies and agrees to defend and
hold Horizon harmless from and against losses, claims, damages, liabilities,
costs and expenses (including, without limitation, attorneys' fees and court
costs) incurred by Horizon as a result of any breach of this Agreement by Mikart
or the manufacture, package or storage of any Products by Mikart. Horizon hereby
indemnifies and agrees to defend and hold Mikart harmless from and against
losses, claims, damages, liabilities, costs and expenses (including, without
limitation, attorneys' fees and court costs) incurred by Mikart as a result of
any breach of this Agreement by Horizon, the storage, sale or distribution of
the Products, or any failure by Horizon to provide any instructions regarding
the proper use of the Products to any user thereof.

     8.2 Insurance. Each party hereto shall maintain with a financially sound
and reputable insurer throughout the term of this Agreement comprehensive
general liability insurance, including, without limitation, product liability
insurance with liability limits of at least $[***] per occurrence and in the
aggregate. Each party hereto shall also name the other party as an additional
insured party on its policy and provide the other party with such evidence
thereof as is reasonably requested by the other party from time to time.

                                    ARTICLE 9
                  WARRANTIES AND REPRESENTATIONS OF THE PARTIES
                  ---------------------------------------------

     9.1 Additional Representations and Warranties of Mikart. Mikart hereby
additionally represents and warrants to Horizon the following:

          (a) Mikart is a corporation duly organized and existing in good
     standing under the laws of the State of Georgia;

          (b) There are no material adverse claims pending or, to the best of
     Mikart's knowledge, threatened against Mikart by any entity with respect to
     the Products;

          (c) Mikart is neither a party to nor otherwise bound by any agreement
     or instrument which prohibits or prevents it from performing its
     obligations under this Agreement; and

                                       10
<PAGE>   11

          (d) Mikart's manufacturing, packaging and storage facilities comply in
     all material respects with all applicable federal, state and local laws,
     rules and regulations in the Territory.

          (e) Mikart is using a combination of internal and external resources
     to assess and make any necessary changes to its information technology
     systems to ensure that they will function without error in connection with
     the date January 1, 2000. Mikart has communicated with (and will continue
     to communicate with) its suppliers and others with whom it does business to
     monitor and evaluate such "Year 2000" conversion.

Nonetheless, Mikart does not expect such conversion to have a material adverse
effect on its ability to perform its obligations under this Agreement.

     9.2 Additional Representations and Warranties of Horizon. Horizon hereby
additionally represents and warrants to Mikart the following:

          (a) Horizon is a corporation  duly  organized  and existing  under the
     laws of the State of Delaware;

          (b) There are no material adverse claims pending or, to the best of
     Horizon's knowledge, threatened against Horizon by any entity with respect
     to any of its products or business;

          (c) Horizon is neither a party to nor otherwise bound by any agreement
     or instrument which prohibits or prevents it from performing its
     obligations under this Agreement; and

          (d) Horizon owns all of the Health Registrations and holds a valid
     license to use the Trademarks and has the full power and authority to grant
     to Mikart the right to manufacture and purchase the Products under the
     Health Regulations and to use the Trademarks in connection therewith, all
     in accordance herewith.

                                   ARTICLE 10
                CONFIDENTIALITY AND NONSOLICITATION OF PERSONNEL
                ------------------------------------------------

     10.1 Confidentiality. Each party hereto acknowledges that it has been and
will be exposed to certain "Confidential Information" and "Trade Secrets" (both
as hereinafter defined) of the other party in connection with the transactions
contemplated by this Agreement and that its unauthorized use or disclosure of
such information or data could cause immediate and irreparable harm to such
other party. Accordingly, except to the extent that it is necessary to use such
information or data to perform its obligations under this Agreement, neither
party shall, without the express prior written consent of the other party,
redistribute, market, publish, disclose or divulge to any person or entity, or
use or modify for use, directly or indirectly, in any way for any person or
entity: (a) any of the other party's Confidential Information during the term of
this Agreement and for a period of three (3) years after any expiration or
termination of this Agreement; and (b) any of the other party's Trade Secrets at
any time during which such information constitutes a trade secret under
applicable law. For purposes hereof, "Confidential Information" shall mean all
competitively sensitive, non-public information (other than "Trade Secrets") of
or about a party which is not generally known by or available to such party's
competitors, and "Trade Secrets" shall mean "Trade Secrets" as defined under
applicable law.

                                       11
<PAGE>   12

     10.2 Nonsolicitation of Personnel. Neither party hereto shall, without the
prior written consent to the other party, either directly or indirectly, alone
or in conjunction with any other person or entity, solicit or attempt to solicit
any "key or material" employee, consultant, contractor or personnel of such
other party in the State of Georgia to terminate, alter or lessen his or her
affiliation with such other party at any time during the term of this Agreement
and for a period of one (1) year thereafter.

                                   ARTICLE 11
                             ARBITRATION OF DISPUTES
                             -----------------------

     All disputes arising out of or in connection with the interpretation,
application or enforcement of this Agreement shall be settled by final and
binding arbitration. Such arbitration shall be conducted in Atlanta, Georgia,
pursuant to the commercial arbitration rules of the American Arbitration
Association in effect at the time the arbitration is commenced. The decision of
the arbitrators, which may include interest, shall be final and binding on the
parties hereto and may be entered and enforced in any court of competent
jurisdiction by any party. The arbitration shall be pursued and brought to
conclusion as rapidly as possible. The prevailing party in the arbitration
proceeding shall be awarded reasonable attorneys' fees, expert witness costs and
expenses, and all other costs and expenses incurred in connection with such
proceeding, unless the arbitrators shall for good cause determine otherwise.

                                   ARTICLE 12
                                     NOTICES
                                     -------

     12.1 Delivery. All notices, consents, requests and other communications
hereunder shall be in writing and shall be sent by hand delivery, by certified
or registered mail (return-receipt requested), or by a recognized national
overnight courier service as set forth below:

          If to Mikart:  Mikart, Inc.
                         1750 Chattahoochee Avenue
                         Atlanta, Georgia 30318
                         Attention: Miguel I. Arteche

          If to Horizon: Horizon Pharmaceutical Corporation
                         660 Hembree Parkway
                         Suite 106
                         Roswell, Georgia 30076
                         Attention: Brent Dixon

                                       12
<PAGE>   13

     12.2 Effective Time. Notices delivered pursuant hereto shall be deemed
given: (a) at the time delivered, if personally delivered; (b) at the time
received, if mailed; and (c) one (1) business day after timely delivery to the
courier, if by overnight courier service.

     12.3 Changes. Either party hereto may change the address to which notice is
to be sent by written notice to the other party in accordance with the
provisions of this Article 12.

                                   ARTICLE 13
                                  MISCELLANEOUS
                                  -------------

     13.1 Severability. If any provision of this Agreement is held to be
invalid, illegal or unenforceable, the validity, legality and enforceability of
the remaining provisions shall not in any way be affected or impaired, and the
parties shall use their best efforts to substitute a valid, legal and
enforceable provision, which, insofar as practical, implements the purpose of
this Agreement.

     13.2 Counterparts. This Agreement may be executed in one or more
counterparts, each of which shall be deemed an original, but all of which
together shall be deemed one and the same instrument.

     13.3 Governing Law. This Agreement shall be governed by, and any matter or
dispute arising out of this Agreement shall be determined by, the laws of the
State of Georgia.

     13.4 Headings: Gender. "Article," "Section" and other headings contained in
this Agreement are for reference purposes only and shall not affect in any way
the meaning or interpretation of this Agreement. All personal pronouns used in
this Agreement shall include the other genders, whether used in the masculine,
feminine or neuter gender, and the singular shall include the plural and vice
versa, whenever and as often as may be appropriate.

     13.5 Entire Agreement. This Agreement represents the entire agreement of
the parties with respect to its subject matter. Any and all prior discussions or
agreements with respect hereto are merged into and superseded by the terms of
this Agreement. This Agreement may be modified or amended only in writing signed
by both parties which expressly refers to this Agreement and states an intention
to modify or amend it. No such amendment or modification shall be effected by
use of any purchase order, acknowledgment, invoice or other form of either party
and in the event of conflict between the terms of this Agreement and any such
form, the terms of this Agreement shall control.

     13.6 Notices. Any notice or payment required or permitted hereunder shall
be in writing and sent by certified mail, overnight express, or personally
delivered, addressed to the party to receive the notice as set out below.

     13.7 No Assignment. Neither party hereto may assign this Agreement, in
whole or in part, without the prior written consent of the other party (which
consent shall not be unreasonably withheld or delayed), and any attempted
assignment not in accordance herewith shall be null and void and of no force or
effect.

                                       13
<PAGE>   14

     13.8 Binding Effect. This Agreement shall be binding upon and shall inure
to the benefit of the parties hereto and their respective successors, heirs,
representatives and permitted assigns.

     13.9 Interpretation. This Agreement was fully negotiated by both parties
hereto and shall not be construed more strongly against either party hereto
regardless of which party is responsible for its preparation.

     13.10 No Consequential Damages. Neither party to this Agreement shall have
any liability to the other party for any consequential or indirect damages
arising out of any breach of this Agreement, including, without limitation, loss
of profit, loss of use or business stoppage.

     13.11 Further Assurances. Upon the reasonable request of the other party,
each party hereto agrees to take any and all actions necessary or appropriate to
give effect to the terms set forth in this Agreement.

     IN WITNESS WHEREOF, the parties hereto have caused their duly authorized
representatives to execute this Agreement as of the day and year first above
written.

                                  "Mikart"

                                  MIKART, INC.


                                  By:__________________________________________
                                       Miguel I. Arteche, President


                                  "Horizon"

                                  HORIZON PHARMACEUTICAL
                                  CORPORATION


                                  By:__________________________________________
                                       Brent Dixon, President



                                     14
<PAGE>   15


                                        [***] - CONFIDENTIAL TREATMENT REQUESTED


                        Exhibit A: Product Specifications
                        ---------------------------------


Robinul(R) Tablets [***]
------------------------

         [***]


Robinul(R) Forte Tablets [***]
------------------------------

         [***]


                                       15