Impax Sued Based On Anda Amendment For Additional Dosage Forms Of Generic OPANA® ER

July 28, 2008

HAYWARD, Calif. (July 28, 2008) – IMPAX Laboratories, Inc. today announced Endo Pharmaceuticals, Inc. (“Endo”) and Penwest Pharmaceuticals, Co. (“Penwest”) have filed suit for patent infringement based on the Company’s amendment to its existing Abbreviated New Drug Application (“ANDA”) for oxymorphone hydrochloride extended-release tablets CII, generic of Opana® ER, adding new 7.5 mg, 15 mg and 30 mg strengths. In connection with this amendment, IMPAX provided notice to Endo and Penwest that its submission includes a Paragraph IV certification stating the Company believes its product does not infringe any valid and enforceable patent, including U.S. Patent Nos. 7,276,250, 5,662,933 and 5,958,456.

As previously announced, IMPAX had filed its ANDA with respect to the 5 mg, 10 mg, 20 mg and 40 mg dosage strengths of Opana ER. Endo and Penwest filed suit against IMPAX alleging infringement of U.S. Patent Nos. 5,662,933 and 5,958,456. IMPAX denies that any valid, enforceable patent claim is infringed by its ANDA product and will continue to vigorously defend this lawsuit.

Endo Pharmaceuticals Holdings Inc. and Penwest Pharmaceuticals Co. manufacture and market Opana ER for the treatment of moderate to severe pain. According to Wolters Kluwer Health, U.S. sales of Opana ER tablets were approximately $100 million in the 12 months ended May 2008. On March 3, 2008 Endo announced that it had received approval of the 7.5 mg, 15 mg and 30 mg strengths and the launch of these additional dosage forms on April 1, 2008.

About IMPAX Laboratories, Inc.

IMPAX Laboratories, Inc. is a technology based specialty pharmaceutical company applying its formulation expertise and drug delivery technology to the development of controlled-release and specialty generics in addition to the development of branded products. IMPAX markets its generic products through its Global Pharmaceuticals division and markets its branded products through the IMPAX Pharmaceuticals division. Additionally, where strategically appropriate, IMPAX has developed marketing partnerships to fully leverage its technology platform. IMPAX Laboratories is headquartered in Hayward, California, and has a full range of capabilities in its Hayward and Philadelphia facilities. For more information, please visit the Company's Web site at:

"Safe Harbor" statement under the Private Securities Litigation Reform Act of 1995:

To the extent any statements made in this news release contain information that is not historical, these statements are forward-looking in nature and express the beliefs and expectations of management. Such statements are based on current expectations and involve a number of known and unknown risks and uncertainties that could cause IMPAX's future results, performance or achievements to differ significantly from the results, performance or achievements expressed or implied by such forward-looking statements. Such risks and uncertainties include, but are not limited to, possible adverse effects resulting from the delisting of and suspension of trading in IMPAX's stock, IMPAX’s failure to file any periodic reports subsequent to its quarterly report on Form 10-Q for the quarter ended September 30, 2004, the SEC’s revocation of the registration of IMPAX’s common stock under section 12 of the Securities Exchange Act of 1934, the actual time that will be required to,file a registration statement on Form 10 with respect to such stock, IMPAX's ability to obtain sufficient capital to fund its operations, the difficulty of predicting FDA filings and approvals, consumer acceptance and demand for new pharmaceutical products, the impact of competitive products and pricing, IMPAX's ability to successfully develop and commercialize pharmaceutical products, IMPAX's reliance on key strategic alliances, the uncertainty of patent litigation, the availability of raw materials, the regulatory environment, dependence on patent and other protection for innovative products, exposure to product liability claims, fluctuations in operating results and other risks detailed from time to time in IMPAX's filings with the Securities and Exchange Commission. Forward-looking statements speak only as to the date on which they are made, and IMPAX undertakes no obligation to update publicly or revise any forward-looking statement, regardless of whether new information becomes available, future developments occur or otherwise.

Company Contacts:
IMPAX Laboratories, Inc.
Larry Hsu, Ph.D. President & CEO
(510) 476-2000, Ext. 1111
Arthur Koch, CFO
(215) 933-0351
Mark Donohue, Sr. Director IR (215) 933-3526

Investor Relations Contacts:
Lippert/Heilshorn & Associates, Inc.
Kim Sutton Golodetz
(212) 838-3777
Bruce Voss (
(310) 691-7100