IMPAX Prevails in Alza's Lawsuit Related to Generic Version of Ditropan XL

September 29, 2005

HAYWARD, Calif.--(BUSINESS WIRE)--Sept. 29, 2005--IMPAX Laboratories, Inc. (OTC:IPXL) announced that it has prevailed in its defense of a lawsuit brought by Alza Corporation, a Johnson & Johnson (NYSE:JNJ) unit, alleging patent infringement related to IMPAX's filing of an Abbreviated New Drug Application (ANDA) for a generic version of Ditropan(R) XL (Oxybutynin Chloride) tablets, 5, 10 and 15 mg. Alza Pharmaceuticals markets Ditropan XL for the treatment of urge urinary incontinence.

"In February of this year, we received tentative approval from the U.S. Food and Drug Administration on our ANDA for the 5, 10 and 15 mg dosage forms of our generic version of Ditropan XL," commented Larry Hsu, Ph.D., President of IMPAX. "We believe that we were first to file on the 15 mg dosage form."

According to NDCHealth, sales of Ditropan XL tablets were $395 million, with the 15 mg accounting for $66 million, in the 12 months ended July 2005.

The lawsuit against IMPAX was brought in the United States District Court, Northern District of California. In a previous stipulation, Alza and IMPAX agreed to be bound by the decision as to patent validity in a case involving the same patent brought by Alza against Mylan Laboratories alleging patent infringement on the generic versions of Ditropan XL manufactured by Mylan. Mylan announced on September 28, 2005 that a West Virginia federal district court ruled that Mylan's version does not infringe Alza's patent and that the patent is invalid. Because the patent was found to be invalid, under the stipulation IMPAX will be entitled to judgment in its favor. Final FDA approval of our ANDA, however, may be subject to FDA's resolution of an August 2005 petition filed by Johnson & Johnson to block approval.

Alza has also announced that it intends to appeal this decision. In this event, we believe the IMPAX and Mylan cases will be heard together on appeal.

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 intends to market 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. In particular, the forward-looking statements include statements about IMPAX's estimated timelines and new application filing goals. 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 IMPAX's stock, IMPAX's delay in filing its 2004 Form 10-K and its Form 10-Q's for the first two quarters of 2005, 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.

CONTACT: IMPAX Laboratories, Inc.
Barry R. Edwards, 215-933-0323 Ext. 4360
Arthur A. Koch, Jr., 215-933-0351
Larry Hsu, Ph.D., 510-476-2000 Ext. 1111
Investor Relations Contacts:
Lippert/Heilshorn & Associates, Inc.
Kim Sutton Golodetz, 212-838-3777
Bruce Voss, 310-691-7100

SOURCE: IMPAX Laboratories, Inc.