HAYWARD, Calif.--(BUSINESS WIRE)--IMPAX Laboratories, Inc. (OTC:IPXL) today confirmed that Endo Pharmaceuticals Holdings Inc. and Penwest Pharmaceuticals Co. have filed a lawsuit against the Company in the United States District Court for the District of Delaware alleging patent infringement related to IMPAX's filing of an Abbreviated New Drug Application (ANDA) with the U.S. Food and Drug Administration (FDA) for oxymorphone hydrochloride extended-release tablets CII, a generic version of Opana® ER.
