Endo, Penwest file lawsuit against Impax on generic Opana

Nov 15 (Reuters) - Penwest Pharmaceuticals Co (PPCO.O) and Endo Pharmaceuticals, a unit of Endo Pharmaceuticals Holdings Inc (ENDP.O), filed a lawsuit against Impax Laboratories Inc IPXL.PK in connection with Impax's application for a generic version of Opana extended-release pain-reliever tablets.

The lawsuit alleges infringement of certain U.S. patents that cover the Opana ER formulation and is in response to a series of notices that Impax had sent to Endo and Penwest, the companies said in a statement.

In October, Impax said U.S. health regulators rescinded its filing for a generic version of Opana ER. (Reporting by Nachiket Kelkar in Bangalore; Editing by Vinu Pilakkott)