A Bayer AG (BAYN) unit sued generic drug maker Watson Pharmaceuticals Inc. (WPI) for allegedly infringing two U.S. patents for Staxyn, a medicine approved in the U.S. in 2010 for treatment of male erectile dysfunction.

Bayer Pharma AG contends that Parsippany, New Jersey-based Watson is planning to market a copy of Staxyn, a minty preparation that dissolves in the mouth, before the patent protections expire.

“Watson has acted with full knowledge” of the patents “without a reasonable basis for believing that it would not be liable for infringing,” Leverkusen, Germany-based Bayer said in a complaint filed today in federal court in Wilmington, Delaware.

Watson, which also makes a generic version of the Lipitor cholesterol drug, said in a statement today that it would buy Iceland’s Actavis Group hf for about $5.6 billion to create the world’s third-largest maker of generic drugs.

Charlie Mayr, a Watson spokesman, didn’t immediately return a phone call seeking comment on the lawsuit.

The case is Bayer v. Watson, U.S. District Court, District of Delaware (Wilmington).

To contact the reporter on this story: Phil Milford in Wilmington, Delaware, at pmilford@bloomberg.net

To contact the editor responsible for this story: Michael Hytha at mhytha@bloomberg.net.