Duramed Pharmaceuticals Inc., a subsidiary of Barr Pharmaceuticals Inc., said Dec. 14 it is suing Watson Pharmaceuticals Inc. and Sandoz, alleging they infringed the patent protecting Duramed’s Seasonale oral contraceptive.

In September 2006, Watson launched Quasense, a generic version of Seasonale, after final approval from the U.S. Food & Drug Administration, according to Barr.