A Salt Lake City-based unit of Watson Pharmaceuticals Inc., the biggest U.S. maker of generic birth-control pills, has accused Barr Pharmaceuticals Inc. of infringing eight patents for a skin patch to control overactive bladder.

Watson Pharmaceuticals' subsidiary Watson Laboratories Inc., in a lawsuit filed Thursday, contends Barr's application to the U.S. Food and Drug Administration to make its own extended-release oxybutynin transdermal system violates patents awarded since 1997 related to Watson's Oxytrol patch.

The infringement "will cause Watson irreparable harm," unless the court blocks sale of Barr's copy of the patch, lawyers for Watson said in a complaint filed in federal court in Wilmington, Del.

Under federal law, the filing of the lawsuit stays FDA approval of Barr's proposed product for 30 months, or until and if the court renders judgment in favor of Barr, California-based Watson Pharmaceuticals said in a statement Friday.

New Jersey-based Barr "believes it is the first to file" for FDA approval for generic Oxytrol, which has annual U.S. sales of about $39 million, the company said in a statement Friday.