Watson Pharmaceuticals, Inc, a leading specialty pharmaceutical company, announced that its subsidiary Watson Laboratories, Inc has filed a lawsuit in the US District Court of Delaware against Barr Pharmaceuticals, Inc and its subsidiary Barr Laboratories, Inc for infringement of patents listed in the Orange Book for Watson's product Oxytrol (Oxybutynin Transdermal System).

The lawsuit is based upon an Abbreviated New Drug Application (ANDA) filed by Barr requesting approval to market and sell a generic version of Oxytrol to be sold in the United States prior to the expiration of the Orange Book listed patents. In its Notice Letter to Watson, Barr alleges that patents covering Oxytrol are invalid, unenforceable and/or will not be infringed by Barr's manufacture, use or sale of the product described in its ANDA.

The filing of this lawsuit is provided for by the Hatch-Waxman Act, a federal statute governing certain aspects of generic drug approvals. Under that statute, the filing of the lawsuit stays any FDA approval of the Barr ANDA until the earlier of a district court judgment in favour of Barr or 30 months from Watson's receipt of Barr's Notice Letter.