Adams Respiratory to settle patent suit on guaifenesin

March 21 (Reuters) - Adams Respiratory Therapeutics Inc. ARXT.O said it agreed to settle a patent litigation against two subsidiaries of Pharmaceutical Holdings Corp. for infringing patents related to a treatment for chest congestion.

Adams had sued Mutual Pharmaceuticals Co. and United Research Laboratories Inc. after the companies sought regulatory approval to manufacture and sell a generic version of single-ingredient guaifenesin extended-release tablets prior to the expiration of Adams' patent.

Under the settlement, Adams granted the companies a non-exclusive, royalty-free conditional license, with the right to grant a single sub-license under its patents, to sell certain licensed products in the United States beginning no earlier than July 1, 2012. (Reporting by Shailesh Kuber in Bangalore)