WASHINGTON(Reuters) – The U.S. Supreme Court Monday refused to consider an appeal by U.S. antitrust authorities who wanted antitrust charges to be reinstated against drug maker Schering-Plough . The justices rejected a request by the Federal Trade Commission to review a U.S. appeals court ruling that rejected an earlier finding by the FTC that Schering-Plough had illegally kept cheaper versions of its blood pressure drug K-Dur off the market. The ruling last year by a panel of the Court of Appeals for the 11th Circuit overturned a 2003 FTC decision which concluded Schering-Plough’s patent settlements with Upsher-Smith Laboratories and American Home Products, now Wyeth , amounted to pay-offs not to compete. The three-judge panel said companies were within their rights to use their patents to lock competitors out of the market. Wyeth agreed to settle with the FTC in 2002. K-Dur is a potassium chloride supplement often prescribed to patients undergoing treatment for high blood pressure. Schering-Plough’s patent on K-Dur is set to expire on Sept. 1. Under federal law, drugmakers are allowed to seek U.S. Food and Drug Administration approval for generic versions of brand-name drugs such as K-Dur before a drug’s patent expires. They must certify that the patent is invalid or will not be infringed by the new generic version. Schering-Plough has repeatedly maintained that the K-Dur patent settlements were legal. The U.S. Justice Department urged the Supreme Court to reject the FTC’s appeal, even though it acknowledged the case raised important and complex issues about the treatment under the antitrust laws of settlements in patent cases. It cited the lack a split by the appeals courts on the issue and said the case did not present an appropriate opportunity for the high court to decide the proper standards for distinguishing between legitimate and illegitimate patent settlements.