PITTSBURGH (AP) — Mylan Inc. is being sued by Schering Corp. and MSP Singapore over plans to make a generic version of the cholesterol drug Vytorin. Mylan asked for FDA approval for a range of doses of Ezetimibe and Simvastatin tablets, or Vytorin. That triggered a patent lawsuit from Schering and partner MSP Singapore on Dec. 16, filed in U.S. District Court of the District of New Jersey. Merck & Co. completed its $41 billion buyout of Schering in November. The companies had been jointly selling Vytorin before the buyout. Mylan said the doses of Vytorin for which it wants to make generic copies had sales of $1.6 billion during the 12 months ended Sept. 30.