Earlier this year Vytorin’s effectiveness was called into question, producing a marketing problem for its manufacturer, Merck and Schering-Plough. This time the allegations are more serious. The FDA warned the public about muscle injuries linked to simvastatin, which is used in the controversial cholesterol drug Vytorin, and the heart-rhythm medication amiodarone. The FDA issued a warning to those taking simvastatin to watch out for symptoms of cramps, pain, tenderness, stiffness or spasm in their muscles. Simvastatin is marketed as Zocor and is known as a statin.