The U.S. Food and Drug Administration said it is conducting a review of the cholesterol drug Vytorin based on preliminary results from a recent study.

The agency said it will review Merck and Schering Plough Pharmaceuticals' recent trial once the FDA receives the final study results on the drug, which is a combination of Zetia (ezetimibe) and Zocor (simvastatin) in one tablet.

Merck and Schering Plough last week released data showing that the combination drug failed to slow progression of heart disease better than Zocor, which is less expensive.

The FDA said that study was not designed to detect any difference in risk of having a heart attack or stroke between the two treatments. The agency said an ongoing trial is designed to evaluate the effect of Vytorin versus Zocor on heart disease and stroke.

Merck issued a statement Friday in support of the the controversial clinical trial. "We stand behind Vytorin and Zetia and stand behind our science that has brought these cholesterol-lowering medications to millions of people around the world," Peter S. Kim, president of Merck Research Laboratories, said.

Copyright 2008 by United Press International