(Reuters) - U.S. health regulators on Thursday approved a blood clot preventer developed by Merck & Co for use by patients who have had a heart attack or who suffer from blockages in the arteries of the legs. The drug, vorapaxar, was approved to reduce the risk of heart attacks, stroke, cardiovascular death and the need for procedures to improve blood flow to the heart, the Food and Drug Administration said. Merck will sell the new medicine under the brand name Zontivity. The approval follows a recommendation for its use by an FDA advisory panel that voted 10-1 in favor of the drug in January. The approval had been delayed over safety concerns due to serious and sometimes fatal bleeding in patients who were given the drug in clinical trials. Zontivity is not approved for use in patients who have suffered a stroke, as those patients were found to be at particularly high risk of dangerous bleeding.

               "In patients who have had a heart attack or who have peripheral arterial disease, this drug will lower the risk of heart attack, stroke, and cardiovascular death," Ellis Unger, director of the Office of Drug Evaluation I in the FDA's Center for Drug Evaluation and Research, said in a statement.Zontivity works by preventing platelets in the blood from clumping together and forming clots in the arteries, which can lead to heart attacks and strokes.

              Each year about 190,000 Americans have a second heart-related event, according to Merck. Zontivity is expected to be used in addition to standard therapy given to prevent a second heart attack - typically aspirin and the clot preventer Plavix.