Officials at drugmaker Merck & Co. say they will take more time to decide what to do about an experimental blood thinner that gave disappointing results in a second big study.

The study was aimed at preventing repeat heart attacks and strokes in people who had already suffered one.

The drug, vorapaxar, (vor-uh-PACKS-ahr) did lower the risk of these problems. But it also raised the risk of major bleeding, including dangerous bleeding in the head, which largely canceled out the drug's benefit.

The study involved more than 26,000 patients in 32 countries.

Results were discussed Saturday at an American College of Cardiology conference in Chicago and published by the New England Journal of Medicine.