In the new study of apixaban, researchers assigned almost 5,600 patients with atrial fibrillation and an increased risk of stroke (due to age or prior stroke, for instance) to one of two groups: apixaban, at 5 milligrams taken twice daily; or aspirin, with doses ranging from 81 to 324 milligrams per day.
The study was done at 522 centers in 36 countries from late 2007 to late 2009. The researchers wanted to compare which drug was better at preventing stroke or blockages due to blood clots elsewhere in the body, called systemic embolism.
Among patients on apixaban, there were 51 strokes or embolisms, or 1.6 percent per year, compared to 113 such events, or 3.7 percent, among those on aspirin.
While apixaban patients experienced 44 major bleeding events, aspirin takers had 39, but the difference was not great enough to be significant from a statistical point of view, Diener said.
The study was funded by Bristol-Myers Squibb and Pfizer, who are working jointly to develop apixaban.
The drug has been shown in previous research to be better at preventing dangerous leg blood clots and lung clots after hip replacement surgery than an older drug, enoxaparin.
Apixaban works by blocking a crucial step in the formation of blood clots. The study of the drug's effects on stroke prevention was actually halted early after one year, Diener said, because of the huge difference found between the two drugs and the superiority of apixaban.
The new drug isn't yet approved by the FDA and Diener couldn't predict when that might happen. Results of another study, a head-to-head comparison of apixaban against warfarin, is due out in August, he said.
A 55 percent reduction in stroke risk compared to aspirin is impressive, said Dr. Larry Chinitz, professor of medicine at the New York University School of Medicine and director of the Heart Rhythm Center at NYU
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