Researchers at the University of Illinois at Chicago College of Medicine released a study last week blaming Viagra's link to heart attacks and strokes on the drug's tendency to cause platelets to aggregate.
According to the study, which appears in the January 10 issue of the scientific journal Cell, Viagra elevates levels of a cell compound known as cyclic guanosine monophosphate (cGMP), which encourages platelets to amass.
Researchers say that Viagra is unlikely to cause a heart condition in healthy people but may present a risk "for patients with preexisting conditions such as atherosclerosis." Platelet aggregation can lead to clotting that blocks a blood vessel, a condition called thrombosis that often leads to heart attacks and strokes. Over 16 million men worldwide have taken Viagra since its approval in 1998.