Thienopyridine derivatives versus aspirin for preventing stroke and other serious vascular events in high vascular risk patients

Most strokes and heart attacks are caused by a blood clot blocking the blood supply to part of the brain (to cause stroke) or to the heart (to cause a heart attack). Aspirin prevents blood clots forming, and it can reduce the risk of a further heart attack or stroke in people who have had a stroke or heart attack or other symptoms of vascular disease. Clopidogrel and ticlopidine are two similar drugs called thienopyridines which prevent clots in a different way to aspirin. This review of 10 trials comparing either clopidogrel or ticlopidine with aspirin in about 27,000 people found that clopidogrel and ticlopidine were at least as effective as aspirin for the prevention of stroke and heart attacks, and might be slightly more effective. In terms of adverse effects, compared with aspirin, clopidogrel and ticlopidine caused less stomach upset and less bleeding from the gut, but more diarrhoea and skin rash. Ticlopidine produced more of these last two adverse effects than clopidogrel when compared with aspirin. Ticlopidine can also cause suppression of the bone marrow production of blood cells, which can be a serious complication. Clopidogrel is therefore the thienopyridine of choice since it is safer and better tolerated. However, since it is substantially more expensive than aspirin and not clearly more effective, it should generally only be used instead of aspirin in patients who are unable to take aspirin.