For most people who need protection from the blood clots that cause heart attack and stroke, daily low-dose aspirin remains the best--and least expensive--choice. For people who need more protection than aspirin alone can provide, prescription clopidogrel (Plavix), either alone or combined with aspirin, is the best choice. Those are some of the conclusions of a new report from Consumer Reports Best Buy Drugs, a public education initiative from Consumers Union, publisher of Consumer Reports.

The experts at Best Buy Drugs evaluated the safety, effectiveness, and cost of aspirin and the other three drugs (all prescription) in the class of medicines called antiplatelets, which reduce heart attack and stroke risk by decreasing the blood's ability to clot. The review involved 39 studies that compared the drugs. It concluded that the vast majority of people who need a blood-thinning drug--those who have risk factors for heart attack or stroke but have not yet had one--can get all the protection they need from aspirin, and at a fraction of the cost of the other drugs. In 2006 doctors prescribed $2.2 billion worth of the heavily advertised Plavix, suggesting that far more people are taking the drug than need to.

People who might need Plavix include those who have already had a heart attack, have had a recent angioplasty and stent implant, or have the "unstable" form of angina (chest pain). A third antiplatelet drug, Aggrenox, is recommended for people who've already had a stroke or transient ischemic attack (mini-stroke). Best Buy Drugs does not recommend the antiplatelet drug ticlopidine (Ticlid) because it has greater risks than the other drugs and there's no evidence that it works any better.

The antiplatelet report is 17th in a series of Best Buy Drug reports. All are available free at Consumer Reports Best Buy Drugs.