Many stroke, heart attack patients may not benefit fr...( BUFFALO N.Y. -- Up to 20 percent of...),Health

BUFFALO, N.Y. -- Up to 20 percent of patients taking aspirin to lower the risk of suffering a second cerebrovascular event do not have an antiplatelet response from aspirin, the effect thought to produce the protective effect, researchers at the University at Buffalo have shown.

Millions of people use low-dose aspirin either for prevention of a second stroke, second heart attack or second episode of peripheral artery disease, said Francis M. Gengo, Pharm.D., lead researcher on the study.

Gengo is professor of neurology in the UB School of Medicine and Biomedical Sciences and professor of pharmacy practice in the UB School of Pharmacy and Pharmaceutical Sciences.

In those three indications, its crystal clear that aspirin reduces the risk of a second heart attack or stroke in most patients. But we have known for years that in some stroke and heart attack patients, aspirin has no preventive effect.

With no definitive data on the frequency of this condition, known as aspirin resistance, physicians were left with a best guess of between 5 and 50 percent, said Gengo.

UB researchers now have confirmed the 20 percent figure through a strictly controlled study conducted over 29 months in 653 consecutive stroke patients seen at Dent Neurologic Institute offices in the Buffalo suburbs Amherst and Orchard Park.

Results of the study were published Jan. 28 on the Journal of Clinical Pharmacologys website as a document of interest and will appear in a future issue of the journal.

Aspirin lowers the risk of a cardiovascular event by preventing blood platelets from aggregating in the arteries and obstructing blood flow. If blood drawn from a patient taking aspirin shows that platelets are still aggregating, that patient is diagnosed as being aspirin resistant. If a stroke patient has a second stroke while on aspirin, the patient has experienced what is known as clinical aspirin failure.

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