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WARFARIN OR ASPIRIN TREATMENT REDUCED INCIDENCE OF STROKE BY 81%

Executive Summary

WARFARIN OR ASPIRIN TREATMENT REDUCED INCIDENCE OF STROKE BY 81% versus placebo in 588 patients with atrial fibrillation participating in one treatment arm of the Stroke Prevention in Atrial Fibrillation Study, according to a preliminary report of the study in the March 22 New England Journal of Medicine. The incidence of stroke in 393 patients receiving either warfarin or aspirin was 1.3% a year compared to a rate of 8.3% a year in the 195 patients receiving placebo. A second treatment arm for patients unwilling or unable to take warfarin compared only aspirin against placebo. Analyzing the data on patients taking aspirin from both treatment arms, the investigators found that there was a 49% reduction in the rate of stroke, from 6.3% a year in the placebo group to a 3.2% rate with aspirin. The study was coordinated by the neurology division at the University of Texas Health Science Center in San Antonio and funded by the National Institute of Neurological Disorders and Stroke. At a March 21 press conference on the National Institutes of Health campus in Bethesda, Maryland, one of the lead investigators of the study, David Sherman, MD, University of Texas Health Science Center, explained that "the aim of our study was to detect a way to reduce the incidence of stroke in patients with atrial fibrillation" since one out of every six stroke patients has the condition. Atrial fibrillation, Sherman estimated, affects over one million Americans and is associated with more than 75,000 strokes each year. The study, as initially proposed, was to have enrolled over 1,600 atrial fibrillation patients and studied the effect of warfarin and aspirin treatment on the incidence of stroke in 15 centers over three years with a one year follow-up. However, Sherman noted, the study's monitoring committee, which was reviewing unblinded data every six months, recommended a halt in the study in November 1989 because "they felt that the benefit of aspirin or warfarin was of such a magnitude that they felt it was no longer ethical to continue an inactive placebo arm in the study." Over 1,200 patients had been studied for an average of 13 months by the time the study was halted. The preliminary report on the study in the NEJM, however, did not analyze the comparable efficacy of warfarin versus aspirin. The question of appropriate therapy was further complicated by a finding of the study that patients over 75, who were excluded from the warfarin group, did not benefit from aspirin use. Sherman noted that a follow-up study is underway comparing the two treatments in the atrial fibrillation population. "We will continue to enroll patients for the remainder of 1990 [and] will follow them for another year and a half," Sherman reported. "So hopefully by 1992 we will be able to resolve the question of the appropriate patients to receive aspirin or warfarin." The NINDS study is the first to show the benefit of daily aspirin use for preventing stroke in patients with atrial fibrillation. However, the study confirms the findings of a small Danish study, reported last year, which suggested that warfarin could reduce strokes in this patient population, but did not find a positive benefit from aspirin. The study population, on average, was older in the Danish study, which may have affected the aspirin results. SmithKline Beecham's Ecotrin 325 mg tablets were used in the study. DuPont supported a pilot study that was the precursor of the NINDS study. The company has embarked on an a large-scale clinical program with over 3,000 patients currently enrolled to develop Coumadin (warfarin) as a protective agent against thrombus. DuPont currently has four studies underway testing low dose combinations of Coumadin and aspirin for primary prevention of myocardial infarction; treatment of unstable angina; prevention of reocclusion after a coronary bypass operation; and prevention of stroke in a population with carotid artery stenosis. The company is also considering conducting a fifth study in post-MI patients.
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