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Aspirin as Good as Warfarin for Some Stroke Prevention

It's easier to use and equally effective against blocked brain arteries

WEDNESDAY, March 30, 2005 (HealthDay News) -- Large doses of ordinary aspirin are as effective as the anticoagulant drug warfarin in preventing stroke in people with partial blockages of the brain arteries, a new trial shows.

Intracranial stenosis, as this artery-blocking condition is formally known, causes about 10 percent of the strokes in the United States each year. Neurologists have long tried to prevent those strokes by giving patients warfarin, better known as Coumadin.

However, "aspirin should [now] be used in preference to warfarin for people with intracranial arterial stenosis," concludes the study, published in the March 31 issue of the New England Journal of Medicine.

"This should have a major impact on clinical practice," said lead researcher Dr. Marc I. Chimowitz, professor of neurology at Emory University. "We surveyed the doctors in the study and they said aspirin should be adopted as the therapy."

The study enrolled 569 people diagnosed with brain artery blockage after they had either full-blown strokes or short-lived "transient ischemic attacks," or mini-strokes. Half of the patients were put on warafarin; the other half took 1,300 milligrams per day of aspirin.

The 1,300 milligram dosage -- much larger than the 81 to 325 milligrams a day prescribed to prevent heart attack and stroke in otherwise healthy patients -- was used because it "is the only dosage that we have evidence is as good as warfarin for this condition," Chimowitz explained.

After an average follow-up of 1.8 years, the incidence of major problems tracked in the study -- a stroke caused by a blocked artery, brain hemorrhage or death from a blood vessel-related cause -- was virtually the same in both groups: 22.1 percent for those taking aspirin vs. 21.8 percent for those taking warfarin.

The trial was cut short, however, because the incidence of major problems such as heart attack or sudden death was much higher for those taking warfarin. For example, while just under 3 percent of participants taking aspirin experienced heart attack or sudden death within the nearly two years of follow-up, 7.3 percent of patients taking warfarin experienced this type of serious cardiac event.

Some controversy may linger as to the amount of aspirin to be prescribed for people with the condition, because the amount used in the study was so much larger than that used for other preventive purposes, Chimowitz said. However, he noted that the incidence of hemorrhage -- the major adverse side effect associated with large doses of aspirin -- was not dangerously high.

An accompanying editorial by Dr. Walter J. Koroshetz, director of the stroke service at Massachusetts General Hospital in Boston, struck a slightly skeptical note.

Warfarin is potentially more effective than aspirin, Koroshetz said, and its results in the trial were poor simply because it is so difficult to manage, requiring frequent blood tests to ensure that its dosage keeps blood clotting within an effective range.

Patients taking warfarin were within that range only 63 percent of the time in this study, Koroshetz added, and 28 percent of the people in this 'within-range' group dropped out of the study.

For warfarin users who kept within the safe range, stroke rates were actually five times lower than for those without such dose control, Korshetz pointed out, while their risk of serious heart problems was about 40 times lower.

"The problem with Coumadin was that so many patients were not in the therapeutic range," Koroshetz said. "Why were they not in the therapeutic range? Because they had their blood checked and adjustments made only once a month. To keep them in the therapeutic range, you must check more frequently."

That is precisely the point made in the study, Chimowitz said -- that the ease of use of aspirin outweighs the potentially higher effectiveness of warfarin.

There still can be a role for warfarin for people with intracranial stenosis, Koroshetz contended. For example, it might be used to tide patients over during periods where their symptoms indicate that they are at especially high stroke risk.

"We could put them on warfarin for a short period, then switch to aspirin for the longer period," he said.

More information

You can learn about the role of aspirin in preventing stroke and heart attack from the American Heart Association

SOURCES: Marc I. Chimowitz, M.D., professor of neurology, Emory University, Atlanta, Ga.; Walter J. Koroshetz, M.D., director, stroke service, Massachusetts General Hospital, Boston; March 31, 2005, New England Journal of Medicine
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