|
E-mail this page to a friend!
Aspirin is Safer than Warfarin and Just as Effective
for Blocked Brain Arteries
March 31, 2005 - To reduce the risk of stroke,
partial blockage of arteries in the brain (intracranial stenosis) has
for decades been treated with drugs such as aspirin and warfarin that
reduce blood clotting. Doctors, however, have never had good evidence
for choosing one therapy over the other. Now, results of a double-blind,
randomized clinical trial show for the first time that aspirin works as
well as warfarin with fewer side effects.
"This trial is good news. A simple low-cost drug
works just as well as one that requires complicated and expensive
monitoring and dose adjustments," says John R. Marler, M.D., the
Associate Director for Clinical Trials at NINDS. The study appears in
the March 31, 2005, issue of the New England Journal of Medicine.
The study was funded by the National Institute of
Neurological Disorders and Stroke (NINDS), part of the National
Institutes of Health (NIH).
Intracranial stenosis is caused by atherosclerosis
— fatty deposits that build up on the inner walls of the arteries and
restrict blood flow. Intracranial stenosis causes about 10 percent of
the 900,000 strokes and transient ischemic attacks (TIAs) in the United
States each year.
TIAs are transient strokes that last only a few
minutes and occur when the blood supply to part of the brain is briefly
interrupted. People with a stroke or TIA due to intracranial stenosis
have a greatly increased risk of a second stroke — as much as 15 percent
per year.
Studies in the 1950s suggested that anticoagulants
(a class of drugs that reduce blood clotting), such as warfarin, can
reduce the risk of stroke in people with this disease.
In the new study, called the Warfarin Aspirin
Symptomatic Intracranial Disease (WASID) trial, investigators at 59
medical centers across the United States, led by Marc I. Chimowitz,
M.D., of Emory University in Atlanta, compared warfarin to 1300
milligrams (mg) per day of aspirin in a total of 569 patients for an
average of 1.8 years. All of the patients had a greater than 50 percent
blockage of a major intracranial artery and had experienced a TIA or
non-disabling stroke within the 90 days prior to their enrollment in the
study.
The investigators found that about 22 percent of
the patients had a subsequent ischemic stroke (caused by blockage of an
artery), brain hemorrhage, or death from other blood vessel-related
causes, regardless of whether they received aspirin or warfarin.
However, the rates of major hemorrhage and death
from all causes were significantly higher in the patients treated with
warfarin (event rates for aspirin compared to warfarin, respectively,
were 3.2 percent vs. 8.3 percent for major hemorrhage and 4.3 percent
vs. 9.7 percent for death).
Enrollment in the study was terminated earlier than
originally planned on the recommendation of an independent Data and
Safety Monitoring Board because of concern for the safety of the
patients given warfarin.
Since warfarin treatment is a more expensive and
complicated therapy than aspirin, not using warfarin and preventing the
bleeding complications associated with it would save more than $20
million per year in the United States, Dr. Chimowitz estimates.
"The results of this study are only relevant to
people with intracranial stenosis," Dr. Chimowitz notes. People who are
receiving warfarin for other conditions, such as an irregular heart
rhythm (called atrial fibrillation) or clots in the legs or lung, should
not stop taking the drug, as studies have found that it is the best
option in those conditions, he cautions.
The dose of aspirin used in this study — 1300 mg —
is much higher than the daily doses typically prescribed, which range
from 81 to 325 mg. While there is some concern that doses of 1300 mg
aspirin may increase the risk of gastrointestinal bleeding, the
investigators chose this dose because it was the only amount for which
earlier studies had provided good preliminary data.
"This is the only dose we know is as effective as
warfarin for this disease, since it was the only dose studied. We just
don't know how other doses of aspirin would stack up," says Dr.
Chimowitz.
The major bleeding risk on high dose aspirin in
WASID was similar to the major bleeding risk in other stroke trials that
have evaluated lower doses of aspirin (e.g. 325 mg per day), he adds.
Most experts believe there are no advantages to
aspirin doses greater than 325 mg for stroke prevention, and the U.S.
Food and Drug Administration-approved dose of aspirin for prevention of
vascular events is 50-325 mg. Patients should consult their physicians
before beginning any long-term or high-dose aspirin treatment regimen.
Even with treatment, the rates of ischemic stroke
in this clinical trial were substantially higher than in stroke
prevention trials that have evaluated aspirin and warfarin in patients
with other causes of stroke. This underscores that patients with
intracranial stenosis are at particularly high risk for stroke and that
better therapies are needed, the investigators note.
The NINDS is a component of the National Institutes
of Health within the Department of Health and Human Services and is the
nation's primary supporter of biomedical research on the brain and
nervous system.
Click to More Senior News on the
Front Page
Copyright: SeniorJournal.com |
