At least 40 million Americans take a daily dose of aspirin to prevent heart disease or stroke. But a new study finds that coated or buffered pills may not deliver the same benefits as the basic tablet.
The study, published Tuesday in Circulation, a journal produced by the American Heart Association, was undertaken to examine "aspirin resistance," the theory that the drug cannot help certain individuals ward off heart disease because in such people, for whatever reason, the drug fails to discourage blood platelets from clotting — its primary preventive benefit.
First, the good news: University of Pennsylvania researchers studied 400 healthy adults and found no cases of true aspirin resistance, even though some doctors (not associated with the new study) had speculated that as much as 40 percent of the population did not benefit from aspirin therapy. But even patients who appeared to be resistant in early rounds of the new study were later found not to have the problem, leading one researcher to report that if resistance actually exists, "the incidence is vanishingly small."
Questioning a Popular Treatment
What the team did discover, however, is that the coating on certain aspirin may interfere with the delivery of the drug in the body, limiting its effectiveness.
The findings have high stakes — both because coated aspirin brands are among the most widely sold on the market and because doctors typically prescribe pricier prescription drugs, like Plavix, to patients believed to be resistant to aspirin's effects. Bayer, the world's largest manufacturer of brand-name aspirins, many of them coated, partly financed the new study, but disputes some of its findings, according to The New York Times.
The company released a statement insisting that coated aspirin prevents clotting as effectively as uncoated formulations. (Both are equally effective for pain relief.) But Garret FitzGerald, chairman of pharmacology at the University of Pennsylvania and a co-author of the new study, maintained there's no reason for patients to purchase anything other than a cheaper, uncoated generic.
"These studies question the value of coated, low-dose aspirin," FitzGerald said in a statement. "This product adds cost to treatment without any clear benefit. Indeed, it may lead to the false diagnosis of aspirin resistance and the failure to provide patients with an effective therapy."
While many people prefer coated aspirin because it is easier on the stomach, it has not been proven to lessen the risk of gastrointestinal bleeding, a major potential side effect of all aspirin.
What the Findings Mean to You
So how should anyone already taking aspirin respond to the new findings? Cardiologist Robert Bonow, a Northwestern University medical professor and past president of the American Heart Association, says the association has long discouraged patients who have had heart bypass surgery or live with a stent from using coated aspirin in their ongoing treatment. "Those recommendations are already out there," he says. "It's pretty strongly worded that those patients should not use coated aspirin because of prior studies showing a variability of effectiveness."
Variability in the effectiveness of coated aspirin as a preventive measure against heart attack or stroke is the major finding of this new study, Bonow says. The inconsistent results it found in subjects who took coated aspirin, he says, may lead the heart association to change its recommendations for anyone taking aspirin as a preventive.
"The guidelines we have for taking aspirin to prevent heart attacks don't specify" whether you should take coated or uncoated pills, Bonow says. "It's quite possible that a study like this, which is pretty important, could lead to changes in those recommendations. The guidelines committee will need to weigh this.
"But personally, as a doctor who sees patients, I think this is important information," he adds. "First, the fact that there does not appear to be a lot of aspirin resistance, and also this concern that coated aspirin may not be doing the best job for everybody."
Patients should consult their physician before beginning an aspirin regimen, Bonow advises, pointing out that a daily aspirin is not necessarily recommended for people with a low risk of heart attack or stroke, as the risk of gastrointestinal bleeding may outweigh the preventive benefit.
"We don't recommend aspirin for everybody," he says. "But if you do have a higher risk, where aspirin would be a good idea," your doctor may now determine that "coated aspirin may not be the best way to go."