Docs May be Overdosing Aspirin in Treating Heart Attacks
DURHAM, NC – When it comes to aspirin, less is more in the
early treatment of a heart attack, say researchers at Duke
University Medical Center. But many physicians may not be
getting the message.
In a study appearing in the January 15 issue of the journal
Circulation, researchers show that a low dose of aspirin
appears to be just as effective as a higher dose of the drug in
the initial treatment of ST-elevation myocardial infarction
(STEMI), one of the most common types of heart attack. They
also say a lower dose is safer, because it is associated with
"We have known for almost 20 years that a low-dose of
aspirin (162 milligrams) given in the early stages of a heart
attack can save lives," says Jeffrey Berger, MD, a cardiologist
at Duke and lead author of the study. "Yet the majority of the
doctors in this country are still prescribing 325 milligrams
despite the lack of evidence showing that more is better."
Aspirin is one of the most widely prescribed drugs in the
world, and Berger says people -- physicians included -- may
underestimate its power. "We know that a single dose of just
100 milligrams of aspirin can completely block within minutes
the formation of blood clots," he says. That's critical in
treating a heart attack because clots can clog arteries and
block blood from reaching the heart.
But taking aspirin comes at a cost. The very same mechanism
that can break up life-threatening clots can increase the
chance of serious bleeding, which could lead to the need for a
transfusion, a stroke or even death. "So we need to be very
careful in how much aspirin we prescribe," says Berger.
Berger led a team of researchers in reviewing the effects of
a low versus a high dose of aspirin in nearly 50,000 patients
suffering from STEMI in two international trials.
Three-quarters of the patients got a low dose of aspirin (162
mg or less) and the rest got a higher dose. Investigators
tracked death rates and episodes of serious bleeding in both
groups for up to 30 days following therapy.
They found no difference between the two groups in terms of
short-term outcomes, except for a difference in bleeding: Those
patients who took the higher dose of aspirin had significantly
more bleeding than those who took the lower dose.
The study does not provide the definitive answer regarding
dosing because it was observational in nature, and the
participants in the trials were not randomized to preset dosing
levels or compared with controls. Still, Berger feels it offers
enough evidence to suggest that clinicians take another look at
"If a lower dose of aspirin is just as good -- and more may
be harmful -- why risk it?"
Doctors may be over prescribing aspirin simply because of
the say it is manufactured and sold, says Berger. The most
common and easily used form of aspirin on the market is either
an 81 or a 325 milligram tablet - no single, 162 milligram
product is readily available. In addition, Berger says
physicians who already realize that 162 milligrams is
effective, might simply assume that twice as much is better,
despite evidence to the contrary.
Co-authors of the study include Christopher Granger, Eric
Ohman, Robert Harrington, Robert Califf, Amanda Stebbins and
senior author, Eric Peterson, all from Duke Clinical Research
Institute; Paul Armstrong, from the University of Alberta;
Frans Van der Werf, of Gasthuisberg University Hospital,
Belgium; Harvey White, from Auckland City Hospital, New
Zealand; and R. John Simes, from the University of Sydney.