Thursday, January 10, 2008

Lower doses of aspirin are safer and as effective
By Kelly Winget

Lower doses of aspirin are equally as effective in the early treatment of heart attacks and might be safer because lower doses reduce the risk of serious bleeding, according to a new study by Duke and DCRI researchers.

Researchers found that a low dose of aspirin (162 mg or less) was just as effective at reducing blood clots in patients with ST-elevation myocardial infarction (STEMI) as higher doses of aspirin. STEMI is one of the most common types of heart attack. The study results are published in the January 15 issue of Circulation.

"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 Dr. Jeffrey Berger, 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 frequently prescribed drugs, and it is highly effective. Even 100 milligrams can stop the formation of blood clots, which is vital when treating a heart attack patient, said Berger. Blood clots can clog arteries and prevent blood from reaching the heart.

But aspirin can also increase the risk of serious bleeding, which could mean a possible transfusion, stroke or even death for the patient. “We need to be very careful in how much aspirin we prescribe," said Berger.

Berger led a study that reviewed the effects of a low versus a high dose of aspirin in nearly 50,000 patients who were diagnosed with STEMI in two international trials. Three-quarters of the patients received 162 mg or less, and the rest got a higher dose. The research team also tracked death rates and incidences of serious bleeding in both groups for up to 30 days following therapy.

The only difference in outcomes was that the patients who received the higher doses of aspirin had a significantly higher rate of bleeding. The studies were observational only, and participants were not randomized, but Berger believes the study offers strong support for lowering the amount of aspirin that physicians use to treat their heart attack patients.

One possible reason for treating patients with higher doses of aspirin is the way it is manufactured and sold, said Berger. The most common strength of aspirin on the market is either an 81 or a 325 milligram tablet - no single, 162 milligram product is readily available. Physicians might also assume that the higher dose is more effective.

DCRI co-authors of the study include Christopher Granger, MD; Magnus Ohman, M.B, CH.B; Robert Harrington, MD, director of the DCRI; Robert Califf, MD, director of the DTMI; Amanda Stebbins and senior author, Eric Peterson, MD.