Aspirin: High or Low Dose? No significant difference.

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Researchers report no significant difference in high versus low dose aspirin in preventing recurring cardiovascular events.

Each year, more than one million Americans suffer a heart attack and nearly all patients are prescribed a daily aspirin and an antiplatelet medication during recovery. However, the optimal aspirin dose has been unclear. Now, new research from Brigham and Women's Hospital (BWH) reports that there is no significant difference between high versus low dose aspirin in the prevention of recurring cardiovascular events in patients who suffer from acute coronary syndromes (ACS), which are characterized by symptoms related to obstruction in coronary arteries, which supply blood to the heart. These findings are presented at the American College of Cardiology Scientific Sessions on March 24, 2012.

"We observed no difference between patients taking a high dose versus a low of aspirin as it relates to cardiovascular death, heart attack, stroke or stent thrombosis," said Payal Kohli, MD,cardiology fellow at BWH and researcher in the TIMI Study Group, who is the lead author on this study. "Interestingly, we did find a dramatic difference in practice patterns of physicians in North America compared to those in the rest of the world," Kohli said. "North American physicians prescribed a high dose of aspirin for two-thirds of all their patients, while the exact reverse was true of the rest of the world. International physicians prescribed a low dose of aspirin to more than two-thirds of their patients." Dr. Stephen D. Wiviott, a cardiologist at BWH and researcher in the TIMI Study Group, is the senior author on the study.

Researchers analyzed data from more than 11000 patients from around the world that were enrolled in the TRITON-TIMI 38 trial, which randomized ACS patients to receive either clopidigrel or prasugrel, two different antiplatelet medications. Some patients were prescribed high doses of aspirin following a heart attack, while others, low doses. The aspirin dose was prescribed at the clinician investigator's discretion and the analysis included 7,106 patients who received low dose aspirin, defined as 150 mg or less, and 4,610 patients who received high dose aspirin, defined as 150 mg or more. Researchers reported that there was no significant difference observed in the prevention of the combination of heart attack, stroke, cardiovascular death or the prevention of stent thrombosis between the groups that received high or low dose aspirin. Prasugrel was more effective at preventing major adverse cardiovascular events than clopidogrel, regardless of whether patients received low or high dose aspirin.

Researchers also present that patients who received high dose aspirin were more likely to have more cardiac risk factors and have higher cholesterol. Patients who received low dose aspirin were more likely to be white and have no prior history of high blood pressure.

The authors caution that because this is not a randomized study, there may be other treatment differences that could have affected the results and a randomized controlled trial would be needed to definitively establish that no difference existed in outcomes between aspirin dose regimens. These data are, however, consistent with previous reports.

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