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What Aspirin Dose Is Safest and Most Effective for Preventing Heart Disease?
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What is the problem and what is known about it so far?
Aspirin and clopidogrel (Plavix) are drugs that block the ability of platelets to stick together and form clots. Because the drugs prevent clotting, they may also cause bleeding. Doctors often prescribe daily aspirin to prevent future blood clots in people who have had or are at high risk for heart attacks and strokes. In these groups, the benefits of preventing clots outweigh the risk for bleeding. However, different doses of aspirin may have different benefits and risks. For example, lower aspirin doses may cause less bleeding but may be less effective at preventing clots. Also, higher aspirin doses may be more effective at preventing clots but may cause more bleeding.
Why did the researchers do this particular study?
To see which dose of aspirin seems to be safest and most effective.
Who was studied?
Almost 15 600 people at risk for heart attack and stroke who were taking aspirin. All had been participants in a study of whether clopidogrel and aspirin prevented more heart attacks and strokes than aspirin alone.
How was the study done?
The researchers grouped together participants who were taking lower and higher aspirin doses. They then followed them over time and compared the number of people in each group who died or had heart attacks, strokes, or bleeding events.
What did the researchers find?
Outcomes did not obviously differ between people who took lower and higher aspirin doses. However, people who took higher aspirin doses together with clopidogrel may have been slightly more likely to die or have a heart attack, stroke, or bleeding event.
What were the limitations of the study?
The findings are not definitive because participants were not assigned at random to receive higher and lower aspirin doses.
What are the implications of the study?
Higher daily aspirin doses are not clearly better than lower doses. Higher doses may cause more harm, especially for people taking clopidogrel. Lower doses may be equally effective and safer.
Article and Author Information
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The summary below is from the full report titled “Aspirin to Prevent Cardiovascular Disease: The Association of Aspirin Dose and Clopidogrel With Thrombosis and Bleeding.” It is in the 17 March 2009 issue of Annals of Internal Medicine (volume 150, pages 379-386). The authors are S.R. Steinhubl, D.L. Bhatt, D.M. Brennan, G. Montalescot, G.J. Hankey, J.W. Eikelboom, P.B. Berger, and E.J. Topol, on behalf of the CHARISMA Investigators.
