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Question:
Is there a difference between low dose and regular dose aspirin for preventing heart attack and stroke?
Is there any difference in the efficacy of low dose aspirin vs. regular dose (325mg) aspirin when being taken for preventing heart attacks and strokes?
submitted by Alan from Boston, Massachusetts on 2/24/10
Answer:
by Texas Heart Institute cardiologist, Jose G. Diez, MD
Aspirin is a key medication used to prevent formation of blood clots by preventing the aggregation of blood cells called platelets. These cells when activated by physical or chemical elements produce many inflammatory and thrombogenic substances. Aspirin inhibits the formation of thromboxane.
It has been identified that long-term aspirin dosages as low as 30 mg/d are adequate to fully inhibit platelet thromboxane production, dosages as high as 1300 mg/d are approved for use. In the United States, 81 mg/d of aspirin is prescribed most commonly (60%), followed by 325 mg/d (35%). Currently available clinical data do not support the routine, long-term use of aspirin dosages greater than 75 to 81 mg/d in the setting of cardiovascular disease prevention. Higher dosages, which may be commonly prescribed, do not better prevent events but are associated with increased risks of gastrointestinal bleeding. Ref: JAMA. 2007;297(18):2018-2024.
The European experience was reviewed in 2002 and an analysis of over 20,000 patients treated with antiplatelet agents (mainly aspirin) indicate that high doses of 500-1500 mg aspirin daily (which are more gastrotoxic) are no more effective than medium doses of 160-325 mg/day or low doses of 75-150 mg/day). Results from trials of lower doses are less conclusive. Hence, the available evidence supports daily doses of aspirin in the range 75-150 mg for the long term prevention of serious vascular events in high-risk patients. BMJ 2002.
In general, the recommended dose of aspirin would be 81 mg daily for secondary prevention, apart from an acute situation and perhaps in the initial 4 weeks after a stent placement, where 325 mg would be preferable for at least one month. Then, decreasing to 81 mg a day.
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Updated March 2010
