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BMJ. 2007 May 19; 334(7602): 1028.
PMCID: PMC1871776
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Aspirin works best in small doses

Aspirin is the most commonly used drug in the world. In the United States alone, one third of the adult population—some 50 million people—take an aspirin a day to protect themselves from strokes and heart attacks and to help prevent a cardiovascular death. Most people take no more than 325 mg, and some considerably less. But doses up to 1300 mg a day are approved by the US regulatory authorities. What is the best dose for most people?

A systematic review concludes that patients taking aspirin long term do best on doses of 75-81 mg a day. Higher doses don't work better but do increase the risk of side effects, especially gastrointestinal bleeding. The authors estimate that if all American patients took 325 mg a day there would be 900 000 more major bleeds each year than if their daily dose was 81 mg. Buffered or enteric coated aspirins seem no safer than traditional pills.

The authors took a close look at eight randomised trials and three observational studies comparing different doses in patients with established cardiovascular disease. The trials included nearly 10 000 people taking 30-1300 mg a day. None reported better outcomes for patients taking higher doses.


  • JAMA 2007;297:2018-24 [PubMed]

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