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Bleeding Risk with Low-Dose Aspirin and with Clopidogrel
Risk for bleeding with low-dose aspirin was low in this meta-analysis, which lacked sufficient data to allow conclusions to be drawn about risk for bleeding with clopidogrel versus aspirin.
Aspirin is commonly used for preventing atherosclerotic events. Prior systematic reviews of the risk for bleeding with aspirin included studies of high-dose aspirin. In this meta-analysis, supported by a manufacturer of aspirin, the authors calculated the risk, relative to placebo, for bleeding with low-dose aspirin (defined as 75 mg–325 mg/day) for primary or secondary prevention of vascular disease. They also searched for all studies with clopidogrel in a treatment arm. Most patients in the included studies did not have histories of stroke.
Meta-analysis across nine studies (>53,000 patients total) and adjusted for treatment duration showed that the rate of major bleeding with placebo was 0.18% per year. Low-dose aspirin increased that rate by an additional 0.13% per year (relative risk, 1.7). Only three eligible studies involved clopidogrel, and the results could not be combined because of different comparison groups. The authors annualized the data from a single randomized controlled trial showing higher risk for major gastrointestinal bleeding with aspirin than with clopidogrel; they reported a risk difference of 0.12% per year (Lancet 1996; 348:1329).
Comment: The risk for bleeding with low-dose aspirin relative to placebo in this meta-analysis is similar to the bleeding risk reported in a prior large meta-analysis of all antiplatelet agents (Journal Watch Neurology March 28 2002). The current meta-analysis does not provide new information on the relative risks for bleeding with aspirin versus clopidogrel. Also left unresolved is a commonly encountered quandary: determining whether the benefits of antiplatelet agents outweigh the risks for bleeding in a person with a history of a major bleed, such as a GI bleed or an intracranial hemorrhage, because these patients typically are excluded from trials.
— Eric Cheng, MD, MS, and Barbara Vickrey, MD, MPH
Dr. Cheng is Assistant Professor of Neurology, VA Greater Los Angeles Healthcare System/University of California, Los Angeles.
Dr. Vickrey is Professor, Department of Neurology, University of California Los Angeles School of Medicine, Los Angeles.
Published in Journal Watch Neurology October 31, 2006
Citation(s):
McQuaid KR and Laine L. Systematic review and meta-analysis of adverse events of low-dose aspirin and clopidogrel in randomized controlled trials. Am J Med 2006 Aug; 119:624-38.
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