The safety of clopidogrel.

IMPORTANCE OF THE FIELD: Clopidogrel is an antiplatelet prodrug widely used in acute coronary syndromes and after intravascular stent placement. Acute or chronic use can cause bleeding, a major adverse effect, which can lead to drug discontinuation or noncompliance with therapy. AREAS COVERED IN THIS REVIEW: The mechanism of action of clopidogrel, safety of different loading doses of clopidogrel, its use as a solitary antiplatelet agent and concomitant use with other antiplatelet agents such as aspirin and warfarin are discussed. Thrombotic thrombocytopenic purpura, a rare but important adverse event, has also been reviewed. Literature searches including randomized controlled trials were conducted in Medline. WHAT THE READER WILL GAIN: Clinicians will be able to understand the safety profile of using different doses of clopidogrel and the incidence of bleeding when used alone or in combination with other antiplatelet agents. TAKE HOME MESSAGE: Compared to aspirin, clopidogrel when taken alone causes less severe bleeding and less intracranial hemorrhage. Higher loading dose of clopidogrel is associated with increased bleeding. When combined with other antiplatelet agents, risk of bleeding increases, but like any other drug, the risks have to be weighed against potential benefits.