Clopidogrel and thrombotic thrombocytopenic purpura: no clear case for causality.

Although the antiplatelet agent clopidogrel is associated with an increased incidence of thrombotic thrombocytopenic purpura (TTP), available evidence is not sufficient to establish or disprove a causal relationship. We review and assess the evidence and case reports linking clopidogrel use with TTP and discuss how to approach the risk of TTP in patients taking clopidogrel.