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TTP Associated with Clopidogrel

The antiplatelet drug clopidogrel (Plavix) is used commonly in patients with cerebrovascular and coronary disease. During the past several years, cases of thrombotic thrombocytopenic purpura (TTP) have occurred among patients who were treated with ticlopidine (Ticlid), a similar antiplatelet drug. These investigators describe 11 cases of TTP associated with clopidogrel; cases were identified by surveying hematologists, blood banks, and the drug manufacturer.

All patients had thrombocytopenia and microangiopathic hemolysis, and most showed neurologic changes or increases in serum creatinine levels. Patients were 35 to 70 years old; 6 were female, and 5 were taking concomitant cholesterol-lowering drugs (atorvastatin and simvastatin). In 10 of the 11 cases, clopidogrel had been used for 2 weeks or less when TTP was diagnosed; the other case was diagnosed after nearly a year of use. All patients were treated with plasma exchange, and 1 died. Two patients experienced recurrent episodes of TTP during the several months after initial responses to plasma exchange.

Comment: Although the exact mechanism is unclear, it is highly likely that clopidogrel, like ticlopidine, causes TTP in rare cases. Clopidogrel-associated TTP usually occurs soon after the drug is initiated. An editorialist uses these data to emphasize the need for more rigorous post-market surveillance for drug side effects.

— AS Brett

Published in Journal Watch General Medicine July 4, 2000

Citation(s):

Bennett CL et al. Thrombotic thrombocytopenic purpura associated with clopidogrel. N Engl J Med 2000 Jun 15 342 1773-1777.

• Medline abstract (Free)

Wood AJJ. Thrombotic thrombocytopenic purpura and clopidogrel -- A need for new approaches to drug safety. N Engl J Med 2000 Jun 15 342 1824-1826.

• Medline abstract (Free)

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