Thrombocytopenia after treatment with platelet glycoprotein IIb/IIIa inhibitors.

Abciximab, eptifibatide, and tirofiban are the three drugs approved by the US Food and Drug Administration designed to block platelet aggregation by binding glycoprotein IIb/IIIa. Results from large therapeutic trials demonstrate that all three agents induce thrombocytopenia in approximately 1% to 5% of cardiac patients. Thrombocytopenia is typically rapid in onset and antibody mediated. In vitro evidence suggests abciximab-induced thrombocytopenia is associated with antibodies directed to murine sequences within the chimeric anti-IIb/IIIa molecule. In addition, abciximab, eptifibatide, and tirofiban also function as mixed agonist-antagonists in vivo, inducing neoepitopes within the glycoprotein IIb/IIIa receptor that may react with pre-existing or induced antibodies. Screening for the development of these antibodies may reduce the incidence of thrombocytopenia associated with these agents, but it may limit their chronic usage.