Effects of platelet inhibitors on the platelet aggregation induced by plasma from patients with thrombotic thrombocytopenic purpura.

Antiplatelet drugs have been used in the treatment of thrombotic thrombocytopenic purpura (TTP) but there in vivo efficacy remains controversial. It has been shown that, in vitro, the plasmas obtained from patients with TTP induced the aggregation of washed platelets from normal donors as well as patients in remission. The effects of platelet inhibitors on the TTP plasma-induced platelet aggregation were examined. It was found that aspirin, indomethacin, ibuprofen, sulfinpyrazone, 5, 8, 11, 14-eisacotetraynoic acid, prostaglandin E1, prostaglandin I2, dBcAMP, apyrase, creatine phosphate/creatine phosphokinase, antimycin, 2-deoxy-D-glucose, dipyridamole, clofibrate, dextran 40, dextran 70, dibucaine, xylocaine, methylmaleimide, and ethylenediamine tetraacetic acid had little or no effect at all. These data lead us to conclude that at least in certain cases, antiplatelet drugs probably play a limited role in the treatment of patients with TTP.