Drs Steinherz and Miller have questioned our failure to consider vincristine as an antiplatelet agent and the statement in our recent article that the action of Vinca alkaloid on platelet function is unknown. They cite their publication1 as evidence for the in vivo antiplatelet effect of vincristine, which they suggest accounts for the therapeutic effect in TTP observed by us.They described an inhibition of second-phase platelet aggregation to epinephrine and ADP, but found collagen-induced aggregation unimpaired, in a "large percentage" of children receiving multidrug therapy, including vincristine, for leukemia and solid tumors. In their patients with leukemia, platelet function was abnormal before administration of vincristine. We do not interpret these data as proof of a significant antiplatelet effect of vincristine. In their article in the British Journal of Haematology,1 the authors cautiously stated on page 447 that "the findings seem to be related to the
GUTTERMAN LA, Stevenson TD. Vincristine and Platelet Function-Reply. JAMA. 1982;248(16):1974–1975. doi:10.1001/jama.1982.03330160026015
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