To the Editor.—
In their article on the "Treatment of Thrombotic Thrombocytopenic Purpura With Vincristine" (1982;247:1433), Gutterman and Stevenson attribute the possible beneficial effect of the drug to its effect on the endothelial cells.1 They consider the vincristine sulfate treatment aside from agents that inhibit platelet aggregation, and state that the effect of Vinca alkaloids on platelets has not been defined.Vinca alkaloids dissolve microtubules and impair the particular cell function with which these structures appear to be associated. When platelets are incubated in vitro with Vinca alkaloids, the microtubules are disrupted, the discoid platelet becomes relatively spherical,2 and interference with normal aggregation occurs.3 We have demonstrated in vivo that a large percentage of patients receiving vincristine have a demonstrable thrombocytopathy with absent second-phase platelet aggregation to epinephrine and adenosine diphosphate (ADP).4 Therefore, the possible therapeutic effect of vincristine in thrombotic thrombocytopenic purpura (TTP) may be
Steinherz PG, Miller DR. Vincristine and Platelet Function. JAMA. 1982;248(16):1974. doi:10.1001/jama.1982.03330160026014
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