Platelet function after the administration of chlorpromazine to human subjects

Chlorpromazine is known to inhibit platelet function in vitro. The intramuscular injection of 50 mg to human volunteers caused only minor changes in platelet function. There was a small, but significant, reduction in the platelet count, the second phase of the double-wave of adenosine diphosphate-induced aggregation and the rate of 5-hydroxytryptamine-induced aggregation. Patients on high doses of chlorpromazine had no demonstrable abnormality of platelet function. This suggests that chlorpromazine, despite its inhibitory effect on platelet function in vitro, is unlikely to interfere with either haemostasis or thrombogenesis after its administration to man.