Platelet shape change in patients with psychiatric disorders and treated with phenothiazines, thioxanthines, butyrophenones, benzodiazepines, tricyclic antidepressants and beta-adrenergic blocking agents.

Platelet shape change responses to 5-hydroxytryptamine were examined in 11 normal subjects and in 78 patients with psychiatric disorders receiving one or more of the following classes of drug: phenothiazine, thioxanthine, butyrophenone, tricyclic antidepressant, benzodiazepine or lithium. Approximately 37% of patients received a single drug, the remainder up to 4 other compounds in addition to the main drug. Platelet shape change induced by 5-hydroxytryptamine (0.25, 2.5 or 25 nmol/ml) was significantly inhibited in patients treated with phenothiazines, thioxanthines and butyrophenones (haloperidol). Tricyclic antidepressants, lithium and benzodiazepines had no effect on 5-hydroxytryptamine-induced shape change. In contrast, a combination of lithium plus chlorpromazine significantly enhanced platelet shape change. Potentiation of noradrenaline-induced aggregation was approximately 50% in normal subjects. This degree of potentiation was not altered in the drug-treated patients although there were quantitative reductions in magnitude of response. Platelet shape change in addition to platelet aggregation may be used as a pharmacological tool to investigate the aetiology of psychiatric disorders and, perhaps eventually, to monitor the clinical efficacy of drug therapy.