PLATELET SHAPE CHANGE IN PATIENTS WITH PSYCHIATRIC DISORDERS AND TREATED WITH PHENOTHIAZINES, THIOXANTHINES, BUTYROPHENONES, BENZODIAZEPINES, TRICYCLIC ANTIDEPRESSANTS AND β-ADRENERGIC BLOCKING AGENTS

Platelet shape change responses to 5-HT 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 anti depressant, benzodiazepine or lithium. Approximately 37% of patients received one drug; the remainder received up to 4 other compounds in addition to the main drug. In some patients it was difficult to decide which was the main drug given therapeutically. Platelet shape change induced by 5-HT was significantly inhibited in patients treated with phenothiazines, thioxanthines and butyrophenones (haloperidol). Tricyclic antidepressants, lithium and benzodiazepines had no effect on 5-HT-induced shape change. Noradrenaline (NA) was also used to potentiate 5-HT-induced shape change. Inhibition of NA-induced potentiation was approximately 50% in normal subjects. This degree of potentiation was not altered in the drug-treated patients although there were quantitative reductions in the magnitude of responses. The use of platelet shape change rather than aggregation may be used as a pharmacological tool to investigate the aetiology of psychiatric disorders and possibly at a later stage to monitor the clinical efficacy of drug therapy.