The ralationship between changes in 5-HT induced platelet aggregation and clinical state in patients treated with fluphenazine.

Platelet aggregation responses to 5-HT and adenosine diphosphate were examined in a population of eighteen patients treated with fluphenazine decanoate for longer than one year. 5-HT induced aggregation was enhanced in ten subjects. This enhancement was similar to that previously described in patients receiving chlorpromazine. Patients who showed enhanced 5-HT induced aggregation showed less rateable psychopathology and less extrapyramidal side-effects than patients who did not show enhancement. These findings suggest that platelet aggregation responses could be used to identify patients who could be safely withdrawn from long-term neuroleptic therapy.