Effect of clozapine treatment on serotonin-2-receptor binding in the blood platelets of schizophrenic patients.

The effect of clozapine and typical neuroleptic drug treatment on platelet serotonin2 (5-HT2) binding kinetic constants (Kd, Bmax) was studied in schizophrenic patients. Both treatments increased Bmax by a comparable amount, indicating increased numbers of 5-HT2 sites, although not all typical neuroleptic drugs were effective in this regard. Clozapine, but not typical neuroleptic drugs, increased Kd, indicating a lower affinity of the 5-HT2 sites for 5-HT. In a multiple regression model, low Bmax at baseline predicted poor outcome on Brief Psychiatric Rating Scale measures in the clozapine-treated patients but not the neuroleptic-treated patients.