D1, D2, and 5-HT2 receptor occupancy in relation to clozapine serum concentration: a PET study of schizophrenic patients

Abstract

The results confirm in an extended series of patients that clozapine is atypical with regard to degree of D2 receptor occupancy, a finding that may explain the lack of extrapyramidal side effects. The combination of relatively high D1, low D2, and very high 5-HT2 receptor occupancy values is unique to clozapine. Clozapine serum concentrations have not been unequivocally shown to predict clinical effects. In this study, concentration did not predict degree of occupancy in brain. Thus, careful clinical titration cannot be replaced by monitoring of drug concentrations for optimization of clozapine treatment in individual patients.