Striatal dopamine-2 receptor occupancy in psychotic patients treated with risperidone

Seventeen psychiatric patients (11 with schizophrenia, 5 with other psychotic disorders, and 1 with obsessive-compulsive disorder) were examined by single photon emission computed tomography with I-123-iodobenzamide (IBZM) as tracer. Patients were treated with risperidone in two different dosage groups (3 mg and 8 mg) and haloperidol (10-20 mg) and compared with eight healthy control subjects. There was a statistically significant difference in basal ganglia/frontal cortex ratios of IBZM binding between controls and all treatment groups. A statistically significant difference was also found concerning these ratios and percentage of dopamine D-2 receptor occupancy rates between the treatment groups with lowest ratios and highest percentage of D-2 receptor occupancy in the group of patients treated with haloperidol, followed by the group treated with 8 mg of risperidone and the group treated with 3 mg of risperidone. Copyright (C) 1996 Elsevier Science Ireland Ltd.