Extrastriatal dopamine D2 receptor occupancy in olanzapine-treated patients with schizophrenia

Olanzapine is described as a multi-acting receptor-targeted antipsychotic agent. Although regional differences of dopamine D₂ receptor occupancy, i.e., limbic selectivity, were reported for olanzapine, contradictory results were also reported. We measured dopamine D₂ receptor occupancy of olanzapine in extrastriatal regions in patients with schizophrenia using positron-emission tomography with ¹¹C]FLB457 and the plasma concentrations of olanzapine. Ten patients with schizophrenia taking 5–20 mg/day of olanzapine participated. Dopamine D₂ receptor occupancy in the temporal cortex ranged from 61.1 to 85.8%, and plasma concentration was from 12.7 to 115.4 ng/ml. The ED₅₀ value was 3.4 mg/day for dose and 10.5 ng/ml for plasma concentration. The ED₅₀ values obtained in this study were quite similar to those previously reported in the striatum. In conclusion, although the subjects and methods were different from previous striatal occupancy studies, these results suggest that limbic occupancy by olanzapine may not be so different from that in the striatum.