The important finding by Nordström et al illustrates that olanzapine occupies a high level of dopamine D2 receptors in the human putamen of patients receiving maintenance doses of olanzapine. Although this high level of 68% to 84% occupancy of D2 is the same as that found with the traditional antipsychotic drugs that usually elicit parkinsonism,1 none of the 3 olanzapine-treated patients studied revealed any extrapyramidal signs. Nordström et al appropriately conclude that the high D2 occupancy indicates that olanzapine differs considerably from clozapine, which has a low D2 occupancy.
Seeman P. Positron Emission Tomography Finding of a High Striatal D2 Receptor Occupancy in Olanzapine-Treated Patients—Reply. Arch Gen Psychiatry. 1998;55(3):284. doi: