[Theory in antipsychotic drug therapy for schizophrenia]

In Japan, antipsychotic polypharmacy with high doses for schizophrenia has been traditionally used. However, antipsychotic polyphamacy with high doses provide disadvantages for patient. Recent PET studies show that dopamine D2 occupancy with antipsychotics is important for the treatment of schizophrenia. First, antipsychotics become effective only at which their D2 occupancy exceeds 65%. Second, antipsychotics with D2 occupancy below 90% rarely causes occupancy exceeds 65%. Second, antipsychotics with D2 occupancy below 90% rarely causes extrapyramidal side effect. These results suggest that monopharmacy which uses a single antipsychotic agent with appropriate dose is recommended for schizophrenia treatment.