Changes in psychopharmacotherapy for patients with schizophrenia in a psychiatric institution in Japan: A 12-year prescription survey pre- and post-introduction of clozapine

Abstract

Psychopharmacotherapy for patients with schizophrenia in Japan has a long history of polypharmacy, which is rare worldwide but remains a critical problem. One reason for this is that clozapine was not available in Japan until 2009. We aimed to investigate the changes in psychopharmacotherapy in patients with schizophrenia over 12 years pre- and post-introduction of clozapine to clarify how psychopharmacotherapy for patients with schizophrenia has changed with the introduction of clozapine. We retrospectively collected data from the medical records of inpatients diagnosed with schizophrenia at the Okayama Psychiatric Medical Center. Chlorpromazine equivalent (CP-eq) decreased from 1276.6 mg/day in 2009 to 613.9 mg/day in 2020. The prescribed daily dose/defined daily dose (PDD/DDD) decreased from 3.0 in 2009 to 1.2 in 2020. The monotherapy rate increased from 24.4 % in 2009 to 74.6 % in 2020. Our institution began using clozapine in 2010, and the prescription rate for clozapine increased to 37.3 % in 2020. The prescription rate for more than three antipsychotics decreased from 27.8 % in 2009 to 0.8 % in 2020.The increase in clozapine prescription has contributed to an increased rate of antipsychotic monotherapy and a decreased rate of polypharmacy, promoting the optimization of schizophrenia medication. Clozapine therapy should be further promoted in Japan to reduce treatment-resistant schizophrenia due to polypharmacy as much as possible.