ASSOCIATIONS OF CLOZAPINE AVAILABLE INSTITUTION AND THE DIAGNOSIS OF SUBGROUPS ABOUT TREATMENT-RESISTANT SCHIZOPHRENIA OR NOT WITH A HIGHER RATE OF ANTIPSYCHOTIC MONOTHERAPY AND LOWER OTHER CONCOMITANT PSYCHOTROPICS IN OVERALL SCHIZOPHRENIA TREATMENT: A REAL-WORLD NATIONWIDE STUDY
Authors: Ochi *Shinichiro , Kodaka Fumitoshi , Hasegawa Naomi , Iga Jun-Ichi , Kashiwagi Hiroko , Komatsu Hiroshi , Tagata Hiromi , Tsuboi Takashi , Numata Shusuke , Iida Hitoshi , Igarashi Shun , Ohi Kazutaka , Fukumoto Kentaro , Muraoka Hiroyuki , Matsumoto Junya , Miura Kenichiro , Ueno Shu-Ichi , Watanabe Koichiro , Inada Ken , Hashimoto Ryota , Yasui-Furukori Norio 
Published: February 2025

Abstract

Background
Antipsychotics are used in treatment of schizophrenia. Although antipsychotic monotherapy is recommended in most guidelines, the prescription rate of antipsychotic polypharmacy is still high, and the rates of antipsychotics and other concomitant psychotropics are different among each institution.
Although the detailed causes for these differences are not well known, one of the reasons of psychotropics polypharmacy, including antipsychotics polypharmacy, may be associated with severity of schizophrenia including treatment resistant schizophrenia (TRS). With regard to TRS, institutions with a low TRS examination rate was associated with a low clozapine prescription rate. Thus, the differences of institutions, which is available to clozapine prescriptions or not, may be affected the treatment characteristics of overall schizophrenia in each institution.

Aims & Objectives
We examined the characteristics of psychotropic prescriptions, including antipsychotics, at the time of discharge depending on whether the institutions were available to clozapine prescriptions or not.

Methods
We assessed 8155 schizophrenia patients nationwide from 207 institutions from 2017 to 2020 in Japan. We divided patients into clozapine-available institutions (CAI) group and clozapine-unavailable institutions (CUI) group. We analyzed and compared the psychotropic prescription data at discharge between two groups. We defined “antipsychotic monotherapy” as the prescription of a single antipsychotic regardless of concomitant use of other psychotropics, and we defined “complete antipsychotic monotherapy” as the prescription of a single antipsychotic without concomitant use of other psychotropics. Furthermore, to investigate that the diagnosis of subgroups about TRS or not may influence the treatment, we analyzed the description of subgroups about TRS (DSTRS) or no description of subgroups about TRS (NDSTRS), and we divided the patients into four groups such as CAI with DSTRS, CAI with NDSTRS, CUI with DSTRS, and CUI with NDSTRS, and compared between four groups using the same method. We defined p &lt;1.9 × 10-3 (0.05/27) as significant by post hoc analyses for multiple comparisons of categories.

Results
The number of patients was 6793 in the CAI group and 1362 in the CUI group. The rate of antipsychotic monotherapy in the CAI group was significantly higher than that in the CUI group (58.3% vs 50.7%), and the rate of complete antipsychotic monotherapy in the CAI group was significantly higher than that in the CUI group (20.4% vs 15.6%). The rate of DSTRS was significantly lower in the CAI group than the CUI group (43.6% vs 49.4%). The rate of antipsychotic monotherapy (56.0%) and complete antipsychotic monotherapy (20.0%) in the CAI group except patients prescribed clozapine were also significantly higher than that in the CUI group. The rate of antipsychotic monotherapy in the CAI with DSTRS group (63.3%) and the rate of complete antipsychotic monotherapy in the CAI with DSTRS group (22.6%) were significantly higher than that in the other three groups.

Discussion & Conclusion
Both establishment of clozapine prescription and the precise diagnosis of subgroups about TRS or not at discharge in each institution would lead clinicians to the treatment which may contribute to the higher psychotropic monotherapy rate for overall schizophrenia treatment.