Associations between clozapine availability, the diagnosis of treatment-resistant schizophrenia subgroups, antipsychotic monotherapy, and concomitant psychotropics among patients with schizophrenia: a real-world nationwide study

Abstract

Background and hypothesis: The rate of antipsychotic polypharmacy is high. One risk factor for antipsychotic polypharmacy may be the severity of schizophrenia, including treatment-resistant schizophrenia (TRS). We hypothesized that the institutions that are able to prescribe clozapine present differences in pharmacological treatment even before TRS is diagnosed.

Study design: A total of 8155 patients with schizophrenia were divided into the clozapine-available institution (CAI) group and the clozapine-unavailable institution (CUI) group. The psychotropic prescription rates at discharge were compared between the two groups. Furthermore, to investigate whether the diagnosis of TRS subgroups influenced treatment efficacy, we compared CAIs and CUIs with descriptions of subgroups with TRS (DSTRS) and those without descriptions of subgroups with TRS (NDSTRS).

Results: Compared to the CUI group, the rates of both antipsychotic monotherapy (58.3% vs. 50.7%; P = 2.4 × 10-7) and antipsychotic monotherapy without the concomitant use of other psychotropics (20.4% vs. 15.6%; P = 3.8 × 10-5) were significantly higher in the CAI group. The rate of antipsychotic monotherapy in the CAI with DSTRS group (63.3%) was significantly higher than that in the CAI with NDSTRS group (54.5%; P = 1.4 × 10-12), the CUI with DSTRS group (49.6%; P = 4.9 × 10-9), and the CUI with NDSTRS group (50.9%; P = 2.0 × 10-8). The rate of antipsychotic monotherapy without the concomitant use of other psychotropics in the CAI with DSTRS group (22.6%) was also significantly higher than that in the CAI with NDSTRS group (18.7%; P = 4.7 × 10-4), the CUI with DSTRS group (15.9%; P = 5.5 × 10-4), and the CUI with NDSTRS group (15.2%; P = 8.0 × 10-5). There was no significant difference in these rates between the other groups.

Conclusions: Both the availability of clozapine prescriptions and the precise diagnosis of TRS subgroups at discharge can promote the development of an organizational culture that facilitates the treatment of patients with schizophrenia.

Keywords: EGUIDE; guidelines; implementation strategy; polypharmacy; treatment-resistant schizophrenia.