Treatment Continuation of Asenapine or Olanzapine in Japanese Schizophrenia Patients: A Propensity Score Matched Study

Objective: Asenapine is a second-generation antipsychotic agent that is classified as a multi-acting receptor-targeted antipsychotic and is similar to olanzapine. Our study aimed to compare the treatment continuation rate and reason for discontinuation of asenapine or olanzapine in schizophrenia using real-world data. Methods: This design was a retrospective study. The primary endpoint was Kaplan–Meier estimates of the continuation rate at six months, with the propensity score method applied to adjust for potential confounders. Results: A total of 95 patients were analyzed in this study (asenapine, n = 46; olanzapine, n = 49). Matched data were adjusted to consider six covariates (age, sex, chlorpromazine equivalent, diazepam equivalent, history of clozapine use, and history of modified electro convulsive therapy). The continuation rate at six months was 27.3% (95% CI, 15.6–47.6) in the asenapine group and 50.8% (95% CI, 34.3–75.3) in the olanzapine group (hazard ratio, 0.41; 95% CI, 0.21–0.82; P = 0.0088 by the Log rank test) in matched data. Cases of discontinuation because of the lack of efficacy were almost as frequent for asenapine (13.0%) as for olanzapine (10.2%). Discontinuation due to bitter taste (6.5%) and burden of the dosing method (6.5%) were observed only with asenapine, whereas anticholinergic side effects such as dry mouth (4.1%) and constipation (2.0%) were observed only with olanzapine. Conclusion: The low continuation rate of asenapine in real-world data may be related to specific factors such as bitter taste and burden of the dosing method.