Drug Utilization of Japanese Patients Diagnosed with Schizophrenia: An Administrative Database Analysis

Background and objective Patient characteristics require consideration for optimal treatment in order to achieve clinical remission for an improved quality of life and social functioning. Prior evidence supports long-acting injectable antipsychotics (LAIs) in the relapse prevention of schizophrenia. This study aimed to characterize Japanese patients diagnosed with schizophrenia and to compare the outcomes of LAIs and oral antipsychotics (AP) in re-hospitalization or emergency room visit rates. Methods Diagnostic Procedure Combination (DPC) designated hospital data in Japan with ICD-10 code F20x between July 2013 and June 2015 were obtained from the Medical Data Vision Co. Ltd. Patients were divided into sub-groups in order to filter co-diagnostic conditions. Differences across sub-groups were assessed using a Chi square test or ANOVA. The incidence rate ratio (IRR) was calculated to compare the re-hospitalization (30 days post discharge) or emergency room visit rates between pharmacotherapy groups of oral versus LAI or typical versus atypical within LAI patients. Adjusted estimates were provided by propensity scores that were assigned for age, gender, and Charlson co-morbidity index (CCI) scores. Results A quarter of the data sourced were attributed to codiagnosis with dementia/delirium with antipsychotic prescriptions despite reported risks of antipsychotic use. After adjusting for age, gender, and co-morbidity, LAI reduced re-hospitalization and emergency (ER) visit rates more than oral APs (LAI vs. oral IRR = 0.38 (95% CI 0.17-0.74), IRR = 0.56 (95% CI 0.34-0.91), respectively). Conclusion The study findings demonstrate usage of DPC hospital data in schizophrenia pharmacotherapy based on classification of co-diagnoses. In comparison with oral APs only, LAI utilization can provide an opportunity for reduced re-hospitalization and ER visit rates among patients with schizophrenia.