Antipsychotic Polypharmacy Is Associated With Adverse Drug Events in Psychiatric Inpatients: The Japan Adverse Drug Events Study.

Background: Antipsychotic (AP) polypharmacy (APP), the coprescription of more than 1 AP, is frequently practiced in psychiatric inpatients and is considered to be a risk factor for adverse drug events (ADEs). However, the association between APP and ADEs among psychiatric inpatients has not been well investigated.
Methods: The Japan Adverse Drug Events (JADE) study was a series of cohort studies conducted in several clinical settings. In particular, the JADE study for psychiatric inpatients was a retrospective cohort study of 448 psychiatric inpatients with a cumulative 22,733 patient-days. We investigated the relationship between APP, defined as a concurrent prescription of 2 or more APs and ADEs. We also assessed the relationship between potential risk factors for ADEs due to APs.
Results: Among the 448 patients included in this study, 106 patients (24%) had APP and the remaining 342 patients were prescribed 1 AP or none. Risperidone was the most frequent drug (25%, 109/442 AP prescriptions) used, and levomepromazine was most frequently prescribed as a concurrent medication with other APs (91%, 29/32). The median number of ADEs among the patients with APP was significantly higher than in those without APP (P = 0.001). Antipsychotic polypharmacy was a risk factor for the occurrence of first (adjusted hazard ratio, 1.54; 95% confidence interval, 1.15-2.04) and second (adjusted hazard ratio, 1.99; 95% confidence interval, 1.40-2.79) ADEs.
Conclusions: Antipsychotic polypharmacy was a risk factor for the occurrence of single and multiple ADEs. Antipsychotic polypharmacy should be conservatively and minimally practiced.
Competing Interests: N.A. received grants from the Pfizer Health Research Foundation (13-9-004) and the Osaka Medical Research Foundation for Intractable Diseases (28-2-1); however, the funding sources had no further role in the preparation, data collection, or writing of this manuscript. The other authors declare no conflicts of interest.
(Copyright © 2021 The Author(s). Published by Wolters Kluwer Health, Inc.)