Comparison of Standard and Two-Injection Start Regimens of Long-Acting Injectable Aripiprazole Monohydrate in Female Patients With Schizophrenia and Bipolar Disorder

Background: Long-acting injectable (LAI) antipsychotics improve adherence and reduce relapse in severe mental illnesses. A new two-injection start (TIS) regimen of aripiprazole monohydrate LAI has recently been introduced as an alternative to the standard initiation regimen. Evidence on its clinical benefits, particularly in females with schizophrenia or bipolar disorder, remains limited. Methods: This retrospective cohort study included 87 female inpatients diagnosed with schizophrenia or bipolar disorder. Participants were divided into two groups according to initiation protocol: The standard regimen (400 mg injection plus 14 days of oral aripiprazole) or the TIS regimen (two 400 mg injections with a single 20 mg oral dose). Clinical outcomes were compared between groups, including time to discharge, rehospitalization rates, and symptom change. Results: Of the total sample, 47 patients received the TIS regimen and 40 the standard regimen. Baseline demographic and clinical features were comparable between groups. Time to discharge was significantly shorter in the TIS regimen group (mean 8.1 vs. 11.8 d, P = 0.042). Rehospitalization rates within 1 year were lower in the TIS regimen group (17.0% vs. 37.5%, P = 0.031), and time to rehospitalization was longer ( P = 0.027). Adherence patterns favored the TIS regimen, with a higher proportion of regular use. In the schizophrenia subgroup, PANSS reductions from admission to discharge were greater with the TIS regimen. Adverse events were infrequently documented. Conclusions: Aripiprazole monohydrate LAI initiation with the TIS regimen was associated with shorter hospitalization and more favorable rehospitalization outcomes compared with the standard protocol in female patients.