Switching strategies for antipsychotic monotherapy in schizophrenia: a multi-center cohort study of aripiprazole

Rationale: Changing antipsychotics of patients with chronic schizophrenia involves several risks. Switching to aripiprazole is especially difficult. We investigated switching methods and related factors for successful switching patients with chronic schizophrenia to aripiprazole. Objectives: This study was a multi-center historical cohort study and approved by the research ethics committee of Okayama University Hospital and Okayama Psychiatric Medical Center. We compared survival proportions of 178 chronic schizophrenia patients who continued aripiprazole monotherapy for 6 months after non-direct switching (add-on switching (n = 45), cross switching (n = 62)) or direct switching (n = 71). We adjusted possible confounders using a Cox proportional hazards model. Results: Of patients with chronic schizophrenia, 56.7% (101/178) were switched to aripiprazole monotherapy, and 55.0% (98/178) showed improvement in symptoms as demonstrated by the Clinical Global Impression Severity score. Kaplan-Meier survival curves showed that non-direct switching had a higher survival proportion than direct switching (log-rank test, p = 0.012). Even after adjusting for several variables using a Cox proportional hazards model, add-on switching had a significantly lower hazard at 6 months than direct switching (hazard ratio 0.42, 95% confidence interval 0.21–0.82, P = 0.01). In cases of switching to aripiprazole for psychiatric symptoms, non-direct switching had a lower hazard than direct switching (hazard ratio 0.41, 95% confidence interval 0.21–0.81, P = 0.01) but was not significant for adverse reaction. When aripiprazole was switched from olanzapine, add-on switch showed the lowest hazard ratio for continuation (hazard ratio 0.29, 95% confidence interval 0.07–1.11, P = 0.07). Conclusions: Flexibility in strategies when switching to aripiprazole may induce a better outcome for patients with chronic schizophrenia.