The factors associated with clozapine polypharmacy for schizophrenia patients discharged from a large public psychiatric hospital in Taiwan, 2006–2021

Clozapine treatment continues to be recognized as the gold standard for managing treatment-resistant schizophrenia. Combining clozapine with other antipsychotics (i.e., clozapine polypharmacy) has emerged as an option for clozapine-resistant schizophrenia. We aimed to investigate the factors associated with clozapine polypharmacy in schizophrenia patients discharged on clozapine from a public psychiatric hospital. The analysis included patients with schizophrenia who were discharged between 2006 and 2021 and prescribed clozapine upon discharge. All patients were divided into 2 groups: clozapine monotherapy and clozapine polypharmacy. Multivariate logistic regression was used to identify factors associated with clozapine polypharmacy. A total of 1396 (42.7%) schizophrenia patients discharged on clozapine polypharmacy. In a multivariate logistic regression model, the clozapine polypharmacy was more likely to be male gender, to be younger, to be earlier age of onset, to have a greater number of previous hospitalizations, to have a shorter length of hospital stay, and to have a lower clozapine daily dose. The prevalence of clozapine significantly increased from 22.4% in 2006 to 50% in 2021. Compared with clozapine monotherapy, clozapine polypharmacy was associated with male gender, younger, earlier age of onset, a greater number of previous hospitalizations, shorter length of hospital stay, and lower clozapine daily dose. The utilization of clozapine polypharmacy has seen a significant increase over time. Further research is necessary to clarify its efficacy, safety, and overall risk/benefit ratio.