Clozapine Augmentation with Antipsychotics among Patients with Schizophrenia Spectrum Disorders in the Ontario Forensic Psychiatry System

BACKGROUND: Clozapine augmentation with antipsychotics (CAA) is commonly used to treat complex cases in forensic psychiatric settings. This study aims to investigate the prevalence and determinants of CAA among individuals with schizophrenia spectrum disorders within the Ontario forensic system. METHODS: A retrospective analysis was conducted on 262 patients in forensic psychiatric settings who were prescribed clozapine during the 2014/15 reporting year. The mean age of the patients was 41 years (SD = 11.8), and 227 of them (86.6%) were male. For comparative analysis, the patients were categorized into two groups: clozapine monotherapy and CAA. Logistic regression analysis was then applied to evaluate factors associated with CAA. RESULTS: Nearly half (48.5%) of forensic psychiatric patients on clozapine received antipsychotic augmentation. CAA was more prevalent among patients with violent offenses (adjusted odds ratio [aOR] 4.32, 95% confidence interval [CI]: 1.02-18.27, p = 0.047), and absconsion incidents (aOR 2.55 95% CI: 1.16-5.58, p = 0.019). Patients with a good treatment response (aOR of 0.25, 95% CI: 0.11-0.54, p <0.001) and a history of self-harm were less likely to be prescribed CAA (aOR of 0.32, 95% CI: 0.12-0.85, p = 0.022). CONCLUSION: Patients with severe symptoms and significant risk profiles were more likely to receive CAA. Capacity development and further research are needed to support an effective and safe clozapine therapy strategy.