A population-based cost-effectiveness analysis of olanzapine and risperidone among ambulatory patients with schizophrenia.

BACKGROUND Olanzapine and risperidone are atypical antipsychotics exhibiting different pharmacological properties that are likely to translate into differences in outcomes, tolerability and safety. As well, their acquisition cost differs. These differences may impact their cost-effectiveness. OBJECTIVE To estimate the incremental cost-effectiveness ratio (ICER) of olanzapine and risperidone in an outpatient population. METHODS We carried out a cost-effectiveness analysis based on resource utilization data gathered from Quebec's provincial health insurance board databases. Patients previously diagnosed with schizophrenia who received a first prescription of olanzapine or risperidone between 1 January 1997 and 31 August 1999 were followed for 365 days. Absence of hospitalization for mental illness served as the clinical indicator of effectiveness. Direct health care costs for mental illness were considered. Adjusted ICERs were calculated, and their 95% confidence intervals (CI) were assessed using a non-parametric bootstrap. RESULTS A total of 6,334 patients were included in the analysis. The ICER for olanzapine was (CA$) 86,918 (95%CI, 27,709 to 237,040) per additional effective treatment per year, among patients hospitalized prior to their treatment. Among those who were not hospitalized prior to their treatment, olanzapine was dominated (95%CI, CA$1.7M to dominated). CONCLUSION Results suggest that, in this population, direct mental health care costs could be minimized by using risperidone instead of olanzapine as the initial treatment.