Purpose: To compare the incidence rates of diabetes mellitus and dyslipidemia in ambulatory first-time users of risperidone and olanzapine.
Methods: The database for the Prescription Drug Insurance Plan in the province of Quebec was used as the data source for a population-based cohort study. Denominalized data were extracted for all ambulatory patients who first received an atypical antipsychotic between 1 January 1997 and 31 August 1999. Eligible patients were categorized as taking: no antidiabetic medication; no lipid reducing medication; neither type of medication. Those who started to use an outcome drug (an antidiabetic or lipid-lowering medication) before the end of the follow-up period (31 August 2000) were considered to have developed the corresponding outcome disease. Incidence rate ratios (IRR) (and 95% confidence intervals) for initiating antihyperglycemic or lipid-lowering drug treatment, or both were calculated. Outcomes on risperidone were compared to those on olanzapine.
Results: A total of 19 582 eligible patients were included in the analysis. Relative to risperidone, olanzapine was associated with a higher risk of initiating a pharmacologic treatment for diabetes [IRR: 1.33 (1.03-1.74)], dyslipidemia [IRR: 1.49 (1.22-1.83)], or either condition [1.47 (1.23-1.76)].
Conclusions: Olanzapine seems to be associated with a higher risk of developing diabetes and/or dyslipidemia than risperidone. Further prospective studies are needed to rigorously assess the safety of olanzapine.