Venous thromboembolism among elderly patients treated with atypical and conventional antipsychotic agents

BACKGROUND: Some antipsychotic agents have been indicated as a possible risk factor for venous thromboembolism (VTE) in adult patients with psychiatric disorders. The aim of this study was to estimate the effect of atypical and conventional antipsychotic agents on the risk of hospitalization for VTE among elderly patients. METHODS: We conducted a retrospective cohort study on nursing home residents in 5 states. We used data from the Minimum Data Set to identify 19 940 new users of antipsychotic agents and 112 078 nonusers. Hospitalization with VTE as primary discharge diagnosis was determined during a 6-month follow-up period using Medicare inpatient claims. Cox proportional hazards models provided estimates of effect adjusted for confounders. RESULTS: The rate of hospitalization for VTE was 0.91 per 100 person-years. Venous thrombosis accounted for 77.6% of events and 22.4% were pulmonary embolisms. Relative to nonusers, the rate of hospitalization for VTE was increased for users of atypical antipsychotic agents, including risperidone (adjusted hazard ratio HR], 1.98; 95% confidence interval CI], 1.40-2.78), olanzapine (adjusted HR, 1.87; 95% CI, 1.06-3.27), and clozapine and quetiapine fumarate (adjusted HR, 2.68; 95% CI, 1.15-6.28). No increased rate was associated with phenothiazines (adjusted HR, 1.03; 95% CI, 0.60-1.77) or other conventional agents (adjusted HR, 0.98; 95% CI, 0.52-1.87). CONCLUSIONS: Atypical antipsychotic agents appear to increase the risk of VTE. However, these events are rare, and in clinical practice the absolute risk should be weighed against the effectiveness of these medications in the elderly population.