The Influence of Oseltamivir Treatment on the Risk of Stroke after Influenza Infection

Abstract

Objectives: It was the aim of this study to examine the influence of the antiviral medication oseltamivir on stroke and transient ischemic attack (TIA) in adults diagnosed with influenza. Methods: This retrospective cohort study used medical and pharmaceutical claims data from May 2000 to September 2006 from an administrative claims database. Episodes of stroke/TIA in the 6 months after influenza in adults (aged ≥18 years) prescribed oseltamivir within 1 day before or 2 days after influenza diagnosis (oseltamivir cohort), and adults prescribed no antivirals (comparison cohort) were compared using multivariate analyses adjusted for demographic and clinical risk factors. Results: The oseltamivir cohort comprised 49,238 patients and the comparison cohort 102,692 patients. Oseltamivir was associated with a 28% reduction in risk of stroke/TIA in the 6 months after influenza [hazard ratio (HR) 0.72; 95% CI 0.62–0.82] and with significant reductions after 1 and 3 months. In patients <65 years of age, there was a 34% risk reduction with oseltamivir after 6 months (HR 0.66; 95% CI 0.56–0.77) and also significant reductions after 1 and 3 months. In those aged ≥65 years, there was a 51% reduction in risk after 1 month (HR 0.49; 95% CI 0.27–0.91). Conclusions: Prescription of oseltamivir for influenza is associated with a reduced risk of stroke/TIA.