An association between the influenza antiviral medication oseltamivir and neuropsychiatric events has been suggested by post-marketing case reports in Japan. This possible association was not supported by cohort studies in the U.S. conducted prior to the 2009 influenza A (H1N1) pandemic, when usage rates were comparatively low. We assessed oseltamivir safety before and during the pandemic using biologically plausible risk intervals, particularly focusing on psychiatric events.
Outpatients with influenza episodes from January 2007 through June 2010 were identified using diagnosis codes and positive tests at eight health care systems (sites) in the Vaccine Safety Datalink Project. Oseltamivir-treated and untreated patients were matched according to calendar week, age, sex, site, and propensity for treatment. Within this matched cohort, conditional logistic regression models were used to estimate the risk of four neuropsychiatric and five other adverse events (AEs) during pre-specified risk intervals.
Among 27 684 matched pairs, no associations were identified between oseltamivir treatment and any pre-defined AE. The absolute risks of incident psychiatric events in the 1–7 day risk interval were 0.126% for oseltamivir-treated and 0.105% for untreated patients (odds ratio = 1.21, 95% confidence interval [CI]: 0.74, 1.97; risk difference = 0.022%, 95% CI: −0.035%, 0.078%); the most common diagnosis was unspecified anxiety state. Results were similar for 1–14 and 1–2 day risk intervals and for pediatric/adolescent subgroups.
Consistent with prior U.S. cohort studies, no evidence was identified for an increased risk of neuropsychiatric or other AEs following oseltamivir treatment. Safety should be prospectively monitored to inform antiviral medication usage recommendations. Copyright © 2012 John Wiley & Sons, Ltd.