Incidence of neuropsychiatric adverse events in influenza patients treated with oseltamivir or no antiviral treatment

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Abstract
Aims: The association between neuropsychiatric events and antiviral treatments for influenza has been under scrutiny. In this study, the incidence of neuropsychiatric events in influenza patients dispensed oseltamivir or no antiviral was assessed using a large US medical claims database. Methods: Propensity score balanced cohorts from a prior study of influenza patients with and without oseltamivir exposure were expanded and reanalysed in this retrospective study. Patients ≥ 1 year with an influenza diagnosis [International Classification of Disease, 9th revision (ICD-9) 487.XX] during the study period (1 November 1999 to 30 April 2005) were identified and grouped into two cohorts: those dispensed oseltamivir [n = 60,267, 60,834 incident cases (ICs)] and those dispensed no-antiviral (n = 175,933, 183,786 ICs). Cohorts were stratified by age: ≤ 17 years (oseltamivir, n = 20,501 ICs; no-antiviral, n = 84,871 ICs) and ≥ 18 years (oseltamivir, n = 40,333 ICs; no-antiviral, n = 98,915 ICs). Medical claims in the 30 days (overall analysis) or 14 days (stratified analysis) after diagnosis were searched for indications of neuropsychiatric events. Claims-based outcome measures included three hierarchical neuropsychiatric categories: one broad, one restrictive (excluding particular disorders/conditions) and one limited to central nervous system (CNS)-specific disorders. Results: In the overall analysis, no increase in the incidence of claims-based neuropsychiatric events was detected in the patients dispensed oseltamivir vs. those dispensed no antiviral. Claims-based neuropsychiatric events were also reported with a similar frequency in patients ≤ 17 years and ≥ 18 years who did and did not receive antivirals. Conclusion: In this retrospective cohort study, no increase in claims-based neuropsychiatric events was detected in influenza patients who were and were not exposed to oseltamivir.