Oseltamivir effectiveness in seasonal influenza patients taking symptomatic therapy: retrospective analysis of RCT data

Aims: The effectiveness of oseltamivir to improve seasonal influenza symptoms in clinical practice was analyzed using pooled data from patients who were also taking analgesics and other over-the-counter (OTC) medications. Methods: Data were pooled from 1,709 patients aged 13 - 64 years with confirmed seasonal influenza who enrolled in six randomized, placebo-controlled trials of oseltamivir (75 mg b.i.d. for 5 days) and took OTC analgesics (+/- other medications). Rates of improvement of seven symptoms, two functional measures (sleep quality and ability to undertake usual activities) and fever (body temperature) were calculated between Days 1 and 6 of illness. Time to reach defined tolerability thresholds was compared using Kaplan-Meier analysis. Two subgroup analyses were performed in patients taking cough and cold remedies (n = 635) and antibiotics (n = 175) in addition to analgesics. Results: Six symptoms and both functional measures improved faster with oseltamivir than placebo, including nasal congestion (difference in rate, 19.3%), cough (34.1%), sleep quality (13.7%) and ability to perform usual activities (12.0%). Results in the Analgesics + cough/cold subgroup analysis were similar. In the Analgesics + antibiotics subgroup, three symptoms and both functional measures improved faster with oseltamivir. In all three analyses, median time to reach tolerability thresholds for all measures was faster in oseltamivir patients than placebo patients. Conclusions: Oseltamivir treatment of patients with seasonal influenza already receiving OTC medications produced a faster reduction in severity of most symptoms and a quicker return to ability to perform normal activities compared with patients who took OTC medications and placebo.