Oseltamivir is appropriate for the treatment of acute, uncomplicated influenza A or B illness in adults and pediatric patients, including neonates greater than 2 weeks of age. Neonates less than 2 weeks of age may also receive oseltamivir for treatment of influenza, but safety and efficacy in this population have not been established. Multiple national advisory bodies have endorsed the use of oseltamivir as soon as possible (ideally less than 48 hours after symptom onset) for patients hospitalized with influenza or with significant comorbidities making them at high risk for complications. There is some evidence in hospitalized patients that oseltamivir can have efficacy up to 4 to 5 days after symptoms onset and hence, recommendations endorse ordering oseltamivir for hospitalized patients with severe or progressive influenza illness or those patients at high risk of developing complications, regardless of the time of symptom onset. Individuals at high risk for complications include young children (less than two years of age), those in nursing homes, those 65 years of age or older, obese, pregnant, patients with pulmonary, liver, renal, or cardiovascular disease, malignancy, neurodevelopmental disorders, metabolic disorders, epilepsy, muscular dystrophy, and immunosuppression. Empiric treatment with oseltamivir can shorten the duration of illness and is thus recommended for healthy individuals with symptoms suggestive of influenza, even before confirmation testing if treatment can commence within 48 hours of symptoms. Oseltamivir is also useful for influenza prophylaxis within 48 hours of contact with an infected individual in adults and children greater than 1 year of age.
Recommendations endorsing oseltamivir as the drug of choice for treatment and prophylaxis of illness caused by avian influenza strains, including the highly pathogenic avian influenza A (H5N1), come from the Centers for Disease Control and Prevention (CDC) and World Health Organization (WHO).