Oseltamiwir

Oseltamiwir, also spelled oseltamivir in some contexts, is an antiviral medication used to treat and prevent influenza A and B infections. It is a prodrug that is rapidly converted in the liver to the active metabolite oseltamivir carboxylate, which inhibits the viral neuraminidase enzyme. By blocking neuraminidase, oseltamivir reduces release of new viral particles from infected cells and limits the spread of infection in the respiratory tract.

Indications for oseltamivir include the treatment of uncomplicated influenza and the post-exposure prevention of influenza in exposed individuals. For treatment, it is most effective when started as soon as possible after symptom onset, ideally within 48 hours. For prophylaxis, it is used after exposure to influenza and continued for the recommended duration, with dosing guided by age and weight.

Oseltamivir is administered orally as capsules or as an oral suspension. The active metabolite is primarily eliminated by the kidneys, and dose adjustments are recommended in renal impairment. Common adverse effects reported include nausea and vomiting; other possible effects include headache and abdominal pain. Rare but notable concerns include neuropsychiatric symptoms, particularly in children and adolescents. Serious reactions such as hypersensitivity or severe skin reactions are uncommon but require medical attention.

Resistance can occur through mutations in the neuraminidase gene, though such resistance is not widespread across circulating strains. Drug interactions are limited, and renal dosing adjustments may be necessary for patients with kidney impairment.

Oseltamiwir was developed and marketed under brand names such as Tamiflu and is available as a generic in many markets. It is one component of influenza management, alongside vaccination and other preventive measures.