Overview
Oseltamivir, widely known by its brand name Tamiflu, is an antiviral medication used to treat and prevent influenza A and influenza B viruses. It is most effective when initiated within 48 hours of symptom onset.

Mechanism of Action
It is a neuraminidase inhibitor. It blocks the function of the viral neuraminidase enzyme on the surface of the influenza virus, preventing the release of newly formed viral particles from infected host cells, thus halting the spread of the virus within the respiratory tract.

Dosage and Administration
For treatment in adults, the standard dose is 75 mg twice daily for 5 days. For prophylaxis (prevention), it is 75 mg once daily for 10 days. Pediatric dosing is strictly weight-based. It should be taken with food to reduce stomach upset.

Side Effects
The most common side effects are nausea and vomiting, particularly after the first few doses. There have been post-marketing reports of rare but serious neuropsychiatric events, such as delirium and abnormal behavior, predominantly in pediatric patients.

Contraindications
Contraindicated in patients with a known hypersensitivity to oseltamivir. Dosage adjustment is required for patients with severe renal impairment.