What's oseltamivir phosphate for?

Oseltamivir phosphate is an antiviral medication (the salt form of oseltamivir, the active drug in Tamiflu). It’s used to:

- Treat influenza A and B in people (usually started within 48 hours of symptoms) to shorten illness and reduce symptoms.
- Prevent influenza after exposure (post-exposure prophylaxis) for people at risk or close contacts.

How it works: it inhibits neuraminidase, an enzyme influenza viruses use to spread from infected cells.

Common dosing (general guidelines; exact dose by age/weight and kidney function):
- For treating adults: typically 75 mg twice daily for 5 days.
- For preventing flu after exposure (prophylaxis): usually 75 mg once daily for about 10 days (instructions vary by age/weight and risk).
- Pediatric dosing depends on age/weight.

Notes:
- Start as soon as possible after flu symptoms begin.
- Not a substitute for flu vaccination.
- Possible side effects include nausea, vomiting, diarrhea, and headache; rare neuropsychiatric effects have been reported in some children.
- Dose adjustments may be needed for kidney problems.
- If you’re considering using it, talk to a healthcare provider for the right dose and duration for your situation.