Tamiflu (Oseltamivir) Dosing for Adults
For adults, the standard dose of Tamiflu is 75 mg orally twice daily for 5 days for treatment of influenza, and 75 mg once daily for prophylaxis. 1, 2, 3
Treatment Dosing
- Standard adult dose: 75 mg orally twice daily for 5 days 1, 2, 3
- Timing is critical: Initiate treatment within 48 hours of symptom onset for maximum effectiveness 3, 4
- Earlier is better: Treatment started within 12 hours of symptom onset provides an additional 74.6 hours of illness reduction compared to starting at 48 hours, and within 24 hours provides an additional 53.9 hours of benefit 4
- Late treatment may still help: Treatment after 48 hours in patients with moderate-to-severe or progressive disease has shown some benefit and should be strongly considered 1
Prophylaxis Dosing
- Post-exposure prophylaxis: 75 mg orally once daily for at least 10 days following close contact with an infected individual 2, 3
- Seasonal prophylaxis: 75 mg orally once daily for up to 6 weeks during a community outbreak 2, 3
- Immunocompromised patients: May continue prophylaxis for up to 12 weeks 3
Renal Impairment Adjustments
Dose reduction is mandatory for patients with moderate to severe renal impairment 1, 2, 3:
- Creatinine clearance 10-30 mL/min (treatment): 75 mg once daily for 5 days 1, 2
- Creatinine clearance 10-30 mL/min (prophylaxis): Either 30 mg once daily for 10 days OR 75 mg every other day for 10 days (5 total doses) 1, 2
- End-stage renal disease not on dialysis: Oseltamivir is not recommended 3
Administration Considerations
- Food intake: Can be taken with or without food, though administration with meals may improve gastrointestinal tolerability 1, 2, 3
- Formulations available: 30 mg, 45 mg, and 75 mg capsules, plus oral suspension (6 mg/mL when reconstituted) 2, 3
- Common adverse effects: Nausea and vomiting are the most common side effects (approximately 10% of patients), typically mild, transient, and resolve within 1-2 days 4, 5
Clinical Pearls
- Efficacy data: The standard 75 mg twice daily dose reduces illness duration by approximately 29 hours (25% reduction) compared to placebo 6
- Higher doses: A study of 150 mg twice daily in hospitalized adults showed no additional benefit over standard dosing for influenza A, though there was improved virologic response in influenza B 7
- Not a vaccine substitute: Oseltamivir does not replace annual influenza vaccination 3
- Live vaccine interaction: Avoid live attenuated influenza vaccine (LAIV) within 48 hours before oseltamivir use, and do not use oseltamivir for 14 days after LAIV vaccination 2