Tamiflu Dosing for Adults
For a healthy adult with normal renal function, the recommended dose of Tamiflu (oseltamivir) is 75 mg orally twice daily for 5 days for treatment, or 75 mg once daily for 10 days for post-exposure prophylaxis. 1, 2, 3
Treatment Regimen
- Standard dose: 75 mg orally twice daily for 5 days 1, 2, 3
- Critical timing: Treatment must be initiated within 48 hours of symptom onset for maximum effectiveness 1, 2, 3
- Administration: Can be taken with or without food, though taking with meals reduces gastrointestinal side effects 1, 3, 4
The FDA label confirms that food does not significantly affect drug absorption (AUC 6218 ng∙h/mL fasted vs 6069 ng∙h/mL fed), so the recommendation to take with food is purely for tolerability. 4
Prophylaxis Regimen (Post-Exposure)
- Standard dose: 75 mg orally once daily for 10 days 1, 2, 3
- Critical timing: Must be initiated within 48 hours of exposure to an infected individual 1, 3
Available Formulations
- Capsules: 30 mg, 45 mg, and 75 mg 1, 2
- Oral suspension: 6 mg/mL when reconstituted (75 mg dose = 12.5 mL) 1, 3
Common Side Effects and Management
- Gastrointestinal effects: Nausea and vomiting occur in approximately 10-15% of patients 1, 3
- Severity: These effects are typically mild and transient 1
- Management strategy: Taking oseltamivir with food significantly reduces the severity of nausea and vomiting 1
- Discontinuation rate: Only approximately 1% of patients discontinued therapy due to gastrointestinal side effects in clinical trials 1
Critical Drug Interaction to Avoid
- Live attenuated influenza vaccine (LAIV): Avoid LAIV within 48 hours before oseltamivir use 1, 3
- Post-vaccination timing: Do not use oseltamivir for 14 days after LAIV vaccination, as it may interfere with vaccine efficacy 1, 3
Common Pitfall: Delayed Treatment
Do not wait for laboratory confirmation before initiating treatment. Empiric treatment should be started immediately in patients with influenza-like illness during periods of local influenza activity. 3 Delaying treatment beyond 48 hours of symptom onset significantly reduces efficacy. 2, 3
Renal Function Considerations (For Context)
While the question specifies normal renal function, it's important to note that no dose adjustment is needed when creatinine clearance is ≥30 mL/min. 2 For patients with CrCl 10-30 mL/min, the treatment dose would be reduced to 75 mg once daily (instead of twice daily) for 5 days. 1, 2
Clinical Efficacy Evidence
Research demonstrates that oseltamivir reduces the duration of illness by up to 1.5 days and severity by up to 38% when initiated within 36 hours of symptom onset, with earlier initiation associated with faster resolution. 5 The drug is effective against both influenza A and B strains. 2, 5