Oseltamivir (Tamiflu) Dosing
For adults, the standard dose is 75 mg twice daily for 5 days for treatment and 75 mg once daily for prophylaxis; for children ≥12 months, dosing is weight-based ranging from 30-75 mg twice daily for treatment and once daily for prophylaxis, with renal dose adjustments required when creatinine clearance is 10-30 mL/min. 1, 2
Adult Dosing
Treatment (5 days)
- Standard dose: 75 mg orally twice daily 1, 2
- Can be taken with or without food, though administration with meals may improve GI tolerability 1
Prophylaxis
- Post-exposure: 75 mg once daily for 10 days 1, 2
- Community outbreak: 75 mg once daily for up to 6 weeks 2
Pediatric Dosing (≥12 months)
Treatment (5 days) - Weight-Based 1
- ≤15 kg (≤33 lb): 30 mg twice daily
- >15-23 kg (33-51 lb): 45 mg twice daily
- >23-40 kg (51-88 lb): 60 mg twice daily
- >40 kg (>88 lb): 75 mg twice daily
Prophylaxis (10 days) - Weight-Based 1
Same doses as treatment but administered once daily instead of twice daily
Infants 9-11 months 1
- Treatment: 3.5 mg/kg/dose twice daily for 5 days
- Prophylaxis: 3.5 mg/kg/dose once daily for 10 days
Term Infants 0-8 months 1
- Treatment: 3 mg/kg/dose twice daily for 5 days
- Prophylaxis: 3 mg/kg/dose once daily (only for 3-8 months; not recommended for <3 months unless critical situation) 1
Important caveat: The 2019 AAP guidelines 1 note that oseltamivir is FDA-approved for children as young as 2 weeks, and given preliminary pharmacokinetic data, can be used in both term and preterm infants from birth when benefits outweigh risks. However, dosing for premature infants requires special consideration based on postmenstrual age due to immature renal function 1.
Renal Dose Adjustments
Creatinine Clearance 10-30 mL/min 1, 2, 3
Treatment:
- 75 mg once daily for 5 days (reduced from twice daily)
Prophylaxis:
- 30 mg once daily for 10 days, OR
- 75 mg once every other day for 10 days (5 total doses)
The evidence supporting these renal adjustments comes from population pharmacokinetic modeling 3 that demonstrated these regimens provide oseltamivir carboxylate exposures similar to or above those achieved with standard dosing in patients with normal renal function.
End-Stage Renal Disease on Hemodialysis 4
Treatment:
- 30 mg after each hemodialysis session
- If diagnosis occurs between HD sessions, give 30 mg immediately, then 30 mg after next HD session
Prophylaxis:
- 30 mg after every other hemodialysis session
This dosing is based on pharmacokinetic modeling showing oseltamivir carboxylate clearance is dramatically faster during HD (7.43 L/min) versus between sessions (0.19 L/min) 4.
Formulations 1, 2
- Capsules: 30 mg, 45 mg, 75 mg
- Oral suspension: Powder reconstituted to 6 mg/mL final concentration
- 30 mg dose = 5 mL
- 45 mg dose = 7.5 mL
- 60 mg dose = 10 mL
- 75 mg dose = 12.5 mL
If commercial suspension unavailable, capsules can be opened and mixed with sweetened liquid, or pharmacies can compound suspension (6 mg/mL concentration) 1.
Critical Clinical Considerations
Timing is essential: Treatment should begin within 48 hours of symptom onset for maximum benefit 2. Recent evidence 5 suggests that current dose reductions for mild-to-moderate renal impairment may delay achievement of therapeutic concentrations early in infection, potentially reducing efficacy. The first dose should always be the full 75 mg (or weight-appropriate dose in children) to rapidly achieve therapeutic levels, with subsequent doses adjusted for renal function 5.
Large body mass: Patients with larger body mass may require proportionately higher initial doses to achieve therapeutic concentrations quickly 5. Standard dosing may be inadequate in this population.
Duration: The standard 5-day treatment course is supported by clinical trials 1. For prophylaxis, 10 days post-exposure is standard, though community outbreak prophylaxis can extend to 6 weeks 2.
Resistance monitoring: While most influenza strains remain oseltamivir-sensitive, the H275Y mutation in influenza A(H1N1)pdm09 confers resistance 6. Local surveillance data should guide empiric treatment decisions 7.