Oseltamivir Dosing
For adults and adolescents ≥13 years: use 75 mg twice daily for 5 days for treatment, or 75 mg once daily for 10 days for prophylaxis. 1
Treatment Dosing
Adults and Adolescents (≥13 years)
- 75 mg orally twice daily for 5 days 2, 1
- Administer without regard to meals, though taking with food may reduce GI side effects 3, 2
Pediatric Patients (1-12 years) - Weight-Based Dosing
Treatment duration: 5 days, twice daily 2, 1
- ≤15 kg: 30 mg twice daily
- >15-23 kg: 45 mg twice daily
- >23-40 kg: 60 mg twice daily
- >40 kg: 75 mg twice daily
Infants (2 weeks to <1 year)
- 3 mg/kg/dose twice daily for 5 days 2, 4
- FDA approved for infants as young as 2 weeks 2
- Use weight-based dosing when possible; age-based dosing available if weight unknown 3
Preterm Infants (based on postmenstrual age)
Dosing is LOWER than term infants due to immature renal function 2
- <38 weeks postmenstrual age: 1.0 mg/kg twice daily
- 38-40 weeks postmenstrual age: 1.5 mg/kg twice daily
- >40 weeks postmenstrual age: 3.0 mg/kg twice daily
Critical caveat: For extremely preterm infants (<28 weeks), consult pediatric infectious disease specialist 2
Prophylaxis Dosing
Adults and Adolescents (≥13 years)
- 75 mg once daily for 10 days (post-exposure) 1
- Up to 6 weeks for community outbreak 1
- Up to 12 weeks in immunocompromised patients 1
Pediatric Patients (1-12 years)
Same weight-based doses as treatment, but ONCE daily for 10 days 2, 1
- ≤15 kg: 30 mg once daily
15-23 kg: 45 mg once daily
23-40 kg: 60 mg once daily
40 kg: 75 mg once daily
Infants (3-11 months)
Renal Impairment Dosing (Adults)
Dose adjustments required when creatinine clearance ≤60 mL/min 1
Treatment Regimen (5 days)
- CrCl >60-90 mL/min: 75 mg twice daily (no adjustment)
- CrCl >30-60 mL/min: 30 mg twice daily 3, 1, 5
- CrCl >10-30 mL/min: 30 mg once daily 3, 1, 5
- ESRD on hemodialysis: 30 mg immediately, then 30 mg after every hemodialysis cycle (max 5 days) 1, 6
- ESRD on CAPD: Single 30 mg dose 1, 7
- ESRD not on dialysis: NOT recommended 1
Prophylaxis Regimen (10 days)
- CrCl >60-90 mL/min: 75 mg once daily
- CrCl >30-60 mL/min: 30 mg once daily 1, 5
- CrCl >10-30 mL/min: 30 mg every other day OR 75 mg every other day 3, 1
- ESRD on hemodialysis: 30 mg immediately, then 30 mg after alternate hemodialysis cycles 1, 6
- ESRD on CAPD: 30 mg immediately, then 30 mg once weekly 1, 7
Immunocompromised Patients
Use conventional dose (75 mg twice daily) for 10 days rather than 5 days 8, 9
- Standard 75 mg twice daily achieves near-maximal effect; higher doses provide no additional benefit 9
- Extended 10-day duration limits viral rebound 8, 9
- Prophylaxis may be extended up to 12 weeks 1
Formulation Details
Oral suspension concentration: 6 mg/mL (changed from previous 12 mg/mL) 2, 10
- 30 mg dose = 5 mL
- 45 mg dose = 7.5 mL
- 60 mg dose = 10 mL
- 75 mg dose = 12.5 mL
Storage after constitution: 17 days refrigerated (2-8°C) or 10 days at room temperature (20-25°C) 1
If commercial suspension unavailable, capsules may be opened and mixed with sweetened liquid, or pharmacies can compound suspension (final concentration 6 mg/mL) 2, 1
Critical Timing Considerations
Treatment must begin within 48 hours of symptom onset for benefit 11, 9
- Starting within 12 hours reduces illness duration by additional 74.6 hours compared to starting at 48 hours 11
- Starting within 24 hours reduces illness duration by additional 53.9 hours 11
- Early therapeutic concentrations are crucial - delayed attainment reduces or negates efficacy 12
Common Pitfalls
Renal dosing errors: Current guidelines for mild-moderate renal impairment focus on steady-state rather than early therapeutic concentrations, potentially reducing efficacy 12. Consider maintaining first dose at 75 mg, then reducing subsequent doses based on renal function 12.
Large body mass: Standard dosing may be inadequate in patients with significantly elevated body mass; consider proportionately larger first dose 12.
Premature infants: Do NOT use term infant dosing - significantly higher drug concentrations occur due to immature renal clearance 3, 2. Use postmenstrual age-based dosing.
Resistance monitoring: H275Y mutation in influenza A(H1N1)pdm09 confers oseltamivir resistance, though most strains remain sensitive 13.