Pediatric Dosing for Tamiflu (Oseltamivir)
For children ≥1 year, use weight-based dosing: 30 mg twice daily for ≤15 kg, 45 mg twice daily for >15-23 kg, 60 mg twice daily for >23-40 kg, and 75 mg twice daily for >40 kg, administered for 5 days when treating influenza. 1, 2
Weight-Based Dosing Algorithm for Children ≥1 Year
Treatment dosing (5 days):
- ≤15 kg (≤33 lb): 30 mg twice daily = 5 mL oral suspension 1, 2
- >15-23 kg (>33-51 lb): 45 mg twice daily = 7.5 mL oral suspension 1, 3, 2
- >23-40 kg (>51-88 lb): 60 mg twice daily = 10 mL oral suspension 1, 3, 2
- >40 kg (>88 lb): 75 mg twice daily = 12.5 mL oral suspension 1, 4, 2
Prophylaxis dosing (10 days): Use the same weight-based doses but give once daily instead of twice daily 1, 4, 2
Infant Dosing (<1 Year)
Critical distinction: Term vs preterm infants must be made before dosing. 1
Term Infants (≥37 weeks gestation at birth):
- 0-8 months: 3 mg/kg per dose twice daily = 0.5 mL/kg oral suspension 1, 4, 2
- 9-11 months: 3.5 mg/kg per dose twice daily 1, 4
- Treatment duration: 5 days 1
- Prophylaxis (3-8 months only): 3 mg/kg once daily for 10 days 1
Preterm Infants (based on postmenstrual age = gestational age + chronological age):
- <38 weeks PMA: 1.0 mg/kg twice daily 1
- 38-40 weeks PMA: 1.5 mg/kg twice daily 1
- >40 weeks PMA: 3.0 mg/kg twice daily 1
Never use the 3 mg/kg term infant dose for preterm infants—this causes toxic drug accumulation due to immature renal function. 1, 4
Renal Impairment Adjustments
For creatinine clearance 10-30 mL/min: Reduce to once daily dosing instead of twice daily 1, 4
- Give the child's weight-based dose once daily for 5 days (treatment) 1
- For prophylaxis: give half the standard once-daily dose daily, OR give the full once-daily dose every other day for 10 days (5 total doses) 1
No dose adjustment needed for CrCl ≥30 mL/min 1, 3
Administration Considerations
Give oseltamivir with food to reduce gastrointestinal side effects (nausea/vomiting occur in ~10% of patients). 1, 4, 3
Oral suspension concentration: 6 mg/mL when reconstituted by pharmacist 1, 2
Initiate treatment within 48 hours of symptom onset for maximum benefit—this reduces illness duration by 1-1.5 days. 4, 5
Critical Pitfalls to Avoid
- Never use the fixed unit doses (30,45,60,75 mg) intended for children ≥1 year in infants <1 year—these doses are too high 1
- Never confuse GFR with creatinine clearance when adjusting for renal impairment 1
- Never use term infant dosing for preterm infants without calculating postmenstrual age first 1, 4
- Never confuse treatment dosing (twice daily) with prophylaxis dosing (once daily) 4
Adolescents and Adults (≥13 Years)
Standard dose: 75 mg twice daily for 5 days (treatment) or 75 mg once daily for 10 days (prophylaxis) 1, 4, 2