Pediatric Oseltamivir (Tamiflu) Dosing
For pediatric patients with influenza, oseltamivir dosing is weight-based for children ≥12 months and age/weight-based for infants, with treatment initiated within 48 hours of symptom onset at 75 mg twice daily for adolescents ≥13 years, weight-tiered doses (30-75 mg twice daily) for children 1-12 years, and 3-3.5 mg/kg twice daily for infants <12 months, all given for 5 days. 1, 2, 3
Treatment Dosing (5 Days, Twice Daily)
Adolescents (≥13 years)
- 75 mg orally twice daily for 5 days (12.5 mL of oral suspension if using liquid formulation) 1, 2, 3
Children (1-12 years) - Weight-Based Dosing
- ≤15 kg (≤33 lb): 30 mg twice daily = 5 mL oral suspension 1, 2, 3
- >15-23 kg (>33-51 lb): 45 mg twice daily = 7.5 mL oral suspension 1, 2, 3
- >23-40 kg (>51-88 lb): 60 mg twice daily = 10 mL oral suspension 1, 2, 3
- >40 kg (>88 lb): 75 mg twice daily = 12.5 mL oral suspension 1, 2, 3
Infants (<12 months) - Age-Based Dosing
- 9-11 months: 3.5 mg/kg per dose twice daily 1, 2, 4
- Term infants 0-8 months: 3.0 mg/kg per dose twice daily 1, 2, 4
Preterm Infants - Postmenstrual Age-Based Dosing
Preterm infants require substantially lower doses due to immature renal function: 1, 2
- <38 weeks postmenstrual age: 1.0 mg/kg twice daily 1, 2
- 38-40 weeks postmenstrual age: 1.5 mg/kg twice daily 1, 2
- >40 weeks postmenstrual age: 3.0 mg/kg twice daily 1, 2
Prophylaxis Dosing (10 Days, Once Daily)
Adolescents (≥13 years)
Children (≥1 year)
- Same weight-based doses as treatment, but once daily instead of twice daily for 10 days: 1, 2, 3
- ≤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)
- 3.0 mg/kg once daily for 10 days 1, 2
- Prophylaxis is NOT recommended for infants <3 months unless the situation is judged critical due to limited safety data 1
Critical Timing Considerations
Treatment must be initiated within 48 hours of symptom onset for maximum effectiveness, reducing illness duration by 1-1.5 days in otherwise healthy patients. 1, 2, 5 However, treatment should NOT be withheld in high-risk or hospitalized patients even when presenting beyond 48 hours, as these patients still derive substantial benefit. 2
Do not delay treatment while waiting for laboratory confirmation in high-risk patients, as rapid antigen tests have poor sensitivity. 2
Renal Impairment Adjustments
For patients with creatinine clearance 10-30 mL/min: 1, 2
- Treatment: 75 mg once daily (instead of twice daily) for 5 days
- Prophylaxis: 30 mg once daily for 10 days OR 75 mg every other day for 10 days (5 total doses)
Formulation and Administration
Oseltamivir is available as: 1, 3
- Capsules: 30 mg, 45 mg, 75 mg
- Oral suspension: 6 mg/mL when reconstituted (preferred for patients who cannot swallow capsules)
- Can be taken with or without food
- Taking with food may improve gastrointestinal tolerability, as nausea and vomiting are common adverse effects occurring in 5-15% of patients
- Capsules can be opened and contents mixed with liquid if patient cannot swallow whole
Important Drug Interaction
Avoid live attenuated influenza vaccine (LAIV) within 48 hours before oseltamivir administration, and do not use oseltamivir for 14 days after LAIV vaccination. 1, 2 This is because oseltamivir may inhibit viral replication of the vaccine strain, reducing vaccine effectiveness.
Common Pitfalls to Avoid
- Do not use age-based dosing when weight is known for children ≥12 months - weight-based dosing is more accurate 6
- Do not forget to adjust dosing for preterm infants based on postmenstrual age (gestational age + chronological age), not just chronological age 1, 2
- Do not withhold treatment in high-risk patients presenting >48 hours after symptom onset - they still benefit significantly 2
- Do not use standard pediatric dosing in patients with renal impairment - dose reduction is mandatory when creatinine clearance <60 mL/min 1