What is the recommended dose of Tamiflu (oseltamivir) for children?

Oseltamivir (Tamiflu) Dosing for Children

For children ≥1 year old, oseltamivir dosing is weight-based: ≤15 kg receive 30 mg, >15-23 kg receive 45 mg, >23-40 kg receive 60 mg, and >40 kg receive 75 mg, administered twice daily for 5 days for treatment or once daily for 10 days for prophylaxis. 1

Weight-Based Dosing for Children ≥1 Year

The FDA-approved dosing strategy uses body weight to determine appropriate doses 1:

Treatment (twice daily for 5 days):

• ≤15 kg (≤33 lb): 30 mg twice daily 2, 3, 1
• >15-23 kg (>33-51 lb): 45 mg twice daily 2, 3, 1
• >23-40 kg (>51-88 lb): 60 mg twice daily 2, 3, 1
• >40 kg (>88 lb): 75 mg twice daily 2, 3, 1

Prophylaxis (once daily for 10 days):

• Same weight-based doses as treatment, but administered once daily instead of twice daily 2, 1

Infants <1 Year Old

For infants younger than 1 year, age-based mg/kg dosing is recommended 4, 3:

Treatment (twice daily for 5 days):

• 9-11 months: 3.5 mg/kg per dose twice daily 3, 5
• 0-8 months (term infants): 3.0 mg/kg per dose twice daily 4, 3, 5
• <3 months: 3.0 mg/kg per dose twice daily 4

Prophylaxis:

• 3-11 months: 3.0 mg/kg once daily for 10 days 4
• <3 months: Not recommended unless situation is judged critical due to limited safety data 4

Preterm Infants

Preterm infants require special dosing based on postmenstrual age (gestational age + chronological age) due to immature renal function 3, 6:

• <38 weeks postmenstrual age: 1.0 mg/kg twice daily 3, 6
• 38-40 weeks postmenstrual age: 1.5 mg/kg twice daily 3, 6
• >40 weeks postmenstrual age: 3.0 mg/kg twice daily 3, 6

Formulation and Administration

Oral suspension is the preferred formulation for children who cannot swallow capsules 1:

• Available as powder that pharmacists reconstitute to 6 mg/mL concentration 2, 1
• Volume conversions: 30 mg = 5 mL, 45 mg = 7.5 mL, 60 mg = 10 mL, 75 mg = 12.5 mL 6, 1
• Capsules (30 mg, 45 mg, 75 mg) can be opened and mixed with liquid if needed 6

Administer with food to improve tolerability, as nausea and vomiting occur in approximately 10% of patients 2, 6

Renal Impairment Adjustments

For children with creatinine clearance 10-30 mL/min 6:

• Treatment: 75 mg once daily (instead of twice daily) for 5 days
• Prophylaxis: 30 mg once daily OR 75 mg every other day for 10 days

Oseltamivir is not recommended for end-stage renal disease patients not on dialysis 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 and decreasing complications like acute otitis media by 44% 2, 1

Prophylaxis should begin within 48 hours of exposure to an infected individual 6, 1

Common Pitfalls to Avoid

• Do not use age-based dosing for children ≥1 year when weight is known—weight-based dosing is more accurate 3
• Do not underdose infants 12-23 months—research shows the 30 mg unit dose may be insufficient for some children in this age range, with 60% having subtherapeutic exposures 5
• Do not use standard pediatric dosing for preterm infants—they require lower mg/kg doses due to immature renal clearance 4, 3
• Do not withhold treatment while awaiting laboratory confirmation in high-risk patients—empiric treatment should be initiated based on clinical suspicion 6