What is the recommended dosage of Tamiflu (oseltamivir) for a pediatric patient with influenza?

Tamiflu (Oseltamivir) Pediatric Dosing

For pediatric patients, Tamiflu dosing is weight-based for children ≥12 months and age/weight-based for infants, with treatment consisting of twice-daily dosing for 5 days and prophylaxis once-daily for 10 days. 1, 2, 3

Treatment Dosing (5 days, twice daily)

Children ≥12 months to 12 years (Weight-Based)

• ≤15 kg (≤33 lb): 30 mg twice daily = 5 mL oral suspension twice daily 1, 2, 3
• >15-23 kg (>33-51 lb): 45 mg twice daily = 7.5 mL oral suspension twice daily 1, 2, 3
• >23-40 kg (>51-88 lb): 60 mg twice daily = 10 mL oral suspension twice daily 1, 2, 3
• >40 kg (>88 lb): 75 mg twice daily = 12.5 mL oral suspension twice daily 1, 2, 3

Adolescents ≥13 years

• 75 mg twice daily for 5 days (same as adult dosing) 1, 4, 3

Infants <12 months (Age-Based)

• 9-11 months: 3.5 mg/kg per dose twice daily for 5 days 1, 4
• Term infants 0-8 months: 3 mg/kg per dose twice daily for 5 days 1, 4, 3

Preterm Infants (Postmenstrual Age-Based)

Preterm infants require substantially lower doses due to immature renal function 1:

• <38 weeks postmenstrual age: 1.0 mg/kg twice daily 1, 4
• 38-40 weeks postmenstrual age: 1.5 mg/kg twice daily 1, 4
• >40 weeks postmenstrual age: 3.0 mg/kg twice daily 1, 4

Prophylaxis Dosing (10 days, once daily)

Children ≥12 months to 12 years

Use the same weight-based doses as treatment, but once daily instead of twice daily for 10 days following exposure 1, 2, 4:

• ≤15 kg: 30 mg once daily 1, 2

• 15-23 kg: 45 mg once daily 1, 2

• 23-40 kg: 60 mg once daily 1, 2

• 40 kg: 75 mg once daily 1, 2

Adolescents ≥13 years

• 75 mg once daily for 10 days 1, 4

Infants 3-11 months

• 3 mg/kg once daily for 10 days 1, 4
• Prophylaxis is NOT recommended for infants <3 months unless the situation is judged critical due to limited safety data 1

Renal Impairment Adjustments

For patients with creatinine clearance 10-30 mL/min 1, 2, 4:

• Treatment: 75 mg once daily (instead of twice daily) for 5 days 1, 4
• Prophylaxis: 30 mg once daily for 10 days OR 75 mg every other day for 10 days (5 total doses) 1, 4

Critical Timing Considerations

Treatment must be initiated within 48 hours of symptom onset for maximum effectiveness, reducing illness duration by 1-1.5 days 1, 4, 3. However, treatment should not be withheld in high-risk or hospitalized patients even when presenting beyond 48 hours, as substantial benefit still occurs 4.

Prophylaxis should be initiated within 48 hours following close contact with an infected individual 1, 4.

Formulation and Administration

Available Formulations

• Oral suspension: 6 mg/mL when reconstituted (preferred for children who cannot swallow capsules) 1, 4, 3
• Capsules: 30 mg, 45 mg, 75 mg 1, 4

Administration Tips

• Take with food to reduce nausea and vomiting, which occur in approximately 14% of children treated with oseltamivir versus 8.5% with placebo 1
• Capsules can be opened and contents mixed with liquid if needed 1
• If commercial suspension is unavailable, pharmacies can compound a suspension based on package insert instructions 1

Common Pitfalls to Avoid

• Always verify current weight before dosing to avoid errors 2
• Do not use prophylaxis dosing for treatment (once daily vs. twice daily is a critical distinction) 1, 2
• Remember preterm infants require postmenstrual age-based dosing, not just chronological age, to avoid toxicity 1, 4
• Avoid live attenuated influenza vaccine (LAIV) within 48 hours before oseltamivir, and do not use oseltamivir for 14 days after LAIV vaccination 1, 4