What is the recommended dosage of Oseltamivir (Tamiflu) for pediatric patients?

Oseltamivir Pediatric Dosing

For pediatric patients, oseltamivir dosing is weight-based for children ≥1 year and age/weight-based for infants <1 year, with treatment initiated within 48 hours of symptom onset for maximum effectiveness. 1, 2

Treatment Dosing (5 days, twice daily)

Children ≥1 Year to 12 Years (Weight-Based)

• ≤15 kg (≤33 lb): 30 mg twice daily (5 mL oral suspension) 1, 3, 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 or one 75 mg capsule) 1, 3, 2

Adolescents ≥13 Years

• 75 mg twice daily for 5 days 1, 4, 2

Infants <1 Year (Age-Based)

• 9-11 months: 3.5 mg/kg per dose twice daily 1, 5
• Term infants 0-8 months: 3 mg/kg per dose twice daily 1, 5
• Infants <3 months: 3 mg/kg per dose twice daily 6

Critical caveat: Research demonstrates that the 3 mg/kg dose produces target drug exposures in infants 0-8 months, though variability is greater in infants <3 months of age. 5 The 3.5 mg/kg dose for 9-11 month-olds is based on pharmacokinetic data showing faster drug clearance in this age group. 5

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

Important note: Postmenstrual age = gestational age + chronological age. 1 Standard weight-based dosing is inappropriate for premature infants and may lead to toxic drug concentrations. 6

Prophylaxis Dosing (10 days, once daily)

Initiate within 48 hours following close contact with an infected individual. 1, 2

Children ≥1 Year to 12 Years (Weight-Based)

• ≤15 kg: 30 mg once daily (5 mL oral suspension) 1, 3
• >15-23 kg: 45 mg once daily (7.5 mL oral suspension) 1, 3
• >23-40 kg: 60 mg once daily (10 mL oral suspension) 1, 3
• >40 kg: 75 mg once daily (12.5 mL oral suspension) 1, 3

Adolescents ≥13 Years

• 75 mg once daily for 10 days post-exposure or up to 6 weeks during community outbreak 1, 2

Infants 3-11 Months

• 3 mg/kg once daily for 10 days 6, 1

Critical limitation: Prophylaxis is not recommended for infants <3 months unless the situation is judged critical, due to limited safety data. 6, 1

Renal Impairment Adjustments

For patients with creatinine clearance 10-30 mL/min: 1, 3

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

Oseltamivir is not recommended for end-stage renal disease patients not undergoing dialysis. 2

Formulation and Administration

Available Formulations

• Capsules: 30 mg, 45 mg, 75 mg 1, 2
• Oral suspension: 6 mg/mL when reconstituted (preferred for children who cannot swallow capsules) 1, 3, 2

Administration Tips

• May be taken with or without food, though administration with food improves gastrointestinal tolerability and reduces nausea/vomiting (occurring in 5-15% of patients) 1, 4
• Capsules can be opened and contents mixed with liquid if needed 1
• If commercial suspension unavailable, pharmacies can compound using capsule contents with simple syrup or Ora-Sweet SF to achieve 6 mg/mL concentration 1

Critical Timing Considerations

Treatment must be initiated within 48 hours of symptom onset for maximum effectiveness in reducing illness duration (by up to 1.5 days) and severity. 1, 3, 7 Earlier initiation within this window is associated with faster symptom resolution. 7

Common Pitfalls to Avoid

• Do not use age-based dosing when weight is known for children ≥1 year—weight-based dosing is preferred 1, 4
• Verify current weight before prescribing to avoid dosing errors 3
• Do not use standard pediatric dosing for preterm infants—postmenstrual age-based dosing is essential 6, 1
• Do not withhold treatment while awaiting laboratory confirmation in high-risk patients with suspected influenza 1

Special Populations

Immunocompromised Patients

Prophylaxis may be continued for up to 12 weeks during community outbreaks. 2

Pregnancy

Oseltamivir can be used during pregnancy with no contraindication. 1

Patients with Chronic Conditions

Asthma, chronic pulmonary disease, cardiovascular disease, diabetes, and immunodeficiency are not contraindications to oseltamivir use. 1