What is the recommended pediatric dosing of oseltamivir (Tamiflu) for treatment and prophylaxis, including age and weight considerations?

Pediatric Oseltamivir (Tamiflu) Dosing

Oseltamivir dosing in children is weight-based for those ≥12 months and mg/kg-based for infants <12 months, with treatment given twice daily for 5 days and prophylaxis once daily for 10 days. 1

Treatment Dosing (5 days, twice daily)

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

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

Term Infants <12 months (mg/kg-Based)

• 9–11 months: 3.5 mg/kg per dose twice daily 1, 2
• 0–8 months (term infants): 3 mg/kg per dose twice daily 1, 2

Critical caveat: The CDC recommends 3 mg/kg twice daily for ALL infants <12 months, while the AAP differentiates between 0–8 months (3 mg/kg) and 9–11 months (3.5 mg/kg). 1 The 3.5 mg/kg dose for 9–11 month-olds is based on pharmacokinetic data showing this achieves target drug exposures in this age group. 3

Preterm Infants (Postmenstrual Age-Based)

Preterm infants require substantially lower doses due to immature renal function—using term infant dosing can lead to toxic drug concentrations. 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

For extremely preterm infants (<28 weeks postmenstrual age), consult a pediatric infectious disease specialist before initiating therapy. 1

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 1, 2
• ≤15 kg: 30 mg once daily 1
• >15–23 kg: 45 mg once daily 1
• >23–40 kg: 60 mg once daily 1
• >40 kg: 75 mg once daily 1

Infants 3–11 months

• 3 mg/kg once daily for 10 days 1, 2

Infants <3 months

• Prophylaxis is NOT recommended for infants <3 months unless the situation is judged critical due to limited safety and efficacy data 1

Renal Impairment Adjustments

Dose adjustments are mandatory for creatinine clearance <60 mL/min to prevent toxicity. 1, 2

Treatment Dosing

• CrCl 10–30 mL/min: 75 mg once daily (instead of twice daily) for 5 days 1, 2

Prophylaxis Dosing

• CrCl 10–30 mL/min: 30 mg once daily for 10 days OR 75 mg every other day for 10 days (5 total doses) 1, 2

Formulation and Administration

Oral Suspension

• Concentration: 6 mg/mL when reconstituted 1, 2
• Available as: 30 mg, 45 mg, and 75 mg capsules, plus powder for oral suspension 1, 2
• If commercial suspension unavailable: Pharmacies can compound a 6 mg/mL suspension by opening capsules and mixing contents with simple syrup or Ora-Sweet SF per package instructions 1

Measuring Devices

• For infants <12 months: Use a calibrated 3-mL or 5-mL oral syringe for accurate measurement of small volumes—the standard syringe supplied with commercial product is inadequate 4
• Never use household spoons for measurement 4

Timing and Food

• Administer with food to reduce nausea and vomiting, which occur in approximately 10% of patients 5, 4
• Initiate treatment within 48 hours of symptom onset for maximum effectiveness; earlier treatment (within 12–24 hours) provides substantially greater benefit 1, 6, 7
• Treatment started within 12 hours reduces illness duration by an additional 74.6 hours compared to treatment at 48 hours 7

Clinical Benefits

Oseltamivir reduces illness duration by approximately 1–1.5 days (26–36% reduction) when started early. 5

• Decreases severity of symptoms including cough, coryza, and fever 5
• Reduces risk of secondary complications, particularly acute otitis media, by 44% 5
• When started within 12 hours in children 1–3 years, reduces acute otitis media incidence by 85% 6
• Reduces parental work absenteeism by approximately 3 days 6

Common Pitfalls to Avoid

• Do NOT use weight-based categorical dosing (≤15 kg = 30 mg) for infants <12 months—this applies only to children ≥12 months 4
• Do NOT apply term infant dosing to preterm infants—postmenstrual age-based dosing is required to avoid toxicity 1
• Do NOT delay treatment waiting for laboratory confirmation during influenza season—clinical judgment is sufficient 8
• Do NOT stop therapy early even if symptoms improve before day 5—complete the full 5-day course to ensure adequate viral suppression 4
• Do NOT confuse treatment dosing (twice daily) with prophylaxis dosing (once daily) 8, 4

Special Populations

FDA Approval

• Approved for treatment in children as young as 2 weeks of age 1, 2
• Can be used from birth (including preterm infants) because benefits likely outweigh risks, though FDA approval is for ≥2 weeks 1

Immunocompromised Patients

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