Pediatric Oseltamivir (Tamiflu) Dosing
For children ≥12 months, use weight-based dosing twice daily for 5 days: ≤15 kg receive 30 mg, >15–23 kg receive 45 mg, >23–40 kg receive 60 mg, and >40 kg receive 75 mg; for infants <12 months, use age-based mg/kg dosing with critical adjustments for preterm infants based on postmenstrual age. 1, 2
Weight-Based Dosing for Children ≥12 Months
Treatment regimen (5 days, twice daily):
- ≤15 kg (≤33 lb): 30 mg twice daily = 5 mL oral suspension 1, 2
- >15–23 kg (>33–51 lb): 45 mg twice daily = 7.5 mL oral suspension 1, 2
- >23–40 kg (>51–88 lb): 60 mg twice daily = 10 mL oral suspension 1, 2
- >40 kg (>88 lb): 75 mg twice daily = 12.5 mL oral suspension 1, 2
These weight categories apply ONLY to children ≥12 months—never use these fixed doses for infants <12 months. 1, 3
Age-Based Dosing for Term Infants <12 Months
For term infants (≥37 weeks gestation at birth), use mg/kg dosing twice daily for 5 days:
- 9–11 months: 3.5 mg/kg per dose twice daily 1, 2
- 0–8 months (term): 3.0 mg/kg per dose twice daily 1, 2
Example: A 4.5 kg term infant aged 6 months receives 13.5 mg (4.5 kg × 3 mg/kg) = 2.25 mL of 6 mg/mL suspension twice daily. 1
Critical Adjustments for Preterm Infants
Preterm infants require substantially lower doses based on postmenstrual age (PMA = gestational age + chronological age) due to immature renal function—using term-infant dosing will cause toxic drug accumulation: 1, 3
| Postmenstrual Age | Dose | Example (4.5 kg infant) | Volume (6 mg/mL) |
|---|---|---|---|
| <38 weeks PMA | 1.0 mg/kg twice daily | 4.5 mg | 0.75 mL |
| 38–40 weeks PMA | 1.5 mg/kg twice daily | 6.75 mg | 1.1 mL |
| >40 weeks PMA | 3.0 mg/kg twice daily | 13.5 mg | 2.25 mL |
For extremely preterm infants (<28 weeks gestation), consult pediatric infectious disease before initiating therapy. 1
Adolescents and Adults (≥13 Years)
75 mg twice daily for 5 days (12.5 mL oral suspension or one 75 mg capsule). 1, 2
Renal Impairment Adjustments
For creatinine clearance 10–30 mL/min:
- Treatment: Reduce to 75 mg (or weight-based dose) once daily (instead of twice daily) for 5 days 1, 2
- Prophylaxis: 30 mg once daily OR 75 mg every other day for 10 days 1, 2
For creatinine clearance >30–60 mL/min: 30 mg twice daily for treatment, 30 mg once daily for prophylaxis 2
Oseltamivir is not recommended for end-stage renal disease patients not on dialysis. 2
Prophylaxis Dosing (Post-Exposure)
Use the same weight-based or age-based doses as treatment, but once daily (instead of twice daily) for 10 days following close contact with an infected individual: 1, 2
- Children ≥12 months: Same weight-based doses once daily 1, 2
- Infants 3–11 months: 3.0 mg/kg once daily 1, 2
- Infants <3 months: Prophylaxis is not recommended unless the situation is judged critical due to limited safety data 1, 2
Formulation and Administration
The oral suspension (6 mg/mL when reconstituted) is the preferred formulation for infants and young children who cannot swallow capsules. 1, 2
Use a calibrated 3–5 mL oral syringe for accurate measurement—never use household spoons or the syringe supplied with the commercial product for infant doses. 1
Capsules (30 mg, 45 mg, 75 mg) can be opened and mixed with liquid if needed. 1
Administer with food to reduce nausea and vomiting, which occur in approximately 10–15% of patients and typically resolve within 1–2 days. 1, 4, 5
Critical Timing for Maximum Efficacy
Initiate treatment within 48 hours of symptom onset—earlier initiation (within 12–24 hours) provides substantially greater benefit. 1, 4, 6
- Treatment started within 12 hours reduces illness duration by an additional 74.6 hours compared to treatment at 48 hours 4
- Treatment within 24 hours reduces illness duration by 3.5 days in children with influenza A 6
- In children 1–3 years, oseltamivir started within 12 hours reduced acute otitis media by 85% 6
Do not withhold treatment while awaiting laboratory confirmation in high-risk patients—rapid antigen tests have poor sensitivity. 7
High-Risk Populations Requiring Treatment
All children in the following categories should receive oseltamivir regardless of vaccination status or time since symptom onset: 7
- Children <2 years of age 7
- Hospitalized children 7
- Children with severe or complicated illness 7
- Children with chronic conditions (asthma, cardiac disease, diabetes, immunodeficiency) 7
Treatment should still be given beyond 48 hours in high-risk children, as they continue to benefit from later initiation. 7
Common Pitfalls to Avoid
Never use the weight-based categorical dosing (30 mg, 45 mg, 60 mg, 75 mg) for infants <12 months—these doses are too high and apply only to children ≥12 months. 1, 3
Never apply term-infant dosing (3 mg/kg) to preterm infants—they require postmenstrual age-based dosing to avoid toxicity. 1, 3
Never round doses inappropriately for infants—calculate the exact mg/kg dose and measure the corresponding volume precisely with a calibrated oral syringe. 1
Do not confuse GFR with creatinine clearance when making renal adjustments. 3
Do not stop treatment early even if symptoms improve before day 5—complete the full 5-day course to ensure adequate viral suppression. 1
Safety Profile
When age-appropriate dosing is applied, the safety profile in infants is comparable to that in older children. 1
Gastrointestinal effects (nausea, vomiting, diarrhea) are the most common adverse events, occurring in 10–15% of patients, and are mild, transient, and less likely when taken with food. 1, 4, 5
Controlled trials have failed to establish any link between oseltamivir and neuropsychiatric events. 7
Only approximately 1% of patients discontinue oseltamivir due to gastrointestinal side effects. 1