Tamiflu (Oseltamivir) Dosing for Pediatric Influenza
Oseltamivir should be initiated immediately in all children with suspected influenza, using weight-based dosing for children ≥12 months and mg/kg dosing for infants <12 months, without waiting for confirmatory testing. 1, 2
Treatment Dosing by Age and Weight
Infants 0-8 Months
- 3 mg/kg per dose twice daily for 5 days 1, 2, 3
- This translates to 0.5 mL/kg of oral suspension (6 mg/mL concentration) per dose 2
- Example: An 8 kg infant receives 24 mg (4 mL) twice daily 2
Infants 9-11 Months
Children ≥12 Months (Weight-Based)
| Weight | Dose | Volume (6 mg/mL suspension) |
|---|---|---|
| ≤15 kg (≤33 lb) | 30 mg twice daily | 5 mL |
| >15-23 kg (>33-51 lb) | 45 mg twice daily | 7.5 mL |
| >23-40 kg (>51-88 lb) | 60 mg twice daily | 10 mL |
| >40 kg (>88 lb) | 75 mg twice daily | 12.5 mL |
Preterm Infants (Special Dosing)
Dosing based on postmenstrual age (gestational age + chronological age): 1, 2
- <38 weeks: 1.0 mg/kg twice daily
- 38-40 weeks: 1.5 mg/kg twice daily
- >40 weeks: 3.0 mg/kg twice daily
Critical Timing Considerations
Initiate treatment immediately upon clinical suspicion—do not delay for laboratory confirmation. 2, 3 The greatest benefit occurs when started within 48 hours of symptom onset, reducing illness duration by approximately 36 hours (26% reduction). 2, 4 However, treatment should still be given beyond 48 hours in high-risk children (age <2 years, severe illness, hospitalized patients, or those with underlying conditions), as they continue to benefit from later initiation. 1, 2
Starting treatment within 12 hours provides maximal benefit, reducing acute otitis media by 85% in young children with influenza A. 4
High-Risk Populations Requiring Treatment
All children in these categories should receive oseltamivir regardless of vaccination status or illness severity: 1, 2
- All children <2 years of age (highest risk for complications, hospitalization, and death) 1, 2
- All hospitalized children with suspected influenza 2
- Children with severe, complicated, or progressive illness 1, 2
- Children with chronic conditions: asthma, cardiac disease, immunodeficiency, diabetes, neurological disease, renal disease 1
Formulation and Administration
Oral suspension (6 mg/mL) is the preferred formulation for children who cannot swallow capsules. 1, 3 The suspension must be constituted by a pharmacist prior to dispensing. 1, 3 If commercial suspension is unavailable, pharmacies can compound it from capsules to achieve the same 6 mg/mL concentration. 1, 2
Administer with food to reduce gastrointestinal side effects, though this is not required. 1, 2, 3
Expected Efficacy
For influenza A infections, oseltamivir started within 24 hours shortens illness duration by 3.5 days (from 6.5 to 3.0 days) and reduces parental work absenteeism by 3.0 days. 4 The drug reduces otitis media risk by 34% in treated children. 2 Oseltamivir demonstrates less pronounced efficacy against influenza B, reducing illness duration from 173.9 to 110.0 hours, but treatment is still recommended. 2, 4
Common Side Effects and Safety
Vomiting occurs in approximately 5-15% of children but is generally mild and transient. 2 Diarrhea may occur in infants <1 year. 2 Despite historical concerns, controlled trials have failed to establish any link between oseltamivir and neuropsychiatric events. 2
Prophylaxis Dosing (≥1 Year Old)
Use the same weight-based doses as treatment, but once daily instead of twice daily for 10 days following exposure to confirmed influenza. 1, 3 For infants 3-11 months, use 3 mg/kg once daily for 10 days. 3 Prophylaxis is not recommended for infants <3 months unless the situation is judged critical. 1
Renal Impairment Adjustments
For creatinine clearance 10-30 mL/min: 75 mg once daily for treatment (instead of twice daily). 1
Critical Pitfalls to Avoid
- Do not withhold treatment while awaiting test results—rapid antigen tests have poor sensitivity and negative results should not rule out influenza. 2
- Do not refuse treatment beyond 48 hours in high-risk children—they continue to benefit from later initiation. 1, 2
- Do not underdose infants—use the age-appropriate mg/kg dosing, not weight-based tiers. 1, 2
- Do not use live attenuated influenza vaccine (LAIV) within 48 hours before oseltamivir or for 14 days after oseltamivir. 5