Oseltamivir Post-Exposure Prophylaxis in Pediatric Patients
Oseltamivir is FDA-approved for post-exposure prophylaxis starting at 1 year of age, with weight-based once-daily dosing for 10 days following close contact with an infected individual. 1
Age-Based Eligibility for Prophylaxis
- FDA approval for prophylaxis begins at 1 year of age, not earlier. 1
- Prophylaxis is NOT recommended for infants younger than 3 months due to limited safety and efficacy data in this age group. 2
- For infants 3–11 months, prophylaxis may be considered in critical situations (e.g., outbreak control), using 3 mg/kg once daily for 10 days, though this remains off-label. 2, 3
Weight-Based Prophylaxis Dosing (Children ≥1 Year)
The prophylaxis regimen is once daily for 10 days after exposure (or up to 6 weeks during community outbreaks). 2, 1
| Body Weight | Prophylaxis Dose | Volume (6 mg/mL suspension) |
|---|---|---|
| ≤15 kg | 30 mg once daily | 5 mL |
| >15–23 kg | 45 mg once daily | 7.5 mL |
| >23–40 kg | 60 mg once daily | 10 mL |
| >40 kg | 75 mg once daily | 12.5 mL |
Timing of Prophylaxis Initiation
- Initiate prophylaxis within 48 hours following close contact with a confirmed or suspected influenza case for maximum effectiveness. 1
- The duration of protection lasts only as long as oseltamivir dosing is continued. 1
Special Populations Requiring Dose Adjustment
Preterm Infants (If Prophylaxis Is Deemed Critical)
- Prophylaxis is generally not recommended for preterm infants due to limited data. 2
- If absolutely necessary, use postmenstrual age (PMA)-based dosing at half the treatment dose (once daily instead of twice daily):
- <38 weeks PMA: 1.0 mg/kg once daily
- 38–40 weeks PMA: 1.5 mg/kg once daily
40 weeks PMA: 3.0 mg/kg once daily 3
Renal Impairment
- For creatinine clearance 10–30 mL/min: reduce to 30 mg once daily for 10 days OR 75 mg every other day for 10 days (5 total doses). 2, 1
- For creatinine clearance >30–60 mL/min: use standard weight-based dosing at 30 mg once daily. 1
- ESRD patients not on dialysis: oseltamivir prophylaxis is not recommended. 1
Immunocompromised Patients
- Prophylaxis may be extended up to 12 weeks during community outbreaks in immunocompromised children. 1
Formulation and Administration
- Use the oral suspension formulation (6 mg/mL) for accurate dosing in young children. 2, 1
- Administer with food to reduce gastrointestinal side effects (nausea, vomiting occur in 10–15% of patients). 3, 4
- Use a calibrated 3-mL or 5-mL oral syringe for precise measurement; do not use household spoons. 2, 3
- If commercial suspension is unavailable, pharmacies can compound a 6 mg/mL suspension per package insert instructions. 2, 1
Critical Pitfalls to Avoid
- Do not confuse prophylaxis dosing (once daily) with treatment dosing (twice daily)—this is the most common prescribing error. 3
- Do not use prophylaxis in infants <3 months unless the situation is judged critical by an infectious disease specialist. 2
- Do not apply the weight-based categorical dosing (≤15 kg = 30 mg) to infants <12 months; use 3 mg/kg dosing instead. 3, 5
- Do not assume term-infant dosing for preterm infants; always calculate PMA and adjust accordingly. 2, 3
- Do not extend prophylaxis beyond 10 days for post-exposure (unless community outbreak or immunocompromised). 2, 1
Comparison with Treatment Dosing
- Treatment uses the same mg/kg or weight-based dose but twice daily for 5 days, whereas prophylaxis is once daily for 10 days. 2, 1
- The total drug exposure over 10 days of prophylaxis approximates the 5-day treatment course. 3
Safety Profile
- Gastrointestinal effects (nausea, vomiting, diarrhea) occur in 10–15% of patients and typically resolve within 1–2 days. 3, 4
- Taking oseltamivir with food significantly reduces the severity of these symptoms. 4
- Only approximately 1% of patients discontinue therapy due to adverse effects. 4
- Hypersensitivity reactions, including anaphylaxis, have been reported postmarketing but are rare. 2