Oseltamivir Dosing for a 22.1 kg Child
For a child weighing 22.1 kg and aged ≥12 months, administer oseltamivir 45 mg twice daily for 5 days for influenza treatment, or 45 mg once daily for 10 days for post-exposure prophylaxis. 1
Weight-Based Dosing Algorithm
This child falls into the >15 kg to ≤23 kg weight category, which determines the 45 mg dose. 1, 2
The pediatric weight-based dosing categories for children ≥12 months are: 1, 2
- ≤15 kg: 30 mg per dose
- >15 kg to 23 kg: 45 mg per dose ← This patient
- >23 kg to 40 kg: 60 mg per dose
- >40 kg: 75 mg per dose
Treatment vs. Prophylaxis Regimens
For Treatment (Confirmed or Suspected Influenza)
- Dose: 45 mg twice daily 1
- Duration: 5 days 1, 2
- Timing: Initiate within 48 hours of symptom onset for maximum benefit; earlier initiation (≤36 hours) yields faster symptom resolution 2, 3
For Post-Exposure Prophylaxis
- Dose: 45 mg once daily 1, 4
- Duration: 10 days (standard post-exposure) 1, 4
- Extended duration: Up to 6 weeks during community outbreaks 4
- Timing: Start within 48 hours following close contact with an infected individual 4
Formulation and Administration
Use the oral suspension formulation (6 mg/mL concentration) for accurate dosing. 1
- 45 mg dose = 7.5 mL of the 6 mg/mL oral suspension 1, 2
- If commercial suspension is unavailable, pharmacies can compound it to the same 6 mg/mL concentration 1, 2
- Administer with food to significantly reduce gastrointestinal side effects (nausea and vomiting) 1, 2, 5
Critical Dosing Pitfalls to Avoid
Do not round up to the next weight category. A child weighing 22.1 kg remains in the >15 to ≤23 kg bracket and should receive 45 mg, not 60 mg. 1 Rounding up inappropriately increases the risk of adverse effects without additional benefit.
Do not use age-based dosing for this patient. Weight-based categorical dosing takes precedence for children ≥12 months. 1
Ensure accurate measurement using a calibrated oral dosing device that precisely measures 7.5 mL. 1
Renal Function Considerations
For patients with normal renal function, no dose adjustment is needed. 1, 4
If this child had creatinine clearance 10-30 mL/min, the dose would require reduction to 45 mg once daily for treatment (instead of twice daily) or 30 mg once daily for prophylaxis. 1, 2 However, this is uncommon in otherwise healthy children.
Monitoring and Adverse Effects
Gastrointestinal symptoms (nausea and vomiting) are the most common adverse effects, occurring in approximately 10-15% of patients. 2, 5, 6
- These symptoms are typically mild and transient, resolving within 1-2 days 2, 5
- Taking oseltamivir with food significantly reduces their severity 1, 2, 5
- In pediatric treatment trials, vomiting occurred in 16% of oseltamivir recipients versus 8% on placebo 5
- Only approximately 1% of patients discontinue therapy due to gastrointestinal effects 2
Other potential adverse effects include headache and skin reactions, which are generally mild. 1, 2
Treatment Completion
Complete the full 5-day treatment course even if symptoms improve earlier, to ensure adequate viral suppression and help prevent resistance. 2 For prophylaxis, continue the full 10-day course. 1, 4