Tamiflu Dosing for a 19.5kg Patient
For a patient weighing 19.5 kg, the recommended dose of Tamiflu (oseltamivir) is 45 mg twice daily for 5 days for treatment, or 45 mg once daily for 10 days for prophylaxis. 1
Weight-Based Dosing Algorithm
This patient falls into the >15 kg to ≤23 kg weight category, which requires the 45 mg dose 2, 1, 3:
- ≤15 kg: 30 mg per dose
- >15 to 23 kg: 45 mg per dose (this patient at 19.5 kg)
- >23 to 40 kg: 60 mg per dose
- >40 kg: 75 mg per dose
Formulation and Administration
Use the oral suspension formulation (6 mg/mL concentration) with 7.5 mL delivering the 45 mg dose 2, 1:
- Administer with food to reduce gastrointestinal side effects such as nausea and vomiting 1, 3
- Use a calibrated oral dosing device to ensure accurate measurement of 7.5 mL 1
- If oral suspension is unavailable, pharmacies can compound it to the same 6 mg/mL concentration 2
Treatment vs. Prophylaxis Dosing
For treatment (confirmed or suspected influenza):
- 45 mg twice daily for 5 days 2, 1, 3
- Initiate within 48 hours of symptom onset for maximum benefit 3
- Do not withhold treatment in high-risk patients even if presenting beyond 48 hours 3
For prophylaxis (post-exposure or seasonal):
- 45 mg once daily for 10 days (post-exposure) 2, 1, 3
- May extend to 6 weeks during community outbreaks 1
Critical Pitfalls to Avoid
Do not round up to the next weight category - a child weighing 19.5 kg should receive 45 mg, not 60 mg, as they remain in the >15 to ≤23 kg bracket 1. This is a common dosing error that can lead to unnecessary adverse effects.
Do not use the 30 mg dose - although this patient is close to 15 kg, they exceed the threshold and require the higher 45 mg dose per established weight-based guidelines 2.
Renal Function Considerations
For this patient with normal renal function, no dose adjustment is needed 2, 3. However, if creatinine clearance were 10-30 mL/min, the dose would need reduction to 75 mg once daily for treatment or 30 mg once daily for prophylaxis 2, 3.
Monitoring and Adverse Effects
Monitor for gastrointestinal symptoms (nausea, vomiting, diarrhea), which are typically mild and transient, especially when taken with food 1, 3, 4. Complete the full 5-day treatment course even if symptoms improve earlier 1.