What is the appropriate oral oseltamivir (Tamiflu) dose for a child weighing 80 lb (≈36 kg)?

Oseltamivir Dosing for an 80 lb Child

For a child weighing 80 lb (approximately 36 kg), the appropriate oseltamivir dose is 60 mg orally twice daily for 5 days for treatment, or 60 mg once daily for 10 days for prophylaxis. 1

Weight-Based Dosing Algorithm

An 80 lb child falls into the >23 kg to 40 kg (>51 lb to 88 lb) weight category, which requires:

• Treatment regimen: 60 mg (10 mL of 6 mg/mL oral suspension) twice daily for 5 days 1
• Prophylaxis regimen: 60 mg (10 mL of 6 mg/mL oral suspension) once daily for 10 days 1

The American Academy of Pediatrics uses the following weight-based categories for children ≥12 months of age 1:

• ≤15 kg (≤33 lb): 30 mg per dose

• 15–23 kg (>33–51 lb): 45 mg per dose

• >23–40 kg (>51–88 lb): 60 mg per dose ← This applies to your 80 lb patient

• 40 kg (>88 lb): 75 mg per dose

Formulation and Administration

• Use the oral suspension formulation (6 mg/mL concentration) with 10 mL delivering the 60 mg dose 1, 2
• If the child can swallow capsules, two 30 mg capsules may be used instead of the liquid formulation 2
• Administer with food to reduce gastrointestinal side effects (nausea and vomiting occur in approximately 10% of patients) 1, 3, 4
• If commercial suspension is unavailable, pharmacies can compound it to the same 6 mg/mL concentration 1, 2

Critical Timing Considerations

• Initiate treatment within 48 hours of symptom onset for maximum benefit 1, 2, 4
• Starting within 12–24 hours provides substantially greater effectiveness—treatment within 12 hours reduces illness duration by an additional 74.6 hours compared to starting at 48 hours 4
• For prophylaxis, begin within 48 hours after close contact with a confirmed influenza case 5, 2

Clinical Benefits of Early Treatment

• Reduces illness duration by approximately 1–1.5 days (26–36% reduction) 3, 6
• Decreases severity of cough, nasal congestion, and fever 3, 6
• Lowers risk of secondary complications, particularly acute otitis media, by approximately 44% 3, 4

Common Pitfalls to Avoid

• Do not round down to 45 mg simply because the child is closer to the lower end of the weight range—80 lb clearly exceeds 51 lb, placing them in the 60 mg category 1
• Do not confuse treatment dosing (twice daily) with prophylaxis dosing (once daily) 1, 5
• Do not stop therapy early even if symptoms improve before day 5—complete the full 5-day course 5
• Do not delay treatment while awaiting laboratory confirmation during influenza season; clinical judgment is sufficient 5
• Do not use household spoons for measurement—use a calibrated oral dosing syringe or device that accurately measures 10 mL 5, 2

Renal Function Considerations

• No dose adjustment is needed for children with normal renal function 3
• If creatinine clearance is 10–30 mL/min, reduce to 60 mg once daily for treatment (instead of twice daily) 1, 2
• For prophylaxis with creatinine clearance 10–30 mL/min, give 30 mg once daily or 60 mg every other day 1, 2