Tamiflu Dosage for a 9 kg Child
For a child weighing 9 kg who is ≥12 months old, administer 30 mg (5 mL of oral suspension) twice daily for 5 days for treatment, or 30 mg once daily for 10 days for prophylaxis. 1, 2, 3
Age-Specific Dosing Considerations
The correct dose depends critically on whether this child is younger or older than 12 months:
For Children ≥12 Months (Weight-Based Categorical Dosing)
- Treatment regimen: 30 mg orally twice daily for 5 days 1, 2, 3
- Prophylaxis regimen: 30 mg orally once daily for 10 days 1, 2, 3
- This applies to all children weighing ≤15 kg who are at least 12 months old 1, 2
- The 30 mg dose equals 5 mL of the 6 mg/mL oral suspension 1, 3
For Infants <12 Months (mg/kg-Based Dosing)
If this 9 kg child is younger than 12 months, do not use the 30 mg categorical dose—instead, calculate based on actual body weight:
- Infants 9-11 months: 3.5 mg/kg per dose twice daily = 31.5 mg (approximately 5.25 mL) twice daily for treatment 1, 2, 4
- Infants 0-8 months: 3.0 mg/kg per dose twice daily = 27 mg (4.5 mL) twice daily for treatment 1, 2, 4
- Prophylaxis for infants 3-11 months: 3.0 mg/kg once daily for 10 days 1, 2
- Prophylaxis is not recommended for infants <3 months unless the situation is critical 1, 2, 3
For Preterm Infants (Postmenstrual Age-Based Dosing)
If this child was born prematurely, dosing must be based on postmenstrual age (gestational age + chronological age), not weight alone:
- <38 weeks postmenstrual age: 1.0 mg/kg twice daily = 9 mg (1.5 mL) 1, 2
- 38-40 weeks postmenstrual age: 1.5 mg/kg twice daily = 13.5 mg (2.25 mL) 1, 2
- >40 weeks postmenstrual age: 3.0 mg/kg twice daily = 27 mg (4.5 mL) 1, 2
Critical Pitfalls to Avoid
- Never apply the ≤15 kg categorical dose (30 mg) to infants <12 months old—this dosing scheme is exclusively for children ≥12 months 2, 5
- Never use term-infant dosing for preterm infants—immature renal function requires lower, postmenstrual age-adjusted doses to prevent toxic drug accumulation 1, 2, 5
- Never round up to the next weight category—a 9 kg child remains in the ≤15 kg bracket and should not receive 45 mg 2
- Never use household spoons for measurement—always use a calibrated oral syringe, particularly for infants requiring precise mg/kg dosing 2, 5
Formulation and Administration
- Use the oral suspension formulation (6 mg/mL concentration) for young children 1, 3
- If commercial suspension is unavailable, pharmacies can compound it according to package insert instructions 1, 6, 3
- Administer with food to reduce gastrointestinal side effects (nausea, vomiting), which occur in approximately 10-15% of patients 6, 7
- For infants <12 months requiring small volumes, use a 3-mL or 5-mL calibrated oral syringe for accurate measurement 2, 5
Timing and Clinical Context
- Initiate treatment within 48 hours of symptom onset for maximum benefit; starting within 12-24 hours provides substantially greater effectiveness 2, 5, 7
- Early treatment reduces illness duration by approximately 1-1.5 days (26-36% reduction) and decreases secondary complications like otitis media by 44% 5, 8
- Complete the full 5-day treatment course even if symptoms improve earlier 2, 5
- For prophylaxis, initiate within 48 hours following close contact with an infected individual 1, 3
Special Populations
- Renal impairment: For creatinine clearance 10-30 mL/min, reduce treatment dose to 30 mg once daily (instead of twice daily) for 5 days 1, 6, 3
- Immunocompromised patients: Prophylaxis may be extended up to 12 weeks during community outbreaks 3
- Consultation recommended: For infants <1 year, especially neonates or those with low body weight, consider consulting a pediatric infectious disease specialist 1, 5