Amoxicillin Dosing for a 10-Year-Old Child on BID Regimen
For a 10-year-old child weighing 33.75 kg, the appropriate amoxicillin dose on a twice daily (BID) regimen is 45 mg/kg/day divided into 2 doses, which equals 759 mg per dose (approximately 750 mg) twice daily. 1
Dosing Calculation
The FDA-approved amoxicillin dosing for children weighing less than 40 kg follows these guidelines:
For mild to moderate infections:
- 25 mg/kg/day divided every 12 hours (BID) or
- 20 mg/kg/day divided every 8 hours (TID)
For severe infections or lower respiratory tract infections:
- 45 mg/kg/day divided every 12 hours (BID) or
- 40 mg/kg/day divided every 8 hours (TID) 1
For this 33.75 kg child:
- Mild/moderate infection BID dosing: 33.75 kg × 25 mg/kg/day ÷ 2 = 421.9 mg per dose
- Severe infection BID dosing: 33.75 kg × 45 mg/kg/day ÷ 2 = 759.4 mg per dose
Clinical Evidence Supporting BID Dosing
Recent evidence supports that BID dosing of amoxicillin is as effective as TID dosing:
A 2019 study using real-time PCR to measure bacterial load in group A streptococcal pharyngitis found no statistical difference in bacterial eradication between once-daily, twice-daily, and three-times-daily amoxicillin regimens 2
For community-acquired pneumonia, the American Academy of Pediatrics recommends amoxicillin 90 mg/kg/day in 2 doses as the preferred treatment for children ≥5 years old 3
Important Considerations
Infection type matters:
- For mild/moderate infections: 25 mg/kg/day (421.9 mg BID)
- For severe or respiratory infections: 45 mg/kg/day (759.4 mg BID)
Duration of therapy:
- For most infections: minimum of 48-72 hours beyond symptom resolution
- For Streptococcus pyogenes infections: minimum 10 days to prevent acute rheumatic fever 1
Administration guidance:
- Take at the start of a meal to minimize gastrointestinal intolerance 1
- Ensure full course completion even if symptoms improve
Practical dosing:
- For a 33.75 kg child, the calculated dose of 759.4 mg would typically be rounded to 750 mg BID for severe infections
- For mild infections, 421.9 mg would typically be rounded to 400 mg or 425 mg BID
Cautions and Monitoring
- Monitor for allergic reactions, which occur in approximately 0.9% of patients 4
- Watch for gastrointestinal side effects (diarrhea, nausea, vomiting)
- Assess clinical response within 48-72 hours; failure to improve warrants reevaluation
BID dosing offers the advantage of improved compliance compared to TID dosing while maintaining similar efficacy, making it an appropriate choice for pediatric patients.