Amoxicillin Dosing for an 11-Year-Old Weighing 76 Pounds
For an 11-year-old patient weighing 76 pounds (34.5 kg), the recommended dose of amoxicillin 400mg/5ml suspension depends on the indication: for mild to moderate respiratory infections, give 8.6 mL (approximately 690 mg) twice daily; for severe infections or high pneumococcal resistance areas, give 17.2 mL (approximately 1380 mg) twice daily. 1
Weight-Based Dosing Calculation
The patient weighs 76 pounds, which converts to 34.5 kg 1
For mild to moderate respiratory tract infections, the Infectious Diseases Society of America recommends 45 mg/kg/day divided into 2 doses 1
- Calculation: 34.5 kg × 45 mg/kg/day = 1552.5 mg/day
- Per dose: 776 mg twice daily
- Volume per dose: 9.7 mL of 400mg/5ml suspension twice daily 1
For severe infections or areas with high pneumococcal resistance (>10%), the Infectious Diseases Society of America recommends 90 mg/kg/day divided into 2 doses 1
- Calculation: 34.5 kg × 90 mg/kg/day = 3105 mg/day
- Per dose: 1552.5 mg twice daily
- Volume per dose: 19.4 mL of 400mg/5ml suspension twice daily 1
Indication-Specific Dosing Algorithm
For Community-Acquired Pneumonia (Mild to Moderate)
- Standard dose: 45 mg/kg/day in 2 doses = approximately 9.7 mL twice daily 1
- Treatment duration: 10 days 1
- Clinical improvement should occur within 48-72 hours; if not, reevaluation is necessary 1
For Severe Pneumonia or High-Resistance Areas
- High dose: 90 mg/kg/day in 2 doses = approximately 19.4 mL twice daily 1
- This regimen is indicated for children with recent antibiotic exposure within 30 days, daycare attendance, age <2 years, or geographic areas with >10% penicillin-resistant S. pneumoniae 1
For Group A Streptococcal Pharyngitis
- The American Academy of Family Physicians recommends 50-75 mg/kg/day divided into 2 doses for 10 days 1
- For this 34.5 kg patient: 1725-2587.5 mg/day total
- Volume: 10.8-16.2 mL twice daily, not exceeding 1000 mg per dose 1
Maximum Dose Considerations
- The maximum daily dose of amoxicillin should not exceed 4000 mg/day regardless of weight 1
- For this patient, even the high-dose regimen (3105 mg/day) remains well below this maximum 1
Treatment Duration and Monitoring
- Standard treatment duration for respiratory infections is 7-10 days, with pneumonia specifically requiring 10 days 1
- Children on appropriate therapy should demonstrate clinical improvement within 48-72 hours 1
- If no improvement occurs within this timeframe, reevaluation and further investigation are necessary 1
Critical Dosing Pitfalls to Avoid
- Do not use age-based dosing alone—this 11-year-old requires weight-based calculation to avoid underdosing 2
- Verify the suspension concentration (400mg/5mL in this case) before calculating volume to prevent dosing errors 1
- For β-lactamase-producing organisms (H. influenzae, M. catarrhalis), amoxicillin-clavulanate should be used instead of amoxicillin alone at 90 mg/kg/day of the amoxicillin component 1, 3
- Complete the full course even if symptoms improve before completion 1