Amoxicillin Dosing Calculation for 56 kg Child at 50 mg/kg/day
For a 56 kg child receiving amoxicillin 50 mg/kg/day using the 400 mg/5 mL suspension, give 35 mL per day, divided as 17.5 mL twice daily.
Calculation Breakdown
Total daily dose needed:
- 56 kg × 50 mg/kg/day = 2,800 mg/day
Volume calculation with 400 mg/5 mL suspension:
- Concentration: 400 mg per 5 mL = 80 mg/mL
- Volume needed: 2,800 mg ÷ 80 mg/mL = 35 mL/day
Dosing schedule:
- Twice daily (every 12 hours): 17.5 mL per dose 1
- Three times daily (every 8 hours): 11.7 mL per dose 1
Recommended Approach
The twice-daily regimen (17.5 mL every 12 hours) is preferred for several reasons:
- FDA labeling for children ≥40 kg supports 50 mg/kg/day divided every 12 hours for mild-to-moderate infections 1
- Improved adherence with fewer daily doses 2
- Comparable efficacy to three-times-daily dosing for most common pediatric infections 3
Important Considerations
Maximum dose ceiling: While this child's calculated dose (2,800 mg/day) exceeds typical adult maximum doses (1,500-1,750 mg/day for standard infections), the FDA label supports weight-based dosing up to 500 mg every 8 hours or 875 mg every 12 hours in children ≥40 kg 1. For this 56 kg child at 50 mg/kg/day, the dose remains appropriate for conditions requiring standard amoxicillin therapy.
Clinical context matters: The 50 mg/kg/day dose is appropriate for Group A Streptococcus pharyngitis, mild-to-moderate skin infections, and uncomplicated urinary tract infections 4, 5. Higher doses (80-90 mg/kg/day) would be needed for pneumococcal infections with intermediate penicillin resistance 4, 5.
Administration: Give at the start of meals to minimize gastrointestinal side effects 1. Shake suspension well before each dose.