Amoxicillin Dosing for 5-Year-Old, 32 kg Female
For a 5-year-old female weighing 32 kg, prescribe amoxicillin 90 mg/kg/day divided into 2 doses (1440 mg/day total, or approximately 720 mg twice daily), which translates to 14.4 mL of the 250 mg/5 mL suspension twice daily.
Dosing Rationale
The appropriate dose depends on the indication, but for most common pediatric infections requiring amoxicillin in this age group, high-dose amoxicillin (80-90 mg/kg/day) is the standard of care 1.
Standard Dosing by Indication:
For Community-Acquired Pneumonia (CAP):
- Preferred regimen: 90 mg/kg/day in 2 doses (maximum 4 g/day) 1
- For this 32 kg child: 1440 mg/day = 720 mg twice daily = 14.4 mL twice daily of 250 mg/5 mL suspension
- This high-dose regimen provides optimal coverage against Streptococcus pneumoniae, including penicillin-resistant strains 1
For Acute Otitis Media or Sinusitis:
- Same high-dose regimen (80-90 mg/kg/day) is recommended, particularly for children in daycare or with recent antibiotic exposure 2
- Alternative: 45 mg/kg/day in 3 doses for less severe cases, but high-dose is increasingly preferred
For Group A Streptococcal Infections:
- Lower dose acceptable: 50-75 mg/kg/day in 2 doses 1
- For this child: 800-1200 mg/day = 400-600 mg twice daily
Practical Dosing Calculation
Using the 250 mg/5 mL suspension:
- High-dose (90 mg/kg/day): 32 kg × 90 mg = 2880 mg/day ÷ 2 doses = 1440 mg per dose = 14.4 mL twice daily
- Standard-dose (45 mg/kg/day): 32 kg × 45 mg = 1440 mg/day ÷ 2 doses = 720 mg per dose = 7.2 mL twice daily
Important Clinical Considerations
Maximum Dose Concerns:
This child's calculated dose (2880 mg/day) does NOT exceed adult maximum doses. The adult maximum is typically 4000 mg/day 1. However, there is a documented tendency for clinicians to underdose larger children due to concerns about exceeding "adult doses" 3, 4. This is inappropriate—weight-based dosing should be maintained up to the adult maximum.
Duration of Therapy:
- CAP: 5-7 days is typically adequate; recent evidence suggests 3 days may be non-inferior for uncomplicated cases, though 7 days showed slightly faster cough resolution 5
- Acute otitis media/sinusitis: 5-10 days depending on severity 2
Resistance Considerations:
High-dose amoxicillin (80-90 mg/kg/day) is specifically recommended to overcome intermediate penicillin resistance in S. pneumoniae (MIC ≤2.0 μg/mL) 1. This dosing achieves adequate middle ear fluid and lung tissue concentrations even against resistant organisms 6, 7.
Common Pitfalls to Avoid:
Underdosing larger children: Studies show children >20 kg frequently receive <40 mg/kg/day when they should receive 80-90 mg/kg/day 3, 4
Inappropriate dose capping: Don't arbitrarily limit to "adult doses" if weight-based calculation is below 4000 mg/day
Wrong frequency: High-dose amoxicillin should be given twice daily, not three times daily, for improved compliance without compromising efficacy 8
Switching to amoxicillin-clavulanate unnecessarily: Reserve for treatment failure or β-lactamase-producing organisms 2, 9
Safety Profile:
Amoxicillin overdoses in children are remarkably well-tolerated. Even doses exceeding 200 mg/kg have not been associated with significant clinical symptoms 10, 11. The primary concern with very high doses (>100 mg/kg/day) is theoretical neurotoxicity at concentrations >140 mg/L, but this is rare with standard high-dose regimens 12.
The recommended 90 mg/kg/day regimen for this 32 kg child (2880 mg/day total) is both safe and appropriate for treating common pediatric bacterial infections requiring amoxicillin.