Maximum Amoxicillin Dose for Obese Children
The maximum daily dose of amoxicillin for obese children is 4000 mg/day (4 g/day), regardless of weight, even when weight-based dosing calculations exceed this amount. 1
Standard Weight-Based Dosing Framework
For most pediatric infections, amoxicillin dosing follows these weight-based guidelines:
- Mild to moderate infections: 45 mg/kg/day divided into 2 doses 2, 3
- Severe infections or high-resistance areas: 90 mg/kg/day divided into 2 doses 2, 3, 1
- Group A Streptococcal pharyngitis: 50-75 mg/kg/day in 2 doses for 10 days 3, 1
Critical Dosing Cap for Obese Children
When calculated weight-based doses exceed 4000 mg/day, the dose should be capped at the maximum adult dose of 4000 mg/day. 1 This is particularly relevant for obese children, as a child weighing ≥45 kg receiving high-dose therapy (90 mg/kg/day) would exceed this maximum.
Practical Application
- Children weighing ≥40 kg: Maximum dose is 4000 mg/day (e.g., 2000 mg twice daily) 1
- For a 50 kg obese child requiring high-dose therapy: Calculate 90 mg/kg/day = 4500 mg/day, but cap at 4000 mg/day 1
Evidence-Based Rationale for Dose Capping
The practice of capping amoxicillin doses in obese children is supported by pharmacokinetic principles:
- Obese children experience decreased weight-normalized clearance and volume of distribution compared to normal-weight children 4
- Standard weight-based dosing in obese children results in higher absolute doses that still meet target exposures despite altered pharmacokinetics 4
- Primary care physicians already prescribe significantly lower-than-calculated doses in heavier children, with most capping at standard adult doses 5
Clinical Considerations
When High-Dose Therapy is Indicated
Use 90 mg/kg/day (maximum 4000 mg/day) for: 2, 3
- Recent antibiotic use within 4-6 weeks
- Areas with high penicillin-resistant S. pneumoniae prevalence
- Severe respiratory tract infections
- Treatment failure on standard dosing
Monitoring Parameters
- Assess clinical response at 48-72 hours 2, 3
- Lack of improvement warrants reevaluation or antibiotic change 2, 3
- Complete the full prescribed course even if symptoms improve 3
Common Pitfall to Avoid
Do not blindly calculate weight-based doses without applying the maximum daily cap. 1 A survey of guideline authors revealed that 67% would prescribe the standard adult dose when calculated doses exceeded it, while only 33% would prescribe the higher calculated dose—demonstrating lack of consensus but practical preference for dose capping. 5