Amoxicillin-Clavulanate Dosing for a 3-Year-Old Child with Acute Sinusitis
For a 3-year-old child weighing 30 pounds (13.6 kg) with acute sinusitis, administer 12.3 mL of the 600 mg/42.9 mg per 5 mL suspension (Augmentin ES-600) twice daily for 10 days.
Dose Calculation
The recommended dose is 90 mg/kg/day of amoxicillin component with 6.4 mg/kg/day of clavulanate, divided into 2 doses, which is the high-dose regimen indicated for pediatric sinusitis. 1
Step-by-Step Calculation:
- Weight conversion: 30 pounds = 13.6 kg
- Daily amoxicillin dose: 90 mg/kg/day × 13.6 kg = 1,224 mg/day
- Per-dose amoxicillin: 1,224 mg ÷ 2 = 612 mg per dose
- Using 600 mg/42.9 mg per 5 mL suspension: 612 mg ÷ 600 mg × 5 mL = 5.1 mL per dose
However, the FDA-approved formulation for high-dose therapy in children aged 3 months and older is the 400 mg/57 mg per 5 mL suspension for the every-12-hour regimen. 2
Recalculation Using Standard Available Formulation:
- Per-dose amoxicillin needed: 612 mg
- Using 400 mg/57 mg per 5 mL suspension: 612 mg ÷ 400 mg × 5 mL = 7.65 mL per dose, rounded to 7.5 mL twice daily
Alternatively, using the 200 mg/28.5 mg per 5 mL suspension: 612 mg ÷ 200 mg × 5 mL = 15.3 mL per dose, rounded to 15 mL twice daily 2
Rationale for High-Dose Therapy
This 3-year-old requires high-dose amoxicillin-clavulanate (90 mg/kg/day) rather than standard-dose (45 mg/kg/day) because children under age 2 years, those in daycare, or those with recent antibiotic exposure require enhanced coverage against β-lactamase-producing organisms and potentially resistant S. pneumoniae. 1, 3
- The 14:1 ratio of amoxicillin to clavulanate in the high-dose formulation minimizes gastrointestinal side effects while maintaining efficacy against resistant organisms 1
- High-dose therapy achieves 90-92% predicted clinical efficacy against major pathogens including drug-resistant Streptococcus pneumoniae, β-lactamase-producing Haemophilus influenzae, and Moraxella catarrhalis 4, 5
Treatment Duration and Monitoring
The standard treatment duration is 10 days for pediatric acute bacterial sinusitis. 1, 2, 5
- Reassess at 72 hours (3 days): If no improvement or worsening symptoms occur, switch to alternative therapy 1, 3
- Clinical success rates with twice-daily dosing are 88-93% and are associated with significantly less diarrhea compared to three-times-daily regimens 6, 7
Critical Pitfalls to Avoid
Do not substitute formulations incorrectly—the 250 mg/125 mg tablet contains different clavulanate ratios than the 250 mg/62.5 mg chewable tablet and they are not interchangeable. 2
Do not use standard-dose therapy (45 mg/kg/day) for this child, as inadequate dosing leads to treatment failure rates of 20-25% against resistant organisms. 1, 8
Ensure the child completes the full 10-day course even after symptoms improve, as premature discontinuation increases relapse risk. 3