Augmentin Dosing for a 60 kg Child with Sinusitis
For a 60 kg child with acute bacterial sinusitis, prescribe high-dose amoxicillin-clavulanate at 90 mg/kg/day of the amoxicillin component (5400 mg/day total amoxicillin), divided into two doses of 2700 mg twice daily, for 10-14 days. 1
Dosing Algorithm
Step 1: Determine Disease Severity and Risk Factors
The American Academy of Pediatrics guidelines stratify treatment based on:
- Moderate to severe illness (high fever ≥39°C, purulent nasal discharge for ≥3 consecutive days)
- Recent antibiotic exposure (within 30 days)
- Daycare attendance
- Age <2 years
Any of these factors warrant high-dose amoxicillin-clavulanate rather than standard-dose amoxicillin alone. 1
Step 2: Calculate the Dose
For this 60 kg child:
- High-dose regimen: 80-90 mg/kg/day of amoxicillin component
- Calculation: 90 mg/kg × 60 kg = 5400 mg/day
- Divided dosing: 2700 mg twice daily (every 12 hours)
- Maximum per dose: 2000 mg (this child exceeds the maximum)
Critical caveat: The guidelines specify a maximum of 2 g (2000 mg) per dose. 1 Therefore, cap the dose at 2000 mg twice daily (4000 mg/day total) rather than the calculated 2700 mg per dose.
Step 3: Select the Appropriate Formulation
- For children ≥40 kg: Use adult formulations (875 mg/125 mg tablets)
- Practical dosing: Give 2 tablets of 875 mg/125 mg twice daily = 1750 mg amoxicillin per dose
- Alternative: Use 500 mg/125 mg tablets, 4 tablets twice daily = 2000 mg per dose
The IDSA guidelines strongly recommend amoxicillin-clavulanate over amoxicillin alone as first-line therapy for children with acute bacterial rhinosinusitis. 2 This reflects the increasing prevalence of β-lactamase-producing Haemophilus influenzae and Moraxella catarrhalis.
Duration of Therapy
Treat for 10-14 days in children. 2 The longer duration (compared to 5-7 days in adults) accounts for:
- Higher bacterial loads in pediatric sinusitis
- Immature immune systems
- Better eradication rates with extended therapy
An alternative approach is to continue antibiotics for 7 days after symptom resolution, resulting in a minimum 10-day course. 1
Important Clinical Considerations
Why High-Dose Amoxicillin-Clavulanate?
The high-dose regimen (90 mg/kg/day) achieves adequate sinus fluid concentrations to overcome:
- Penicillin-resistant Streptococcus pneumoniae (MIC 2-4 mcg/mL)
- β-lactamase-producing organisms (H. influenzae, M. catarrhalis)
The clavulanate component at 6.4 mg/kg/day inhibits all β-lactamase-producing strains. 1
Administration Tips
- Give at the start of meals to minimize gastrointestinal side effects and enhance clavulanate absorption 3
- Shake suspension well before each dose
- Refrigerate reconstituted suspension; stable for 10 days 3
Common Pitfalls to Avoid
Don't substitute formulations: Augmentin ES-600 (90/6.4 mg/kg/day formulation) contains different clavulanate ratios than standard suspensions and is NOT interchangeable 3
Don't underdose large children: While this 60 kg child approaches adult weight, pediatric dosing guidelines still apply through age 18 years
Watch for diarrhea: Protocol-defined diarrhea occurs in 11-13% of patients on high-dose formulations, but discontinuation is rarely needed 3
Don't use for viral rhinosinusitis: Reserve antibiotics for true bacterial sinusitis (symptoms >10 days without improvement, or worsening after initial improvement) 1
When to Reassess
If symptoms worsen after 48-72 hours or fail to improve after 3-5 days:
- Consider treatment failure
- Evaluate for complications (orbital cellulitis, intracranial extension)
- Consider alternative antibiotics or imaging
- Refer to otolaryngology if toxic-appearing 1, 2
Evidence Quality Note
The recommendation for amoxicillin-clavulanate over amoxicillin alone in children is graded as strong with moderate-quality evidence by IDSA. 2 Recent adult data from 2026 showed no difference between the two agents 4, but pediatric guidelines appropriately account for higher rates of β-lactamase-producing organisms in children and their attendance at daycare settings.