What is the appropriate dosing of Augmentin (amoxicillin/clavulanate) oral suspension for an 18‑month‑old child weighing 11.8 kg?

Augmentin Dosing for 18-Month-Old, 11.8 kg Child

For an 18-month-old child weighing 11.8 kg, prescribe Augmentin ES-600 suspension at 5.3 mL twice daily (providing 90 mg/kg/day of amoxicillin) for most respiratory tract infections, or standard Augmentin suspension at 4.7 mL twice daily (45 mg/kg/day) for uncomplicated infections in low-resistance areas.

Dosing Algorithm

High-Dose Regimen (Augmentin ES-600: 600 mg/42.9 mg per 5 mL)

• Indication: β-lactamase-producing organisms (H. influenzae, M. catarrhalis), recent antibiotic use (<30 days), daycare attendance, moderate-severe illness, or high local pneumococcal resistance
• Dose: 90 mg/kg/day of amoxicillin component
• Calculation: 11.8 kg × 90 mg/kg = 1,062 mg/day ÷ 2 doses = 531 mg per dose
• Volume: 531 mg ÷ 120 mg/mL = 4.4 mL twice daily (or use weight-based chart: approximately 5.3 mL twice daily per FDA label) 1
• Duration: 10 days for otitis media/sinusitis; 5-10 days for pneumonia 2, 3

Standard-Dose Regimen (Augmentin 400 mg/57 mg per 5 mL)

• Indication: Uncomplicated infections, no recent antibiotics, low local resistance (<10% penicillin-nonsusceptible S. pneumoniae)
• Dose: 45 mg/kg/day of amoxicillin component
• Calculation: 11.8 kg × 45 mg/kg = 531 mg/day ÷ 2 doses = 265.5 mg per dose
• Volume: 265.5 mg ÷ 80 mg/mL = 3.3 mL twice daily (round to 3.5 mL twice daily)
• Alternative: Can use 3-times-daily dosing at 2.3 mL per dose if preferred 4

Clinical Context-Specific Recommendations

Acute Otitis Media

• First-line: High-dose amoxicillin-clavulanate (90/6.4 mg/kg/day) if recent antibiotic exposure, daycare attendance, or concurrent conjunctivitis 5
• Target: β-lactamase-producing H. influenzae (58-82% of strains) and M. catarrhalis 5
• Evidence: 96% eradication of S. pneumoniae, 92.6% eradication of H. influenzae at days 4-6 1

Acute Bacterial Sinusitis

• Age <2 years or daycare: High-dose amoxicillin-clavulanate (80-90 mg/kg/day) 4
• Age ≥2 years, uncomplicated: Standard amoxicillin 45 mg/kg/day acceptable in low-resistance areas 4
• Clinical cure: 95.8% in sinusitis patients with high-dose formulation 1

Community-Acquired Pneumonia

• β-lactamase-producing H. influenzae: Amoxicillin-clavulanate 45 mg/kg/day (3 doses) or 90 mg/kg/day (2 doses) 2, 3
• Preferred over plain amoxicillin when β-lactamase production suspected 2

Critical Prescribing Details

Administration

• Timing: Give at start of meals to minimize GI intolerance and enhance clavulanate absorption 1
• Preparation: Shake suspension vigorously before each dose 1
• Storage: Refrigerate after reconstitution; stable for 10 days 1

Safety Profile

• Diarrhea incidence: 6.3-12.9% with high-dose formulation 1, 6
• Protocol-defined diarrhea: 11.1% (ES-600) vs 9.4% (standard) - not significantly different 1
• Discontinuation rate: <2% due to adverse events 1
• All adverse events: Mild and self-limiting in 12.1% of patients 6

Common Pitfalls to Avoid

1. Do NOT substitute formulations: ES-600 contains different clavulanate concentrations than standard suspensions and they are NOT interchangeable 1

2. Do NOT underdose: This 11.8 kg child needs the full calculated volume - rounding down risks treatment failure, especially with resistant organisms

3. Do NOT use adult tablets: ES-600 suspension is specifically formulated for pediatric dosing; adults should receive 500 mg or 875 mg tablets 1

4. Do NOT extend beyond 10 days without reassessment: Standard duration is 5-10 days depending on infection type 1

5. Monitor for augmented clearance: In critically ill children (post-cardiac surgery, ICU patients), clearance may be significantly increased requiring 4-hourly dosing instead of standard 6-hourly 7

Formulation Selection

Choose Augmentin ES-600 when:

• Recent antibiotic use (<30 days)
• Daycare attendance
• Age <2 years
• Moderate-severe illness
• Treatment failure on standard amoxicillin
• High local resistance rates

Choose standard Augmentin when:

• Uncomplicated infection
• No recent antibiotics
• Low local resistance
• Mild illness in older toddler

The 14:1 amoxicillin-to-clavulanate ratio in ES-600 provides enhanced amoxicillin exposure while maintaining adequate β-lactamase inhibition with lower clavulanate-related diarrhea compared to older 7:1 formulations 5, 1.