What dose in milliliters of amoxicillin/clavulanic acid suspension (457 mg/5 mL) should be administered every 12 hours for 7 days to a 2‑year‑5‑month‑old child weighing 19.5 kg?

Co-amoxiclav Dosing for 2-Year-5-Month-Old Child (19.5 kg)

For a 19.5 kg child aged 2 years 5 months, administer 10 mL of co-amoxiclav 457mg/5mL (400mg amoxicillin/57mg clavulanate per 5mL) every 12 hours for 7 days.

Dosing Calculation and Rationale

Weight-Based Dosing

• Target dose: 45 mg/kg/day of amoxicillin component for moderate to severe infections 1
• Calculation: 19.5 kg × 45 mg/kg/day = 877.5 mg/day total amoxicillin
• Per dose (q12h): 877.5 mg ÷ 2 = 438.75 mg per dose
• Volume required: 438.75 mg ÷ 400 mg per 5 mL = approximately 10 mL per dose 1

Formulation Selection

The 457mg/5mL suspension (400mg amoxicillin/57mg clavulanate per 5mL) is the appropriate high-dose formulation for this child 1. This provides:

• Per 10 mL dose: 800 mg amoxicillin + 114 mg clavulanate
• Daily total: 1600 mg amoxicillin (82 mg/kg/day) + 228 mg clavulanate

Clinical Context for Dosing

For otitis media, sinusitis, lower respiratory tract infections, or more severe infections, the FDA-approved dosing is 45 mg/kg/day every 12 hours using the 400mg/57mg per 5mL formulation 1. The twice-daily regimen is preferred as it is associated with significantly less diarrhea compared to three-times-daily dosing 1.

For less severe infections, a lower dose of 25 mg/kg/day every 12 hours could be considered, which would be approximately 5.5 mL per dose 1. However, given the lack of specific clinical context and the trend toward higher dosing for resistant pathogens, the standard 45 mg/kg/day dosing is recommended 2, 3.

Guideline Support

The Pediatric Infectious Diseases Society/Infectious Diseases Society of America guidelines recommend high-dose amoxicillin-clavulanate (80-90 mg/kg daily of amoxicillin with maximum 6.4 mg/kg clavulanic acid daily) for enhanced activity against beta-lactamase-producing H. influenzae and resistant S. pneumoniae 2. For β-lactamase-producing H. influenzae, amoxicillin-clavulanate at 45 mg/kg/day in 3 doses or 90 mg/kg/day in 2 doses is preferred 3.

Important Caveats

• Aspartame content: The 400mg/57mg formulation contains aspartame and should not be used in phenylketonuric patients 1
• Administration: Can be given without regard to meals, though absorption of clavulanate is slightly better with food 1
• Duration: 7 days is appropriate for most respiratory infections; acute otitis media may require 10 days 1
• Tolerability: Gastrointestinal side effects (particularly diarrhea) are the most common adverse events but are generally mild 4, 5

Monitoring

Watch for:

• Diarrhea (most common side effect, less frequent with q12h dosing) 1, 4
• Skin rashes 6
• Clinical response within 48-72 hours; if no improvement, consider treatment failure and alternative pathogens 2