Dosing Calculation for Co-amoxiclav Oral Suspension
For a 10-year-old child weighing 24.9 kg requiring approximately 560 mg of amoxicillin every 12 hours after abdominal surgery, administer 9.5 mL of the 600 mg/42.9 mg per 5 mL suspension twice daily.
Calculation Rationale
The FDA-approved co-amoxiclav 600 mg/42.9 mg per 5 mL suspension is specifically designed for pediatric dosing at 90 mg/kg/day of amoxicillin divided every 12 hours 1. This formulation provides 600 mg of amoxicillin per 5 mL.
For this patient:
- Target dose: ~560 mg amoxicillin per dose (approximately 45 mg/kg per dose, or 90 mg/kg/day)
- Weight: 24.9 kg
- Calculation:
- Exact dose = 24.9 kg × 45 mg/kg = 1,120.5 mg per day ÷ 2 = 560.25 mg per dose
- Volume needed = (560 mg ÷ 600 mg) × 5 mL = 4.67 mL per dose
However, the FDA dosing table for this formulation recommends 9.0 mL twice daily for children weighing 24 kg 1. Given this patient weighs 24.9 kg (essentially 25 kg), the appropriate volume would be approximately 9.5 mL twice daily, which provides 570 mg of amoxicillin per dose.
Clinical Context for Post-Surgical Use
For complicated intra-abdominal infections in pediatric patients, guidelines support ampicillin-sulbactam (the IV equivalent of co-amoxiclav) at 200 mg/kg/day of the ampicillin component divided every 6 hours 2. When transitioning to oral therapy post-operatively, the 600 mg/5 mL formulation at 90 mg/kg/day divided every 12 hours provides appropriate coverage 1.
Administration Instructions
- Administer at the start of meals to minimize gastrointestinal intolerance and enhance clavulanate absorption 1
- Shake suspension well before each use 1
- Duration: Typically 7-10 days for intra-abdominal infections, though this should be guided by clinical response and source control 2
- Storage: Refrigerate reconstituted suspension; stable for 10 days 1
Important Caveats
The 600 mg/42.9 mg per 5 mL formulation is not interchangeable with other co-amoxiclav suspensions (125/31 mg per 5 mL or 250/62 mg per 5 mL) due to different clavulanate concentrations 1. Using the wrong formulation could result in either inadequate amoxicillin dosing or excessive clavulanate exposure with increased diarrhea risk.
For children weighing ≥40 kg, adult formulations (tablets) should be used instead, as experience with the 600 mg/5 mL suspension in this weight range is limited 1.