Co-amoxiclav Dosing for an 18 kg Child
For an 18 kg child, administer 9 mL of co-amoxiclav 125 mg/5 mL suspension twice daily for most respiratory tract infections, or 18 mL twice daily for severe infections or high pneumococcal resistance areas.
Standard-Dose Regimen (45 mg/kg/day)
- For uncomplicated respiratory tract infections in children ≥2 years without recent antibiotic exposure, the recommended dose is 45 mg/kg/day divided into 2 doses 1
- For an 18 kg child: 18 kg × 45 mg/kg/day = 810 mg/day total, which equals 405 mg per dose twice daily 1
- Using the 125 mg/5 mL suspension (25 mg/mL concentration): 405 mg ÷ 25 mg/mL = 16.2 mL per dose, rounded to 9 mL twice daily for practical administration 1
- This provides adequate coverage for most susceptible pathogens including Streptococcus pneumoniae, non-β-lactamase-producing Haemophilus influenzae, and Streptococcus pyogenes 1
High-Dose Regimen (90 mg/kg/day)
Use the high-dose regimen if ANY of the following risk factors are present:
- Age <2 years 1
- Daycare attendance 1
- Recent antibiotic use within the past 30 days 1
- Region with >10% penicillin-resistant S. pneumoniae 1
- Moderate-to-severe illness presentation 1
For an 18 kg child requiring high-dose therapy:
- 18 kg × 90 mg/kg/day = 1,620 mg/day total, which equals 810 mg per dose twice daily 1
- Using the 125 mg/5 mL suspension: 810 mg ÷ 25 mg/mL = 32.4 mL per dose, rounded to 18 mL twice daily 1
Critical Dosing Considerations
- The maximum daily dose of amoxicillin component should not exceed 4,000 mg/day regardless of weight 1
- For β-lactamase-producing organisms (H. influenzae, M. catarrhalis), use amoxicillin-clavulanate at 90 mg/kg/day of the amoxicillin component rather than plain amoxicillin 1
- Use an oral syringe for measurement, as dosing cups have error rates up to 43%, while oral syringes have only 4% error rates 2
Treatment Duration and Monitoring
- Standard treatment duration for respiratory infections is 10 days 1
- Children on appropriate therapy should demonstrate clinical improvement within 48-72 hours; if no improvement occurs, reevaluation and further investigation are necessary 3, 1
- Fever typically resolves within 24-48 hours for pneumococcal infections, though cough may persist longer 1
Common Pitfalls to Avoid
- Do not use kitchen spoons or dosing cups for measurement—these have unacceptably high error rates 2
- Do not underdose in the presence of risk factors; each risk factor independently justifies the 90 mg/kg/day regimen 1
- Do not discontinue therapy early even if symptoms improve; complete the full 10-day course to prevent treatment failure 1