Co-amoxiclav Dosing for a 5-Year-Old Child Weighing 21 kg
For a 5-year-old child weighing 21 kg, the recommended dose is 5 mL of the 125/31 suspension three times daily, providing approximately 125 mg of amoxicillin per dose (375 mg total daily). 1
However, this standard dosing provides only approximately 18 mg/kg/day of amoxicillin, which is substantially below the recommended therapeutic doses for most bacterial infections requiring co-amoxiclav. 1
Critical Dosing Considerations
Standard vs. High-Dose Regimens
The appropriate dose depends entirely on the indication and risk factors:
For most respiratory tract infections and β-lactamase producing organisms:
- The American Academy of Pediatrics recommends 45 mg/kg/day in 3 doses OR 90 mg/kg/day in 2 doses of the amoxicillin component 1, 2
- For a 21 kg child, this translates to either:
- 315 mg three times daily (945 mg/day total), OR
- 945 mg twice daily (1890 mg/day total) 1
High-dose regimen (90 mg/kg/day) is specifically indicated for: 1
- Children <2 years of age
- Daycare attendance
- Recent antibiotic use (within 30 days)
- Incomplete Haemophilus influenzae type b vaccination
- Geographic areas with high pneumococcal resistance (>10%)
- Moderate to severe illness
- Concurrent purulent acute otitis media
Practical Dosing with Available Suspension
The 312.5 mg/5 mL suspension (125 mg amoxicillin/31.25 mg clavulanate per 5 mL) is NOT the appropriate formulation for achieving recommended therapeutic doses in a 21 kg child. 1
To achieve proper dosing:
- For 45 mg/kg/day regimen: Would require approximately 7.5 mL three times daily of the 125/31 suspension 1
- For 90 mg/kg/day regimen: Would require approximately 15 mL twice daily of the 125/31 suspension, OR preferably use the 250/62 suspension at 7.5 mL twice daily 1
Common Pitfalls to Avoid
Critical dosing errors occur when: 1
- Using age-based dosing instead of weight-based dosing for serious infections
- Failing to verify the suspension concentration before calculating volume
- Using subtherapeutic doses, which leads to treatment failure and promotes antimicrobial resistance
- Not considering risk factors that mandate high-dose therapy
The American Academy of Pediatrics explicitly warns that subtherapeutic doses fail to achieve adequate serum and tissue concentrations to overcome even susceptible organisms, and treatment failure with resistant organisms is inevitable when standard doses are not used. 1
Treatment Duration and Monitoring
- Standard treatment duration is 7-10 days for most infections, with 10 days specifically recommended for pneumonia and acute otitis media 1, 2
- Children should demonstrate clinical improvement within 48-72 hours 3
- If no improvement or worsening occurs after 72 hours, reevaluation and consideration of switching antibiotics or further investigation is necessary 1