What is the recommended dose of co-amoxiclav (amoxicillin/clavulanic acid) 312.5/5ml preparation for a 9-year-old child weighing 35kg with a suspected bacterial infection and no known allergy to penicillin?

Co-Amoxiclav Dosing for a 9-Year-Old Child (35kg) with Suspected Bacterial Infection

For a 9-year-old child weighing 35kg with suspected bacterial infection, administer 10 ml of the 312.5mg/5ml preparation (250mg amoxicillin/62.5mg clavulanate per 5ml) three times daily, providing 750mg amoxicillin per dose or 2250mg total daily. 1

Age-Based Dosing Algorithm

The 312.5mg/5ml preparation is specifically the 250/62 suspension formulation, which is indicated for children aged 7-12 years. 1 This formulation provides:

• 250mg amoxicillin + 62.5mg clavulanate per 5ml
• Standard dose: 5ml three times daily for children 7-12 years 1
• For a 35kg child, this provides approximately 21 mg/kg/day of amoxicillin component 1

When High-Dose Therapy is Required

However, if this child has ANY of the following risk factors, you must use the high-dose regimen (90 mg/kg/day) instead: 1, 2

• Age <2 years (not applicable here)
• Daycare attendance 1
• Recent antibiotic use within past 30 days 1, 2
• Incomplete Haemophilus influenzae type b vaccination 1
• Geographic area with >10% penicillin-resistant S. pneumoniae 1
• Moderate to severe illness 1
• Concurrent purulent acute otitis media 1

For high-dose therapy (90 mg/kg/day): 1

• This 35kg child requires 3150mg amoxicillin daily (1575mg twice daily)
• The 250/62 suspension cannot achieve this dose practically
• You would need approximately 31.5ml twice daily of the 250/62 suspension, which is impractical
• Switch to a higher concentration formulation or use tablets to achieve proper dosing 1

Critical Dosing Verification Steps

Before dispensing, verify: 1

1. Confirm the exact suspension concentration - the 312.5mg/5ml designation suggests 250mg amoxicillin + 62.5mg clavulanate per 5ml 1
2. Assess for risk factors requiring high-dose therapy 1, 2
3. Maximum daily dose: Do not exceed 4000mg amoxicillin per day regardless of weight 1, 3

Treatment Duration and Monitoring

• Standard duration: 10 days for most bacterial respiratory infections 1, 4
• Clinical improvement expected within 48-72 hours 1, 2
• If no improvement by 72 hours: Reevaluate diagnosis, consider atypical pathogens, assess for complications, or switch antibiotics 1, 2

Common Pitfalls to Avoid

The most critical error is using standard-dose therapy when high-dose is indicated. 1 This leads to:

• Treatment failure with resistant organisms 1
• Inadequate tissue concentrations 1
• Promotion of antimicrobial resistance 1

The second major pitfall is miscalculating the suspension concentration. 1 Always verify whether you have 125/31 or 250/62 suspension before calculating volume, as dosing errors are common when providers assume the wrong concentration. 1

Adverse Effects

Common adverse effects include: 1, 5

• Diarrhea (occurs in approximately 25% vs 15% placebo) 5
• Nausea and vomiting 1
• Rash 1
• The 14:1 ratio formulation (used in high-dose therapy) causes less diarrhea than other amoxicillin-clavulanate preparations 1