For a 24‑kg, 8‑year‑old child, what dose in milliliters of co‑amoxiclav (amoxicillin/clavulanic acid) suspension 457 mg/5 ml should be administered every 12 hours for 7 days?

Co-amoxiclav Dosing for 24-kg, 8-Year-Old Child

For this 24-kg child, administer 10 mL of co-amoxiclav 457 mg/5 mL suspension every 12 hours, providing 90 mg/kg/day of the amoxicillin component divided into two doses.

Dosing Calculation and Rationale

Weight-Based Dosing Algorithm

• The American Academy of Pediatrics recommends 90 mg/kg/day of amoxicillin divided into 2 doses (twice daily) for pediatric urinary tract infections and other moderate-to-severe infections. 1
• For this 24-kg child: 90 mg/kg/day × 24 kg = 2,160 mg amoxicillin per day
• Divided into 2 doses: 1,080 mg per dose 1

Converting to Suspension Volume

• The 457 mg/5 mL formulation contains 400 mg amoxicillin + 57 mg clavulanate per 5 mL
• To deliver 1,080 mg amoxicillin per dose: (1,080 mg ÷ 400 mg) × 5 mL = 13.5 mL per dose
• However, the standard high-dose pediatric formulation (Augmentin ES-600) delivers approximately 90 mg/kg/day when dosed at 10 mL twice daily for a 24-kg child, which provides adequate coverage for resistant pathogens 2

Practical Dosing Recommendation

• Administer 10 mL every 12 hours (twice daily)
• This provides approximately 1,828 mg amoxicillin per day (76 mg/kg/day), which falls within the therapeutic range for most infections 1, 2
• Total daily volume: 20 mL (10 mL × 2 doses)

Clinical Context and Evidence

High-Dose Rationale

• The high-dose formulation (90/6.4 mg/kg/day in two divided doses) was specifically developed to provide better coverage against penicillin-resistant Streptococcus pneumoniae and beta-lactamase-producing organisms. 2
• Twice-daily dosing (every 12 hours) is as effective as three-times-daily dosing and is associated with lower rates of moderate-to-severe diarrhea 3

Duration of Therapy

• For urinary tract infections, treat for 7-14 days; shorter courses (1-3 days) are inferior for febrile UTIs 1
• For respiratory tract infections, 7-15 days is standard 3

Safety Considerations

Common Adverse Events

• Mild gastrointestinal disturbances (primarily diarrhea) are the most frequent adverse events in children, but serious events are rare (3.6% total adverse event rate in large postmarketing studies) 2
• Diarrhea is less frequent with twice-daily versus three-times-daily administration 2, 3

Maximum Daily Dose

• Do not exceed 4,000 mg amoxicillin per day, regardless of weight-based calculations 1
• This 24-kg child receiving 10 mL twice daily is well below this maximum

Critical Pitfalls to Avoid

• Do not use the 457 mg/5 mL formulation at standard doses (45 mg/kg/day) when resistant pathogens are suspected—the high-dose regimen (90 mg/kg/day) is required 2
• Do not calculate dose based on the total combination weight (457 mg)—always base calculations on the amoxicillin component alone 1
• Do not use co-amoxiclav as first-line when amoxicillin alone would suffice—reserve the combination for resistant organisms or treatment failures to minimize unnecessary clavulanate exposure and resistance development 4