What is the appropriate dose of co‑amoxiclav (amoxicillin/clavulanic acid) 625 mg tablet for a 9‑year‑old boy weighing 50 lb?

Co-Amoxiclav Dosing for a 9-Year-Old Weighing 50 lbs

For a 9-year-old boy weighing 50 lbs (22.7 kg), the appropriate dose of co-amoxiclav depends on the indication, but standard dosing is 5 mL of 250/62 suspension three times daily, providing approximately 250 mg of amoxicillin per dose (750 mg total daily, or 33 mg/kg/day). 1

Weight Conversion and Dosing Framework

• The child weighs 50 lbs = 22.7 kg (using the conversion 1 kg = 2.2 lbs). 2

• Age-based dosing is the primary framework for co-amoxiclav in children, rather than strict weight-based calculations for standard infections. 3

• For children aged 7–12 years, the recommended dose is 5 mL of 250/62 suspension three times daily, which delivers approximately 250 mg of amoxicillin per dose. 1, 3

Indication-Specific Dosing Adjustments

Standard Respiratory Tract Infections (Mild to Moderate)

• The standard regimen of 5 mL of 250/62 suspension three times daily is appropriate for uncomplicated respiratory infections in this age group without high-risk features. 1, 3

• This provides a total daily amoxicillin dose of 750 mg/day (33 mg/kg/day), which is adequate for susceptible pathogens including Streptococcus pneumoniae, non-β-lactamase-producing Haemophilus influenzae, and Streptococcus pyogenes. 1

High-Dose Regimen (Severe Infections or Resistant Organisms)

• High-dose co-amoxiclav (90 mg/kg/day of amoxicillin component) is indicated when any of the following risk factors are present: 2, 1, 3

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

• For this 22.7 kg child requiring high-dose therapy, the calculation is: 90 mg/kg/day × 22.7 kg = 2,043 mg/day, divided into two doses of approximately 1,020 mg each. 2, 1

• The high-dose formulation provides a 14:1 ratio of amoxicillin to clavulanate (90 mg/kg amoxicillin with 6.4 mg/kg clavulanate), which achieves tissue concentrations adequate to overcome penicillin-resistant S. pneumoniae with MICs up to 2–4 mg/L. 3, 4

Practical Administration

Standard Dose (Most Common Scenario)

• 5 mL of 250/62 suspension three times daily (every 8 hours). 1, 3

• Treatment duration: 7–10 days for most respiratory infections, with 10 days preferred for pneumonia and acute otitis media. 2, 1, 3

High-Dose Regimen (If Risk Factors Present)

• Use the high-dose suspension formulation (typically 600 mg/5 mL or similar concentration). 3

• Administer twice daily (every 12 hours) rather than three times daily. 2, 3

• Maximum single dose: 2,000 mg per administration regardless of weight. 3

• Maximum daily dose: 4,000 mg/day of the amoxicillin component. 2, 1

Critical Dosing Considerations

Verify Suspension Concentration

• Always verify the suspension concentration (125/31,250/62, or higher-dose formulations) before calculating volume to avoid dosing errors. 3

• The 250/62 formulation is specifically indicated for children over 6 years of age for standard dosing. 3

When to Use High-Dose Therapy

• Switch to high-dose amoxicillin-clavulanate if: 2, 1, 3
  • Treatment failure after 48–72 hours on standard therapy
  • Suspected β-lactamase-producing organisms (H. influenzae, M. catarrhalis)
  • Any of the high-risk factors listed above are present

Clinical Monitoring

• Clinical improvement should occur within 48–72 hours of starting appropriate therapy. 2, 1, 3

• If no improvement or worsening after 48–72 hours: 2, 1

  • Reassess the diagnosis
  • Consider atypical pathogens and potentially add a macrolide
  • Evaluate for complications or alternative diagnoses
  • Consider switching to high-dose formulation if not already prescribed

Treatment Duration

• Complete the full course (7–10 days) even if symptoms improve earlier to prevent resistance and recurrence. 2, 1

• For acute otitis media and pneumonia, a 10-day course is recommended. 1, 3

• Continue therapy for at least 48–72 hours after complete resolution of symptoms. 2

Common Pitfalls to Avoid

• Do not underdose: Using subtherapeutic doses fails to achieve adequate tissue concentrations and promotes antimicrobial resistance. 1

• Do not use adult dosing: Although children weighing ≥ 40 kg may receive adult doses for some indications, this 22.7 kg child requires pediatric weight-based or age-based dosing. 2, 1

• Do not prescribe antibiotics for viral infections: Most upper respiratory tract infections are viral and do not benefit from antibiotics. 3

• Verify the indication: Ensure the child meets criteria for bacterial infection (e.g., acute bacterial rhinosinusitis requires persistent symptoms > 10 days, severe symptoms, or "double sickening"). 3

Adverse Effects

• The most common adverse effects are mild gastrointestinal disturbances (diarrhea, nausea, vomiting), which occur in approximately 25% of patients on high-dose therapy versus 15% on placebo. 3, 4

• Diarrhea is generally less frequent with twice-daily dosing compared to three-times-daily administration. 4

• The high-dose 14:1 ratio formulation causes less diarrhea than other amoxicillin-clavulanate preparations while maintaining efficacy. 3