What is the appropriate amoxicillin dosage (200 mg per 5 mL) for a child weighing 18.69 kg?

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Last updated: September 28, 2026 • View editorial policy

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Amoxicillin Dosing for 18.69 kg Child

For a child weighing 18.69 kg, the appropriate amoxicillin dose depends on the infection severity and type, but generally ranges from 467-842 mg per dose using the 200 mg/5 mL suspension.

Dosing by Indication

For Mild to Moderate Infections (Ear/Nose/Throat, Skin, Genitourinary)

  • Standard dose: 25 mg/kg/day divided every 12 hours 1

    • Calculation: 18.69 kg × 25 mg/kg/day = 467 mg/day
    • Per dose: 234 mg every 12 hours
    • Volume: Approximately 6 mL every 12 hours (using 200 mg/5 mL suspension)

  • Alternative: 20 mg/kg/day divided every 8 hours

    • Per dose: 125 mg every 8 hours
    • Volume: Approximately 3 mL every 8 hours

For Severe Infections or Lower Respiratory Tract Infections

  • High dose: 45 mg/kg/day divided every 12 hours 1

    • Calculation: 18.69 kg × 45 mg/kg/day = 841 mg/day
    • Per dose: 421 mg every 12 hours
    • Volume: Approximately 10.5 mL every 12 hours (using 200 mg/5 mL suspension)

  • Alternative: 40 mg/kg/day divided every 8 hours

    • Per dose: 250 mg every 8 hours
    • Volume: Approximately 6 mL every 8 hours

For Pneumococcal Pneumonia (Community-Acquired Pneumonia)

High-dose amoxicillin is preferred: 90 mg/kg/day divided into 2 doses 2, 3

  • Calculation: 18.69 kg × 90 mg/kg/day = 1,682 mg/day
  • Per dose: 841 mg every 12 hours
  • Volume: Approximately 21 mL every 12 hours (using 200 mg/5 mL suspension)

Alternative: 45 mg/kg/day in 3 divided doses

  • Per dose: 280 mg every 8 hours
  • Volume: Approximately 7 mL every 8 hours

For Group A Streptococcus Infections

  • Dose: 50-75 mg/kg/day in 2 divided doses 2, 3
    • Calculation: 18.69 kg × 50-75 mg/kg/day = 935-1,402 mg/day
    • Per dose: 467-701 mg every 12 hours
    • Volume: Approximately 12-17.5 mL every 12 hours

Key Clinical Considerations

Duration of Therapy

  • Minimum: Continue for 48-72 hours beyond symptom resolution 1
  • Streptococcus pyogenes infections: Minimum 10 days to prevent acute rheumatic fever 1
  • Community-acquired pneumonia: Recent evidence supports 3-day courses for uncomplicated cases, though 5-7 days remains standard 4

Administration

  • Give at the start of meals to minimize gastrointestinal intolerance 1
  • Shake suspension well before each use
  • Can mix with formula, milk, fruit juice, water, or cold drinks if needed 1

Common Pitfalls

Underdosing in larger children: Research demonstrates that children in higher weight categories systematically receive lower mg/kg doses than recommended 5, 6. For this 18.69 kg child, ensure the full calculated dose is prescribed, not a rounded-down "convenient" volume.

Resistance considerations: With increasing pneumococcal resistance, high-dose amoxicillin (80-90 mg/kg/day) is now standard for pneumonia and serious infections 2, 7. The lower doses (25-45 mg/kg/day) are appropriate only for mild infections with susceptible organisms.

Twice-daily vs. three-times-daily dosing: Twice-daily dosing improves compliance and is pharmacokinetically appropriate for most indications 8. The higher per-dose amount with twice-daily dosing maintains adequate time above MIC.

Storage

  • Reconstituted suspension: Discard after 14 days 1
  • Refrigeration preferred but not required 1

References

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Professional Medical Disclaimer

This information is intended for healthcare professionals. Any medical decision-making should rely on clinical judgment and independently verified information. The content provided herein does not replace professional discretion and should be considered supplementary to established clinical guidelines. Healthcare providers should verify all information against primary literature and current practice standards before application in patient care. Dr.Oracle assumes no liability for clinical decisions based on this content.