Amoxicillin 400mg/5ml Dosing for a 36-Pound 2-Year-Old
For a 2-year-old weighing 36 pounds (16.4 kg), the recommended dose is 45 mg/kg/day divided into 2 doses for mild to moderate respiratory infections, which equals approximately 370 mg per dose or 4.6 mL of the 400mg/5ml suspension twice daily. 1
Weight-Based Calculation
- Convert weight: 36 pounds = 16.4 kg
- Standard dosing for mild-moderate infections: 45 mg/kg/day divided every 12 hours 1, 2
- Daily dose: 16.4 kg × 45 mg/kg = 738 mg/day
- Per-dose amount: 738 mg ÷ 2 = 369 mg per dose
- Volume calculation: 369 mg ÷ (400 mg/5 mL) = 4.6 mL twice daily 1
Indication-Specific Adjustments
For Severe Infections or High-Risk Situations
If the child has any of the following risk factors, increase to 90 mg/kg/day (approximately 9.2 mL twice daily): 1
- Age under 2 years 1
- Daycare attendance 1
- Recent antibiotic use within past 30 days 1
- Geographic area with >10% penicillin-resistant S. pneumoniae 1
- Severe infection requiring hospitalization 1
Specific Infections
- Community-acquired pneumonia (mild-moderate): 45 mg/kg/day = 4.6 mL twice daily 1
- Community-acquired pneumonia (severe): 90 mg/kg/day = 9.2 mL twice daily 1
- Group A Streptococcal infections: 50-75 mg/kg/day = 5.1-7.7 mL twice daily 1
- Acute otitis media (uncomplicated): 45 mg/kg/day = 4.6 mL twice daily 1
Treatment Duration and Monitoring
- Standard duration: 7-10 days for most respiratory infections 1
- Pneumonia specifically: 10 days of treatment 1
- Expected improvement: Clinical improvement should occur within 48-72 hours; if no improvement, reevaluation is necessary 1
- Streptococcal infections: Minimum 10 days to prevent acute rheumatic fever 2
Administration Instructions
- Give at the start of meals to minimize gastrointestinal intolerance 2
- Shake suspension well before each use 2
- Refrigeration is preferable but not required 2
- Discard unused suspension after 14 days 2
Critical Dosing Considerations
The maximum daily dose should not exceed 4000 mg/day regardless of weight 1. For this 16.4 kg child, even the high-dose regimen (1476 mg/day) is well below this maximum.
Common Pitfalls to Avoid
- Underdosing: The older recommendation of 40 mg/kg/day is inadequate for resistant S. pneumoniae, particularly during viral coinfection 3. Current guidelines recommend 45-90 mg/kg/day depending on severity 1.
- Age-based vs. weight-based dosing: Always use weight-based calculations rather than age-based approximations for accuracy 1, 4.
- Incomplete treatment course: Complete the full prescribed duration even if symptoms improve before completion 1.