Amoxicillin Dosing for a 33.5 kg Child
For a child weighing 33.5 kg, the standard amoxicillin dose is 500 mg every 12 hours (or 250 mg every 8 hours) for mild to moderate infections, or 875 mg every 12 hours (or 500 mg every 8 hours) for severe infections or lower respiratory tract infections. 1
Weight-Based Dosing Algorithm
Since this child weighs 33.5 kg (between 23-40 kg), the dosing follows the FDA-approved weight-based recommendations 1:
For Mild to Moderate Infections (Ear/Nose/Throat, Skin, Genitourinary):
- Standard dose: 25 mg/kg/day divided every 12 hours 1
- Calculation: 33.5 kg × 25 mg/kg = 837.5 mg/day = approximately 420 mg every 12 hours 1
- Practical dosing: 500 mg every 12 hours (or 250 mg every 8 hours) 1
For Severe Infections or Lower Respiratory Tract Infections:
- High dose: 45 mg/kg/day divided every 12 hours 1
- Calculation: 33.5 kg × 45 mg/kg = 1507.5 mg/day = approximately 750 mg every 12 hours 1
- Practical dosing: 875 mg every 12 hours (or 500 mg every 8 hours) 1
Indication-Specific Considerations
For community-acquired pneumonia, the Infectious Diseases Society of America recommends 90 mg/kg/day in 2 doses for severe infections or areas with high pneumococcal resistance 2, which would translate to approximately 1500 mg/day divided into two 750 mg doses for this 33.5 kg child 2.
For Group A Streptococcal infections (such as pharyngitis or scarlet fever), the recommended dose is 50-75 mg/kg/day in 2 doses 2, which equals approximately 840-1260 mg/day, or 420-630 mg every 12 hours 2.
Treatment Duration
- Respiratory tract infections: 7-10 days 2
- Pneumonia: 10 days minimum 2
- Streptococcal infections: At least 10 days to prevent acute rheumatic fever 1
- General guideline: Continue for 48-72 hours beyond symptom resolution 1
Critical Dosing Considerations
Maximum daily dose: For children weighing less than 40 kg, do not exceed the weight-based calculations; for children ≥40 kg, adult dosing applies (maximum 875 mg every 12 hours for severe infections) 1.
Administration: Give at the start of meals to minimize gastrointestinal intolerance 1.
Clinical monitoring: Expect improvement within 48-72 hours; if no improvement occurs, reevaluation is necessary 2.
High-resistance areas: In regions with high prevalence of penicillin-resistant Streptococcus pneumoniae (>10%), consider the higher dose of 90 mg/kg/day 2, 3.