What is the recommended dose of amoxicillin for a 33kg pediatric patient with normal kidney function?

Amoxicillin Dosing for a 33kg Pediatric Patient

For a 33kg child with normal kidney function, amoxicillin should be dosed at 25-45 mg/kg/day divided every 12 hours (or 20-40 mg/kg/day divided every 8 hours) depending on infection severity, which translates to approximately 400-750 mg per dose twice daily or 250-500 mg per dose three times daily. 1

Standard Dosing Framework

The FDA-approved dosing for pediatric patients weighing less than 40 kg follows a weight-based calculation 1:

Mild to Moderate Infections

• 25 mg/kg/day divided every 12 hours (approximately 400 mg twice daily for 33kg child)
• Alternative: 20 mg/kg/day divided every 8 hours (approximately 220 mg three times daily)
• Indications: Ear/nose/throat infections, skin/skin structure infections, genitourinary tract infections 1

Severe Infections or Lower Respiratory Tract Infections

• 45 mg/kg/day divided every 12 hours (approximately 750 mg twice daily for 33kg child)
• Alternative: 40 mg/kg/day divided every 8 hours (approximately 440 mg three times daily)
• Required for: Lower respiratory tract infections (any severity), severe ear/nose/throat infections, severe skin infections 1

Practical Calculation for 33kg Patient

For mild-moderate infections:

• 33 kg × 25 mg/kg/day = 825 mg/day total → 412.5 mg every 12 hours (round to 400-500 mg twice daily)
• Or 33 kg × 20 mg/kg/day = 660 mg/day total → 220 mg every 8 hours (round to 250 mg three times daily)

For severe infections:

• 33 kg × 45 mg/kg/day = 1485 mg/day total → 742.5 mg every 12 hours (round to 750 mg twice daily)
• Or 33 kg × 40 mg/kg/day = 1320 mg/day total → 440 mg every 8 hours (round to 500 mg three times daily)

Important Clinical Considerations

Dosing Frequency Selection

• Twice-daily dosing improves compliance and is pharmacokinetically appropriate for most infections 2
• Research demonstrates that 25 mg/kg twice daily achieves adequate plasma concentrations above MIC for >50% of the dosing interval for most common pathogens 2
• Three-times-daily dosing may be preferred for severe infections or highly resistant organisms 1

Duration of Therapy

• Minimum 48-72 hours beyond symptom resolution or evidence of bacterial eradication 1
• Minimum 10 days for Streptococcus pyogenes infections to prevent acute rheumatic fever 1
• For community-acquired pneumonia, 3-day courses show non-inferiority to 7-day courses for uncomplicated cases 3

Formulation Selection

For a 33kg child, tablets or capsules are preferred over suspension:

• 500 mg tablets twice daily for mild-moderate infections
• 875 mg tablets twice daily for severe infections (if child can swallow)
• If suspension required: Use 250 mg/5 mL strength for easier volume administration 1

Critical Safety Points

Renal Function Monitoring

• No dose adjustment needed with normal renal function 1
• If creatinine clearance <30 mL/min, avoid 875 mg doses and reduce frequency 1
• The American Academy of Pediatrics emphasizes documenting weight on every prescription for pharmacist verification 4

Common Pitfalls to Avoid

• Do not exceed adult maximum doses: Total daily dose should not exceed 3000 mg/day even in severe infections 1
• Ensure adequate dosing for resistant organisms: Standard 40 mg/kg/day dosing is inadequate for penicillin-resistant Streptococcus pneumoniae; consider 75-90 mg/kg/day in areas with high resistance 5
• Take with food: Administer at the start of meals to minimize gastrointestinal intolerance 1
• Complete full course: Emphasize adherence even after symptom resolution to prevent treatment failure 6

When to Consider Higher Dosing (75-90 mg/kg/day)

• Acute otitis media in regions with high penicillin-resistant S. pneumoniae prevalence 5
• Treatment failure with standard dosing 5
• Documented infection with intermediate-susceptibility organisms 7