Amoxicillin Dosing for Pediatric Infections
For most pediatric infections requiring amoxicillin, prescribe 80-90 mg/kg/day divided into two or three doses, with specific adjustments based on the child's age, weight, and infection severity.
Weight-Based Dosing Algorithm
For Children ≥3 Months and <40 kg
Standard-dose infections (Ear/Nose/Throat, Skin, Genitourinary - Mild/Moderate):
- 25 mg/kg/day divided every 12 hours, OR
- 20 mg/kg/day divided every 8 hours 1
High-dose infections (Lower Respiratory Tract, Severe infections, Acute Otitis Media):
- 80-90 mg/kg/day divided into 2-3 doses 2, 3, 1
- This translates to approximately 45 mg/kg/day every 12 hours OR 40 mg/kg/day every 8 hours for FDA-labeled dosing 1
For Children <3 Months (Neonates)
- Maximum 30 mg/kg/day divided every 12 hours due to immature renal function 1
- Recent evidence suggests twice-daily dosing for first 2 days of life, then three times daily from day 3 onward 4
For Children ≥40 kg
- Dose as adults: 500 mg every 12 hours (mild/moderate) or 875 mg every 12 hours (severe) 1
- Critical caveat: Do NOT exceed adult maximum doses even if weight-based calculation suggests higher doses 5, 6
Infection-Specific Recommendations
Acute Otitis Media
- 80-90 mg/kg/day for 10 days if child has NOT received amoxicillin in past 30 days 3
- Use amoxicillin-clavulanate if received amoxicillin within 30 days or has concurrent purulent conjunctivitis 3
- WHO guideline for resource-limited settings: 40 mg/kg twice daily for 5 days 7
Community-Acquired Pneumonia
- Children <3 years: 80-100 mg/kg/day in three divided doses for 10 days (pneumococcal coverage) 8
- Children ≥3 years: Same dosing if clinical picture suggests pneumococcal infection 8
- Consider macrolide instead if atypical bacteria suspected 2, 8
Group A Streptococcal Pharyngitis
- 50 mg/kg once daily (max 1000 mg) for 10 days, OR
- 25 mg/kg twice daily (max 500 mg per dose) for 10 days 9
Critical Dosing Pitfalls
The obesity paradox: Small children often receive appropriate high doses (80-90 mg/kg/day), while larger children systematically receive inadequate doses because clinicians hesitate to exceed "adult maximum doses" 5, 6. Children weighing >60 kg frequently receive <40 mg/kg/day—well below recommended dosing for resistant organisms 5.
Weight-based dosing is mandatory for children <40 kg to avoid this systematic underdosing 10. For children ≥40 kg, use weight-based dosing unless it exceeds the adult maximum dose for that specific indication 10.
Practical Prescribing Details
Your prescription should specify:
- Total daily dose in mg/kg
- Number of divided doses per day
- Duration of therapy
- Child's current weight
- Specific indication 11
Example: "Amoxicillin 80 mg/kg/day (total 1200 mg/day for 15 kg child) divided every 12 hours for 10 days for acute otitis media. Weight: 15 kg."
Duration of Therapy
- Streptococcal infections: Minimum 10 days to prevent rheumatic fever 1
- Pneumococcal pneumonia: 10 days with beta-lactam 8
- Uncomplicated infections: Continue 48-72 hours beyond clinical improvement 1
- Emerging evidence: 3-day courses may be adequate for stabilized pneumonia patients, though this requires clinical stability at day 3 12
Renal Impairment Adjustments
For children with severe renal impairment (GFR <30 mL/min):
- GFR 10-30: 500 mg or 250 mg every 12 hours
- GFR <10: 500 mg or 250 mg every 24 hours
- Hemodialysis: Additional dose during and after dialysis 1