Amoxicillin Dosing for Children
For most pediatric infections, prescribe amoxicillin 45 mg/kg/day divided twice daily (every 12 hours) for mild-to-moderate illness, or 80–90 mg/kg/day divided twice daily for severe infections, resistant organisms, or when risk factors for treatment failure are present. 1
Standard Dosing by Infection Type and Severity
Mild-to-Moderate Infections (Ear/Nose/Throat, Skin, Genitourinary)
- Dose: 25 mg/kg/day divided every 12 hours OR 20 mg/kg/day divided every 8 hours 2
- Practical application: For a 20 kg child, this equals approximately 250 mg twice daily or 133 mg three times daily 1
- FDA-approved indications: Otitis media, pharyngitis, skin infections caused by susceptible organisms 2
Severe Infections and Lower Respiratory Tract Infections
- Dose: 45 mg/kg/day divided every 12 hours OR 40 mg/kg/day divided every 8 hours 2
- Applies to: Community-acquired pneumonia, severe otitis media, any infection requiring enhanced pneumococcal coverage 1
- Duration: 10 days is standard, though 5-day courses show comparable cure rates in uncomplicated outpatient CAP 3
High-Dose Therapy (80–90 mg/kg/day)
Use high-dose amoxicillin when ANY of these risk factors are present: 1, 3
- Age < 2 years
- Daycare attendance
- Antibiotic use within the past 30 days
- Moderate-to-severe illness
- Community pneumococcal resistance > 10%
- Suspected resistant Streptococcus pneumoniae (penicillin MIC > 2.0 µg/mL)
- Dosing: 80–90 mg/kg/day divided every 12 hours 1, 3
- Example: For a 28 kg child, prescribe approximately 640 mg twice daily (total 1,280 mg/day) 1
- Rationale: Achieves middle-ear and sinus fluid concentrations sufficient to overcome intermediate resistance 1, 3
Specific Clinical Scenarios
Group A Streptococcal Pharyngitis
- Dose: 50 mg/kg/day divided twice daily 1
- Duration: 10 days mandatory to prevent acute rheumatic fever 1, 2
- Example: For a 34 kg child, prescribe 850 mg twice daily 1
- Alternative: 50–75 mg/kg/day divided twice daily is also acceptable 1
Acute Otitis Media
- Standard dose (≥2 years, no risk factors): 45 mg/kg/day divided twice daily 3
- High dose (any risk factor present): 80–90 mg/kg/day divided twice daily 3
- Duration: 10 days 3
Acute Bacterial Sinusitis
- Standard dose (≥2 years, mild disease, no recent antibiotics): 45 mg/kg/day divided twice daily 3
- High dose (risk factors present): 80–90 mg/kg/day divided twice daily 3
- Duration: 10 days or 7 days after symptom resolution, whichever is completed first 3
Resistant Pneumococcal Infections (Penicillin MIC > 2.0 µg/mL)
- Dose: 90 mg/kg/day divided every 12 hours 1
- Alternative: 45 mg/kg/day divided every 8 hours 1
- For a 20 kg child: Approximately 920 mg twice daily 1
- Critical point: Do NOT cap at adult maximum doses; weight-based dosing must be maintained 1
Dosing Frequency: Twice Daily vs. Three Times Daily
- Twice-daily dosing is preferred for improved adherence and equivalent efficacy 3, 4, 5
- Evidence: Studies demonstrate no significant difference in treatment failure rates between BID and TID regimens at equivalent total daily doses 4, 5
- Practical advantage: Simplifies administration and improves compliance without compromising outcomes 3
Treatment Duration
- Streptococcal pharyngitis: 10 days mandatory 1, 2
- Acute otitis media: 10 days 3
- Community-acquired pneumonia:
- Acute bacterial sinusitis: 10 days 3
Special Populations
Infants < 3 Months
- Maximum dose: 30 mg/kg/day divided every 12 hours 2
- Rationale: Incompletely developed renal function affects amoxicillin elimination 2
Children with Severe Malnutrition
- Dose unchanged: Use standard weight-based dosing unless severe diarrhea, renal failure, or shock is present 1
- Evidence: Amoxicillin absorption and clearance are largely unaffected by severe malnutrition 1
Renal Impairment (Weight > 40 kg)
- GFR 10–30 mL/min: 250–500 mg every 12 hours 2
- GFR < 10 mL/min: 250–500 mg every 24 hours 2
- Hemodialysis: Additional dose during and at end of dialysis 2
When to Escalate Therapy
Switch to High-Dose Amoxicillin-Clavulanate (80–90 mg/kg/day of amoxicillin component)
- No clinical improvement after 48–72 hours of standard amoxicillin 1, 3
- Suspected β-lactamase-producing organisms (Haemophilus influenzae, Moraxella catarrhalis) 1, 3
- Preferred formulation: 14:1 amoxicillin-to-clavulanate ratio to reduce diarrhea risk 1
Add a Macrolide (Do NOT Substitute)
- Children > 3–5 years with suspected atypical pathogens (Mycoplasma pneumoniae, Chlamydophila pneumoniae) 1, 3
- Persistent symptoms after 48 hours despite stable clinical condition 3
- Azithromycin dosing: 10 mg/kg on day 1, then 5 mg/kg daily on days 2–5 1
Add Clindamycin or Switch to Cephalexin
- Suspected Staphylococcus aureus infection (empyema, necrotizing pneumonia, post-influenza pneumonia) 1
Critical Pitfalls to Avoid
- Never cap amoxicillin doses at adult maximums (e.g., 500 mg twice daily) for children > 15 kg; this leads to underdosing and treatment failure 1
- Do not use standard-dose amoxicillin when any resistance risk factor is present; this increases treatment failure and promotes resistance 3
- Do not substitute a macrolide for amoxicillin in pneumonia; macrolides should only be added when atypical pathogens are suspected 3
- Do not use amoxicillin-clavulanate as first-line therapy unless β-lactamase-producing organisms are suspected or prior amoxicillin has failed 3
- Do not shorten streptococcal pharyngitis treatment below 10 days; this is required to prevent acute rheumatic fever 1, 2
Administration Instructions
- Take at the start of a meal 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
- Alternative administration: May mix with formula, milk, fruit juice, water, or cold drinks; consume immediately 2