Amoxicillin Dosing in Children
For most common pediatric infections, amoxicillin should be dosed at 45-90 mg/kg/day divided into 2 doses (every 12 hours), with the specific dose depending on infection severity and pathogen susceptibility. 1
Standard Dosing by Infection Type and Severity
For Children ≥3 Months and <40 kg
Mild to Moderate Infections (Ear/Nose/Throat, Skin, Genitourinary):
- 25 mg/kg/day divided every 12 hours OR 20 mg/kg/day divided every 8 hours 1
Severe Infections (Ear/Nose/Throat, Skin, Genitourinary):
- 45 mg/kg/day divided every 12 hours OR 40 mg/kg/day divided every 8 hours 1
Lower Respiratory Tract Infections (all severities):
- 45 mg/kg/day divided every 12 hours OR 40 mg/kg/day divided every 8 hours 1
Specific Pathogen-Directed Dosing
For Streptococcus pneumoniae with penicillin MIC <2.0 µg/mL:
- 90 mg/kg/day in 2 doses OR 45 mg/kg/day in 3 doses 2
For Group A Streptococcus:
For Haemophilus influenzae (β-lactamase negative):
- 75-100 mg/kg/day in 3 doses 2
Infants <3 Months (≤12 weeks)
Maximum dose: 30 mg/kg/day divided every 12 hours due to immature renal function 1. This conservative dosing is critical because neonates have incompletely developed renal clearance mechanisms.
Modifications for Special Circumstances
Severe Penicillin Allergy
If true severe penicillin allergy (anaphylaxis, Stevens-Johnson syndrome), amoxicillin is absolutely contraindicated. Alternative antibiotics depend on the infection:
- For pneumococcal infections: Use second/third-generation cephalosporins (cefpodoxime, cefuroxime, cefprozil), oral levofloxacin, or oral linezolid 2
- For Group A Streptococcus: Use oral clindamycin 40 mg/kg/day in 3 doses 2
- For MSSA: Use oral cephalexin 75-100 mg/kg/day in 3-4 doses OR oral clindamycin 30-40 mg/kg/day in 3-4 doses 2
Important caveat: Approximately 10% cross-reactivity exists between penicillins and cephalosporins, so cephalosporins should be avoided in patients with documented severe penicillin reactions 2.
Renal Impairment
For GFR 10-30 mL/min:
- 500 mg or 250 mg every 12 hours (depending on infection severity) 1
For GFR <10 mL/min:
- 500 mg or 250 mg every 24 hours (depending on infection severity) 1
For hemodialysis patients:
- 500 mg or 250 mg every 24 hours
- Administer an additional dose both during and at the end of dialysis 1
Critical note: Patients with GFR <30 mL/min should NOT receive the 875 mg dose 1. Dose reduction is generally not required unless renal impairment is severe.
Administration Guidelines
Timing and Duration
- Administer at the start of meals to minimize gastrointestinal intolerance 1
- Continue for minimum 48-72 hours beyond symptom resolution or bacterial eradication 1
- For Streptococcus pyogenes infections: Treat for at least 10 days to prevent acute rheumatic fever 1
Formulation Considerations
The WHO recommends using 250 mg and 500 mg dispersible tablets as the standard pediatric formulation for ease of administration and dose accuracy 4. For oral suspension, shake well before each use and discard unused portions after 14 days 1.
Common Pitfalls to Avoid
Underdosing larger children: Studies show children >60 kg frequently receive <40 mg/kg/day when they should receive higher doses for resistant organisms 5. Don't automatically cap at "adult doses" - calculate based on weight and infection severity.
Overdosing small infants: Neonates and young infants require lower doses (30 mg/kg/day maximum) due to immature renal function 1, 6.
Inadequate dosing for resistant pneumococcus: The shift to 80-90 mg/kg/day occurred in 2014 due to increasing intermediate penicillin resistance 5. Standard 40 mg/kg/day dosing is insufficient for resistant strains 7.
Viral coinfection: Amoxicillin middle ear fluid penetration is significantly reduced during viral coinfection, potentially requiring higher doses (75-90 mg/kg/day) for acute otitis media 7.
Prescription clarity: Always document on the prescription: total daily dose, number of divided doses, duration of therapy, indication, and child's weight 8.