What is the maximum recommended dose of amoxicillin for a 4‑year‑old child weighing 13 kg?

Maximum Amoxicillin Dose for a 4-Year-Old Weighing 13 kg

For a 4-year-old child weighing 13 kg, the maximum recommended dose of amoxicillin is 90 mg/kg/day divided into 2 doses (585 mg twice daily), which should not exceed the absolute maximum of 4000 mg/day regardless of weight. 1, 2, 3

Weight-Based Dosing Algorithm

The appropriate amoxicillin dose depends on the infection severity and local resistance patterns:

Standard Dosing (Mild-Moderate Infections)

• 45 mg/kg/day divided every 12 hours for uncomplicated respiratory tract infections, skin infections, and genitourinary infections 1
• For this 13 kg child: 292.5 mg twice daily (approximately 293 mg BID) 1
• This provides adequate coverage for most susceptible pathogens including Streptococcus pneumoniae, Haemophilus influenzae (non-β-lactamase producing), and Streptococcus pyogenes 1

High-Dose Regimen (Severe Infections or High Resistance)

• 90 mg/kg/day divided every 12 hours for community-acquired pneumonia, particularly in areas with >10% penicillin-resistant S. pneumoniae, children <2 years old, recent antibiotic exposure within 30 days, daycare attendance, or severe infections 1, 2
• For this 13 kg child: 585 mg twice daily 1, 2
• The Infectious Diseases Society of America recommends this high-dose regimen as first-line treatment for presumed bacterial pneumonia in outpatient settings 2

Absolute Maximum Limit

The FDA-mandated absolute maximum is 4000 mg/day (4 g/day) regardless of weight 1, 3, 4

• This 13 kg child is well below this threshold even at the highest recommended weight-based dose (1170 mg/day total) 1, 3

Indication-Specific Considerations

Community-Acquired Pneumonia

• The American Academy of Pediatrics and Infectious Diseases Society of America recommend 90 mg/kg/day in 2 doses for children <5 years with presumed bacterial pneumonia 1, 2
• This provides optimal coverage for β-lactamase-producing organisms and penicillin-resistant S. pneumoniae 2, 3

Group A Streptococcal Infections

• 50-75 mg/kg/day divided into 2 doses for 10 days, not exceeding 1000 mg per dose 1
• For this 13 kg child: 325-487.5 mg twice daily 1

Acute Otitis Media with Risk Factors

• If β-lactamase-producing organisms are suspected (H. influenzae, M. catarrhalis), consider switching to amoxicillin-clavulanate at 90 mg/kg/day of the amoxicillin component 1, 5

Critical Dosing Considerations

Treatment Duration

• Continue treatment for a minimum of 48-72 hours beyond symptom resolution 1, 4
• For Streptococcus pyogenes infections, treat for at least 10 days to prevent acute rheumatic fever 1, 4
• For pneumonia, the standard duration is 10 days 1, 2

Monitoring Response

• Children on appropriate therapy should demonstrate clinical improvement within 48-72 hours 1, 2
• If no improvement occurs within this timeframe, reevaluation and further investigation are necessary 1, 2

Common Pitfalls to Avoid

• Do not use age-based dosing—always calculate based on weight in kg 1, 6
• Do not exceed 4000 mg/day even if weight-based calculations suggest higher doses 1, 3, 4
• Avoid the 875 mg tablet formulation in children with severe renal impairment (GFR <30 mL/min) 4
• Ensure adequate supply when prescribing higher weight-based doses—check that the volume of oral suspension is sufficient to complete the treatment course 6

Administration Recommendations

• Administer at the start of a meal to minimize gastrointestinal intolerance 4
• Shake oral suspension well before each use 4
• Refrigeration of reconstituted suspension is preferable but not required; discard unused portion after 14 days 4