What is the appropriate dose of amoxicillin (amoxicillin) for a 2-year-old (2 y/o) child?

Amoxicillin Dosing for a 2-Year-Old Child

For a 2-year-old child, prescribe amoxicillin 45 mg/kg/day divided into 2 doses (every 12 hours) for mild to moderate respiratory infections, or 90 mg/kg/day divided into 2 doses for severe infections or areas with high pneumococcal resistance. 1

Indication-Based Dosing Algorithm

For Community-Acquired Pneumonia (Most Common Indication)

Mild to Moderate CAP:

• Standard dose: 45 mg/kg/day divided every 12 hours 1
• This translates to approximately 22.5 mg/kg per dose, given twice daily 2
• Treatment duration: 7-10 days, with clinical reassessment at 48-72 hours 1

Severe CAP or High Pneumococcal Resistance Areas:

• High dose: 90 mg/kg/day divided every 12 hours 1, 3
• This provides 45 mg/kg per dose, given twice daily 1
• The higher dose is critical for penicillin-resistant Streptococcus pneumoniae 4, 3

For Group A Streptococcal Infections (Pharyngitis, Scarlet Fever)

• Dose: 50-75 mg/kg/day divided into 2 doses 5, 1
• Duration: 10 days minimum to prevent acute rheumatic fever 2
• Maximum single dose should not exceed 1000 mg 1

For Haemophilus influenzae (β-lactamase negative)

• Dose: 75-100 mg/kg/day divided into 3 doses 5
• If β-lactamase producing, switch to amoxicillin-clavulanate at 45 mg/kg/day in 3 doses or 90 mg/kg/day in 2 doses 5, 1

Critical Dosing Considerations

Maximum Daily Doses:

• The FDA label specifies maximum dosing based on severity: 25 mg/kg/day (mild) to 45 mg/kg/day (severe) for children under 40 kg 2
• However, current guidelines from the Infectious Diseases Society of America recommend up to 90 mg/kg/day for resistant organisms 1, 3, reflecting the evolution of antimicrobial resistance patterns

Twice Daily vs. Three Times Daily:

• Twice-daily dosing (every 12 hours) is preferred for improved compliance and similar efficacy 1, 6
• The American College of Cardiology notes that twice-daily dosing improves adherence compared to three-times-daily regimens 1

Practical Prescribing Example

For a 2-year-old weighing 12 kg with mild CAP:

• 45 mg/kg/day = 540 mg/day total
• 270 mg per dose, given every 12 hours 1
• Using 250 mg/5 mL suspension: approximately 5.4 mL per dose

For the same child with severe CAP or high resistance area:

• 90 mg/kg/day = 1,080 mg/day total
• 540 mg per dose, given every 12 hours 1
• Using 250 mg/5 mL suspension: approximately 10.8 mL per dose

Important Clinical Pitfalls

Viral Coinfection Impact:

• Research demonstrates that viral coinfection in acute otitis media significantly reduces amoxicillin middle ear fluid penetration 4
• Children with viral coinfection had geometric mean concentrations of only 2.7 μg/mL compared to 5.7 μg/mL in bacterial-only infections 4
• This supports using higher doses (75-90 mg/kg/day) when viral coinfection is suspected 4

Inadequate Standard Dosing:

• The traditional 40 mg/kg/day dosing is inadequate for resistant S. pneumoniae, particularly with viral coinfection 4
• Current evidence strongly supports 90 mg/kg/day for optimal eradication of resistant pathogens 1, 3

Administration Tips:

• Give at the start of meals to minimize gastrointestinal intolerance 2
• Shake suspension well before each use 2
• Refrigeration is preferable but not required; discard after 14 days 2

Monitoring and Follow-Up

• Children should show clinical improvement within 48-72 hours 1
• If no improvement occurs, reevaluation is necessary to consider resistant organisms or alternative diagnoses 1
• Complete the full course even if symptoms improve before completion 1