What is the recommended dose of amoxicillin (amoxicillin) for a 5.5kg child with a suspected bacterial infection?

Amoxicillin Dosing for a 5.5kg Child with Suspected Bacterial Infection

For a 5.5kg child with suspected bacterial pneumonia, prescribe amoxicillin 90 mg/kg/day divided into 2 doses (approximately 250 mg twice daily), which equals roughly 2.5 mL of the 250 mg/5 mL suspension twice daily. 1, 2, 3

Weight-Based Calculation

• Total daily dose: 5.5 kg × 90 mg/kg = 495 mg/day 1, 2
• Divided dose: 495 mg ÷ 2 = approximately 247.5 mg per dose (round to 250 mg) 1, 2
• Practical administration: 2.5 mL of 250 mg/5 mL suspension twice daily (every 12 hours) 2, 4

Age and Weight Considerations

• For children under 5 years with presumed bacterial pneumonia, the Infectious Diseases Society of America and Pediatric Infectious Diseases Society recommend 90 mg/kg/day in 2 divided doses 1, 3
• The higher dose of 90 mg/kg/day (rather than 45 mg/kg/day) is specifically recommended to cover penicillin-resistant Streptococcus pneumoniae, which is the most common bacterial pathogen in pediatric community-acquired pneumonia 1, 2, 5
• This child at 5.5 kg is likely under 12 months of age, falling into the "under 5 years" category where bacterial pneumonia is typically caused by S. pneumoniae or H. influenzae 1, 3

Administration Instructions

• Give amoxicillin at the start of meals to minimize gastrointestinal intolerance 4
• The suspension can be placed directly on the child's tongue or mixed with formula, milk, or water and given immediately 4
• Shake the suspension well before each use 4
• Store the reconstituted suspension in the refrigerator (preferred but not required) and discard after 14 days 4

Treatment Duration and Monitoring

• Continue treatment for 7-10 days for respiratory infections 2
• The child should show clinical improvement within 48-72 hours 1, 2, 3
• If no improvement or clinical deterioration occurs within 48-72 hours, reevaluation and further investigation are necessary 1, 3

Critical Pitfall to Avoid

• Do not underdose: Using the standard 40-45 mg/kg/day dose instead of 90 mg/kg/day is the most common error and leads to treatment failure, particularly with resistant pneumococci 5, 6
• Research demonstrates that the traditional 40 mg/kg/day dosing is inadequate to eradicate resistant S. pneumoniae, especially during viral coinfection, and 75-90 mg/kg/day is necessary 6

Special Circumstances

• If the child has inadequate H. influenzae type b vaccination or concurrent purulent acute otitis media, consider amoxicillin-clavulanate instead at 90 mg/kg/day of the amoxicillin component 2
• If community-associated MRSA is suspected based on clinical features (necrotizing pneumonia, empyema), add clindamycin 30-40 mg/kg/day in 3-4 divided doses 3, 5
• For children with non-serious penicillin allergies, consider cephalosporins (cefpodoxime, cefprozil, or cefuroxime) under medical supervision 3, 5