What dose of amoxicillin should be given to an 11.34 kg pediatric patient using a suspension containing 400 mg per 5 mL?

Amoxicillin Dosing for an 11.34 kg Pediatric Patient

For an 11.34 kg child, prescribe amoxicillin 510 mg (approximately 6.4 mL of the 400 mg/5 mL suspension) twice daily for most respiratory tract infections, or 1020 mg (approximately 12.7 mL) twice daily for severe infections or high pneumococcal resistance areas. 1

Standard-Dose Regimen (45 mg/kg/day)

• For mild to moderate respiratory tract infections in children ≥3 months without risk factors (no recent antibiotics, not in daycare, age >2 years), the recommended dose is 45 mg/kg/day divided into 2 doses. 2, 1

• Weight-based calculation: 11.34 kg × 45 mg/kg/day = 510 mg/day total, which equals 255 mg per dose given twice daily. 1

• Volume calculation using 400 mg/5 mL suspension: 255 mg ÷ 400 mg × 5 mL = 3.2 mL per dose, administered twice daily (every 12 hours). 3

• This standard dose provides adequate coverage for penicillin-susceptible Streptococcus pneumoniae, non-β-lactamase-producing Haemophilus influenzae, and Streptococcus pyogenes. 1

High-Dose Regimen (90 mg/kg/day)

• High-dose amoxicillin (90 mg/kg/day) is indicated when ANY of the following risk factors are present: 1

  • Age <2 years 1
  • Attendance at daycare 1
  • Recent antibiotic use within the past 30 days 1
  • Residence in a region where >10% of S. pneumoniae are penicillin-resistant 1
  • Moderate-to-severe illness or hospitalization 2, 1

• Weight-based calculation: 11.34 kg × 90 mg/kg/day = 1020 mg/day total, which equals 510 mg per dose given twice daily. 2, 1

• Volume calculation using 400 mg/5 mL suspension: 510 mg ÷ 400 mg × 5 mL = 6.4 mL per dose, administered twice daily (every 12 hours). 1

• The high-dose regimen achieves middle ear and sinus fluid concentrations sufficient to overcome penicillin-resistant S. pneumoniae with MICs up to 2–4 mg/L. 1

Indication-Specific Dosing

Community-Acquired Pneumonia

• For presumed bacterial pneumonia, use 90 mg/kg/day (510 mg twice daily = 6.4 mL twice daily) to ensure coverage of penicillin-resistant S. pneumoniae. 2, 1, 4

• The Infectious Diseases Society of America and Pediatric Infectious Diseases Society recommend this high-dose regimen as first-line therapy for hospitalized children and those with severe disease. 2, 4

Group A Streptococcal Pharyngitis

• For strep throat, prescribe 50–75 mg/kg/day divided into 2 doses for 10 days. 1

• Weight-based calculation: 11.34 kg × 50 mg/kg/day = 567 mg/day (approximately 285 mg per dose = 3.6 mL twice daily), or 11.34 kg × 75 mg/kg/day = 850 mg/day (approximately 425 mg per dose = 5.3 mL twice daily). 1

• Maximum single dose is 1000 mg, regardless of weight. 1

• The full 10-day course must be completed to prevent acute rheumatic fever, even if symptoms resolve within 3–4 days. 1

Acute Otitis Media

• For children <2 years or with risk factors (daycare, recent antibiotics), use 80–90 mg/kg/day (approximately 6.4 mL twice daily). 1

• For children ≥2 years without risk factors, standard-dose 45 mg/kg/day (approximately 3.2 mL twice daily) is appropriate. 1

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

Treatment Duration and Monitoring

• Continue treatment for a minimum of 48–72 hours beyond symptom resolution or evidence of bacterial eradication. 3

• For respiratory infections, treat for 7–10 days; for pneumonia specifically, 10 days is recommended. 1

• For Group A streptococcal infections, a full 10-day course is mandatory to prevent acute rheumatic fever. 1, 3

• Children on appropriate therapy should demonstrate clinical improvement within 48–72 hours; if no improvement occurs, reevaluation and consideration of resistant pathogens or atypical organisms is necessary. 1

Administration Instructions

• Administer at the start of a meal to minimize gastrointestinal intolerance. 3

• Shake the suspension well before each use. 3

• The required amount of suspension should be placed directly on the child's tongue for swallowing, or mixed with formula, milk, fruit juice, water, or cold drinks and taken immediately. 3

• Store reconstituted suspension in the refrigerator (preferred but not required) and discard after 14 days. 3

Maximum Dosing Limits

• Maximum daily dose: 4000 mg/day (4 g/day), regardless of weight. 1

• For this 11.34 kg child, even the high-dose regimen (1020 mg/day) is well below the maximum daily limit. 1

When to Switch to Amoxicillin-Clavulanate

• If β-lactamase-producing organisms are suspected (treatment failure after 48–72 hours, incomplete H. influenzae type b vaccination, concurrent purulent otitis media), escalate to amoxicillin-clavulanate 90 mg/kg/day of the amoxicillin component divided twice daily. 1

• The high-dose amoxicillin-clavulanate formulation (14:1 ratio) provides adequate clavulanate levels while minimizing diarrhea. 1

Penicillin Allergy Alternatives

• For non-anaphylactic penicillin allergy, second- or third-generation cephalosporins (cefdinir, cefuroxime, cephalexin) are safe alternatives with negligible cross-reactivity risk. 1

• For IgE-mediated (type I) reactions, use clindamycin (10–20 mg/kg/day in 3 doses) or azithromycin (12 mg/kg once daily for 5 days), acknowledging inferior efficacy compared to β-lactams. 1

Common Pitfalls to Avoid

• Do not underdose severe infections—always use 90 mg/kg/day for life-threatening infections, empyema, or documented resistant pneumococcus. 1

• Do not use standard-dose amoxicillin in children <2 years with pneumonia or otitis media—the high-dose regimen is required due to increased risk of resistant pathogens. 1

• Do not prescribe amoxicillin alone if β-lactamase-producing organisms are suspected—switch to amoxicillin-clavulanate. 1

• Do not stop antibiotics early—complete the full course even if symptoms improve, especially for streptococcal infections where 10 days is mandatory to prevent rheumatic fever. 1, 3