What high‑dose amoxicillin liquid suspension regimen (mg/kg per day, dose per 12 hours, volume for 250 mg/5 mL or 400 mg/5 mL formulations) should be prescribed for a 23.5 kg child, and what is the recommended treatment duration?

High-Dose Amoxicillin Liquid Suspension Regimen for a 23.5 kg Child

For a 23.5 kg child requiring high-dose amoxicillin therapy, prescribe 90 mg/kg/day divided into two doses (1,058 mg per dose every 12 hours), which translates to approximately 13 mL of 400 mg/5 mL suspension twice daily for 10 days. 1

Weight-Based Dose Calculation

• The total daily dose is calculated as: 23.5 kg × 90 mg/kg = 2,115 mg per day 1
• Divided into two doses: 1,058 mg every 12 hours (approximately 1,050 mg per dose for practical purposes) 1

Volume Calculations by Formulation

Using 400 mg/5 mL Suspension (Preferred)

• 13 mL twice daily (every 12 hours) 1
• This formulation requires less volume per dose, improving adherence 1

Using 250 mg/5 mL Suspension (Alternative)

• 21 mL twice daily (every 12 hours) 1
• This larger volume may be more difficult for children to tolerate 1

Indications for High-Dose Therapy (90 mg/kg/day)

High-dose amoxicillin is specifically 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 Streptococcus pneumoniae are penicillin-resistant 1

• Presentation with moderate-to-severe illness 1

• The high-dose regimen achieves tissue concentrations sufficient to overcome penicillin-resistant S. pneumoniae with MICs up to 2–4 mg/L 1, 2

• This dosing is endorsed by the Infectious Diseases Society of America (IDSA) and the Pediatric Infectious Diseases Society (PIDS) for presumed bacterial community-acquired pneumonia 1, 3

Treatment Duration

• Complete a full 10-day course for most pediatric respiratory infections, including pneumonia 1, 3
• Continue therapy for at least 48–72 hours after complete resolution of fever and respiratory symptoms 1
• For Group A Streptococcal pharyngitis specifically, the 10-day duration is essential to prevent acute rheumatic fever 1

Expected Clinical Response & Monitoring

• Clinical improvement (reduced fever, improved respiratory effort) should be evident within 48–72 hours of initiating therapy 1, 3
• If no improvement or clinical worsening occurs after 48–72 hours: 1
  • Consider atypical pathogens (Mycoplasma pneumoniae, Chlamydophila pneumoniae) and add a macrolide 1
  • Obtain further diagnostic imaging 1
  • Evaluate the need for hospitalization 1

When to Switch to Amoxicillin-Clavulanate

Switch to high-dose amoxicillin-clavulanate (90 mg/kg/day amoxicillin component + 6.4 mg/kg/day clavulanate) if: 1, 4

• Treatment failure after 48–72 hours on amoxicillin alone 1, 4

• Suspected β-lactamase-producing organisms (H. influenzae, M. catarrhalis) 1, 4

• Incomplete Haemophilus influenzae type b vaccination (< 3 doses) 4

• Concurrent purulent acute otitis media 1

• The high-dose amoxicillin-clavulanate formulation (14:1 ratio) provides adequate clavulanate to inhibit β-lactamase producers while minimizing diarrhea compared with other ratios 1, 4

Maximum Dosing Limits

• Maximum daily dose: 4,000 mg per day (regardless of weight) 1, 3
• For this 23.5 kg child, the calculated dose of 2,115 mg/day is well below the maximum 1

Administration Instructions

• Administer at the start of a meal to minimize gastrointestinal intolerance 5
• Shake the suspension well before each use 5
• Store reconstituted suspension in the refrigerator (preferred but not required) 5
• Discard any unused suspension after 14 days 5

Common Pitfalls to Avoid

• Do not use standard-dose amoxicillin (45 mg/kg/day) when high-risk factors are present—this leads to treatment failure with resistant organisms 1, 4
• Do not prescribe antibiotics for viral upper respiratory infections—approximately 70% of sore throats in primary care are not streptococcal 1
• Verify the suspension concentration (250 mg/5 mL vs 400 mg/5 mL) before calculating volume to avoid dosing errors 1
• Do not stop therapy early even if symptoms improve—complete the full 10-day course to prevent relapse and resistance 1, 3

Alternatives for Penicillin-Allergic Patients

Non-Anaphylactic Penicillin Allergy

• Cephalexin: 20 mg/kg per dose twice daily (maximum 500 mg per dose) for 10 days 1
• Cefdinir or cefuroxime are also appropriate alternatives 1, 3

IgE-Mediated (Type I) Penicillin Allergy

• Clindamycin: 7 mg/kg per dose three times daily (maximum 300 mg per dose) for 10 days 1
• Azithromycin: 12 mg/kg once daily (maximum 500 mg) for 5 days, though efficacy is inferior to β-lactams 1
• Levofloxacin 8–10 mg/kg once daily (maximum 750 mg) for children ≥ 5 years with skeletal maturity 3