What is the appropriate amoxicillin (Amoxil) dose for a 9.5 kg child being treated for a lower respiratory infection such as community‑acquired pneumonia?

Amoxicillin Dosing for a 9.5 kg Child with Lower Respiratory Infection

For a 9.5 kg child with a lower respiratory infection, prescribe amoxicillin 90 mg/kg/day divided into two doses (approximately 427.5 mg per dose, or roughly 11 mL of 200 mg/5 mL suspension twice daily) for 10 days.

High-Dose Regimen is Standard for Pediatric Pneumonia

• The Infectious Diseases Society of America and Pediatric Infectious Diseases Society recommend 90 mg/kg/day of amoxicillin in two divided doses as the standard regimen for presumed bacterial community-acquired pneumonia in children older than 3 months. 1

• This high-dose regimen ensures adequate tissue concentrations to overcome penicillin-resistant Streptococcus pneumoniae (the most common bacterial pathogen) and provides coverage against non-β-lactamase-producing Haemophilus influenzae. 1, 2

• For your 9.5 kg patient: 9.5 kg × 90 mg/kg = 855 mg total daily dose, administered as 427.5 mg every 12 hours. 1

When to Use Standard-Dose (45 mg/kg/day) Instead

• The lower 45 mg/kg/day regimen is appropriate only for children ≥2 years with uncomplicated respiratory infections who have no risk factors for resistant organisms. 1

• Risk factors that mandate the 90 mg/kg/day regimen include:

  • Age <2 years 1
  • Daycare attendance 1
  • Recent antibiotic use (within 30 days) 1
  • Geographic area with >10% penicillin-resistant S. pneumoniae 1
  • Moderate-to-severe illness 1

• Since most children with lower respiratory infections requiring antibiotics have at least one of these risk factors, the 90 mg/kg/day dose should be considered standard practice. 1

Treatment Duration

• Complete a full 10-day course for bacterial pneumonia or lower respiratory tract infection. 1, 3

• While recent evidence suggests 5-day courses may be non-inferior for uncomplicated pneumonia 4, 5, current major guidelines still recommend 10 days, and this remains the safest approach in real-world practice. 1

• Continue therapy for at least 48–72 hours after complete resolution of fever and respiratory symptoms. 1

Expected Clinical Response & When to Escalate

• Clinical improvement (reduced fever, improved respiratory effort) should be evident within 48–72 hours of initiating appropriate therapy. 1, 3

• If no improvement or worsening occurs after 48–72 hours:

  • Consider atypical pathogens (Mycoplasma pneumoniae, Chlamydophila pneumoniae) and add a macrolide (azithromycin 10 mg/kg day 1, then 5 mg/kg days 2–5). 1
  • Switch to amoxicillin-clavulanate 90 mg/kg/day (amoxicillin component) if β-lactamase-producing organisms are suspected. 1, 3
  • Obtain chest radiograph if not already done and consider hospitalization. 1

When to Use Amoxicillin-Clavulanate Instead of Plain Amoxicillin

• Switch to amoxicillin-clavulanate (90 mg/kg/day amoxicillin component + 6.4 mg/kg/day clavulanate) if:

  • Incomplete Haemophilus influenzae type b vaccination (<3 doses) 3
  • Concurrent purulent acute otitis media 1
  • Treatment failure after 48–72 hours on amoxicillin alone 3
  • Suspected β-lactamase-producing H. influenzae or Moraxella catarrhalis 1, 3

• The clavulanate component inhibits β-lactamases produced by 58–82% of H. influenzae isolates and nearly all M. catarrhalis, achieving eradication rates approaching 100%. 1, 2

Practical Administration

• Using 200 mg/5 mL suspension: 427.5 mg per dose = approximately 10.7 mL twice daily (can round to 11 mL for practical dosing). 1

• Using 400 mg/5 mL suspension: 427.5 mg per dose = approximately 5.3 mL twice daily (can round to 5.5 mL). 1

• Maximum daily dose: Do not exceed 4,000 mg/day regardless of weight. 1

Common Pitfalls to Avoid

• Do not use outdated lower doses (e.g., 40 mg/kg/day from older British Thoracic Society 2002 guidelines); these are insufficient for contemporary resistance patterns. 1

• Verify suspension concentration before dispensing to avoid 2-fold dosing errors between 200 mg/5 mL and 400 mg/5 mL formulations. 3

• Do not prescribe antibiotics for viral bronchiolitis (wheezing in infants <2 years); lower respiratory infections in this age group are predominantly viral and do not benefit from antibiotics unless bacterial pneumonia is confirmed. 1

• Ensure adequate hydration and antipyretics are prescribed alongside antibiotics, as fever typically resolves within 24–48 hours but cough may persist longer. 1