What is the appropriate amoxicillin (400 mg/5 mL) dose and dosing schedule for a 54‑lb (≈24.5 kg) child?

Amoxicillin 400mg/5mL Dosing for a 54-Pound Child

For a 54-pound (24.5 kg) child, administer 6 mL of amoxicillin 400mg/5mL suspension twice daily for most common bacterial infections, or 12 mL twice daily for severe infections or high-resistance areas. 1

Weight-Based Dose Calculation

• Child's weight: 54 pounds = 24.5 kg 1
• Standard-dose regimen (45 mg/kg/day): 24.5 kg × 45 mg/kg/day = 1,102.5 mg/day, divided into 2 doses = 551 mg per dose 2, 1
• Volume per dose: 551 mg ÷ 400 mg/5mL = 6.9 mL per dose (round to 6–7 mL twice daily) 1
• High-dose regimen (90 mg/kg/day): 24.5 kg × 90 mg/kg/day = 2,205 mg/day, divided into 2 doses = 1,102.5 mg per dose 2, 1
• Volume per dose: 1,102.5 mg ÷ 400 mg/5mL = 13.8 mL per dose (round to 12–14 mL twice daily) 1

Indication-Specific Dosing Algorithm

Standard-Dose Indications (45 mg/kg/day = 6–7 mL twice daily)

• Uncomplicated respiratory tract infections in children ≥2 years without recent antibiotic exposure 1
• Group A Streptococcal pharyngitis: 50–75 mg/kg/day (6–9 mL twice daily) for 10 days 2, 1
• Acute bacterial sinusitis in children ≥2 years who do not attend daycare and have not received antibiotics in the past 4 weeks 1
• Skin and soft-tissue infections without risk factors for resistant organisms 2, 1

High-Dose Indications (90 mg/kg/day = 12–14 mL twice daily)

Use the high-dose regimen 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
• Community-acquired pneumonia (presumed bacterial) 2, 1
• Acute otitis media with treatment failure or recurrent infection 1, 3

Treatment Duration

• Most respiratory infections: 7–10 days 1
• Community-acquired pneumonia: 10 days (continue at least 48–72 hours after symptom resolution) 2, 1
• Group A Streptococcal pharyngitis: 10 days (to prevent acute rheumatic fever) 1, 4
• Acute otitis media: 10 days for children <2 years; 5–7 days for children ≥2 years with uncomplicated infection 1

Administration Instructions

• Administer at the start of a meal to minimize gastrointestinal intolerance 4
• Shake suspension well before each use 4
• Refrigeration is preferable but not required; discard unused suspension after 14 days 4
• Complete the full prescribed course even if symptoms improve 1

Expected Clinical Response & Monitoring

• Clinical improvement should occur within 48–72 hours of starting appropriate therapy 1
• If no improvement or worsening occurs after 48–72 hours:
  • Consider atypical pathogens (Mycoplasma pneumoniae, Chlamydophila pneumoniae) and add a macrolide 1
  • Obtain further diagnostic evaluation 1
  • Evaluate the need for hospitalization 1

When to Use Amoxicillin-Clavulanate Instead

Switch to amoxicillin-clavulanate (Augmentin) 90 mg/kg/day of the amoxicillin component if: 1, 3

• β-lactamase-producing organisms are suspected (Haemophilus influenzae, Moraxella catarrhalis) 2, 1
• Treatment failure after initial amoxicillin course 1, 3
• Incomplete H. influenzae type b vaccination or concurrent purulent acute otitis media 1

Maximum Dosing Limits

• Maximum single dose: 2,000 mg per administration 1
• Maximum daily dose: 4,000 mg/day (regardless of weight) 1, 5, 4

Penicillin-Allergic Alternatives

• Non-anaphylactic penicillin allergy: Second- or third-generation cephalosporins (cefdinir, cefuroxime, cephalexin) 2, 1
• IgE-mediated (Type I) penicillin allergy: Clindamycin (10–20 mg/kg/day in 3 doses) or azithromycin (12 mg/kg once daily for 5 days), acknowledging inferior efficacy 2, 1

Common Pitfalls to Avoid

• Do not under-dose: The outdated 40 mg/kg/day dosing is no longer recommended; current guidelines support 45–90 mg/kg/day for most bacterial infections 1
• Do not use amoxicillin alone for β-lactamase producers: Switch to amoxicillin-clavulanate if H. influenzae or M. catarrhalis are suspected 1, 3
• Do not discontinue early: Complete the full course even if symptoms improve to prevent relapse and reduce resistance 1
• Do not prescribe without microbiologic confirmation for pharyngitis: Approximately 70% of sore throats are not streptococcal; obtain rapid antigen detection test or throat culture 1