What is the appropriate amoxicillin dosage for a 31‑lb (≈14‑kg) child?

Amoxicillin Dosing for a 31-lb (14-kg) Child

For a 31-lb (14-kg) child, prescribe amoxicillin 630 mg twice daily (45 mg/kg/day) for mild to moderate infections, or 1260 mg twice daily (90 mg/kg/day) for severe infections or when resistant organisms are suspected. 1

Standard Dosing Regimen

For most common bacterial infections, the American Academy of Pediatrics recommends 45 mg/kg/day divided every 12 hours for mild to moderate infections. 1 For a 14-kg child, this equals:

• 630 mg twice daily (45 mg/kg/day × 14 kg = 630 mg/day, divided into 315 mg per dose) 1
• Using 250 mg/5 mL suspension: approximately 6.3 mL twice daily 2

High-Dose Regimen

For severe infections or areas with high pneumococcal resistance (>10%), the Infectious Diseases Society of America recommends 90 mg/kg/day in two divided doses. 1 For a 14-kg child:

• 1260 mg daily = 630 mg twice daily 1
• Using 250 mg/5 mL suspension: approximately 12.6 mL twice daily 2

Indication-Specific Dosing

Respiratory Tract Infections

• Community-acquired pneumonia (≥5 years): 90 mg/kg/day in 2 doses (maximum 4 g/day) 1
• Lower respiratory tract infections: 45 mg/kg/day every 12 hours or 40 mg/kg/day every 8 hours for mild/moderate; 45 mg/kg/day every 12 hours for severe 2

Otitis Media

• Standard dose: 40-45 mg/kg/day in 2 divided doses 1
• For this 14-kg child: 280-315 mg twice daily 1

Streptococcal Pharyngitis

• 50-75 mg/kg/day in 2 doses 1
• For this 14-kg child: 350-525 mg twice daily 1

When to Use High-Dose Therapy

Switch to 90 mg/kg/day when any of the following are present:

• Age <2 years with respiratory infection 1
• Recent antibiotic use within 30 days 3
• Daycare attendance 3
• Geographic area with >10% penicillin-resistant S. pneumoniae 1
• Severe presentation (high fever, marked symptoms) 3
• Treatment failure after 48-72 hours on standard dosing 1

Treatment Duration

• Most infections: 5-10 days 1
• Streptococcal pharyngitis: Minimum 10 days to prevent acute rheumatic fever 2
• Community-acquired pneumonia: 5 days (WHO recommendation with high-quality evidence) 1
• Continue treatment 48-72 hours beyond symptom resolution 2

Practical Administration

• Administer at the start of meals to minimize gastrointestinal intolerance 2
• Amoxicillin can be given without regard to meals, though food may improve tolerability 1
• Shake suspension well before each use 2
• Reconstituted suspension expires after 14 days; refrigeration preferred but not required 2

Monitoring and Treatment Failure

Clinical improvement should occur within 48-72 hours. 1 If no improvement or worsening:

• Reassess diagnosis and consider treatment failure 1
• Evaluate for atypical pathogens or complications 1
• Consider switching to amoxicillin-clavulanate 90 mg/kg/day (amoxicillin component) with 6.4 mg/kg/day clavulanate 4, 3

Critical Pitfalls to Avoid

• Never underdose: Subtherapeutic doses promote antimicrobial resistance and treatment failure 1
• Verify suspension concentration (125 mg/5 mL vs. 250 mg/5 mL) before calculating volume to avoid dosing errors 3
• Do not use 875 mg tablets in children <40 kg; use suspension for accurate weight-based dosing 2
• Avoid prescribing for viral infections: Most upper respiratory infections are viral and do not benefit from antibiotics 3
• Amoxicillin dosing recommendations have increased over time due to rising pneumococcal resistance 1