What is the appropriate dose of Amoxicillin for a 7-year-old, 83-pound patient with standard infection and no severe renal impairment?

Amoxicillin Dosing for 7-Year-Old, 83-Pound Patient

For a 7-year-old child weighing 83 pounds (37.6 kg), the appropriate amoxicillin dose using the 400mg/5mL suspension is 8.5 mL twice daily (45 mg/kg/day) for mild-to-moderate infections, or 17 mL twice daily (90 mg/kg/day) for severe infections or areas with high pneumococcal resistance. 1, 2

Weight-Based Calculation

• Patient weight: 83 pounds = 37.6 kg 1
• Standard dose (45 mg/kg/day): 37.6 kg × 45 mg/kg = 1,692 mg/day, divided into 846 mg per dose twice daily = 8.5 mL of 400mg/5mL suspension twice daily 1, 2
• High dose (90 mg/kg/day): 37.6 kg × 90 mg/kg = 3,384 mg/day, divided into 1,692 mg per dose twice daily = 17 mL of 400mg/5mL suspension twice daily 1, 2

Indication-Based Dosing Algorithm

For Mild-to-Moderate Respiratory Infections

• Dose: 45 mg/kg/day divided every 12 hours (8.5 mL twice daily) 3, 1, 2
• This provides adequate coverage for most susceptible pathogens including Streptococcus pneumoniae, Haemophilus influenzae (non-β-lactamase producing), and Streptococcus pyogenes 1

For Severe Infections or High-Resistance Scenarios

• Dose: 90 mg/kg/day divided every 12 hours (17 mL twice daily) 3, 1, 2
• Use high-dose regimen when:
  • Community-acquired pneumonia in areas with >10% penicillin-resistant S. pneumoniae 1
  • Recent antibiotic exposure within past 30 days 1
  • Daycare attendance 1
  • Severe infections requiring hospitalization 1
  • Age <2 years 1

For Group A Streptococcal Pharyngitis

• Dose: 50-75 mg/kg/day divided into 2 doses for 10 days, not exceeding 1000 mg per dose 1
• For this patient: approximately 940-1,410 mg twice daily = 9.5-14 mL twice daily 1
• Treatment duration must be 10 days to prevent acute rheumatic fever 2

Maximum Dose Considerations

• This patient weighs <40 kg, so pediatric dosing applies 2
• The maximum daily dose should not exceed 4000 mg/day regardless of weight 1
• At 90 mg/kg/day, this patient receives 3,384 mg/day, which is below the maximum 1

Treatment Duration

• Standard respiratory infections: 7-10 days 1
• Pneumonia specifically: 10 days 3, 1
• Streptococcal infections: Minimum 10 days to prevent acute rheumatic fever 2
• Continue treatment for minimum 48-72 hours beyond symptom resolution 2

Monitoring and Follow-Up

• Clinical improvement should be evident within 48-72 hours 1
• If no improvement occurs within this timeframe, reevaluation and further investigation are necessary 1
• Fever typically resolves within 24-48 hours for pneumococcal pneumonia, though cough may persist longer 1

Critical Considerations

• Administration: Take at the start of meals to minimize gastrointestinal intolerance 2
• Shake suspension well before each use 2
• Storage: Refrigeration preferable but not required; discard unused portion after 14 days 2
• For β-lactamase-producing organisms (H. influenzae, M. catarrhalis), consider amoxicillin-clavulanate (Augmentin) at 90 mg/kg/day of the amoxicillin component 1

Common Pitfalls to Avoid

• Do not underdose larger children: Studies show that children >60 kg frequently receive <40 mg/kg/day, which is inadequate for resistant organisms 4
• Do not exceed adult maximum doses prematurely: This patient is well below the 40 kg threshold where adult dosing considerations begin 2, 4
• Do not use 875 mg tablets in children <40 kg: Pediatric suspension dosing is more accurate for weight-based calculations 2