What is the dose of amoxicillin (antibiotic) for a 5-year-old child weighing 45 pounds?

Amoxicillin Dosing for a 5-Year-Old Child Weighing 45 Pounds

For a 5-year-old child weighing 45 pounds (20.4 kg), the amoxicillin dose depends on the infection type and severity: for mild to moderate respiratory infections, give 45 mg/kg/day divided into 2 doses (approximately 460 mg twice daily), and for severe infections or areas with high pneumococcal resistance, give 90 mg/kg/day divided into 2 doses (approximately 920 mg twice daily). 1

Weight-Based Dosing Framework

• Convert the child's weight: 45 pounds = 20.4 kg 1
• Dosing should always be weight-based rather than age-based for pediatric patients 1

Indication-Specific Dosing

For Mild to Moderate Respiratory Infections

• Standard dose: 45 mg/kg/day divided every 12 hours 1, 2
• For this 20.4 kg child: 45 mg/kg/day = 918 mg/day total, or approximately 460 mg twice daily 1
• This applies to uncomplicated pneumonia, bronchitis, and other respiratory tract infections 1

For Severe Infections or High Resistance Areas

• High dose: 90 mg/kg/day divided every 12 hours 1, 2
• For this 20.4 kg child: 90 mg/kg/day = 1,836 mg/day total, or approximately 920 mg twice daily 1
• Use this higher dose when:
  • Severe pneumonia is present 1
  • High pneumococcal resistance is suspected in your area 1
  • Recent antibiotic exposure within the past 3 months 1
  • β-lactamase producing H. influenzae is suspected 1

For Group A Streptococcal Infections (Strep Throat/Scarlet Fever)

• Dose: 50-75 mg/kg/day divided into 2 doses for 10 days 1
• For this 20.4 kg child: approximately 510-765 mg twice daily 1
• Maximum single dose should not exceed 1000 mg 1

Critical Dosing Considerations

• The absolute maximum daily dose is 4000 mg (4 g) per day, regardless of weight 2, 3
• Administer at the start of meals to minimize gastrointestinal intolerance 3
• Twice-daily dosing is preferred over three-times-daily for improved adherence 1, 4

Treatment Duration and Monitoring

• Standard duration: 7-10 days for most respiratory infections 1
• For pneumonia specifically: 10 days of treatment 1
• For streptococcal infections: minimum 10 days to prevent acute rheumatic fever 1, 3
• Children should show clinical improvement within 48-72 hours; if no improvement occurs, reevaluation is necessary 1

Practical Administration

Using standard amoxicillin suspension (250 mg/5 mL):

• For 45 mg/kg/day regimen: Give approximately 9 mL (460 mg) twice daily 1
• For 90 mg/kg/day regimen: Give approximately 18 mL (920 mg) twice daily 1

Common Pitfalls to Avoid

• Do not use age-based dosing—always calculate based on actual weight 1
• Do not underdose in areas with high pneumococcal resistance—use the 90 mg/kg/day regimen 1, 2
• Ensure the prescription specifies: daily dose, number of divided doses, duration of therapy, indication, and child's weight 5
• Most common adverse effects are gastrointestinal disturbances (diarrhea, nausea), which are generally mild 1