What is the appropriate dose of amoxicillin (amoxicillin) for an 11-year-old child weighing 78 pounds, given a concentration of 125 mg per 5 mL?

Amoxicillin Dosing for an 11-Year-Old Weighing 78 Pounds

For an 11-year-old child weighing 78 pounds (35.4 kg), the appropriate dose of amoxicillin 125 mg/5 mL is 25 mg/kg/day divided every 12 hours, which equals approximately 443 mg per dose (17.7 mL) twice daily. 1

Dosage Calculation

The FDA-approved dosing for amoxicillin in pediatric patients is based on weight and severity of infection:

• For mild to moderate infections (ear/nose/throat, skin/skin structure, genitourinary tract):

  • 25 mg/kg/day divided every 12 hours OR
  • 20 mg/kg/day divided every 8 hours 1

• For severe infections or lower respiratory tract infections:

  • 45 mg/kg/day divided every 12 hours OR
  • 40 mg/kg/day divided every 8 hours 1

Step-by-Step Calculation for This Patient

1. Patient weight: 78 pounds = 35.4 kg

2. For mild to moderate infections:

   • 25 mg/kg/day = 25 × 35.4 = 885 mg/day
   • Divided into 2 doses (every 12 hours) = 442.5 mg per dose
   • Using 125 mg/5 mL suspension: 442.5 mg ÷ 125 mg × 5 mL = 17.7 mL per dose

3. For severe infections:

   • 45 mg/kg/day = 45 × 35.4 = 1593 mg/day
   • Divided into 2 doses (every 12 hours) = 796.5 mg per dose
   • Using 125 mg/5 mL suspension: 796.5 mg ÷ 125 mg × 5 mL = 31.9 mL per dose

Administration Guidelines

• Administer at the start of a meal to minimize gastrointestinal intolerance 1
• Treatment should continue for a minimum of 48-72 hours beyond symptom resolution 1
• For Streptococcus pyogenes infections, treatment should continue for at least 10 days to prevent acute rheumatic fever 1
• Shake the oral suspension well before using 1

Special Considerations

• The twice-daily (q12h) regimen is generally preferred over three times daily (q8h) for improved adherence while maintaining similar efficacy for most common infections 2
• For common uncomplicated infections, the twice-daily regimen is appropriate and may improve treatment adherence 3
• The reconstituted suspension must be discarded after 14 days 1
• Refrigeration is preferable but not required 1

Dosing Pitfalls to Avoid

1. Age-based dosing: Always calculate pediatric doses based on weight rather than age to ensure appropriate dosing 3
2. Underdosing: Inadequate dosing may lead to treatment failure and potential development of resistance
3. Overdosing: Excessive doses increase the risk of adverse effects
4. Improper measurement: Use an appropriate measuring device (oral syringe or dosing spoon) rather than household teaspoons for accurate administration
5. Failure to adjust for renal impairment: For patients with impaired renal function (GFR <30 mL/min), dose adjustment is necessary 1

By following these guidelines, you can ensure appropriate and effective amoxicillin dosing for this 11-year-old patient.