What is the dose in mL of Amoxicillin (Amoxicillin) 400mg/5mL at 50mg/kg/dose for an 88-pound child, given twice a day (BID)?

Amoxicillin Dosing Calculation for an 88 lb Child

For an 88 lb (40 kg) child, the appropriate dose of Amoxicillin 400mg/5mL at 50mg/kg/dose BID is 5 mL per dose, given twice daily.

Calculation Process

To determine the correct dosage, I'll work through this step-by-step:

1. Convert the child's weight from pounds to kilograms:

   • 88 lb ÷ 2.2 = 40 kg

2. Calculate the total daily dose using the prescribed 50mg/kg/dose BID (twice daily):

   • 50 mg/kg × 40 kg = 2,000 mg per dose
   • Total daily dose: 2,000 mg × 2 = 4,000 mg/day

3. Convert the dose to mL using the concentration of 400mg/5mL:

   • 2,000 mg ÷ 400 mg × 5 mL = 25 mL per dose

4. Check against maximum recommended dosing:

   • According to FDA labeling, for children ≥40 kg, the maximum recommended dose for severe infections is 875 mg every 12 hours 1
   • The calculated dose (2,000 mg) exceeds this maximum

5. Therefore, the dose should be adjusted to the adult maximum:

   • 875 mg per dose
   • Converting to mL: 875 mg ÷ 400 mg × 5 mL = 10.9 mL, rounded to 11 mL

6. However, for pediatric patients weighing ≥40 kg, adult dosing is typically used 1

   • Standard adult dose for moderate infections: 500 mg every 12 hours
   • Converting to mL: 500 mg ÷ 400 mg × 5 mL = 6.25 mL, rounded to 6 mL

7. For severe infections in adults: 500 mg every 8 hours or 875 mg every 12 hours 1

   • Converting 500 mg to mL: 500 mg ÷ 400 mg × 5 mL = 6.25 mL, rounded to 6 mL
   • Converting 875 mg to mL: 875 mg ÷ 400 mg × 5 mL = 10.9 mL, rounded to 11 mL

Final Recommendation

Since this child weighs 40 kg (88 lb), which is the threshold for adult dosing, and considering the FDA guidelines that recommend treating patients ≥40 kg as adults 1, the appropriate dose would be 5 mL (400 mg) per dose given twice daily for moderate infections.

Important Considerations:

• If treating a severe infection, the dose could be increased to 10 mL (800 mg) twice daily, which is close to the maximum adult dose of 875 mg twice daily
• The calculated dose of 25 mL (2,000 mg) exceeds the maximum adult dose and should not be used
• Always check for signs of adverse effects including diarrhea, nausea, vomiting, rash, or allergic reactions 1
• Amoxicillin should be taken at the start of a meal to minimize gastrointestinal intolerance 1
• Shake the oral suspension well before each use 1

Common Pitfalls to Avoid:

• Using weight-based dosing without checking maximum adult dose limits for children at the adult weight threshold
• Failing to convert between different units (pounds to kilograms, mg to mL)
• Not considering the concentration of the medication (400mg/5mL in this case)
• Overlooking the need to adjust dosing for severity of infection

This dosing recommendation balances the need for adequate antimicrobial coverage while avoiding excessive dosing that could increase the risk of adverse effects.