What is the appropriate vancomycin dosing for a patient with a weight of 109 pounds and height of 145 centimeters?

Vancomycin Dosing for a 109-pound, 145-centimeter Patient

For a patient weighing 109 pounds (49.5 kg) and height of 145 centimeters, the appropriate vancomycin dosing is 30 mg/kg/day divided into two equal doses, which calculates to approximately 750 mg IV every 12 hours, assuming normal renal function.

Weight-Based Dosing Calculation

The FDA-approved vancomycin dosing is based on actual body weight:

1. Convert patient's weight:

   • 109 pounds = 49.5 kg

2. Calculate daily dose:

   • According to guidelines, the appropriate dosage is 30-60 mg/kg/day 1, 2
   • For this patient: 49.5 kg × 30 mg/kg = 1,485 mg/day
   • Rounded to a practical dose: 1,500 mg/day

3. Divide into appropriate intervals:

   • Standard administration is in 2 equally divided doses 2
   • 1,500 mg ÷ 2 = 750 mg every 12 hours

Administration Considerations

• Each dose should be administered over at least 60 minutes to minimize infusion-related reactions 2
• Concentration should not exceed 5 mg/mL (preferably diluted in at least 150 mL of compatible solution) 2
• Infusion rate should not exceed 10 mg/minute to prevent "red man syndrome" 3, 2

Monitoring Recommendations

• Trough levels should be measured just before the fourth or fifth dose (steady state) 1
• Target trough concentrations:
  • 10-15 μg/mL for most infections
  • 15-20 μg/mL for severe infections (endocarditis, osteomyelitis, meningitis, pneumonia) 1

Dose Adjustments

• If renal function is impaired, dosage should be adjusted accordingly
• For patients with renal impairment, the daily dose (mg) is approximately 15 times the glomerular filtration rate in mL/min 2
• Monitoring is especially important in patients with:
  • Severe infections
  • Renal dysfunction
  • Fluctuating volume of distribution
  • Critical illness 1

Common Pitfalls to Avoid

1. Underdosing in severe infections
2. Failure to monitor trough levels
3. Inadequate timing for measuring trough levels (should be just before next dose)
4. Not adjusting dose based on renal function
5. Infusing too rapidly (causing "red man syndrome")
6. Not considering loading dose (25-30 mg/kg) in seriously ill patients 1

Special Considerations

• If the patient has poor renal function, consider extending the dosing interval or reducing the dose
• For serious infections like bacteremia or endocarditis, higher trough levels (15-20 μg/mL) should be targeted 3
• If the patient shows signs of toxicity or inadequate response, consider alternative agents like linezolid 3

Remember that vancomycin dosing should be adjusted based on therapeutic drug monitoring to ensure optimal efficacy while minimizing toxicity.