What is the appropriate vancomycin dose for a 29-year-old patient with impaired renal function (serum creatinine level of 50), weighing 57 kg, diagnosed with meningitis?

Vancomycin Dosing for Meningitis in a Patient with Impaired Renal Function

For a 29-year-old patient with meningitis weighing 57 kg with serum creatinine of 50, the appropriate vancomycin dosing regimen should be 15-20 mg/kg every 12 hours with dose adjustment based on renal function, targeting trough levels of 15-20 μg/mL. 1

Initial Dosing Calculation

• Calculate creatinine clearance using the Cockcroft-Gault equation 2:

  • For a 29-year-old weighing 57 kg with SCr of 50 μmol/L (approximately 0.57 mg/dL):
  • CrCl = [57 × (140 - 29)] / (72 × 0.57) = approximately 95-100 mL/min 2, 3

• Initial vancomycin dose:

  • Loading dose: 25-30 mg/kg (1425-1710 mg) 1
  • Maintenance dose: 15-20 mg/kg (855-1140 mg) every 12 hours 1

Dosing Considerations for Meningitis

• For meningitis, higher vancomycin doses are required to achieve adequate CNS penetration 1, 4
• Target trough serum concentrations of 15-20 μg/mL are recommended to achieve an AUC/MIC ratio >400 1
• Each dose should be administered over 1.5-2 hours when individual doses exceed 1 g to minimize infusion-related reactions 1, 2

Monitoring Parameters

• Measure first trough level before the fourth dose (at steady state) 1
• Obtain trough levels 30 minutes before the next scheduled dose 1, 5
• Monitor renal function regularly throughout therapy 1, 2
• Consider more frequent monitoring if the patient receives concurrent nephrotoxic agents 1

Dose Adjustment

• If trough levels are <15 μg/mL, increase the dose 1
• If trough levels are >20 μg/mL, decrease the dose 1
• If vancomycin MIC is ≥2 μg/mL, consider alternative agents as target AUC/MIC ratios may not be achievable 1, 5

Duration of Therapy

• For bacterial meningitis caused by pneumococci:
  • Continue treatment for 10-14 days depending on clinical response 1
  • For patients who have recovered by day 10, treatment can be stopped 1
  • For patients who have not recovered by day 10, extend treatment to 14 days 1

Clinical Considerations and Pitfalls

• Vancomycin has limited penetration into CSF, even in patients with meningitis 1, 4
• Higher doses may be required to achieve therapeutic CSF concentrations 4
• Monitor for nephrotoxicity, especially with higher trough concentrations 1
• Consider adding rifampicin 600 mg twice daily if the pneumococcus is both penicillin and cephalosporin resistant 1
• Vancomycin-induced nephrotoxicity is defined as multiple (at least 2-3 consecutive) increases in serum creatinine (increase of 0.5 mg/dL or 150% increase from baseline) after several days of therapy 1

Alternative Therapies

• If the patient fails to respond clinically to vancomycin despite appropriate trough levels, consider alternative agents 1, 5
• For pneumococcal meningitis with penicillin and cephalosporin resistance, consider combination therapy with ceftriaxone plus vancomycin plus rifampicin 1