Vancomycin Dosing Based on eGFR
Vancomycin dosing must be adjusted based on renal function, with initial doses of 15-20 mg/kg every 8-12 hours for normal renal function, and dose reductions or interval extensions required when creatinine clearance falls below 100 mL/min, using the FDA-approved dosing table that correlates daily dose with creatinine clearance. 1
Initial Dosing for Normal Renal Function
For patients with normal renal function (CrCl ≥100 mL/min), administer 15-20 mg/kg (based on actual body weight) every 8-12 hours to achieve target trough concentrations of 15-20 mg/L for serious infections. 2
The standard adult dose is 2 g daily divided as either 500 mg every 6 hours or 1 g every 12 hours, with each dose infused over at least 60 minutes or at no more than 10 mg/min, whichever is longer. 1
Loading doses >20 mg/kg are safe and not associated with increased nephrotoxicity compared to lower doses, supporting aggressive initial weight-based dosing. 3
Dose Adjustment for Renal Impairment
The FDA provides a specific dosing table based on creatinine clearance (adapted from the package insert): 1
- CrCl 100 mL/min: 1,545 mg/24h
- CrCl 90 mL/min: 1,390 mg/24h
- CrCl 80 mL/min: 1,235 mg/24h
- CrCl 70 mL/min: 1,080 mg/24h
- CrCl 60 mL/min: 925 mg/24h
- CrCl 50 mL/min: 770 mg/24h
- CrCl 40 mL/min: 620 mg/24h
- CrCl 30 mL/min: 465 mg/24h
- CrCl 20 mL/min: 310 mg/24h
- CrCl 10 mL/min: 155 mg/24h
The general principle is that vancomycin dose per day (in mg) equals approximately 15 times the glomerular filtration rate in mL/min. 1
Critical Considerations for eGFR Calculation
The CKD-EPI equation for estimating GFR provides superior prediction of vancomycin clearance compared to Cockcroft-Gault or MDRD equations in critically ill patients. 4, 5
For ICU patients specifically, cystatin C-guided dosing using eGFRcr-cys significantly improves target trough achievement (50% vs 28%) compared to estimated creatinine clearance. 5
The Cockcroft-Gault formula and MDRD should be used with caution in ICU patients as they correlate poorly with vancomycin clearance. 4
Monitoring Requirements
Measure trough serum concentrations just before the fourth dose at steady-state conditions. 2
Target trough concentrations of 15-20 mg/L are required for serious infections including bacteremia, endocarditis, osteomyelitis, meningitis, and hospital-acquired pneumonia caused by S. aureus. 2
Maintain trough concentrations ≥10 mg/L at minimum to prevent development of resistance. 2
Peak concentration monitoring is not recommended to reduce nephrotoxicity. 2
Special Populations Requiring Adjustment
Elderly patients require greater dosage reductions than expected due to decreased renal function, even when creatinine appears normal. 1
Premature infants have decreased vancomycin clearance as postconceptional age decreases, requiring longer dosing intervals. 1
For functionally anephric patients, give an initial 15 mg/kg dose, then 1.9 mg/kg/24h for maintenance, or 250-1,000 mg every several days. 1
In anuria, 1,000 mg every 7-10 days is recommended. 1
Common Pitfalls to Avoid
Fixed-dose regimens (e.g., 2 g/day) are inappropriate for ICU patients, resulting in only 16.9% achieving target concentrations and 25% experiencing supratherapeutic levels. 6
Female patients are at higher risk of supratherapeutic concentrations (40.4% vs 15.5% in males) when using fixed dosing. 6
Do not use calculated creatinine clearance in patients with shock, severe heart failure, oliguria, obesity, liver disease, edema, ascites, debilitation, malnutrition, or inactivity, as these conditions invalidate standard formulas. 1
Initial doses should never be less than 15 mg/kg, even in mild-to-moderate renal insufficiency, to achieve prompt therapeutic concentrations. 1
Vancomycin trough concentration correlates negatively with eGFR (R²=0.366) and positively with age (R²=0.186), requiring individualized adjustment. 6