Determinants of vancomycin nephrotoxicity when administered to outpatients as a continuous 24-hour infusion

•Nephrotoxicity occurred in only 3.4% of outpatients on vancomycin infusions.•Previous studies reported an incidence of 15–17%.•Lower incidence in this study may be due to more frequent monitoring.•Improved dosing strategies may further reduce the risk of acute kidney injury. Vancomycin continuous infusion (VCI) is used to treat serious Gram-positive infections in outpatients. This study was conducted to retrospectively investigate the rate of nephrotoxicity and associated risk factors in out-patients on VCI between May 2013 and November 2018. Vancomycin concentration was monitored twice-weekly to ensure adequate concentrations while avoiding high concentrations linked to nephrotoxicity (a rise in serum creatinine of ≥50% or 44 µmol/L from baseline). The likelihood of developing nephrotoxicity was evaluated using multivariable logistic regression. The 223 patients treated had a mean (standard deviation) age of 61 (16.7) years, baseline serum creatinine of 83.9 (21.2) µmol/L and estimated glomerular filtration rate (eGFR) of 80.6 (20.1) mL/min/1.73m2. Most patients (66%) were treated for bone and joint infections. Eight patients (3.6%) developed nephrotoxicity. In the most parsimonious model, nephrotoxicity was independently associated with an increased median (interquartile range) weighted-average serum vancomycin concentration (28.0 [24.3–32.6] vs. 22.4 [20.2–24.5] mg/L; odds ratio [OR] 1.25; 95% confidence interval [95% CI] 1.09–1.46; P