Dosing and Exposure of Vancomycin With Continuous Infusion: A Retrospective Study

Vancomycin continuous infusion (CI) has suggested benefits over intermittent infusion: reduced nephrotoxicity, higher target attainment, and simpler therapeutic drug monitoring (TDM). Empiric dosing regimens range from 30-60 mg/kg/day and it is unclear which regimen results in optimal exposure. This study evaluates whether a dosing regimen of 45 mg/kg/day after a 20 mg/kg loading dose for patients with estimated glomerular filtration rate (eGFR) ≥ 50 mL/min results in adequate exposure. We retrospectively analyzed plasma concentrations from patients treated with vancomycin CI as routine clinical care between February and October 2021. Patients under 18 years old, with renal replacement therapy, reduced creatinine clearance (Chronic Kidney Disease Epidemiology Collaboration < 50 mL min/1.73 m²) or outpatient antibiotic therapy were excluded. Dose, renal function, and blood draw procedures were assessed for each measured vancomycin sample. Initially, 121 samples were included. Subsequently, 7 samples, 6 of which with concentrations ≥ 40 mg/L, were verified to be incorrectly drawn and excluded. With doses of 40-50 mg/kg/day concentrations ranged from 18.4-61.0 mg/L. Only 25% were within the target window of 17-25 mg/L and 15% were ≥ 40 mg/L. Supratherapeutic concentrations were observed in 89% of samples from patients dosed 40-60 mg/kg/day with eGFR 50-80 mL/min. Concluding, an empiric dosing regimen of 45 mg/kg results in too high vancomycin exposure and thus we recommend lower doses and differentiation according to renal function. Additionally, when measuring concentrations over 40 mg/L incorrect sampling must be excluded before dose adjustment and the large variability in exposure between patients, warrants the need for swift TDM.