Performance of a vancomycin dosage regimen developed for obese patients

An original and a revised vancomycin dosing protocol for obese patients were compared with respect to attainment of target serum trough vancomycin concentrations and the occurrence of nephrotoxicity. The attainment of target vancomycin trough values (10-20 μg/mL) and nephrotoxicity were compared retrospectively between an original protocol (vancomycin 15 mg/kg i.v. every 8-12 hours), which had been associated with high troughs, and a revised protocol (10 mg/kg i.v. every 12 hours or 15 mg/kg every 24 hours). Patients were included if they were obese (weight ≥ 100 kg and total body weight ≥ 140% of ideal body weight), had normal renal function (creatinine clearance ≥ 60 mL/min), had received i.v. vancomycin for at least 48 hours, and had one evaluable vancomycin trough value. Nephrotoxicity was defined as an increase in serum creatinine concentration of 0.5 mg/dL or of 50% over baseline, whichever was greater. Seventy-four and 64 patients were stratified into groups that had been treated with the revised and original protocols, respectively. The mean ± S.D. maintenance dose was 19 ± 2 mg/kg/day with the revised protocol and 34 ± 7 mg/kg/day with the original protocol (p < 0.001). Compared with the original protocol, the revised protocol resulted in a higher frequency of target troughs (59% versus 36%, p = 0.006) and below-target troughs (23% versus 9%, p = 0.033) and a lower frequency of above-target troughs (18% versus 55%, p < 0.001). Nephrotoxicity occurred in two patients in each group. Compared with the original vancomycin protocol for obese patients, a revised vancomycin protocol using lower total daily doses improved the attainment of target trough concentrations, with minimal nephrotoxicity.