Performance of a vancomycin dosage regimen developed for obese patients.

PURPOSE: 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.
METHODS: 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.
RESULTS: 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.
CONCLUSION: 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.