Performance of a Divided-Load Intravenous Vancomycin Dosing Strategy for Obese Patients

Abstract

Current guidelines recommend vancomycin trough concentrations of 15 to 20 µg/mL in complicated infections and all trough concentrations >10 µg/mL to avoid developing microbial resistance. To date, no published protocol reliably meets these recommendations for obese patients. We assessed the performance of a novel, obese-specific, divided-load vancomycin protocol for attaining target trough concentrations within 12 to 24 hours of dosing initiation, and during maintenance dosing, in obese patients. The protocol was evaluated through prospective medical record review in 54 consecutive obese patients. Vancomycin serum concentrations were drawn before the third and fifth dose after initiation. Steady-state concentrations were drawn after the third dose once maintenance dosing was achieved and periodically thereafter. Within 12 hours after dosing initiation, 48 (89%) study patients exhibited trough concentrations of 10 to 20 µg/mL averaging 14.5 ± 3.2 µg/mL; 51 (94%) study patients exhibited trough concentrations >10 µg/mL within 12 hours after dosing initiation, and 3 (6%) had trough concentrations >20 µg/mL. Thirty-one participants had second trough concentrations drawn within 24 hours of dosing initiation, averaging 15.0 ± 3.1 µg/mL; 24 patients had a total of 32 trough concentrations drawn during maintenance dosing, averaging 15.1 ± 2.5 µg/mL. Obese-specific, divided-load dosing achieved trough concentrations of 10 to 20 µg/mL for 89% of obese patients within 12 hours of initial dosing and 97% of obese patients within 24 hours of initial dosing while preventing doses given during supratherapeutic trough levels; 97% of troughs measured during steady state were within target range.