Elevated vancomycin trough is not associated with nephrotoxicity among inpatient veterans.

Abstract

BACKGROUND: Vancomycin troughs of 15-20 mg/L are recommended in the treatment of invasive staphylococcal disease, higher levels than previously recommended. OBJECTIVE/SETTING: We sought to determine if there was an association between vancomycin trough and nephrotoxicity, defined as 0.5 mg/L or 50% increase in serum creatinine, at a large Veterans Affairs medical center. PATIENTS AND METHODS: We reviewed records of 348 inpatients at our institution who received ≥5 days of vancomycin during 2 time periods when vancomycin dosing protocols differed (May 2005-April 2006 and January 2007-December 2007). Potential risk factors for nephrotoxicity were collected prior to nephrotoxicity onset, and all patients with nephrotoxicity events occurring within 5 days of starting vancomycin were excluded. RESULTS: Overall incidence of nephrotoxicity was 31/348 patients (8.9%). A similar percentage of patients experienced nephrotoxicity in 2005-2006 versus 2007 (16/201 vs 15/147, respectively; P = 0.57), despite a rise in mean (9.7 mg/L in 2005-2006 vs 13.2 mg/L in 2007; P < 0.0001) and highest (11.8 mg/L in 2005-2006 vs 15.7 mg/L in 2007; P < 0.0001) vancomycin trough levels achieved. In a multivariate logistic regression model, only receipt of intravenous contrast dye was significantly associated with nephrotoxicity (OR 4.01, P < 0.001), though there was a trend toward an association between maximum vancomycin trough ≥15 mg/L and nephrotoxicity (OR 2.05, P = 0.082). Overall reversibility of nephrotoxicity either prior to or within 72 hours of vancomycin discontinuation was 77.8%. CONCLUSIONS: We conclude that nephrotoxicity, with higher trough levels occurring at ≥5 days of vancomycin therapy, was uncommon at our institution and typically reversible.