Incidence and predictors of vancomycin-associated nephrotoxicity.

OBJECTIVES

Earlier studies reported a low incidence of vancomycin-associated nephrotoxicity (VAN); however, recent studies have reported higher incidences exceeding 30%. Predictors of nephrotoxicity are not well defined. In this study we aimed to better estimate the incidence and evaluate predictors of VAN in a cohort of patients predominated by long treatment courses.

METHODS

We conducted a retrospective study on patients treated with vancomycin while in the hospital and who were observed closely through the Outpatient Parenteral Antibiotic Therapy program. Nephrotoxicity was defined as an increase in the serum creatinine level of 0.5 mg/dL or 50% from baseline on at least two consecutive readings while taking vancomycin. We compared the patients who developed nephrotoxicity with those who did not with regard to vancomycin dosing, trough levels, baseline serum creatinine, underlying infection, residence in the critical care unit, comorbid conditions, concurrent nephrotoxic treatments, and baseline characteristics.

RESULTS

Of 579 patients, 154 (26.6%) developed nephrotoxicity. Ninety patients developed VAN within the first 14 days of treatment, whereas 64 patients developed nephrotoxicity after 14 days of treatment. The median time to development of nephrotoxicity was 9 days. Admission to the intensive care unit, concurrent use of loop diuretics, and comorbidity with cirrhosis were independently associated with nephrotoxicity. A higher baseline creatinine value was unexpectedly associated with a lower incidence of nephrotoxicity (P = 0.0016).

CONCLUSIONS

VAN is not an uncommon outcome in both short- and long-term treatment courses. Admission to the intensive care unit while receiving treatment, concurrent treatment with a loop diuretic, an underlying diagnosis of cirrhosis, and the initial trough level appear to be the main risk factors for nephrotoxicity. Unexpectedly, elevated baseline creatinine levels appeared to be protective and this could be the result of careful use of vancomycin among individuals with relatively higher baseline creatinine values.