Vancomycin Trough Levels: Cause or Result of Acute Kidney Injury?

clearance of vancomycin to the clearance of the gold standard glomerular filtration rate (GFR) marker inulin is 0.89 in normal volunteers at steady state with endogenous creatinine as a filtration marker the ratio is 0.79 [5] . Therefore, the vancomycin clearance is a better GFR marker than is the creatinine clearance. Thus the interpretation of trough levels needs to be based on the renal function of the treated patient. Vancomycin is only prescribed for infected patients. Obviously, the hemodynamic effects of infection inclusive of systemic sepsis make each patient unique in regard to their risk of AKI in the course of vancomycin treatment. The authors tried to adjust for this with various demographic factors. However, the ways of expressing the trough levels without any information about hemodynamics and the nature of the infections other than the site of infection makes the matching regarding AKI and non-AKI patients unclear. The trough level of any compound is a surrogate for the exposure of the drug in the patient, given that exposure is defined by the area under the concentration curve (AUC) and the trough level is just one point on the AUC. Thus, as renal function falls while other factors remain the same, the trough level of vancomycin will rise. That does not mean that the trough level causes nephrotoxicity but rather is a result of incomplete drug excretion durIn the current issue of the American Journal of Nephrology, Hammoud et al. [1] present a large retrospective study relating the vancomycin trough level in 500 patients with acute kidney injury (AKI). With the widespread use of vancomycin for various infections including resistant organisms such as methicillin-resistant Staphylococcus aureus , the nephrotoxicity of this compound has been reexamined. Early in its development vancomycin was manufactured with various impurities that were believed to be the source of the drug’s nephrotoxic potential [2] . It has been difficult to produce vancomycin nephrotoxicity in experimental animals over the past years although there seems to be a synergistic nephrotoxic effect when combined with aminoglycoside [3, 6] . The instance of nephrotoxicity defined differently by various authors has been estimated to be approximately 5% [4] . The major concern of most infectious disease specialists is to achieve the drug regimen that is necessary to cure the bacterial infection for which the drug was prescribed. Thus, the trough levels as an estimate of drug exposure has become the focus of various guidelines for vancomycin usage. From a renal standpoint, vancomycin is a very interesting compound. The molecular weight is 1,500 and there are no metabolites of significance. Excretion is virtually entirely renal, and in fact, the ratio of the renal Published online: October 28, 2016 Nephrology American Journal of