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The study by Hidayat et al1 raises more questions than it answers and fails to directly support the authors' main conclusions. “Target trough” is not explicitly defined in the “Methods” section: does it mean greater than or equal to 4 times the MIC of the infecting strain or 15 μg/mL or greater? “Corrected trough” (Table 31) also is undefined. It is unclear whether attainment of target trough was assessed based on the corrected or uncorrected trough and whether such attainment was assessed separately for the initial response (Figure 1, first 72 hours only1) and the final response (Figure 2, total treatment course1). Because the final outcome of therapy was not significantly associated (and initial response was only marginally associated) with achievement of target trough and outcomes seemingly were not analyzed in relation to achievement of troughs 15 μg/mL or greater, the basis for the stated requirement for “ . . . aggressive empirical vancomycin dosing to achieve a trough greater than 15 μg/mL” is unclear.1(p2138) Since combination and alternative therapy were not assessed, the findings do not support the suggestion that such measures should be considered for strains with elevated MICs. Regarding nephrotoxicity, it would be important to determine which came first, elevated vancomycin troughs or decreased renal function, because the latter predictably would lead to the former, possibly creating the false impression of vancomycin-induced nephrotoxic effects.
Johnson JR. Vancomycin Levels, Efficacy, and Toxicity. Arch Intern Med. 2007;167(11):1207. doi:10.1001/archinte.167.11.1207-a