Aminoglycoside nephrotoxicity and its predictability

Nephrotoxicity was evaluated in 37 patients receiving aminoglycosides by serial urinary measurements of the low-molecular weight protein beta 2-microglobulin (beta 2m) and the proximal tubular enzymes N-acetyl-glucosaminidase and beta-glucuronidase. Clinical nephrotoxicity, with a rise in serum creatinine greater than 20% of the baseline value, was diagnosed in 15 of 30 evaluable patients. The laboratory diagnosis of nephrotoxicity, defined as a two-fold increase in beta 2m, N-acetylglucosaminidase and beta-glucuronidase, was confirmed in 11/15 patients. Additionally, there were 3 patients in whom there was definitive laboratory nephrotoxicity in the absence of a rise in serum creatinine. The laboratory diagnosis of nephrotoxicity could be made 4.1--5.5 days prior to significant elevation in serum creatinine. The data suggest that beta 2m and enzyme studies are predictors of nephrotoxicity.