Comparative effects of gentamicin and tobramycin on excretion of N-acetyl-beta-D-glucosaminidase.

Patients receiving gentamicin or tobramycin were studied to determine whether there were differences in the urinary excretion of N-acetyl-beta-D-glucosaminidase (NAG) between the two groups. The average daily increases in NAG excretion were significantly higher in the group receiving gentamicin. In individual patients, the best correlation with nephrotoxicity was with high initial rates of NAG excretion. If abnormally high initial rates of increase can serve as a prognosticator of nephrotoxicity, it may be possible to alter aminoglycoside therapy and to avoid renal damage.