Clinical evaluation of urinary N-acetyl-beta-D-glucosaminidase activity in patients receiving aminoglycoside and cephalosporin drugs.

N-acetyl-beta-D-glucosaminidase (NAG) activity in urine was measured as an indicator for detecting the onset of renal damage in patients receiving aminoglycoside and cephalosporin drugs. The studies reveal that gentamicin appears to be most nephrotoxic of the aminoglycoside antibiotics. Polyuria, not oliguria, is the first clinical symptom observed in patients with marked elevation of urinary NAG activity more than 10 mM/hr/day and moderate proteinuria and disturbance of renal function are followed in some cases. Although immediate recovery from these nephrotoxic effects of aminoglycosides and the elevation of urinary NAG activity occurs on prompt withdrawal of the drugs, two autopsied cases receiving prolonged administration of gentamicin, followed marked NAG elevation, show necrosis and exfoliation of tubular epithelial cells with little glomerular injury. The other aminoglycosides, such as amikacin, tobramycin and dibekacin are less nephrotoxic, and the administration of cephalosporin developed no nephrotoxic symptoms nor marked elevation of urinary NAG activity. The results indicate that measurement of urinary NAG activity is useful for the early diagnosis and monitoring of nephrotoxic reactions due to aminoglycosides.