Validity of N-acetyl-beta-D-glucosaminidase (NAG) determination in assessing netilmicin nephrotoxicity in preterm babies.

The supposed nephrotoxicity of netilmicin has been assessed in preterm neonates using the urinary excretion of a lysosomal enzyme as marker: N-acetyl-beta-D-glucosaminidase (NAG). 17 male preterm neonates with birth weight appropriate for gestational age were enrolled in a study where 9 received netilmicin therapy since the first day of life and 8 served as control group. We observed a significant increase in urinary NAG/creatinine ratio during the postnatal days in the netilmicin group babies followed by a regular decrease during the days after the end of therapy. If this increase in lysosomal enzymuria such as NAG could reflect netilmicin nephrotoxicity on the proximal tubular cell, many questions remain unanswered about the exact significance of this finding. In particular, its relation with tubular cell dysfunction remains to be established.