Effects of asphyxia and oral gentamicin on intestinal lactase in the suckling rat

The effect of oral gentamicin on lactase, the major disaccharidase of the neonatal intestine, was studied using the suckling Wistar rat as a model. The jejunal lactase-specific activity of asphyxiated animals given oral gentamicin at a dose of 20 mg/kg/day for two days was significantly decreased compared to that of nonasphyxiated animals given oral saline (P less than 0.01). Although the intestinal lactase-specific activity of nonasphyxiated animals given oral gentamicin at a dose of 20 mg/kg/day for two days was not significantly different from that of animals given oral saline, a high dose of oral gentamicin (160 mg/kg/day) was associated with decreased lactase-specific activity in both the jejunum and ileum. Intramuscular administration of gentamicin was not associated with decreased intestinal lactase-specific activity. More information is needed regarding the mechanism of the biochemical injury associated with the oral use of aminoglycosides and its clinical significance, if any, in the human infant. Until this is known, the potential for such injury should be of special concern where prophylaxis against necrotizing enterocolitis is being considered, particularly in view of the increased tendency for treated infants to become colonized with gram negative organisms resistant to the antibiotic being used.