Lack of nephrotoxicity following 15-day therapy with high doses of colistin in rats

Recent studies suggest that the incidence and severity of systemic toxicity due to colistin administration appear to be overstated. The objective of this study was to investigate colistin-induced nephrotoxicity in Wistar rats. Eighteen adult Wistar rats were divided into three groups: group I (controls, vehicle, n=6) rats were injected intramuscularly (i.m.) with physiological sodium chloride solution and groups II and III (colistin, n=6 each) rats were treated with colistin at a dose of 150,000 or 300,000 IU/kg body weight per day i.m, respectively. The drug injections were applied for 15 days. Twelve hours after the last injection the rats were sacrificed. The kidneys were quickly removed and blood samples were collected. Microscopic examination of the kidneys and measurements of serum creatinine and blood urea nitrogen concentrations were performed. The mean urea nitrogen concentrations were 5.95+/-0.58, 5.75+/-0.61, and 5.77+/-0.87 mmol/l and the mean serum creatinine concentrations were 45.5+/-1.87, 43+/-1.79, and 44+/-2.19 micromol/l in groups I, II, and III, respectively, without any statistical differences between the groups. Exposure to colistin did not cause any histological change in the kidney structure. These results suggest that colistin, when administered alone at usual doses, may not cause nephrotoxicity.