Long-term in vivo carcinogenicity study of nalidixic acid in CDF1 mice

Nalidixic acid (NA), a drug used for the treatment of urinary-tract infections, was administered in the diet to groups of 51 male and 51 female CDF1 mice at concentrations of 0, 0.08 and 0.16% for 76 wk. All the surviving animals were killed at wk 85 after 9 wk on the basal diet. Survival of the treated male and female mice was similar to that of the corresponding controls. The body weights were slightly lower in high- and low-dose males and in high-dose females than in the controls. All groups showed relatively high incidences of tumours of the small intestine, lung and haematopoietic organs in both sexes, of the liver and Harderian gland in males and of the uterus in females. However, there were no statistically significant differences between NA-treated and control mice of either sex in the incidences of tumours in any organs. It was therefore concluded that, under the conditions of this study, NA showed no carcinogenic potential in either male or female CDF1 mice.