[Carcinogenicity study of cholestyramine in mice]

Carcinogenicity study of cholestyramine, an anti-hypercholesterolemic agent, was carried out by feeding B6C3F1 mice of both sexes with the pellet diet in which cholestyramine was admixed at the rates of 1.25, 2.5 and 5%. The animals were fed on the drug-admixed diet for 18 months and on a normal diet for subsequent 3 months. After 32 weeks the mortality of male mice began to increase in the 5% cholestyramine group and the number of dead or moribund mice increased markedly after 60 weeks. Hemorrhage recognized in pleural cavity, heart and other organs, was suggested to be the main cause of death. Some kinds of tumors occurred in each group, but the tumor-incidences seen in mice of 1.25 and 2.5% cholestyramine groups were similar to those in mice of the control group and the occurrence of the specific tumor or an acceleration of tumor-development by feeding cholestyramine were not observed. Furthermore, the tumor-incidence in mice fed on the 5% cholestyramine diet was less than that in mice of the other three groups.