The long-term health effects of chloral hydrate are discussed and its carcinogenicity in mice are reported from the University of California, Davis, and the California School of Public Health, Berkeley. In a group of 8 mice receiving 10 mg/kg, 6 developed hepatic adenomas or carcinomas, an incidence significantly greater than that of 2/19 controls with carcinomas. Of 24 mice receiving 166 mg/kg/daily intake of chloral hydrate in drinking water for 104 weeks, 17 developed hepatic adenomas or carcinomas compared to 3 of 20 controls. Other recent studies have shown chloral hydrate to be genotoxic, causing chromosome changes in vivo and in vitro. 
COMMENT. Many of us who have stocked chloral hydrate in large quantities for use in sedating children for EEGs and other short procedures may want to reconsider its safety and substitute an alternative. Certainly, its chronic long-term use as a sedative in mentally retarded children should be discouraged until further studies are completed. Chloral hydrate is a metabolite of trichloroethylene, a known carcinogen.