In 1988, the United States Environment Protection Autority (EPA) announced the withdrawal of approvals for dimetridazole. The EPA found that dimetridazole was a potential mutagen and carcinogen. Dimetridazole is chemically similar to ipronidazole and metronidazole (chemicals that may also be mutagenic and carcinogenic), and its metabolites are also suspected carcinogens. The EPA found that the available data were inadequate to discount the possibility that dimetridazole was a genotoxic carcinogen, although it allowed the use of dimetridazole under veterinary prescription, provided it is used only on non-food-producing animals.
In 1995, the European Union withdrew dimetridazole as a veterinary medicine over concerns about its potential to act as a carcinogen. In May 2002, the European Union banned the use of dimetridazole as a feed additive after insufficient data had been submitted to meet the requirements for re-evaluation.
In 2002, the Joint Expert Committee on Food Additives reported that dimetridazole is mutagenic in vitro, but there was insufficient evidence to determine whether it is mutagenic in animals. The committee requested that additional studies be done and placed dimetridazole on the inactive list, pending the evaluation of additional human safety data.
In 2002, the APVMA began a review of dimetridazole because of concerns relating to human health risks arising from exposure to residues in chicken, eggs and pork products.