The Food and Drug Administration will soon prohibit all uses of nitrofuran drugs in food-producing animals because they present a public health risk. The ruling is a reaction to evidence that the drugs may induce carcinogenic residues in animal tissues.

Since 1991, nitrofurans have been banned for systemic use in poultry and swine, because the drugs can cause cancer. But topical uses have been allowed, for lack of evidence that this application allows the drugs to reach edible tissues. Now, however, the FDA says it has new evidence that overturns this belief. In a recent study, researchers used carbon-14 radiolabel methods and showed that, in fact, cattle that were treated with ophthalmic preparations had residues of the drugs in their milk and tissues including muscle, kidney, and liver. Because of the risk that these residues could cause cancer, the FDA has decided to tighten regulations and will soon make all uses in food-producing animals illegal. This includes extralabel uses.

Some drug products that will be banned will remain in commercial distribution channels with their old labels that indicate use in food-producing animals. Individuals are reminded, however, that the new rule supersedes these labels and such products cannot be used in food animals.

Nitrofurans, which are effective against a wide range of bacteria, include furazolidone, nitrofurazone, nitrofuratoin, and related compounds.

The rule was published in the Feb. 6, 2002 Federal Register and can be accessed at www.access.gpo.gov/su_docs/fedreg/frcont02.html. Individuals who want to comment on the rule have until April 8, 2002. Unless the FDA modifies the rule or extends the comment period, the rule will go into effect May 7, 2002.