The AVMA reminds veterinarians that the Food and Drug Administration has prohibited all uses of nitrofuran drugs in food-producing animals because they pose a public health risk (see JAVMA, March 15, 2002, page 735). The rule went into effect on May 7, 2002 and is the result of evidence that the drugs may induce carcinogenic residues in animal tissues.
Nitrofurans, which are effective against a wide range of bacteria, include furazolidone, nitrofurazone, nitrofurantoin, and related compounds. At this time, any nitrofuran product found on a dairy farm that is not labeled for cattle constitutes a five-point debit for on-farm milk inspection. Older product stock of furazolidone aerosol (spray) powder and nitrofurazone topical powder that bear an indication for use in cattle will not result in a debit unless the product has exceeded its expiration date. Veterinarians should ask producers to remove in-date product from dairy operations. Trade names include Topazone, Furox aerosol, NFZ Puffer, and P.E.7.
Since 1991, nitrofurans have been banned for systemic use in poultry and swine because the drugs can cause cancer. Topical uses, however, have been allowed because evidence that this application allowed the drugs to reach edible tissues did not exist. Recent evidence, however, shows that cattle treated with ophthalmic preparations can have residues of the drugs in their milk and tissues, including muscle, kidney, and liver, so the FDA decided to disallow even topical use.
Nitrofurans have been added to the Animal Medicinal Drug Use Clarification Act list of drugs prohibited for extralabel use in food-producing animals. The list includes chloramphenicol; clenbuterol; diethylstilbestrol; dimetridazole; ipronidazole; other nitroimidazoles; furazolidone, nitrofurazone, and other nitrofurans; sulfonamide drugs in lactating dairy cattle (except approved use of sulfadimethoxine, sulfabromomethazine, and sulfaethoxypyridazine); fluoroquinolones; and glycopeptides.
Veterinarians are also reminded that dimethylsulfoxide, ionophores, dipyrone, and colloidal silver are also not to be used or stored in dairy farms or fed to lactating dairy cattle.