Approval is being rescinded for three of four arsenic-based drugs that had been used in animal feed. Of the 101 drug products derived from these four drugs, 98 will have their approval withdrawn by the Food and Drug Administration (FDA). The three to be rescinded—roxarsone, arsanilic acid, and carbarsone—were formerly employed by the agriculture industry to encourage weight gain in animals, although these particular drugs had not been in use for several years, and the companies that made them took them off the market and requested that the FDA withdraw their approval. FDA studies have found inorganic arsenic present in animal bodies after animals are fed arsenic-based drugs. The fourth arsenic-based drug—nitarsone—and two combination drugs containing nitarsone are still on the market and used in turkey and chicken production. They are currently the only marketed drug products approved to prevent histomoniasis, a parasitic disease in turkeys and chickens. The FDA has not withdrawn approval for nitarsone and is purportedly seeking additional information to evaluate its danger.
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