According to The New York Times, the U.S. Food and Drug Administration (FDA) has announced that it will rescind approval for three of the four arsenic drugs that had been used in animal feeds at the request of the companies that market them. The companies, Zoetis and Fleming Labs, already had largely withdrawn the three drugs from the market after recent studies showed levels of arsenic in chicken that exceeded amounts that occur naturally.
The compounds—roxarsone, carbarsone, and arsanilic acid—have been used in 101 drugs added to feed for chickens, turkeys, and pigs to prevent disease, increase feed efficiency, and promote growth, according to the Center for Food Safety, which together with several other advocacy groups filed a petition in December 2009 seeking to ban the drugs in animal feeds.
The only remaining arsenic-based animal drug marketed is nitarsone, the only marketed product approved for preventing blackhead (histomoniasis) in turkeys and chickens. The FDA has decided to review the results of its analytical work and evaluate the response from the sponsor of nitarsone to the order issued by the agency prior to reaching any conclusions about whether there may be grounds to initiate proceedings to withdrawal approval of that drug.
The New York Times article
FDA letter (pdf)