Three Arsenic-Based Animal Drugs Withdrawn from Market

Before the government shutdown, the FDA announced that it would rescind approval for three of the four arsenic-based animal drugs that had been used in animal feeds at the request of the companies that marketed them.  The three drugs – roxarsone, carbarsone, and arsanilic acid – are added to animal feed to prevent disease, promote growth, and increase feed efficiency. The companies involved, Zoetis and Fleming Labs, had already withdrawn drug products containing roxarsone, carbarsone, and arsanilic acid generally from the market after recent studies indicated that levels of arsenic in chicken using the animal feed exceeded amounts that occurred naturally. Pfizer, which spun its animal health division off as Zoetis this year, withdrew its roxarsone drug, 3-Nitro, from the market in 2011 after the FDA found inorganic arsenic in chicken livers.

Nitarsone, the last of the four  drugs that public health groups are seeking to ban from animal feeds, is the only known treatment for blackhead, or histomoniasis, a disease that can kill turkeys. The FDA is in the process of completing several scientific studies and reviewing and evaluating information to help the agency more fully evaluate any potential concerns related to the safety of arsenic-based animal drugs. The agency has decided to review this information before reaching any conclusions about whether there may be grounds to initiate proceedings to withdraw approval of nitarsone, the only currently marketed arsenic-based animal drug in the U.S.

The Center for Food Safety and the Institute for Agriculture and Trade Policy  had originally filed a citizen petitions asking the FDA to take steps to revoke the approvals of the four arsenic-based animal drugs. As to roxarsone, carbarsone, and arsanilic acid, the requests were considered moot because of the sponsors’ request for withdrawals, but with the studies pending, the petition on nitarsone was denied.

The issue of arsenic in food has drawn increased public scrutiny since research last year by Consumer Reports found substantial arsenic levels in rice. Arsenic residue in rice often comes from the water used to grow it, and poultry feces are widely used as fertilizer for a variety of crops. The FDA began a risk assessment action in conjunction with the previous reports.