Pig drug may be withdrawn over residues

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Food and Drug Administration officials are working to rescind approval of a swine-use drug that may leave carcinogenic residues in pork.

On April 8, agency officials gave Phibro Animal Health 30 days to request a hearing through which the company could contest the proposal to withdraw carbadox, an antimicrobial. Richard Johnson, chief financial officer for Phibro, said his company will request the hearing.

In a separate announcement, Phibro officials expressed confidence in the safety of carbadox, sold under the trade name Mecadox. Phibro manufactures all drugs sold in the U.S. containing carbadox, according to the FDA.

The FDA’s effort to remove the drug from the market follows a safety re-examination and conclusion that residues of carbadox and its metabolites may threaten the health of people who eat pork, especially pork livers, according to the FDA. Pork livers are in deli meats and in liverwurst, hot dogs, and other types of sausage.

Food and Drug Administration officials have indicated carcinogenic residues from carbadox may increase long-term health risks among people who eat pork livers, which are used in hot dogs, liverwurst, and deli meats.

Dr. Tom Burkgren, executive director of the American Association of Swine Veterinarians, said carbadox is administered most often to prevent diarrheal diseases among pigs during weaning and early growth phases. It’s a common medication in swine medicine, and he expressed hope that safety data from Phibro would prove the drug is safe.

The drug also is approved for livestock production uses, such as accelerating weight gain, and it is available without a prescription or veterinary feed directive, according to FDA drug approval documents.

Michael R. Taylor, FDA deputy commissioner for foods and veterinary medicine, said in the agency’s announcement that Phibro had failed to prove the drug was safe, given evidence it could leave carcinogenic residues.

But the FDA is not recommending that people change their diets.

“Potential cancer risks are based on an assumed lifetime of consuming pork liver or other pork products containing carbadox residues, and short-term changes in diet are unlikely to affect a person’s lifetime risk,” the announcement states. “However, removal of the product from the market will reduce the lifetime risk to consumers, which is why CVM is taking this action.”

Dr. Burkgren expects little change in administration of the drug during the withdrawal proceedings. He noted that the FDA could have issued an emergency order to halt sale of the drug if the concern were greater.

Johnson said in mid-April it was too early to say whether the agency’s announcement would harm Mecadox sales.

The FDA action is based on a July 2014 determination by the Food and Agriculture Organization of the United Nations and the World Health Organization that there are no safe residue concentrations of carbadox or its metabolites in food.

The Phibro announcement indicates carbadox has been approved and sold for more than 40 years, and it was subjected to safety reviews during its original approval and a supplemental approval in 1998.

Phibro officials said that, several years ago, the FDA raised questions about the persistence of carbadox residues found through advances in detection methods. The company has responded with studies and given the FDA data that have “reiterated the safety” of carbadox when used according to label directions.

“As Phibro has told the FDA, our studies are due to be completed in the next 90 days and we expect that the remaining evidence will support the continued safe use of Mecadox,” the announcement states.

Dr. Burkgren acknowledged that carbadox use could rise as restrictions on other antimicrobials increase this December. The FDA, under agreements with pharmaceutical companies, is altering approvals of many antimicrobials administered in feed or water of livestock to eliminate production uses and require veterinary feed directives or prescriptions for purchase. The changes affect antimicrobials that are in drug classes shared with human medicine.