UPDATED: FDA to withdraw approval of carbadox

Agency cites risk of carcinogenic residues in pork derived from carbadox-treated pigs; manufacturer may request hearing on withdrawal.

The U.S. Food & Drug Administration’s Center for Veterinary Medicine (CVM) announced April 8 that it has taken the first step toward rescinding its approval of the use of carbadox to treat swine because the drug may leave trace amounts of a carcinogenic residue.

CVM’s action comes after it recently re-examined the safety profile of the drug and conducted a preliminary risk characterization that indicated that there could be a potential risk to human health from ingesting pork, especially pork liver, derived from carbadox-treated pigs.

“The manufacturer of carbadox has failed to provide sufficient scientific data to demonstrate the safety of this drug, given evidence that carbadox may result in carcinogenic residues,” said Michael R. Taylor, FDA deputy commissioner for foods and veterinary medicine. “As a result, (CVM) is taking legal action to remove this product from the marketplace.”

FDA emphasized that it is not recommending that people make changes in their food choices while the agency is working to remove carbadox from the market. 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. However, removing the product from the market will reduce the lifetime risk to consumers, which is why CVM said it is taking this action.

Carbadox was first approved in the early 1970s for use in swine to control swine dysentery and bacterial swine enteritis. It has also been used for weight gain and feed efficiency.

FDA-approved alternative antibiotics are available for pork producers to treat swine.

According to FDA, in July 2014, the Codex Alimentarius Commission determined that there is no safe level of residue of carbadox or its metabolites in food that represents an acceptable risk to consumers. This was based on conclusions of the U.N. Food & Agriculture Organization/World Health Organization Codex Committee on Residues of Veterinary Drugs in Foods drawn from the available scientific information.

To remove its approval, CVM must first file a Notice of Opportunity for Hearing, which it issued April 8. The notice provides Phibro Animal Health, the manufacturer of carbadox (Mecadox), with an opportunity to request a hearing on whether the approval should be withdrawn. The notice is expected to be published in the Federal Register on April 12. A pre-publication filing of the notice can be downloaded.

The company has 30 days to request a hearing. If the company does not request a hearing, the agency can proceed with removing the animal drug from the market.

CVM said it is committed to working with pork producers to minimize impacts on the swine industry.

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In response, Phibro Animal Health noted that Mecadox (carbadox) has been approved and sold in the U.S. for more than 40 years and is a widely used treatment for controlling bacterial diseases, including salmonella and swine dysentery. Carbadox is not used in human medicine, the class of drug is not considered a medically important antimicrobial and the approved label requires a 42-day withdrawal period pre-slaughter. Phibro noted that, to date, the company has not seen any hazardous residues of carbadox being detected from pig meat treated in accordance with the approved label.

FDA approved the original application for Mecadox in the early 1970s and a supplemental application in 1998, each time as a result of a rigorous safety review. Several years ago, in response to the availability of more advanced analytical detection methods, FDA began to raise questions about the persistence of residues in tissue longer than had been previously determined. Since that time, Phibro said it has cooperated fully with FDA’s inquiries, including undertaking comprehensive, rigorous new studies using the latest and most sensitive technology available. Phibro has been providing the data to FDA as they are generated and in accordance with the schedule submitted to the agency, and to date, that evidence has been positive regarding the safety of carbadox and reiterates the safety of carbadox when used in accordance with the label. As Phibro has told FDA, the studies are due to be completed in the next 90 days, and the remaining evidence is expected to support the continued safe use of Mecadox.

Today’s action by FDA does not prohibit the sale or use of Mecadox in the U.S.

After 40 years, the company said carbadox remains a highly effective treatment for controlling bacterial diseases and swine dysentery.

Phibro emphasized that it has complete confidence in the safety of Mecadox and is disappointed that FDA would take this action when definitive studies are so close to being completed. Under FDA’s process, Phibro intends to request a hearing and refute the allegations.

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