FDA proposes to revoke use of carbadox in medicated swine feed

By David Fairfield, Senior Vice President, Feed

The U.S. Food and Drug Administration (FDA) on Nov. 7 announced the agency is revoking the approved method for detecting residues of carbadox, a new animal drug used in swine feed that has been shown to be carcinogenic in laboratory animals. An approved method is required by the Federal Food, Drug, and Cosmetic Act to show that no residue of carcinogenic concern from a new animal drug persists in any edible tissue or in any food derived from treated animals. FDA is revoking the approved method for carbadox based on its determination that the method is inadequate to monitor the residue of carcinogenic concern. 

Based on the revocation, FDA is also proposing to withdraw approval of all new animal drug applications providing for use of carbadox in medicated swine feed, for which Phibro Animal Health Corp is the sponsor. In addition, in accordance with federal requirements, FDA provided notice of an opportunity for a hearing (NOOH) in which Phibro could provide evidence to demonstrate why the new animal drug applications should not be withdrawn. The deadline for Phibro to make a request and provide supporting evidence for such a hearing is Dec. 7, 2023.

In a press release, Phibro reiterated the safety of its carbadox product – Mecadox® – and stated it intends to defend the continued use of Mecadox® in medicated swine feed.  “Phibro is extremely disappointed in the actions taken by the FDA and believes fully in the safety of Mecadox®. Mecadox® has been approved and sold in the United States for more than 50 years and is a widely used treatment for controlling bacterial diseases in swine, including Salmonella and swine dysentery, resulting in improved health and welfare for newly born and young pigs,” the company said in the release. “Phibro will take appropriate action and next steps to continue to defend swine producers’ ability to use Mecadox® to protect the health and welfare of their animals.”

FDA first made public its concern regarding the adequacy of the approved method for detecting residues of carbadox in 2016. In 2020, FDA issued a proposed order to revoke the carbadox method, and explained that if it finalized the order, the agency intended to issue a NOOH proposing to withdraw approval of all new animal drug applications containing carbadox. After announcing the proposed order, FDA solicited stakeholder comment and held a public hearing on the topic on March 10, 2022.  In this week’s announcement, FDA said “nothing presented [in response to the proposed order] demonstrates that the approved method is adequate to monitor the residue of carcinogenic concern in compliance with FDA’s operational definition of ‘no residue.’ Therefore, FDA is revoking the approved method.”