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FDA Takes New Steps to Withdraw Approval of Swine Drug Carbadox

By David Fairfield
The U.S. Food and Drug Administration (FDA) proposed in the July 20 Federal Register to revoke the approved method for detecting residues of carbadox (trade name Mecadox®)  ̶  a new animal drug used in swine feed  ̶   because the agency has concluded that the method does not meet the requirements of the federal Food, Drug and Cosmetic Act for detecting residues of carcinogenic concern. Further, if the agency’s proposed revocation of the method is finalized, FDA said it intends to publish a notice of opportunity for hearing (NOOH) proposing to withdraw approval of all new animal drug applications for use of carbadox based upon the lack of an approved method for measuring carcinogenic residues.
Mecadox® first was approved by FDA in the early 1970s for use in swine to control swine dysentery and bacterial swine enteritis. The drug also has been used to promote weight gain and feed efficiency. In July 2014, the Codex Alimentarius Commission determined there is no safe level of residues of carbadox or its metabolites in food that represents an acceptable risk to humans.  In April 2016, FDA began to take official actions toward removing approvals for Mecadox® over concerns that the drug may leave trace amounts of a carcinogenic residue.
Phibro Animal Health Corp., the manufacturer of Mecadox®, in a July 17th press release reiterated its belief that the drug remains safe to use, stating that evidence submitted to FDA:
  • Concludes that no carbadox residues of carcinogenic concern can be detected at the end of the labeled withdrawal period.
  • Confirms that carbadox remains a safe drug to control bacterial diseases in swine.
  • Increases understanding of the drug’s metabolism, residue characterization and depletion.
  • Reinforces and affirms prior FDA determinations that use of carbadox is safe as approved.
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