The FDA mulls pulling approval for carbadox, an antibiotic known to cause liver cancer and birth defects in lab animals, raising concern about its impact on human health.
Common Drug Used by Pork Industry Has Human Cancer Risk
STORY AT-A-GLANCE
November 7, 2023, the U.S. Food and Drug Administration announced it is considering withdrawing approval for the antibiotic carbadox, which is added to pig feed to prevent infections and fatten up the animals, due to cancer concerns
The drug has been banned in the European Union since 1999, and in Canada since 2006. China, Brazil, Australia and the UK have also banned it due to concerns over its cancer risks
In 2014, the United Nation’s Codex Committee on Residues of Veterinary Drugs in Foods determined that there is no safe level of residues of carbadox or its metabolites in food that represents an acceptable risk to consumers
Carbadox has been shown to cause liver cancer and birth defects in lab animals, and have long-lasting impacts on the gut microbiome of swine, even after the drug is withdrawn
A 2017 study found carbadox induced transducing bacteriophages with resistance genes to tetracycline, aminoglycoside and beta-lactam antibiotics — three classes of drugs that are commonly used in human medicine. The findings effectively dismisses the drugmaker’s and the National Pork Producers Council’s argument that since carbadox is not used in human medicine, it won’t contribute to drug resistance in humans
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Livestock raised in confined animal feeding operations (CAFOs) are routinely given a range of veterinary drugs to prevent disease, and some of those drugs could potentially impact the health of those who eat their meat.
November 7, 2023, the U.S. Food and Drug Administration announced it is considering withdrawing approval for the antibiotic carbadox1 (brand name Mecadox), which is added to pig feed to prevent infections and fatten up the animals, due to cancer concerns. As noted in the Federal Register:2
"The Food and Drug Administration ... Center for Veterinary Medicine (CVM), is proposing to withdraw approval of all new animal drug applications (NADAs) providing for use of carbadox in medicated swine feed ...
This action is based on CVM's determination that there is no approved regulatory method to detect the residue of carcinogenic concern in the edible tissues of the treated swine."
How a Carcinogen Ended Up Being Used for Decades
Under the Delaney Clause in Section 512 of the Federal Food, Drug, and Cosmetic Act, an animal drug cannot gain FDA approval if it has been found to "induce cancer when ingested by man or animal." In the case of carbadox, the drug was known to cause liver cancer3 and birth defects4 in lab animals.
CVM still approved it under an exception to the Delaney Clause, known as the Diethylstilbestrol "DES" Proviso, which allows a carcinogenic drug to be approved if, under the conditions for use, the drug is found to not have an adverse effect on the animals being treated, and if no drug residues can be found "by an approved regulatory method in any edible tissues of, or food from, the animal."5 As explained by the FDA:6
"In 1998, the FDA’s Center for Veterinary Medicine (CVM) approved the most recent testing method for carbadox based on information available to CVM at that time.
The method relied on measuring the noncarcinogenic residue quinoxaline-2-carboxylic acid (QCA) as a marker to demonstrate when the residue of carcinogenic concern in the edible tissue of carbadox-treated animals dropped to a level that satisfied the DES Proviso.
However, subsequent information showed that carcinogenic residues of carbadox persist longer than previously known. This means that noncarcinogenic QCA is not a reliable marker ...
Specifically, because there is no established relationship between noncarcinogenic QCA measured by the 1998-approved method and the residue of carcinogenic concern, the 1998-approved method does not allow FDA to determine whether the residue of carcinogenic concern can be found in any edible tissue of, or food derived from, the treated animals.
Accordingly, in November 2023, FDA revoked the 1998-approved method. There is currently no approved method for carbadox. Without an approved method, the second prong of the DES Proviso exception to the Delaney Clause, which requires that ‘no residue of such drug will be found …, in any edible portion of such animals after slaughter or in any food yielded by or derived from the living animals,’ is not met."
Action Long Overdue
The thing is, FDA has known the original testing method was inadequate for seven years, if not more. In its 2016 proposal to withdraw the drug, the FDA even noted that:7
"Continued approval of carbadox would expose humans to concentrations of total residues of carcinogenic concern that are approximately 30 times higher (for the approved 42-day withdrawal period) or 11 times higher (for the approved 70-day withdrawal period) than the 0.915 ppb concentration of total residues of carcinogenic concern in liver that would be considered safe."
Mind you, two years before that, in 2014, the United Nation’s Codex Committee on Residues of Veterinary Drugs in Foods determined that "there is no safe level of residues of carbadox or its metabolites in food that represents an acceptable risk to consumers."8
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There is no safe level of residues of carbadox or its metabolites in food that represents an acceptable risk to consumers. ~ UN Codex Committee on Residues of Veterinary Drugs in Foods
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