The New Jersey-based company responded Monday to the FDA’s attempt to have the medicated feed product for swine removed from use, offering data from studies completed by Charles River Laboratories and the University of Edinburgh.
“The new studies leave no doubt about the safety of carbadox, and its benefits in preventing animal suffering and disease are well documented,” said Larry Miller, Chief Operating Officer at Phibro. “Therefore, we believe allowing it to remain a treatment option is the responsible course. We stand ready to work closely with the FDA and answer any questions.”
The feed treatment is used to address bacterial disease in pigs, and is not used in human medicine, the company said. Removing it from use could increase the amount of antibiotics medically important for humans used in animal husbandry, warned Phibro.
In April, the FDA’s Center for Veterinary Medicine (CVM) proposed that approvals be withdrawn for all carbadox based animal drug applications in medicated swine feed. The request came after a finding that use of the product resulted in “residues of carcinogenic concern in the edible tissues of the treated swine,” said the FDA.
The company had until May 12 to request a hearing, and all data and information to support the request for a hearing was due by Monday.
At this time, no decision regarding a hearing on the topic has been published in the Federal Register.
FDA’s suggestion
The CVM had announced the possibility of a hearing taking place to address the move to end approvals for carbadox in medicated swine feeds.
Reportedly, new evidence had been presented showing carcinogenic residue remaining in the edible tissue of swine treated with the product, said the FDA. The drug was found to no longer meet standards as residue of a carcinogenic drug was found after slaughter and the drug was no longer considered to be safe.
“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,” the agency said. “Moreover, the sponsor has not identified an appropriate marker and analytical method to assure that residues of carcinogenic concern are below the level at which the residues present in the total human diet present no significant increase in the risk of cancer to people.”
The drug was known to be a carcinogen, but was approved for use based on the provision that no residue of the product or its metabolite QCA be found in the raw, edible tissue of swine treated with it, the FDA said. The Codex Alimentarius Commission found that there was no safe residue level of the drug in a 2014 review.
Safety studies
Information generated in the safety studies refutes the basis for the CVM’s request to withdraw approval and at the least should demonstrate the need for a hearing on the topic, said Phibro. The studies done were able to extract and analyze the carbadox residue left in tissue at a deeper level than had been previously considered.
“During these studies, no carcinogenic carbadox-derived residues were detected in meat from animals treated as directed with carbadox,” the company said. “Scientists were able to extract 100% of the residues present at the end of the 42-day FDA approved withdrawal period and determined there are no harmful residues present.”
The metabolite that does remain at the end of the 42-period is tissue-bound QCA, which is a non-carcinogenic offshoot of the drug, it said.
Additionally, the data and papers that the FDA used to call question to the drug residue do not demonstrate that it is unsafe and in some instances there were issues with those reports, said Phibro.
“FDA relies on the 2009 Boison, et al. paper to support its assertion that questions have been raised about whether QCA is an appropriate marker for carbadox and desoxycarbadox,” said the company. “An examination of that paper, however, reveals that there were several methodological flaws in Boison, et al.’s study and that FDA has incorrectly interpreted the study.”
Vet survey
In series of telephone surveys conducted from 19 to 27 May, a selection of US veterinarians were asked about use of the drug, according to Phibro. Some of those asked were against the removal of the in-feed medication from the market, the company said. Loss of the product as a treatment option could lead to increased rates of salmonella, swine dysentery and E.coli.
The withdrawal also could cost the US swine industry up to $200m during the first year of its removal, the company reported. And producers could see revenue loss from slower average daily gain in sick pigs and increased animal mortality.