By Ransdell Pierson and Charles Abbott
Dec 11 (Reuters) - In a bid to stem a surge in human resistance to certain antibiotics, U.S. regulators announced new guidelines to phase out their use as a growth enhancer in livestock.
The Food and Drug Administration said the antibiotics could still be used to treat illnesses in animals raised for meat, but should otherwise be pared back over the next three years under a voluntary program to keep them out of the human food supply.
Although voluntary, the agency said it expects drugmakers to fully adhere to the new guidelines and on Wednesday announced that two of these biggest purveyors of those antibiotics had already agreed to narrow their use.
Doctors and hospitals have become increasingly worried in recent years by new strains of bacteria that cannot be controlled by a wide range of current antibiotics. Part of the suspected reason for the emergence of these "superbugs" is that people who have eaten meat that contained antibiotics develop resistance to the drugs as bacteria mutate to thwart them.
"Because antimicrobial drug use in both humans and animals can contribute to the development of antimicrobial resistance, it is important to use these drugs only when medically necessary," the FDA said in a release.
In guidance issued on Wednesday, the FDA asked global drugmakers and animal health companies including Eli Lilly & Co and Zoetis to revise labels of medically important antibiotics by removing references to use in animal production.
Once companies remove farm production uses of their antibiotics from drug labels, it would become illegal for those drugs to be used for those purposes, Deputy FDA Commissioner Michael Taylor said in a conference call with journalists. The agency said about 25 animal health companies could be affected by the guidelines, especially Lilly and Zoetis.
Although the program is meant to be voluntary, Taylor said the FDA would be able to take regulatory action against companies that fail to comply.
The FDA's "final guidance," also brings the drugs under oversight of veterinarians by changing the over-the-counter status of the products.
The FDA said it will require animal pharmaceutical companies to notify the agency within three months of their intent to adopt its strategy. The companies would then have three years to complete the transition process.
Critics on Wednesday said the guidelines give drugmakers too much discretion in policing their own use of antibiotics.
Democratic lawmaker Louise Slaughter called the FDA move an inadequate response to the overuse of antibiotics "with no mechanism for enforcement and no metric for success."
Her view was echoed by consumer and environmental advocacy groups.
"Our fear ... is that there will be no reduction in antibiotic use as companies will either ignore the plan altogether or simply switch from using antibiotics for routine growth promotion to using the same antibiotics for routine disease prevention," said Steven Roach, senior analyst with advocacy group Keep Antibiotics Working.
Morningstar analyst David Krempa said the FDA issued similar voluntary guidelines in April 2012, meant to limit use of important antibiotics in food-producing animals, but they appear to have been largely ignored by farmers.
He said compliance with the FDA's latest set of voluntary guidelines could be equally spotty.
"Compliance will be tough because all the farmers and meat producers know these products increase the size of their animals," Krempa said. "They can continue to use them, and just say there's a disease going through their herds."
But even if antibiotics use in livestock indeed comes down, Krempa said it would be only a "small negative" for Zoetis because it, like other animal health companies, sells such a wide range of products for both livestock and pets.
The FDA said it had already received support for the new measures from Zoetis and Elanco, a unit of Eli Lilly, which sell a large percentage of the products that will eventually be phased out.
Elanco said in a statement that it would voluntarily narrow use of antibiotics used to treat both humans and animals "only to therapeutic purposes of treating, controlling and preventing diseases in animals under the supervision of a veterinarian."
Other companies with animal health businesses include Merck & Co, Novartis AG, Sanofi and Bayer AG.
Bayer and Sanofi said the FDA strategy would not affect the types of products they sell, but both companies said they support the FDA's position.
"It is important that these medically important antibiotics are used responsibly and with veterinary oversight," a Bayer spokeswoman said.