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U.S. Department of Health and Human Services

Animal & Veterinary

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FDA Prohibits Use of Human Anti-Viral Drugs in Poultry

FDA Veterinarian Newsletter November/December 2005 Volume XX, No VI

The Food and Drug Administration (FDA) has issued an order that prohibits the extralabel use in poultry of two classes of approved human anti-influenza drugs to help preserve the effectiveness of these drugs for treating or preventing influenza infections in humans.

The order prohibits the extralabel use of anti-influenza adamantane (amantadine and rimantadine) and neuraminidase inhibitor (oseltamivir and zanamivir) drugs in chickens, turkeys, and ducks.

Extralabel use refers to the use of a human or animal drug that is beyond the scope of the approved labeling.

FDA has not approved any veterinary drugs for the treatment or prevention of influenza A in animals. However, two classes of antiviral drugs are approved in the United States for the treatment or prevention of influenza A in humans. Under the Animal Medicinal Drug Use Clarification Act of 1994 (AMDUCA) veterinarians can legally prescribe extralabel uses of human and animal drugs in animals.

AMDUCA also gives FDA the authority to issue an order prohibiting certain extralabel uses in animals if such use presents a risk to public health. Concerns have been raised by a number of public health organizations, such as the World Health Organization, Food and Agriculture Organization, and the World Organisation for Animal Health, that the extralabel use of these human antiviral drugs in poultry could lead to the emergence of resistant strains of type A influenza. Avian influenza, including the H5N1 subtype, that has been identified in other countries is a type A influenza. Extralabel use of human antivirals in poultry could become a concern if highly pathogenic avian influenza emerged in the United States.

FDA has considered all available information and has concluded that the extralabel use of anti-influenza adamantane and neuraminidase inhibitor drugs in chickens, turkeys, and ducks presents a risk to public health. FDA may add other animal species to the prohibited list as new data become available.

When FDA issued the “Order of Prohibition,” the Agency had not received any reports of extralabel use of these antiviral drugs in the United States by poultry producers.

The Order of Prohibition was issued as a final rule, as called for under AMDUCA, and scheduled to take effect June 20, 2006. Even though the order was issued as a final rule, interested parties may submit comments on this final rule by May 22, 2006. Comments may be submitted electronically through the Federal eRulemaking Portal: http://www.regulations.gov or to the Agency Web site: www.fda.gov/dockets/ecomments. Written comments may be faxed to 301-827-6870, or delivered by mail or hand to: Division of Dockets Management (HFA-305), Food and Drug Administration, 5630 Fishers Lane, Room 1061, Rockville, MD 20852. All comments must be identified by Docket No: 2006N-0106.

Background

Influenza viruses mutate frequently. Some mutations confer drug resistance to influenza viruses. Repeated and improper use of anti-influenza drugs could allow resistant influenza viruses to flourish. FDA is concerned with the ease in which influenza A viruses, which includes H5N1 avian influenza viruses, can become resistant to anti-influenza drugs after exposure. If influenza A viruses, which can infect humans, became resistant to the drugs currently available to treat them, the result would be a clear threat to human health.

In remarks prepared for a March 30 hearing of the House Agriculture subcommittee, Dr. Bruce Gellin, Director of the National Vaccine Program Office of the U.S. Department of Health and Human Services (the parent organization of FDA), described pandemic flu and explained why it was worse than more common types of flu.

Every year, Dr. Gellin explained, “seasonal flu” comes to the United States, infecting 5-20 percent of the U.S. population. The current strain of avian flu, H5N1, is highly contagious and lethal in chickens. In addition, it has been able to infect humans. However, the virus causing the current avian flu is not easily transmitted to humans, either from chickens or from an infected person to a healthy person.

“A pandemic flu is a new influenza virus strain for which humans have little or no immunity, and for which there is no available vaccine. The disease spreads easily person-to-person, causes serious illness, and can sweep across the country and around the globe in very short time,” Dr. Gellin said.

He told the members of Congress at the hearing that “the medical and epidemiological community across the globe has studied structural changes in flu viruses and produced models based on historical pandemics that foreshadow an increasing science-based probability of a pandemic in the near future.”

Information about the pandemic flu may be found at: http://www.pandemicflu.gov.