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U.S. Department of Health and Human Services

Animal & Veterinary

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FDA Issues Guidance on Evaluating the Safety of Antimicrobial New Animal Drugs

FDA Veterinarian Newsletter November/December 2003 Volume XVIII, No 6

FDA has released a new guidance document that for the first time outlines a comprehensive evidence-based approach to preventing antimicrobial resistance that may result from the use of antimicrobial drugs in animals.

Antimicrobial drugs, such as antibiotics, are medicines often used to treat bacterial infections in both humans and animals. Their use has been one of the great advances in modern medicine-helping to prevent many of the leading causes of death for most of human history.

Regardless of why bacteria develop resistance to antimicrobials, when bacteria do develop such resistance, human and animal health is at risk because the medicines that we depend on to treat infections become ineffective. There are several important sources of this problem, including inappropriate use of antibiotics in people, that have been the subject of many public health initiatives by the Department of Health and Human Services and other organizations. The guidance released by FDA is, however, the first that addresses, in a comprehensive manner, the issue of the use of antimicrobials in food-producing animals as a contributing factor to the development of antimicrobial resistance.

The guidance provides a scientific process for assessing the likelihood that an antimicrobial drug used to treat an animal may cause an antimicrobial resistance problem in humans consuming meat or other byproducts from that animal. This process can help prevent antimicrobial drugs with a high risk of causing such problems from being improperly used in food-producing animals, and thereby potentially leading to antimicrobial resistance in humans.

The new guidance encourages drug sponsors to use a risk assessment process to demonstrate that an antimicrobial drug used to treat food-producing animals will not create a risk of antimicrobial resistant bacteria likely to lead to human health problems.

The document, Guidance for Industry #152 ("Evaluating the Safety of Antimicrobial New Animal Drugs with Regard to their Microbiological Effects on Bacteria of Human Health Concern"), is not a regulation. Instead it explains a science-based process drug sponsors may use when they seek approval of an antimicrobial for use in food-producing animals.

Sponsors may still use other methods to establish drug safety for these uses, as long as these methods comply with statutory and regulatory requirements. In general, written guidance helps sponsors understand FDA's process of evaluating whether a proposed product for approval can be used safely and effectively, in this case with respect to risks of creating antimicrobial resistance.

"Resistance to the antimicrobial drugs needed to treat human illnesses is a serious public health threat, and we intend to use the best science-based methods to prevent it," said FDA Commissioner Mark B. McClellan, M.D., Ph.D.

"There are many factors contributing to the development of resistant bacteria. Attacking the problem on all fronts, including the appropriate use of antimicrobial drugs in veterinary medicine, is the best way to protect the health of the public. It's also the best way to promote the safe use of antimicrobials to protect the health of animals, including food-producing animals." Stephen Sundlof, D.V.M., Ph.D., Director of FDA's Center for Veterinary Medicine, added, "This guidance uses science to develop a risk-based approach to the issue of antimicrobial resistance. It permits us to help protect human health while giving veterinarians and livestock producers the tools they need to treat animals."

The pathway suggested in the guidance document establishes a three-part system for determining an antimicrobial drug's potential risk to humans if used to treat food-producing animals. The system's three parts are these:

Part One is the "release assessment," which determines the probability that resistant bacteria will be present in animals as a result of the use of the antimicrobial new drug.

Part Two is the "exposure estimate," which gauges the likelihood that humans would ingest the resistant bacteria.

Part Three is the "consequence assessment," which assesses the chances that human exposure to the resistant bacteria would result in adverse human health consequences. In this context, these are situations in which a physician has difficulty treating a person with an antimicrobial drug because the bacteria infecting the person had acquired resistance to the drug and that resistance came from use of the drug in animals.

Under this system, all of these assessment processes are considered and integrated to determine the overall level of human health risk from resistant bacteria associated with an antimicrobial drug's use in animals.

If the assessments showed that the risks were significant, FDA could deny the application for marketing authorization, thus preventing the use of the drug in food animals, or FDA could approve the drug, but place conditions on its use designed to ensure it would not pose a human health risk.

More information is available online at www.fda.gov/oc/antimicrobial/questions.html.