FDA outlines how to gauge risk that animal drugs will spawn superbugs

Editor's note: This story was updated from its original form to include additional details about the FDA guidelines and comments from a pharmaceutical industry representative.

Oct 27, 2003 (CIDRAP News) – The Food and Drug Administration (FDA) has released a guide to help the drug industry assess the risk that antimicrobial drugs intended for use in food animals will spawn resistant bacteria that could ultimately harm human health.

The 35-page guidance document provides the first outline of "a comprehensive evidence-based approach to preventing the antimicrobial resistance that may result from the use of antimicrobial drugs in animals," the FDA said in releasing the guidelines Oct 24.

Drug manufacturers will not be required to use the risk-assessment process in applying for FDA approval of new drugs, the agency said. But the document will help manufacturers understand how the FDA determines whether a product can be used safely and effectively, officials said.

The document outlines a scientific process for evaluating the risk that an antimicrobial drug for animals will cause a resistance problem in humans who consume meat or other products from the animal, the agency said. The document was first published as a draft in September 2002 and has since been revised.

The recommended risk-assessment process has three parts:

  • Part 1, the "release assessment," addresses the risk that use of a drug will spawn resistant bacteria in animals.
  • Part 2, the "exposure estimate," deals with the likelihood that humans would ingest the resistant bacteria.
  • Part 3, the "consequence assessment," focuses on the chance that human exposure to the resistant bacteria would result in harm.

If the assessment showed that a drug posed significant risks, the FDA could either refuse to license it or limit its use so as to prevent the risk to human health, the agency said.

FDA Commissioner Mark B. McClellan, MD, PhD, commented, "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."

The process can be used to assess risks associated with growth-promoting, or "subtherapeutic," uses of animal drugs as well as those associated with use of drugs to treat infectious diseases, the FDA said.

An official of the Animal Health Institute, a Washington, DC, lobbying group for companies that make animal drugs, hailed the FDA document as a positive step. "I think what's important is the fact they've finally come up with something after 5 years of unpredictability," Ron Phillips, the group's vice president for legislative and public affairs, told CIDRAP News. "I think the public should find it reassuring."

Phillips said the industry has been using the FDA's draft guidance in assessing both new and existing drugs since that document was released in 2002. He said some groups are complaining that the final FDA guidance doesn't set a timeline for risk assessments regarding existing drugs; he asserted that the industry is "well into doing that already."

In revising the guidelines, the FDA made significant changes in its ranking of antimicrobial drugs by their importance to human health, according to Phillips. "There is more of an emphasis, in ranking antibiotics, on those that are used to treat foodborne illness. And that's a very justified, science-based change," he said. He added that in the revision, the FDA addressed some of the industry's concerns but not others.

According to the FDA document, the most important of five criteria the agency used to rank antimicrobials is their effectiveness in combating enteric pathogens that cause foodborne disease; the second criterion is whether the drug is the sole therapy or one of just a few options for treating a serious disease. Antimicrobials listed as "critically important" include the fluoroquinolones, such as ciprofloxacin and levofloxacin; third-generation cephalosporins, such as ceftriaxone; and macrolides, such as erythromycin and clarithromycin.

See also:

American Veterinary Medical Association information on judicious use of antimicrobials
http://www.avma.org/issues/policy/jtua.asp

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