The move is part of the US Food and Drug Administration’s (FDA) ongoing work on its five-year plan addressing antimicrobial stewardship in veterinary settings. The focus of the stewardship project is the inclusion period of antimicrobial drugs in livestock feed, when the products are medically important for humans.
“These research projects will generate publicly available data, which can be used by sponsors of affected approved animal drug applications to update product dosage regimens and better target when and for how long a drug may be used,” the FDA said.
“Defining more targeted durations of use supports the FDA's ongoing efforts to slow the development of antimicrobial resistance by fostering the judicious use of medically important antimicrobial drugs in animals,” the agency added.
Why study duration of antibiotic use in feed?
In 2017, following the start of Guidance for Industry 213, medically important antimicrobials provided to livestock in feed or water had to be gained from a veterinarian, according to information from the FDA. However, a set of those antimicrobials provided in feed did not have an established length of use.
No medically important antimicrobials approved for use in water lacked a defined use period, the agency said.
Currently, there are about 11 individual products and more than 30 pioneer combinations of medicated feed where the duration of use needs to be defined, according to information from the FDA. There also are several generic combinations of medicated feed to be addressed.
In April, FDA announced that it was collecting project proposals to help “target and define” the duration of use for a group of medically important antimicrobials that were approved use in livestock feed. Up to $1.5m in funding was available for the fiscal year 2019 research projects.
The updating process presents a “significant scientific and technical challenge,” the agency said. “Changes to the use conditions of these products will be based on science and available evidence,” it added.
"The new animal drug applications with undefined regimens on product labeling were originally approved long ago, and the information used to support approval did not establish a specifically defined duration of use or minimum duration of use when effectiveness was evaluated," the FDA said. "Substantial evidence of effectiveness means evidence consisting of one or more adequate and well-controlled studies demonstrating that the new animal drug is effective under the conditions of use stated in the approved labeling. For therapeutic indications, this evidence should be established at the lowest approved dose level."
The goal is to have a draft strategy in place by September 2020, which provides a way to “establish defined durations of use,” the agency said. Adding, “We expect this draft guidance will outline a proposed process, including time periods, sponsors can follow to revise the approved conditions of use accordingly.”
Public comment is set to be collected on the draft strategy or guidance document before it is completed and implemented, the agency said.
Highlights from projects selected
The projects selected were each awarded $250,000 for the fiscal year 2019, the FDA said. Depending on funding and progress the projects could be eligible for an additional $250,000 to extend the research into the fiscal year 2020.
“In addition, FDA continues to explore options for expanding the availability of relevant data to address this issue, including the possibility of providing another funding opportunity for research proposals,” the agency said.
Both research studies were designed by researchers with Kansas State University, reported the FDA.
The first project seeks to address targeted durations of use for tylosin phosphate when the drug is issued for feedlot cattle to prevent liver abscesses, the agency said.
The second study is focused on examining the timing and duration of use for chlortetracycline with adult cattle, the agency said. In the study, the medication would be used to address bovine anaplasmosis.