FDA Guidance on Defining Drug Use Durations for Medically Important Antimicrobials

FDA CVM Veterinary Medicine Updates

Published February 12th, 2026

Detected March 12th, 2026

Summary

The FDA has finalized guidance (GFI #273) recommending how animal drug sponsors can voluntarily establish defined durations of use for medically important antimicrobial drugs administered in feed to food-producing animals. Over 100 drugs are affected, and sponsors are expected to submit revised labeling within approximately three years.

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What changed

The FDA has finalized Guidance for Industry (GFI) #273, which provides recommendations for animal drug sponsors to voluntarily establish defined durations of use for certain medically important antimicrobial drugs administered in feed to food-producing animals. This guidance applies to over 100 affected drugs where labeling currently lacks specified administration durations, a situation often stemming from approvals decades ago when antimicrobial resistance was not a primary public health concern. By revising conditions of use to specify how long these drugs may be administered, the FDA aims to ensure their continued effectiveness while minimizing the development of resistance.

Animal drug sponsors with affected products are advised to submit the necessary applications for revised labeling within approximately three years from the guidance's publication date. This action supports the FDA's broader efforts to promote the judicious use of medically important antimicrobials in animals and protect public health. Failure to update labeling may hinder compliance with evolving antimicrobial stewardship expectations and could impact the long-term availability and efficacy of these critical drugs.

What to do next

Review GFI #273 for applicability to approved medically important antimicrobial drugs administered in feed.
Develop a plan to establish defined durations of use for affected products.
Submit necessary applications for revised labeling within the recommended three-year timeframe.

Source document (simplified)

February 12, 2026

Today, the U.S. Food and Drug Administration finalized Guidance for Industry (GFI) #273: Defining Durations of Use for Approved Medically Important Antimicrobial Drugs Fed to Food-Producing Animals. The guidance provides recommendations for how animal drug sponsors may voluntarily establish defined durations of use for certain antimicrobial drugs that are important in human medicine (medically important antimicrobial animal drugs) and have one or more indications that currently lack a defined duration of use.

GFI #273 applies only to medically important antimicrobials given in or on the feed of food-producing animals. The FDA has identified more than 100 affected drugs: List of Approved Medically Important Antimicrobial Drugs Administered in the Feed of Food-Producing Animals that Lack a Defined Duration of Use. All other dosage forms of these drugs (injectable, intramammary, tablet, etc.) already have established durations of use.

When animal drugs do not have a defined duration of use, it means the labeling on the products does not specify how long the products may be administered for an approved use. Many of the antimicrobial drugs affected by this GFI were approved decades ago. At that time, sponsors were not required to determine how long a product may be administered because antimicrobial resistance was not yet a pressing public health concern.

Revising conditions of use to specify when and for how long a drug may be used helps ensure products will remain effective while minimizing food-producing animals’ exposure to antimicrobial drugs.

The FDA anticipates that sponsors of affected products should be able to have revised labeling approved that incorporates the changes discussed in this guidance within approximately three years from the publication date of this final guidance. To achieve this goal, sponsors should submit the various types of submissions for their affected applications in a timely manner as outlined in the guidance.

The efforts to establish durations of use support the FDA's ongoing work to promote judicious use of medically important antimicrobials in animals and protect public health. For more information about the agency’s progress toward defining duration of use, see: FDA Track: Progress on FDA’s Support of Antimicrobial Stewardship in Veterinary Settings.