FDA Finalizes Guidance on Defining Durations of Use for Certain Medically Important Antimicrobial Drugs for Food-Producing Animals

February 12, 2026

FDA Finalizes Guidance on Defining Durations of Use for Approved Medically Important Antimicrobial Drugs Fed to Food-Producing Animals

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.

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