Position on the Judicious Use of Antimicrobials

Antimicrobial agents are necessary to manage infectious diseases in horses, but adverse effects of antimicrobial agents and emergence of multi drug-resistant bacteria require their use to be based on the best evidence and guidelines. Selecting the proper antimicrobial agent and dosage regimen is essential to achieving a successful outcome and minimizing the emergence of resistance. The AAEP recognizes the importance of responsible antimicrobial agents in equine medicine. Additionally, the AAEP realizes that there are some conditions that are self-limiting and will resolve without antimicrobial agents.

To minimize risks and promote effective treatment, the following are general guidelines for the prudent use of antimicrobial agents in horses.

1. To align with an equine practitioner’s professional responsibilities, the equine veterinarian’s primary goal should be to provide clients with the best information and care regarding the prevention and treatment of infections in horses.
2. Antimicrobial agents should be used only within the confines of a valid veterinarian-client-patient relationship; this includes both dispensing and prescriptions.
3. Equine practitioners should:
   a. Participate in continuing education programs that include topics on antimicrobial therapy and emerging and/or development of antimicrobial resistance.
   b. Determine when antimicrobial agents are indicated through laboratory assessment, clinical experience, physical examination, and relevant history.
   c. Avoid use of antimicrobial agents in conditions due to transient, uncomplicated viral infections and inflammatory conditions due to non-bacterial causes including parasites, fungi, immune-mediated processes, and neoplasia.
   d. Avoid or limit the duration of antimicrobial agent use in short, clean, surgical procedures that are completed without complications.
   e. Consider clinical evidence of the identification of the pathogen(s) associated with the disease. Culture and susceptibility testing should be performed when the identity of the organism or the antimicrobial agent susceptibility pattern is unknown.
   f. Submit samples for culture and susceptibility testing to laboratories that follow the standards of the Clinical and Laboratory Standards Institute (CLSI.org). Performing these tests in your practice without the ability to apply these standard methods is not recommended.
   g. Select antimicrobial agents that are appropriate for the target organism and administered at a dosage and route that are likely to achieve therapeutic target concentrations for the pathogen
   h. Antimicrobial agent choices and use regiments should be based on available consensus guidelines, current publications and handbooks, and package insert information. Consider the pharmacokinetic and pharmacodynamic properties of the antimicrobial agent. Consult with a veterinary diagnostic microbiologist, an infectious disease expert, or a veterinary clinical pharmacologist if needed.
   i. Utilize antimicrobial agents at an appropriate dosage for the condition.
   j. Treatment duration should be as short a period of time as reasonable. It is not always necessary to “complete the course” if there is clinical evidence that the infection has resolved.
   k. Whenever possible, prescribe antimicrobial agents that are approved by the regulatory authorities (FDA in the United States) for horses. However, there are many situations in which an approved antimicrobial agent is not active against the bacteria causing infection, or the formulation may not be suitable for the use intended. In these instances, it is acceptable to prescribe extra label medications within the context of the regulations of the Animal Medicinal Drug Use Clarification Act of 1994 (AMDUCA; https://www.fda.gov/animal-veterinary/guidance-regulations/animal-medicinal-drug-use-clarification-act-1994-amduca).
   l. Antimicrobial agents compounded from bulk-chemical substances (API) should be avoided. Compounding in these instances may be considered when there is a lack of availability of an important antimicrobial agent because of shortages or short-term backorder by the drug sponsor, or to prepare a unique formulation on a case-by-case basis. Compounding from bulk chemical substances should never be considered if the sole purpose is to reduce the cost of the antimicrobial agent compared to the commercial (FDA-approved) formulation. The regulations and restrictions for compounding drugs for animal can be found on the FDA resources page (http://www.fda.gov/animal-veterinary/unapproved-animal-drugs/animal-drug-compounding), and in compliance with the FDA Guidance for Industry (GFI #256; https://www.fda.gov/regulatory-information/search-fda-guidance-documents/cvm-gfi-256-compounding-animal-drugs-bulk-drug-substances.
   m. Preserve product integrity with proper handling, storage instructions, and observation of the expiration date.
   n. Antimicrobial agents prescribed for use on-the-farm or stable use should be properly labeled with directions for use and cautionary statements.
   o. Follow appropriate disposal recommendations; do not discard antimicrobial agents in the water supply, landfill, or sewage systems.
   p. When appropriate and feasible for the infection, local therapy (topical, infusions, regional limb perfusions, local implants) are an acceptable alternative to systemic therapy.
   q. Consider use of effective and practical non-antimicrobial treatment alternatives when appropriate and available (excellent wound hygiene, antiseptic wound dressings, biologic therapies, etc.)
   r. Prescribed or dispensed drug quantities should be limited such that stockpiling of antimicrobial agents on the farm is avoided.

Lastly, the AAEP endorses a “One Health” approach with the realization that bacteria can be transmitted from people to horses, horses to horses, horses to people, and to the environment.

Approved by the AAEP board of directors in 2025.