Judicious Therapeutic Use of Antimicrobials

Comment on this policy

Position Statement

When the decision is reached to use antimicrobials for treatment, control, or prevention of disease, veterinarians should strive to optimize therapeutic efficacy and minimize resistance to antimicrobials to protect public and animal health and well-being.


  • Support development of a scientific knowledge base that provides the basis for judicious therapeutic antimicrobial use.
  • Support educational efforts that promote science-based judicious antimicrobial use.
  • Maintain efficacy of antimicrobials by minimizing potential for development and transmission of resistance.
  • Foster an atmosphere within industry research and development programs and government regulatory bodies that facilitate current and future availability of veterinary antimicrobials.


  • Facilitate development and distribution of guidelines on judicious use of antimicrobials.
  • Improve utilization of scientifically based antimicrobial use practices through education of veterinarians and animal owners.

Recognized Needs for Collaboration

  • Establishment of clinically-validated resistance breakpoints.
  •  Improved risk analysis (assessment, management, and communication) regarding determinants of resistance.
    • Improved data collection on antimicrobial use in veterinary and human medicine to better characterize potential selection pressure.
    • Continued improvement in monitoring systems for antimicrobial resistance patterns from bacterial isolates associated with food animals, foods of animal origin, and human patients.
    • Harmonization of data collection and transparency of interpretation.
  • Research to improve or expand scientifically based therapeutic usage of antimicrobials.

Judicious Use Principles

  • Disease prevention strategies, such as appropriate husbandry and hygiene, routine health monitoring, and vaccination, should be included as part of a comprehensive animal/herd health plan. 
  •  Once disease has occurred, other management and intervention strategies may be considered prior to antimicrobial treatment.
  • Judicious use of all antimicrobials should include appropriate veterinary oversight.
  • Extralabel use of antimicrobials must meet all the requirements of the veterinarian-client-patient relationship as defined in the AMDUCA amendments to the Federal Food, Drug, and Cosmetic Act and its regulations.
    • Extralabel use in food animals necessitates an extralabel withdrawal interval to be assigned by the attending veterinarian, on the basis of information on the species, dose, route, and frequency of treatment, in conjunction with available scientific pharmacokinetic data.
  • Antimicrobials requiring a prescription must be used only by, or under the order of, a licensed veterinarian. This should include a veterinarian-client-patient relationship.
  • A Veterinary Feed Directive must be issued only by a licensed veterinarian in the course of the veterinarian’s professional practice. This should include a veterinarian-client-patient relationship.
  • Accurate records of treatment and outcome should be maintained.
  • Antimicrobials should be used in animals only after careful review.
    • Use narrow-spectrum antimicrobials whenever appropriate.
    • Use microbial culture and antimicrobial susceptibility results to aid in the selection of antimicrobials when clinically relevant.
    • Regimens for antimicrobial treatment, control, or prevention of disease should be based upon current scientific and clinical principles, such as microbiological and pharmacological tenets.
    • Antimicrobial use should be confined to appropriate clinical indications. Inappropriate uses such as for uncomplicated viral infections should be avoided.
    • To minimize selective pressure, therapeutic exposure to antimicrobials should be minimized by treating only for as long as needed for the desired clinical response.
    • Limit therapeutic antimicrobial treatment to ill or at-risk animals, treating the fewest animals indicated.
  • Minimize environmental contamination with antimicrobials whenever possible.


*These terms are defined and utilized in this text as applied to the principles of Judicious Use outlined within this document.

Antibiotic--a chemical substance produced by a microorganism which has the capacity, in dilute solutions, to inhibit the growth of or to kill other microorganisms.

Antimicrobial--an agent that kills microorganisms or suppresses their multiplication or growth.

Breakpoint-- a minimum inhibitory concentration (as determined by the Veterinary Antimicrobial Susceptibility Testing subcommittee of the Clinical and Laboratory Standards Institute) selected to predict clinical outcome for a specific veterinary pathogen, in a specific disease, in a specific species, given a specific regimen (dose, route, duration, and frequency) and used to define bacteria isolated from animals as susceptible, intermediate, or resistant.

Broad Spectrum Antimicrobial--a type of antimicrobial effective against a large number of bacterial genera; generally describes antimicrobials effective against both Gram-positive and Gram-negative bacteria.

Narrow Spectrum Antimicrobial--a type of antimicrobial effective against a limited number of bacterial genera; often applied to an antimicrobial active against specific families or categories of bacteria.

Antimicrobial Resistance--a property of microorganisms that confers the ability to inactivate or elude antimicrobials or a mechanism that blocks the inhibitory or killing effects of antimicrobials.

Extralabel Use--extralabel use describes the use of an approved drug in a manner that is not in accordance with the approved labeling, yet meets the conditions set forth by the AMDUCA FDA regulations. Deviations from FDA-approved labeling include use in another species, use for a different indication, use at a different dose or frequency, and use via a different route of administration.

Monitoring--monitoring includes periodic health surveillance of the population or individual animal examination.

Selection Pressure-- action or play of selection mechanisms (eg,  differential mortality or reproduction rates) determining the relative reproductive performance of genotypes, where selection is the differential and nonrandom survival and reproduction of individuals of different genotypes, resulting in a change in the gene frequency in succeeding generations in a population of a given organism.

Therapeutic--treatment, control, and prevention of disease.

Veterinarian/Client/Patient Relationship (VCPR) --The VCPR is the basis for interaction among veterinarians, their clients, and their patients.  A VCPR means that all of the following are required:

  1.  The veterinarian has assumed the responsibility for making clinical judgments regarding the health of the patient and the client has agreed to follow the veterinarians' instructions.
  2. The veterinarian has sufficient knowledge of the patient to initiate at least a general or preliminary diagnosis of the medical condition of the patient.  This means that the veterinarian is personally acquainted with the keeping and care of  the patient by virtue of a timely examination of the patient by the veterinarian, or medically appropriate and timely visits by the veterinarian to the operation where the patient is managed.
  3. The veterinarian is readily available for follow-up evaluation or has arranged for the following: veterinary emergency coverage, and continuing care and treatment.
  4.  The veterinarian provides oversight of treatment, compliance, and outcome.
  5.  Patient records are maintained.
Veterinary Feed Directive (VFD) Drug--The VFD category of medicated feeds was created by the Animal Drug Availability Act of 1996 to provide an alternative to prescription status for certain therapeutic animal pharmaceuticals for use in feed. Any animal feed bearing or containing a VFD drug shall be fed to animals only by or upon a lawful VFD issued by a licensed veterinarian in the course of the veterinarian's professional practice.

 Relevant AVMA Policy: