Characterization of antimicrobial prescription frequency and diversity in a large animal veterinary medical teaching hospital.

Antimicrobials are commonly used in veterinary medicine for therapeutic and prophylactic purposes, but little is known about the frequency with which they are prescribed or the quantity administered, especially in large animals. Furthermore, there are no standardized metrics for characterizing antimicrobial use, which can lead to confusion when comparing antimicrobial use among different units (institution, clinical service, clinician). Because there is no gold standard metric, the most comprehensive characterization of antimicrobial use will be achieved using a variety of metrics. The goal of this study was to characterize antimicrobial use from 2013 to 2018 at a tertiary care teaching hospital for large animals using different metrics, including novel ones. We found that at least one antimicrobial was prescribed in 42% of visits and that antimicrobials were prescribed at a rate of 919 animal-defined daily doses (ADDs) per 1000 animal days. A median of 3.6 ADDs and a mean of 2 different classes of antimicrobial were prescribed per patient, and penicillin was the most commonly used antimicrobial. The prescription diversity, a metric accounting for richness and evenness (similarity of frequencies) of different types of antimicrobials, was 0.82, with 1.0 representing maximal richness and diversity. Antimicrobial use differed significantly by species and by organ system affected for all metrics, though in general antimicrobials were prescribed most frequently and with the largest amounts in animals presenting with integumentary or respiratory signs. Many of our findings were consistent with those of other studies examining antimicrobial use in the species represented in our patient population, but more research is needed to determine how to best characterize antimicrobial use and assess appropriateness of prescribing.