Establishing Decision Limits for Therapeutic Drugs Detected in Animals Exhibited at Livestock Shows
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Food animal species, such as cattle, sheep, goats, and pigs, are widely exhibited at stock shows and fairs across the United States. Animals are judged on phenotypical traits such as muscling, structural correctness, and frame-size. The level of competition is high, increasing the potential for illegal or unethical acts to gain a competitive advantage, such as doping. Antidoping regulation in the livestock show industry often involves drug testing. Detection of therapeutic drugs at very low concentrations in approved animal species raises questions about current anti-doping regulations in exhibition animals. Therefore, the purpose of this research was to identify and address data gaps in the current understanding of drug testing and drug disposition, and to integrate those data with published data to propose an approach to standardizing anti-doping policies, particularly those related to therapeutic drug use. To determine which drugs are most commonly identified in drug testing at livestock shows, a review of historical drug test results from a laboratory in Texas from 1999 to 2017 was performed. A total of 32,027 samples were tested during this period, of which 1,674 (5.2%) tested positive. Positive samples included a total of 42 different drugs and metabolites. Flunixin was the second most commonly identified drug. Currently no nonsteroidal anti-inflammatory drugs (NSAIDs) are approved by the Food and Drug Administration (FDA) for small ruminants, but drugs such as flunixin and meloxicam are used in small ruminants. Additionally, urine is the sample of choice when drug testing exhibition animals but there is a gap in the scientific literature describing drug concentrations in urine of small ruminants. Therefore, pharmacokinetic studies were performed describing plasma and urine concentrations of flunixin meglumine and meloxicam in goats. Drug levels in urine reached peak concentrations between 8 and 12 hours after dosing for both drugs. Urine concentrations for both flunixin and meloxicam fell below the limit of detection (LOD) of 0.5 ng/mL and 1 ng/mL, respectively, by 240 hours. Last, observed and published data, PK/PD modeling results, and measurement uncertainty were integrated to propose a method for establishing decision limits for therapeutic drugs detected in urine from animals exhibited at livestock shows.
Mays, Travis Parker (2019). Establishing Decision Limits for Therapeutic Drugs Detected in Animals Exhibited at Livestock Shows. Doctoral dissertation, Texas A&M University. Available electronically from