Most racehorse drug violations in Louisiana study involved therapeutic medications

"The risk of a therapeutic medication overage can be substantially reduced if the substances are administered at recommended doses."
Image by Jan-martijn Verlaan

A study of medication violations at four major Louisiana racetracks over five years found that the most common breaches involved concentrations of permitted therapeutic drugs that exceeded thresholds established by racing authorities.

Pamela Waller and her fellow researchers in the Louisiana State University study noted that the number of research papers examining the most common drug violations in racehorses is limited.

Their study, reported in the Veterinary Medicine and Science journal, covered the period between 2016 and 2020.

During this five-year period, 27,237 blood samples and 25,672 urine samples collected during the course of normal race-meeting activities at the four tracks were initially screened using liquid chromatography mass spectrometry. Following this, suspect samples were subject to further analysis.

The total number of violations reported was 534, representing 1.01% of the total number of specimens analysed. The total number of violations reported in Thoroughbreds was 210, while the total number of violations in Quarter Horses was 324.

The percentage of total violations was 0.59% for Thoroughbreds specimens and 1.9% for all the Quarter Horse specimens during the five-year study window.

The most frequent violations included concentrations of permitted medications equal to or exceeding regulatory thresholds for clenbuterol (165 violations), non-steroidal anti-inflammatory drugs (NSAIDs) such as phenylbutazone (73 violations), a combination of phenylbutazone with flunixin (45 violations) and the muscle relaxant methocarbamol (40 violations).

Association of Racing Commissioners International (ARCI) Class 4 drugs were the most common violations identified in the study, at 256. This was followed by ARCI Class 3 (215 violations), Class 2 (36 violations), Class 1 (17 violations) and then by Class 5 (10 violations) medications.

Class 1 includes stimulant and depressant drugs that have the highest potential to affect performance and that have no generally accepted medical use racehorses. Class 2 includes drugs that have a high potential to affect performance. These drugs are not generally accepted as therapeutic agents in racehorses. Drugs in this class include psychotropic drugs, certain nervous system and cardiovascular system stimulants, depressants and neuromuscular blocking agents. Injectable local anesthetics are included in this class because of their potential for abuse as nerve blocking agents.

Class 3 includes drugs that may or may not have generally accepted medical use in racehorses. Drugs in this class include bronchodilators, anabolic steroids and other drugs with primary effects on the autonomic nervous system, procaine, anti-histamines with sedative properties and high-ceiling diuretics.

Class 4 includes therapeutic medications that have less potential to affect performance than those in Class 3. These include less potent diuretics, corticosteroids, NSAIDs, anti-histamines, skeletal muscle relaxants without prominent central nervous system effects, expectorants and mucolytics, haemostatics, cardiac glycosides and anti-arrhythmics, topical anaesthetics, anti-diarrheals and mild analgesics.

Class 5 includes therapeutic medications that have localized actions only, such as anti-ulcer drugs, and certain anti-allergic drugs.

The study team characterized the total number of violations as relatively low during the study window, but noted the wide varieties of medications with different pharmacological actions that were found in the horses.

They noted that 28 medications are currently approved for use in performance horses with established thresholds and/or withdrawal guidelines by ARCI. Additionally, there are 11 permitted medications with established thresholds with no withdrawal guidelines for endogenous (arising internally), dietary or environmental substances.

All other drugs that are not regulated by ARCI with appropriate thresholds have a zero-tolerance rule.

“Since the majority of the medication violations were for permitted medications with established threshold and/or withdrawal guidelines, it is extremely important that the racetrack veterinarians and horse trainers are familiar with changes to the ARCI rules and regulations when it comes to using medications in racehorses,” the researchers said.

“The risk of a therapeutic medication overage can be substantially reduced if the substances are administered at recommended doses.

“Conversely, large dose, long half-life substances or formulations structured for prolonged pharmacological effect are at dramatically greater risk of producing an inadvertent therapeutic medication overage.

“Given these circumstances, the optimal strategy is to select medications and administration routes resulting in the shortest detection times possible, and to make statistically appropriate allowance for the major unknown in this process, namely, horse-to-horse biological variability.”

The authors said it is also important that racetrack veterinarians and trainers strictly follow the ARCI Controlled Therapeutic Medication Schedule for Horses in terms of dosing, route of administration, dosing intervals and duration of treatment, and drug formulations in order to avoid medication violations.

“Additionally, the racetrack veterinarians and trainers should also be familiar with rules and regulations established by a Racing Commission in a particular state to avoid any medication violations.”

The study team comprised Waller, Izabela Lomnicka, Cam Lucas, Sara Johnson and Levent Dirikolu.

The medication violations in racehorses at Louisiana racetracks from 2016 to 2020. Pamela Waller, Izabela Lomnicka, Cam Lucas, Sara Johnson, Levent Dirikolu. Veterinary Medicine and Science, 06 January 2022,

The study, published under a Creative Commons License, can be read here.

Latest research and information from the horse world.

Leave a Reply

Your email address will not be published.