In the racing industry, medication use has changed significantly through the years as manufacturers develop new drugs and scientists hone the techniques they use to analyze and identify therapeutic medications, environmental contaminants, and prohibited drug substances. Despite continual changes, medication rules still serve three main purposes to: assure a fair and level playing field; protect the safety and welfare of the horse; and protect the betting public.

Experts discussed the topic during the 2020 American Association of Equine Practitioners’ Convention, held virtually.

“The purpose of equine drug testing is to establish and provide industry integrity for the sport,” said Scott Stanley, PhD, a professor at the University of Kentucky Gluck Equine Research Center with more than 30 years of regulatory drug testing experience. “The perception of integrity is vital for anyone who wants to wager or compete in these particular events.”

Medication regulations are designed to eliminate the use of performance-enhancing drugs while setting appropriate guidelines for the use of legal, therapeutic drugs. Research has resulted in threshold and withdrawal guidelines for the administration of different drugs and, more recently, stand-down or restricted administration times.

“The reason that (equine anti-doping programs are) sophisticated is because many of these drugs are incredibly difficult to detect, and the capabilities of the analytical tools, the software, and the laboratories has substantially increased,” Stanley said.

NSAIDs

Heather Knych, DVM, PhD, Dipl. ACVCP, a professor at the University of California, Davis, School of Veterinary Medicine in the K.L. Maddy Equine Analytical Pharmacology Laboratory, says the most-commonly used medications in the racing industry today are non-steroidal anti-inflammatory drugs (NSAIDs), corticosteroids, and furosemide. Another less commonly used class of drugs are bisphosphonates.

“(NSAIDs are) certainly they a mainstay of treatment in horses with musculoskeletal pain and inflammation,” Knych said, identifying phenylbutazone (Bute), flunixin meglumine (Banamine), and ketoprofen (Ketofen) as the three most common NSAIDs used in racehorses.

Racing regulators have historically permitted NSAID use within 24 hours of race time, though in recent years there have been recommendations to increase that timeframe to no earlier than 48 hours. Some racing jurisdictions are also restricting the “stacking” of NSAIDs, a practice in which two NSAIDs are given in close proximity to each other, generally 48 and 24 hours prior to a race.

Corticosteroids

Corticosteroids are commonly administered as joint injections. Equine veterinarians use several types, and they vary in duration of anti-inflammatory effects. Recent research has found that blood concentrations are not necessarily indicative of corticosteroid concentrations in the joint, especially when vets use long-acting formulations. Further, administration route can influence detection times in the blood, said Knych, with some corticosteroids, such as triamcinolone acetonide, detectable in the blood for longer periods of time after intramuscular administration than intra-articular use.

Many racing jurisdictions and industry organizations are now recommending stand-down times of 14 days or more for intra-articular corticosteroid use and prohibiting corticosteroid stacking.

In North America, furosemide (Lasix) is generally permitted up to four hours prior to post time as a preventive treatment for exercise-induced pulmonary hemorrhage, or EIPH. The widespread use of furosemide as a race-day medication continues to raise concerns about its performance-enhancing effects and potential as a masking agent, Knych said.

Recent research has focused on evaluating furosemide’s efficacy up to 24 hours pre-race, while also seeking to find alternative management strategies for EIPH.

Bisphosphonates

Bisphosphonates such as tiludronate disodium (Tildren) and clondronate (Osphos) are labeled for controlling clinical signs associated with navicular syndrome; however, they are also used extralabel for other indications and reportedly have analgesic (pain-relieving) effects, Knych said.

“In horse racing, there have been concerns about administration of bisphosphonates to young horses, as well as concerns regarding administration to horses in race training,” she said. “The effects of bisphosphonates on the skeleton of young, growing horses is unknown. An additional concern is how might bisphosphonates affect the natural healing processes in young horses undergoing training, especially in high-impact disciplines such as horse racing.”

The lack of research surrounding bisphosphonate use in horses under the age of 4 has prompted some racing jurisdictions to prohibit horses that have received bisphosphonate in the previous six months from entering racetrack premises.