Members of the Kentucky Equine Drug Research Council voted Friday to withdraw existing guidance for racetrack practitioners about the use of fluphenazine after officials became aware that the drug can linger in a horse's body much longer than once thought.
Fluphenazine is used as an anti-psychotic drug in humans and a long-term sedative in horses. Under Kentucky's current guidance, it's considered a Class B drug, meaning it's considered to have a potential to influence racehorses' performance, but not as much potential as those drugs in Class A. Fluphenazine is an oil-based drug and is typically given subcutaneously, meaning under the skin.
Current guidance advises veterinarians to withdraw the drug seven days before a race. Dr. Bruce Howard, equine medical director for the Kentucky Horse Racing Commission, said he got a call from a practicing veterinarian a few months ago asking whether that guidance was correct, which prompted him to do a deep dive into the data available about fluphenazine use in horses.
What he discovered was that the seven day withdrawal suggestion on the books in Kentucky had been in place since 2004, before the advent of instrumentation testing for drugs in post-race samples. The ELISA kit method that was being used at that time was considerably less sensitive than current methods.
(Learn more about drug testing methods and why they matter in this 2014 Paulick Report feature.)
Howard found two unpublished studies, each consisting of only three horses, which claimed the drug could persist “for weeks” in the horse, while a conversation with California officials suggested it may even linger in a horse's system “for months.” That's because, in part, it has a very long half life, meaning the amount of time it takes for the total amount of the drug in the body to be reduced by 50%. While the half life for many drugs can be measured in hours, Howard's findings suggest that of fluphenazine could be 6.8 to 9.6 days. It's also possible that after an initial decrease in drug levels, fluphenazine concentrations might paradoxically increase again about 15 days after dosing.
Other racing groups have suggested that the drug be stopped for 45 to 60 days before racing, or possibly even longer.
“It appears to me from this information that the seven day withdrawal is really inadequate,” said Howard. “I don't think there's a credible study to make a withdrawal recommendation at this time.”
Instead, Howard suggests that trainers request a blood test on horses that have previously had fluphenazine before entering a race to verify whether they're under the required threshold in Kentucky. This could prove especially challenging in situations where a horse may have received the drug at the start of the year, gone to sale as a 2-year-old, and returned with an eye toward making a first start in April or May, as new connections may not know whether the drug had been given or not. In those scenarios, Howard said that a record of a treatment could serve as a “mitigating circumstance” for a trainer who had followed the seven-day guidance before the commission rescinded the guideline.
Fortunately, Howard said there have been no fluphenazine violations in Kentucky since 2009 and several veterinary members of the council agreed they don't think it's commonly used anymore for a variety of reasons.
The council agreed unanimously to rescind the seven-day guidance, on the condition Howard send additional warnings to practicing veterinarians about the issue.
The removal of the rule outlining the seven day guidance will now advance to the full Kentucky Horse Racing Commission for a vote before continuing through the legislature for final approval.
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