Kentucky Rescinds Dextrophan Positives: Blood-Horse 2/21/17

By: Frank Angst

Citing new research that suggests the metabolite of Dextromethorphan, Dextrorphan, can stay in a horse’s system at a wider variance of time than previously realized, the Kentucky Horse Racing Commission earlier this year dropped sanctions in three cases where the metabolite was discovered.

KHRC equine medical director Mary Scollay offered a presentation at the regular KHRC meeting Feb. 21 to explain the new research that led to the stewards rescinding sanctions against at least two trainers while reinstating purse winnings for at least two owners. Also, the KHRC’s lab, LGC Science, updated its findings to consider these tests to report them as “passed.”

The trainers who saw sanctions dropped included Mike Maker, trainer of Harlan’s Howling, who initially tested positive following a Jan. 9, 2016 race at Turfway Park; and Michael Ann Ewing, trainer of Covert Gem, who initially tested positive following a Nov. 28, 2015 race at Churchill Downs. The positives initially were called for findings of the metabolite¬†Dextrorphan.

Dextromethorphan is a common ingredient in human cough suppressants and can be administered to horses as a way to address cribbing, Scollay said. She added that the cases were not rescinded because of a determination of environmental contamination.

Dextromethorphan calls for a Class B (second-highest on the scale) penalty on the Association of Racing Commissioners International’s Uniform Classification Guidelines for Foreign Substances and Recommended Penalties Model Rule, which matches Kentucky guidelines.

Following the new research, LGC Science, which conducts testing for the KHRC, determined the horses passed the post-race tests. Scollay said KHRC staff and LGC Science’s Rick Sams in December reviewed the recently published data before rescinding the previous rulings in January.

The research was conducted in 2014 at University of California-Davis by Carley Corado, Daniel McKemie, and Heather Knych. Published in the American Journal of Veterinary Research as, “Dextromethorphan and Debrisoquine Metabolism and Polymorphism of the Gene for Cytochrome P450 Isozime 2D50 in Thoroughbreds,” the research examined concentrations of dextromethorphan and dextrorphan in blood over time following a standard dose.