Letter to the Editor: Detection of Banned Drugs in Horses

Sarah Andrew

As a Clinical Pharmacologist (human) and an avid horse player, I have grown tired of these instances of biologic samples from horses having banned substances found and the “interesting” explanations as to how the exposure happened. One recent example was a story of a horse in which three samples of blood had metformin (a drug used to treat type II diabetes in humans) detected. The explanation was that a groom and later the trainer was taking metformin and “touched the horse's face.”

This explanation is questionable from a clinical pharmacology standpoint. Metformin for human use is a film coated tablet (coated with a polymer). Unless the individual taking the tablet crushes or chews it (and puts a finger in the mouth), handling the film coated tablet does not transfer metformin to the hands. Additionally, published data shows that the amount of metformin absorbed from an oral dose in a horse ranges from 3.9-7.1% (fed vs fasted state) which is minuscule. Finally, the suggested dose of metformin in horses for approved use is 15 mg/kg (7.5 grams in a 500 kg horse) versus a usual 500 mg dose in a human. Thus, horse exposure from a human dose (by rubbing the face) or even putting a finger/hand in the horse's mouth would be quite a stretch of science.

This story is not the only one that TDN readers have seen over time. We have been subjected to stories of a horse with detectable betamethasone in his blood supposedly not from an intraarticular injection but due to use of a topical product, a horse with dextromethorphan in the blood due to a groom using a cough syrup and urinating in the stall and many other stories. These explanations stretch the science of clinical pharmacology to unreasonable levels.

I'd like to offer my human-based clinical pharmacology expertise to HISA/HIWU to “solve” these human-based inaccurate explanations in terms of horse exposures to banned drugs, gratis.

Horse racing is a great sport with a long tradition. Unfortunately, stories of horses having banned substances (no matter how low the exposure) is a negative for a sport where interest at least in the USA is declining and groups like PETA show up to protest at large racing venues putting more negative attention to the sport. But, worst of all, use of banned substances is bad for the horses and aren't the horses our primary interest/concern?

Joseph S. Bertino Jr., PharmD, FCP, FCCP
Guilderland, New York

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