dextromethorphan | Horse Racing Free Tips

Letter to the Editor: Detection of Banned Drugs in Horses

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?

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

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Del Mar Stewards: Baffert Fined $2,500, Brinkerhoff Handed 45-Day Suspension

Hall of Fame trainer Bob Baffert has been fined $2,500 by the Del Mar stewards, reports the Daily Racing Form, over Merneith's positive for Dextromethorphan in her second-place finish in the fourth race on July 25.

“A number of my staff were sick with COVID this summer, including Merneith's groom,” Baffert told the Paulick Report after the positive result was made public. “I learned he had been taking over-the-counter cough syrups that contained Dextrorphan. This has been an issue in other states where contamination has lead to positive tests. That's what happened here. This is clearly another case of contamination. Ultimately, this is my responsibility. It's really embarrassing for the barn, but that's what happened. #2020 sucks.”

Del Mar stewards also took action against veteran trainer Val Brinkerhoff, suspending him for 45 days and issuing a $3,000 fine over Girl Can Partie returning a positive for Metaproterenol after winning the seventh race on Aug. 1, 2019. Sunday's ruling stated that the penalty was inclusive of a syringe found in Brinkerhoff's truck, which the trainer told DRF was a precaution for colic while shipping a horse to Emerald Downs, also in August of 2019.

‘Clearly Another Case Of Contamination’: CHRB Complaint Reveals Dextorphan Positive In Baffert Trainee

The California Horse Racing Board (CHRB) has filed a complaint against Baffert after his trainee Merneith tested positive for dextorphan this summer. Merneith, who earlier this year was third in the Grade 2 Santa Anita Oaks, received the positive test post-race after she finished second in the fourth race on Del Mar's July 25 card. Baffert trains the daughter of American Pharoah for HRH Prince Sultan Bin Mishal Al Saud.

A split sample confirmed the original violation, according to the Sept. 17 CHRB complaint.

Baffert said the finding was a result of environmental contamination.

“A number of my staff were sick with COVID this summer, including Merneith's groom,” Baffert said via email. “I learned he had been taking over-the-counter cough syrups that contained Dextrorphan. This has been an issue in other states where contamination has lead to positive tests. That's what happened here. This is clearly another case of contamination. Ultimately, this is my responsibility. It's really embarrassing for the barn, but that's what happened. #2020 sucks.”

Dextorphan is a metabolite of dextromethorphan, which is a Class 4 drug according to the Association of Racing Commissioners International's classification system. Class 4 drugs are primarily therapeutic drugs which “may influence performance but generally have a more limited ability to do so” as compared to those in other classes. Dextromethorphan is a common ingredient in human cough syrups, though it can also be a drug of abuse, given its capacity to act as an anesthetic in high doses. It has no Food and Drug Administration-approved use in the horse, but regulators have been told it has been used experimentally to quiet nervous behaviors like cribbing.

The metabolism of dextorphan and dextromethorphan were the subject of a study several years ago in Kentucky. The research found that dextromethorphan breaks down quickly in a horse's body, turning it into dextorphan. But unlike some other substances, dextorphan briefly increases in the horse's system as the dextromethorphan breaks down, and then it tapers off more gradually than testing experts had previously realized. The research in Kentucky led to three dextorphan positives being dismissed — not because the commission agreed they were the result of environmental contamination, but rather because it was unclear when the horses had been exposed to dextromethorphan, given the study results about the drug metabolism.

Dextorphan carries a penalty category of B, which has variable suspension lengths depending upon the number of previous violations within a 365-day period.

News of the dextorphan positive comes hard on the heels of an acknowledgement by Baffert that Gamine tested positive for betamethasone following her third-place effort in the G1 Kentucky Oaks this year. Split sample testing in that case has not yet been completed, but Baffert's attorney maintains the drug was administered in the recommended timeframe outlined by Kentucky's rules. Gamine and Charlatan also tested positive for lidocaine following races at Oaklawn this spring, which Baffert attributed to environmental contamination from an employee's over-the-counter pain patch. He told media he planned to appeal those rulings by Arkansas stewards.

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