07/22/2014 2:01PM

Drug combination sets off rash of positives

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A rash of positive tests in the Mid-Atlantic region for overages of the muscle relaxer methocarbamol is being traced to the use of the drug in conjunction with the painkiller phenylbutazone, a combination that slows the elimination of methocarbamol from a horse’s system, according to racing officials and chemists.

Methocarbamol, a regulated medication commonly used to treat soreness, has come up in three recent post-race samples in Delaware, including two taken from horses trained by Hall of Famer Jonathan Sheppard. In addition, nine trainers in Pennsylvania have been fined $1,000 each for overages of the drug since March, though the positive tests have dried up in the last six weeks, following the publication of a warning on overnight sheets about using the drug in combination with phenylbutazone, which is commonly known as “bute.”

The spate of positives has underlined the unforeseen problems that can arise when racing jurisdictions or sports leagues put in place new rules designed to manage the use of drugs, both regulated and illegal.

Under rules put in place this year in most Mid-Atlantic states, including Delaware but not yet Pennsylvania, trainers and veterinarians have been advised to avoid administering methocarbamol within 72 hours of race, based on studies conducted on horses administered the drug to determine its efficacy and concentration levels in the blood. The study was conducted on 20 horses in a laboratory setting to determine when the effect of methocarbamol would no longer influence a horse’s performance, and it was used to set a threshold level at which the concentration of the drug would be considered a positive, leading to the 72-hour guideline.

“This is not a problem, per se,” Tom Mostoller, the executive director of the Pennsylvania Horsemen’s Benevolent and Protective Association, said of the rash of positives in Pennsylvania. “None of these trainers were trying to do something wrong, and none of them want a positive. But it is one of the battles that you have to fight when you have new rules and you don’t have an exact understanding of how the drugs are used in racing situations.”

According to Dr. Dionne Benson, the executive director of the Racing Medication and Testing Consortium, new research conducted by Dr. Mary Robinson at the University of Pennsylvania has indicated that bute is inhibiting the elimination of methocarbamol from the blood because both take the same chemical pathway to be eliminated from the body. Bute, in fact, takes precedent over methocarbamol, which is why the positives are returning overages for methocarbamol but not bute.

“Imagine you’re waiting on a metered ramp to get onto the highway, and this highway is the exit out of the body,” Benson said. “Only one can go out at a time, and the bute gets to go first.”

In Pennsylvania, where the withdrawal guideline for methocarbamol is 48 hours until the new rules are formally put in place, a notice was added to the overnight sheet at Parx racetrack near Philadelphia and Penn National Race Course in Grantville after the positives started showing up in March. “The latest research indicates a minimum of 72 hours should be used if using [methocarbamol] in conjunction with bute,” the note states. “Please adjust your pre-race treatments accordingly.”

However, even that withdrawal guideline might be too short for horsemen in states where the new rules are in place, such as Delaware, since they use a different threshold to determine a violation. That threshold might require horsemen to stop administering methocarbamol as much as a week before a race if also administering bute.

John Wayne, the executive director of the Delaware Thoroughbred Racing Commission, said the three recent positives in Delaware have not yet been confirmed in split samples, so no stewards’ rulings have been issued. He said he expected to bring up the issue next week at a meeting of the Association of Racing Commissioners International at Del Mar. Wayne is on the RCI’s Drug Testing Standards and Practices Committee.

Wayne also said he hoped the RMTC, which issues recommendations on rules and practices, would clarify the methocarbamol withdrawal time for the states that have adopted the new rules. The RMTC has told racing commissions that the withdrawal times are only “recommendations,” with the concentration level in blood being the ultimate basis for a violation, since dosage can vary as well.

“We’re only following what they directed, so they probably need to put something out on it,” Wayne said.