Consortium addresses drug thresholds

A racing industry group that studies the withdrawal times for medications is recommending that the threshold level for a frequently used leg paint be set at such a low level that it will eliminate use of the substance in oral and intravenous administrations.

The Racing Medication and Testing Consortium recommended on Wednesday that the threshold for the leg paint, dimethyl sulfoxide, or DMSO, be set at 10 micrograms per milliliter of blood plasma. In a release, the consortium said that the level would allow horsemen to continue to use the substance topically but would prohibit horsemen from giving the drug orally or injecting the drug into the bloodstream.

In paste form, DMSO is commonly used to reduce leg inflammation, and it can also be used to deliver drugs such as corticosteroids and antibiotics across the skin and into the bloodstream. However, many regulatory officials have had concerns dating back a decade that the drug was being injected or delivered orally – sometimes in combination with milkshakes – in order to act as a painkiller or to mask the presence of other drugs because of a diuretic side effect.

Veterinarians generally agree that the only proper use of DMSO is as a paste. The new threshold recommendation will “hopefully put an end to any of those other uses,” said Dr. Scot Waterman, the executive director of the consortium, in an interview.

The consortium also issued recommendations on the threshold levels for a variety of other drugs, including anabolic steroids, following the recent completion of studies the organization funded. The recommendations will be forwarded to the Association of Racing Commissioners International, an umbrella group of racing commissions that evaluates proposed medications regulations, to determine if they are suitable for adoption by individual regulatory agencies.

The thresholds that are in place to regulate the use of anabolic steroids were based on previous studies. In the past two years, nearly all racing jurisdictions adopted rules restricting the use of anabolic steroids to therapeutic purposes, regulations that required the use of several different threshold levels because many anabolics, such as testosterone, occur naturally in horses.

The other drugs that the consortium studied to determine threshold levels were glycopyrrolate, a commonly used bronchial dilator; methocarbamol, a muscle relaxant; and firocoxib, a relatively new non-steroidal anti-inflammatory drug that is marketed under the name Equioxx.