US horse racing gets guidance over hallucinogenic drug glaucine

Shavings from the Liriodendron tulipifera can be responsible for elevated readings of glaucine in horses.
Shavings from the Liriodendron tulipifera can be responsible for elevated readings of glaucine in horses. © Jean-Pol GRANDMONTOwn work, CC BY 3.0

Recommendations have been made to the US racing industry over the use of glaucine, a hallucinogenic drug marketed as a cough suppressant.

The purported therapeutic effects of glaucine are bronchodilation and anti-inflammation, and it is reported to be used as a drug of abuse in humans for its psychedelic properties. It has been identified in several recent post-race samples.

The Racing Medication and Testing Consortium (RMTC) said that no glaucine-containing products were FDA-approved in the US.

However, the consortium’s glaucine task force reported that glaucine is not only present in some bulk shavings but is also available in injectable forms online. In shavings, it is a result of the presence of the tulip poplar tree (Liriodendron), which contains several plant alkaloids – two of which are asimilobine and liriodenine. One or both of these alkaloids have been identified in all samples of shavings tested that are positive for glaucine.

Because of glaucine’s presence in bedding, a horse could ingest shavings before a race that could potentially result in a laboratory finding. This potential for inadvertent exposure, as well as intentional exposure, indicates that the simple use of a screening limit alone would likely not be sufficient in controlling the substance.

As a result, the RMTC has issued testing recommendations and penalties for glaucine, noting that horsemen should consider removing horses from bulk shavings at 24 hours pre-race to avoid the possibility of a finding for glaucine. A warning would be issues for a result between 500 picograms/milliliter and below 1 nanogram/milliliter, while and a Class B penalty would be imposed with a reading above 1 nanogram/milliliter.

Liriodendron tulipifera golden autumn leaves and seed cones.
Liriodendron tulipifera golden autumn leaves and seed cones. © Gmihail at Serbian WikipediaCC BY-SA 3.0 rs.

EPM treatment advisory

The Scientific Advisory Committee also issued an important advisory relating to the off-label use of the livestock dewormer Levamisole, which metabolizes to aminorex.

Levamisole is commercially available as a dewormer for cattle, sheep, goats, and pigs. It also has conventional off-label uses in horses as an immunostimulant and as a medication for treatment of equine protozoal myeloencephalitis (EPM).

Levamisole metabolizes in the horse to aminorex and possibly also pemoline, both of which are potent stimulants assigned a 1/A Classification in the Association of Racing Commissioners International Uniform Classification of Foreign Substances.

The identification of either of these substances in a post-race sample is associated with a potential career-ending penalty. In consideration of its conventional use in horses, the RMTC contemplated an administration study to develop guidance on the use of levamisole and surveyed practicing veterinarians on their use of levamisole.

Given the prevalence of compounded levamisole products and that survey results established there is no commonly used treatment protocol, the RMTC determined an administration study would yield limited information.

Therefore, the RMTC recommended that following withdrawal of the medication levamisole-treated horses be subjected to testing before entry to verify that levamisole and its metabolites have been eliminated.

DMSO in horses

The RMTC’s Scientific Advisory Committee has also reported on the results of a study into DMSO (Dimethyl sulphoxide), funded by the American Association of Equine Practitioners.

It was requested that RMTC determine a withdrawal recommendation for intravenous use of medical grade DMSO. Various samples from 30 horses tested by practicing veterinarians in Kentucky, Florida and California were analyzed.

RMTC said that 24 hours after administration, all horses exceeded the 10 micrograms/milliliter threshold, but at the 48-hour mark, all were below.

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