Published March, 2010

The equine pharmacology, therapeutics, and toxicology program at the Gluck Equine Research Center focuses on interactions among performance-enhancing drugs and therapeutic medications in performance horses. Early work focused on the detection of performance-enhancing drugs, and in 1983, U.S. Patent #4,473,640 for morphine detection was awarded.

Soon thereafter, work commenced on the development of highly sensitive enzyme linked immunosorbent assay (ELISA) tests for medications not approved for use in horses. An ELISA test is equivalent to a home pregnancy test; it is highly sensitive, needs only one drop of urine, and can be completed within an hour. These highly sensitive tests revolutionized drug testing in the late 1980s, and this work is ongoing. This technology was licensed to Lexington-based Neogen Corp. In cooperation with Neogen, approximately 100 highly sensitive ELISA tests capable detecting about 300 drugs and therapeutic medications used in performance horses are now available to equine drug testing laboratories worldwide.

Because of the great increase in testing sensitivity associated with the introduction of ELISA tests, it became necessary to specifically identify the close to 50 therapeutic medications used routinely by veterinarians to protect the health and well-being of horses. These medications have been identified and research is underway to ensure they are appropriately regulated in performance horses. As such, there is now a need for defined regulatory thresholds in plasma or urine for these 50 therapeutic medications so the high sensitivity of modern analytical methodology does not interfere with the proper veterinary care of performance horses.

Work from the program first established "proof of principle" of the concept of defined regulatory thresholds for therapeutic medications in equine plasma or urine. The program now focuses on providing the required certified reference standards and stable isotope internal standards necessary for accurate quantification of medications in the regulatory context. A problem in this area is that many of the required standards are standards of unique equine drug metabolites or metabolite fragments.

Additionally, because of the accreditation requirements of forensic laboratories, these reference standards must be prepared for distribution in a facility accredited to International Organization for Standards (ISO) standards and provided with a full ISO/IEC-17025 compliant certificate of analysis. Work on creating and certifying these standards is currently underway in cooperation with two Central Kentucky companies, FrontierBiopharm and the Neogen Corp.

In the area of therapeutics, in the mid-1990s the program identified the unique clinical efficacy of diclazuril and related substances in the prevention and treatment of equine protozoal myeloencephalitis (EPM). This research gave rise to U.S. Patent #5,583,095, which led to the first FDA-approved treatment for equine protozoal myeloencephalitis, Marquis, now marketed by the Bayer Corporation under this patent. Ongoing research is exploring further applications of this therapeutic initiative.

More recently in 1996, the program was awarded U.S. Patent #7,074,843 for novel short-acting equine/veterinary tranquilizer. Other approaches to equine pharmacology and therapeutics in general are in progress.

Thomas Tobin, MVB, MSc, PhD, MRCVS, Dipl. ABT, is a Professor in the Departments of Veterinary Science in the Gluck Equine Research Center and in the Graduate Center for Toxicology.