From Wikipedia, the free encyclopedia

Racehorse drug testing began in the early 1900s. It is the longest established, broadest in scope, and most sensitive drug testing program in existence. Racehorse drug testing is performed within an extremely stringent regulatory context. This testing has shown that the incidence of deliberate use of performance affecting substances in horse racing is extremely small.

Before the mid-1980s, the use of high potency performance altering substances in racing was less well controlled due to the inadequacy of analytical technology. Around that time, highly sensitive ELISA testing of horse urine was introduced to racing regulators by a group at the University of Kentucky. This proprietary technology essentially solved the problem of the abuse of high potency drugs in racing horses. ELISA tests are now marketed worldwide out of Lexington, Kentucky.

The ease with which traces of therapeutic medications and dietary and environmental substances can be detected using current testing technology is leading scientists and regulators away from the "zero tolerance" approach to drug testing, which many authorities now see as outdated. Increasingly common today is the use of regulatory limits or "thresholds" (the urine or blood concentration of a substance below which there is no pharmacological activity, i.e., there is no effect, a so called "No Effect Threshold or NET).

Recent challenges in drug testing include the development of effective regulatory methods for the newer hormonal products such as the various human recombinant erythropoietin products and variants and growth hormones. In 2006 a high-quality ELISA test for human recombinant erythropoietin became available, and racing chemistry has scored a major scientific breakthrough by developing the first Mass Spectral Confirmation method to detect use of human recombinant erythropoietin (rhEPO) in horses or any species.

There are at least 10 million known chemical substances and 4,000 or more prescription medications. Racing regulators in the United States divide drugs and medications into two major groups.

Performance-enhancing substances
Identification of these substances in a horse is viewed with great regulatory concern. Testing for these substances usually proceeds at the highest level of sensitivity possible, so-called "zero-tolerance" testing. About 850 or so substances are classified by the Association of Racing Commissioners International (ARCI) Uniform Classification System for Foreign Substances as potentially performance enhancing in a five class system, the most complete listing of such substances available is found at http://www.arci.com/druglisting.pdf.

Therapeutic Medications
There are approximately 50 plus of these agents used therapeutically in horses in training. Since about 2000, it has come to be more generally accepted that "limitations" on testing for therapeutic medications are necessary. These limitations are variously called "thresholds" or "reporting levels," or "decision levels" (California) depending on the semantic preference of individual jurisdictions. These terms apply to the blood concentration of a medication below which the substance has insignificant pharmacologic affect.

Drugs or Medications Can Influence the Outcome of a Race

Stimulants
Among the equine stimulants are the opiates, which have long been used in racing horses, also the amphetamine-like stimulants, especially methylphenidate (Ritalin). All of these have been widely used, the opiates likely for hundreds of years, and presumably particularly so before testing for these agents was available.

Tranquilizers
Horses can also be medicated to win by relaxing them, and allowing the horse to run its best possible race. The widely used tranquilizer acepromazine, and any number of related or equivalent agents, have been used in this way.

Bronchodilators
Improving a horse's "wind" by opening its airways through the use of bronchodilators may also improve performance, especially in an animal that is sub-clinically broncho-constricted.

Behavorial modifiers
Veterinarians certify horses as being sound in "wind and limb." Obviously, medications that can affect these parameters and also the "attitude" or "behavior" of a horse have the potential to affect both the presentation of a horse and also, presumably, the outcome of a race.

The Introduction of ELISA Testing (1988)
In the mid-1980s, race testing was for all practical purposes dependent on a primary screening technique called Thin Layer Chromatography (TLC). This technology was not particularly sensitive, and in the mid-1980s some horsemen were reportedly using high potency narcotics, stimulants, bronchodilators and tranquilizers with impunity. In 1988 ELISA testing was introduced to racing by a group at the University of Kentucky. The term ELISA is an acronym that stands for Enyme Linked Immuno Sorbent Assay. Simply put, an ELISA test is a variant on the home pregnancy test technology. It requires a drop of urine; it can be performed relatively rapidly, is highly sensitive, and test results can be read by eye.

Mass Spectral Confirmation
While ELISA screening or testing is fast and highly sensitive, it is far from specific. The second and absolutely critical step in the testing process is Mass Spectral confirmation of positive ELISA tests. In this step, the molecule is isolated and its precise mass measured, and the molecule is also broken into a series of fragments. Both the mass and relative proportions of these fragments (the fragmentation pattern) are specific for the given drug, and are then matched with known standards. A full scan mass spectrum, with appropriate matching controls, is the “gold standard” in drug testing.

Zero Tolerance Testing
Zero Tolerance testing is not testing down to "zero" molecules, which no chemist can accomplish, but rather testing to the limit of detection (LOD) of the best available technology. While detecting trace amounts may be an entirely appropriate approach for performance altering substances which have no place in racing, it is not considered appropriate for therapeutic medications. Therapeutic medications are aproved substances used to maintain the health and welfare of horses.

Medication Dosing and Elimination
An equine dose of phenylbutazone contains more phenylbutazone molecules than there are stars in the known universe, that is about 6 followed by 21 zeros. A horse will eliminate the bulk of this dose of phenylbutazone quite rapidly. If phenylbutazone in the horse has a 7.22 hour half-life, 50% of the drug will be eliminated by 7.22 hours after dosing, 75% by 14.5 hours after dosing, 87.5 by about 22 hours after dosing, and exactly 90% 24 hours after dosing. At the end of day 1, when 90% of the drug is eliminated, the pharmacology of the drug is gone, but you still have 6 followed by 20 zeros worth of phenylbutazone molecules in the body. Every day another 90% of the drug in the body will be eliminated, but the chemist can easily find traces of the medication or its metabolites for up to 14 days after administration. After about 22 days 1 molecule still remains in the body. The question now arises of when, precisely, should the chemist stop pursuing these traces?

Thresholds, Including “No Effect Thresholds” (NETs)
The equine blood concentration of a medication below which pharmacologic activity is insignificant.

Withdrawal Time
The length of time after the administration of a medication required for the metabolism and elimination of the medication. After this time the medication has insufficient concentration to produce a pharmacologic effect.

• Equine Drugs, Medications, and Performance Altering Substances: Their Performance Effects, Detection and Regulation. http://thomastobin.com/drugsmeds/drugsmeds.htm

• Stirling K, Bellocq R, and Tobin T: National Horsemen’s Benevolent and Protective Association, Inc. Proposed National Policy on Drug Testing and Therapeutic Medication. J Eq Vet Sci 23(1): 4-5, 18-40, 2003. http://hbpa.org/resources/MedicationPolicy.pdf

• Neogen ELISA tests. http://www.neogen.com/forensickits.htm

• The Horse Doctor. http://www.thomastobin.com

• The Testing Integrity Program (TIP) was organized in 1996 to assist the Drug Testing Standards and Practices Committee of the Racing Commissioners International (RCI). http://testingintegrityprogram.org

• Association of Official Racing Chemists (AORC). http://cobra.vdl.iastate.edu/aorc-2/Mission.htm

• Drugs and the Performance Horse by Thomas Tobin, 463 pages, Charles C. Thomas, Springfield, Illinois, 1981.