DRUG TESTING of racehorses in North America began earnestly in the early 1900's however it was next to impossible to enforce these policies and monitor the use of drugs since at the time there were no definitive tests established to assess the level of substances present.
Moreover, at this introductory stage it was more or less based on an honor system wherein the rules of racing without the aid of performance-enhancing drugs were enacted and the trainers and owners simply agreed to abide by these regulations.
By the 1930's it was widely known that there was rampant drug use, including narcotics, within the horse racing alliance in North America despite the drug bans that had been in place over the preceding years. About this time official drug testing had begun to take hold in other parts of the world.
Finally in 1932 an editorial in The Blood Horse alerted the Federal Bureau of Narcotics of these allegations which prompted them to investigate, leading to over 100 convictions of owners, trainers and other personnel at the racetrack.  Effectively this pressured the horse racing business into adopting more stringent measures that would, in practice, improve the image, integrity and future survival of horse racing.
In view of the novel sanctions imposed on the racing industry together with the proliferation of new race tracks in several states in the US, the National Association of State Racing Commissioners was created. Comprised of racing commissioners from seven states — Florida, Kentucky, Maryland, Michigan, New Hampshire, New Jersey and Ohio — the goal of the organization was to unify the sport within the US and bring to it "forceful and honest nationwide control of racing for the protection of the public". 
One of the first steps in reform was to address the issue of drug testing in consequence of the investigation conducted by the FBI. Although the FBI investigation diminished the use of narcotics in horse racing, it did not however curtail the use of other equally potent drugs. Without existing standards in place the Commission embarked on a program intended to prevent the dispensation of drugs by employing a means of detection. Lacking any decisive or pertinent test method the American authorities sought the help of European experts. 
In France a scientist by the name of Kaufman had developed a test method to detect the presence of drugs in saliva.
A chemist, Mr. C.E. Morgan and a veterinary surgeon, Dr. J.G. Catlett out of the Florida Racing Commission traveled to Paris and London to study this method and on return in 1933 began routine collections and analysis at The Hialeah Park Race Track. 
Soon thereafter "saliva testing" was introduced to other racing states and the incidence of illegal drugging cases quickly subsided in these areas adding credibility to the sport as it further infiltrated the horse racing circuit.
Over the ensuing years more sophisticated methods of detection were developed as did the practice of urine collection as an alternative or complement to saliva. However with these advanced techniques also came the clever introduction of different drugs by zealous individuals seeking to gain profit that were more difficult to detect with each advance in the analytical testing regime.
By the late 1940's, the use of narcotics was surreptitiously replaced with amphetamine-type drugs and other related compounds that mimic the stimulation of the sympathetic nervous system - in other words the part of the central nervous system that activates what is often termed the fight or flight response.  Not long after, local anesthetics such as procaine became evident followed by anti-inflammatory drugs and anabolic steroids. 
It wasn’t until the mid-1980's that a revolutionary new test procedure for high potency drugs was developed - now the backbone of drug screening worldwide. Its inception was directed by the then Kentucky State Racing Commission in response to the widespread and indiscriminate use of powerful narcotics, stimulants, bronchodilators and tranquilizers which eclipsed the less sensitive primary screening test of that time — Thin Layer Chromatography (TLC). 
Although inexpensive and fast, the complexity and potency of these compounds proved to overwhelm the capability of TLC to detect the presence of these drugs in the racehorse.
With the introduction of ELISA (Enzyme Linked Immuno Sorbant Assay) in 1988 — basically a variant on the home pregnancy test technology – the sensitivity of modern drug testing had finally met the needs of the industry, perhaps even more so than necessary. 
Later using more sophisticated adjunct analytical technology, in particular Mass Spectrometry (MS), the window of detection was pushed to extreme limits such that the extraordinary sensitivity complicated the matter further, particularly in the case of the "zero tolerance" concept according to most of those in the business. "Zero tolerance" is the racing regulators' philosophy in regulating drug use in race horses — even trace amounts of drugs are not tolerated.
"To Arthur and other equine medical professionals, zero tolerance has no meaning because some level of drugs can always be found with sensitive enough testing. All states start with a zero-tolerance baseline, but the more progressive jurisdictions, such as California, Louisiana, and Kentucky, have begun instituting threshold levels for various therapeutic medications". 
Perhaps a system of threshold limits is a justifiable solution for this dilemma but how are these limits determined and who really knows what level of a particular drug could potentially have an impact on performance?
Moreover, the use of threshold limits is of course a way around the positive drug tests and not a solution – as long as the level is below the threshold value no one will be punished and the use of drugs will continue.
More importantly, what are the effects of continuous use, regardless of quantity, on the horse? Are many of these drugs truly therapeutic and necessary? Thoroughbreds routinely receive medications whether they have ailments or not.
One must also keep in mind that the predominant basis for administration of drugs in racehorses is related to lameness. Given that a horse can’t effectively perform on compromised legs, it is for this very reason these drugs are still in use – a "Band-Aid" for persistent problems with the fragile prototype of the modern Thoroughbred that clearly lead to disaster.
"A consensus among researchers and surgeons has developed that legal medications and cortisone shots, over time, leave a horse vulnerable to a catastrophic breakdown". 
Drug dependency, as in humans, is not natural and can create a host of chronic and debilitating problems.
The terms "drug abuse" and "drug dependence" are intrinsically indistinguishable.
And therein lies the challenge; moral and ethical conduct does not always prevail on the track — abuse of the innocent by the greed-driven, commercial horse racing industry.
Continue to Part 4 »
Part 1: Introduction | Part 2: Historical Aspects | Part 3: The Inception of Drug Testing | Part 4: Drugs and Their Actions | Part 5: Policies and Tactics | Part 6: Class 3 Drugs — Performance Enhancing or Not? | Part 7: Class 4 Drugs — Harmless Therapeutics? | Part 8: The Unclassifieds | Part 9: The Call for Reform | Part 10: Who Rules?
Image Credit: Vials of blood for drug testing — TheHorse.com.