There is much to say about this classification scheme and its ability to effectively regulate the administration of these drugs to racehorses — none of it positive from the perspective of the horse. It is yet again manipulation in its most flagrant form — an authoritative and ostensibly medical foundation for the categorization of potentially harm-inducing medication simply to permit the usage of drugs without reservation.
A list of the most common permissible and habitually used drugs will cast doubt on their efficacy of promoting welfare to the horse. According to some, the three most widespread performance-enhancing drugs used today are; anabolic steroids (Class 3), corticosteroids (Class 4) and "milkshakes" (bicarbonates — not categorized but regulated by a threshold).  This is by no means an exhaustive list as there is a myriad of drugs routinely used to enhance the physical health of the typical racehorse.
What it does point out however is a glaring contradiction between what is, by and large, perceived to be performance enhancing and what is actually classified as performance-enhancing. As per the recommended guidelines outlined by the ARCI, both corticosteroids (non-steroidal anti-inflammatory drug or NSAID) and bicarbonates belong to categories seemingly benign. So what is the more appropriate assessment regarding these medications?
Moreover, how is it possible to group anabolic steroids in the Class 3 category — "undecided" — may or may not be therapeutic use? It is common knowledge that they are performance-enhancing drugs that build muscle and confer improved endurance. Anabolic steroids carry with them reputed risks and should only be administered to horses who suffer from chronic wasting conditions.
If this is the case, these
ailing horses shouldn’t be racing in the first place. This begs the
question as to why anabolic steroids are even tolerated in NA racing.
After all, these guidelines were created to prevent the use of
performance-enhancing drugs while promoting therapeutic treatment. Or
ban on anabolic steroids proved that when this industry works
collaboratively, game-changing progress can be made in a short period
of time," Phipps said. "We need more of that spirit of
cooperation and a greater sense of urgency". 
It is simply a joke —
ban them — but list them as Class 3?
A minor misdemeanor in the racing world — a proverbial slap on the wrist — is a sinful and self-propagating endorsement for actions instrumented to camouflage the ugly truth. And to think this is only one example of the hundreds of noxious concoctions fed to these vulnerable creatures.
Apart from the Class 1, 2 and 3 drugs with a predisposition to performance-enhancement, there is an increasingly more insidious side of drug use in North American horse racing that is now attracting much attention from racing officials due to the negative publicity it garners from fans, bettors and the rest of the global racing industry.
Two drugs in particular have become ubiquitous, both of which are categorized as therapeutic and are legal in most jurisdictions. These are none other than Salix (Furosemide formerly known as Lasix) an anti-bleeding medication and Phenylbutazone (PBZ) or "Bute", one of the three NSAIDs permitted in controlled quantities on race day by the NTRA (National Thoroughbred Racing Association).
Salix, a powerful diuretic, can be legally administered four hours before a race to horses that have been documented with a history of bleeding.  On the other hand the administration of "Bute" is prohibited within the 24 hours before post time for the race and is controlled by plasma threshold concentrations. No other country in the world permits race day medication nor do they allow horses to run on the threshold levels permitted in North America.
Prior to discussing the effects these drugs have on the Thoroughbred and ostensibly the fine line that divides the terms performance-enhancing and therapeutic or for that matter unsafe, it is worthwhile considering a compilation of rulings documented by the Racing Medication and Testing Consortium (RMTC) for 2010 and 2011 to date.
Since the beginning of 2010 there have been approximately 600 drug infractions in the 38 racing jurisdictions in North America which, by the way, lack standardized drug testing or legality.
Although the RMTC record is not complete as the list is subject to information available through public disclosure, it nonetheless provides an overall representation of the common drugs detected as well as those that are generally less frequently discovered in forensic samples.
Table 2 outlines some of the more common drug violations. Keep in mind that this represents only a small percentage of the actual number of drugs that comprise the list.
Table 2. Drug Violations in Thoroughbred Racing (2010-2011)