Fluphenazine, which is sold in Ireland under the trade name Modicate, is an extremely long-acting cousin of acepromazine or ACP, one of the most widely used equine sedatives on the market.
However, fluphenazine is a human drug that has now crossed over into the equine world.
Fluphenazine is used to treat severely psychotic people but its use in performance horses is becoming more and more widespread.
It is traceable in the horse for up to 45 days, but its therapeutic effects can last for as long as eight months.
It produces mild but long-lasting sedation in the horse, but still allows the animal to focus on a performance event such as show jumping.
It is considered an extremely effective drug in the equine field. Guanabenz is a drug used to treat hypertension in humans, but is also an extremely efficient and long-lasting tranquilliser in horses.
Fluphenazine and Guanabenz were two of five drugs named in an August 5th memo from the International Equestrian Federation's veterinary department to riders warning against the use of sedatives.
Sedatives are used to improve the manageability of "hot" horses, which could otherwise prove unrideable.
The memo stated that Acepromazine, Detomidine, Reserpine, Fluphenazine and Guanabenz had been detected in equine samples.
Detection of these drugs has proved difficult in the past, but improved testing facilities have now resulted in a spate of positive samples. The memo specifically stated that the use of these substances would be viewed as "serious attempts to influence the performance of the horse by medication".
The memo went on to say: "Several of the above substances have no regular place in the horse and are considered as serious infringements of the FEI medication rules."
A third drug, Zuclopenthixol, was also named yesterday. This is another drug that has crossed over from the human field into equine use.
Like Fluphenazine, Zuclopenthixol is used to treat schizophrenia and delusional disorders in humans, but is used as a sedative in horses.