Abstract

Equine doping is defined differently by various sport federations. This act generally modifies animal performance during sporting events.
Drugs which can be used have various chemical structures and properties. Some of them are potentially injurious to the horse's health. Among these substances, non-steroid anti-inflammatory drugs are dangerous because they can mask pain syndromes without suppressing the injuries.

The horse has some physiological and metabolic characteristics which are able to interact with antidoping control results. Regardin this, nutriments have been found to introduce into the animal's system forbidden compounds such as salicylic acid or caffeine. On the other hand, studies on 19 nortestosterone metabolism have shown that this compound, which was previously considered as a xenobiotic, is naturally present in the male horse. Consequently, quantifying doping agents in biological samples is sometimes necessary.

Antidoping control analyses are made on equine urine and/or plasma samples. This double sampling system sometimes permits to date administration of an illegal substance, and gives good reliability regarding results. For the latter reason, a rigorous analytical schedule is employed which includes two steps: screening and confirmation. Knowledge of the pharmacokinetics of doping agents in the equine permits one to discuss analytical results. Data obtained in 1986 for all countries which have antidoping controls showed preponderance of non-steroid anti-inflammatory drugs (37.8%) and local anesthetics or analgesics (14.4%).

Taking into account new analytical chemistry methods, doping rules today are evolving from non detection drug levels towards a controlled medication. Indeed this strict rules, which prohibit all clinical treatments during competition periods, seem too harsh. But developping a controlled medication is not easy, because threshold levels must be determined. For example cumulative levels of phenylbutazone and oxyphenylbutazone must be less than 5 μg/ml in plasma. This involves the knowledge of the relationship between pharmacokinetics and effects on animal performance. Moreover, analysis must be done in standardized operating conditions.