Sometimes a horse will be on medication prescribed by a vet – however the horse can only compete if the drug has worked through the horses’ system.
The withdrawal time for a drug must be decided upon by the treating veterinarian and is likely to be based on the detection time and an added safety margin. This margin will be determined using professional judgment and discretion to allow for individual differences between horses such as size, metabolism, degree of fitness, recent illness or disease etc. to be taken into consideration.
A detection time is not the same as a withdrawal time. The detection time is the approximate period of time for which a drug (or its metabolite) remains in a horse’s system, such that it can be detected by the laboratory and is provided only as a guide.
With all medications, a clinical judgment is essential to ensure that the welfare of the horse is never compromised by administering a drug at a time too close to an event such that it may mask symptoms and could aggravate a clinical condition. Horses with locomotor problems in particular must always be provided with adequate rest.