What are ‘Detection Times’ and ‘Withdrawal Times’?
A ‘Detection Time’ is defined as the interval between the time of the last drug administration and the time at which the observed urine (and plasma) concentrations, in horses during an experiment conducted according to European Horseracing Scientific Liaison Committee (EHLSC) recommendations, are below the harmonised International Screening Limit (ISL) as obtained with the routine analytical method.
The logic behind determining Detection Times is to more accurately record the time taken for a particular substance to pass through the horse’s system and for the levels of the substance to become so low that they are recognised as having ‘no effect’. This data is currently available for a number of frequently used medications in horses. Detection Time studies have been coordinated for several years by a cooperation of European Racing Authorities coming together as the European Horseracing Scientific Liaison Committee (EHSLC); in order to ensure that Detection Times are harmonised across Europe.
A ‘Withdrawal Time’ is basically a Detection Time with an additional length of time added on by a vet using their own discretion and knowledge of the individual situation to allow the substance to take effect and then pass through the horse. It’s very important to remember that all horses are different, and there are no guarantees that a substance will be completely out of a horse’s system even if the drug was given well in advance of the known Detection Time – if a substance is given to a horse at least this far in advance of an intended race, there is a greatly reduced chance of a positive test occurring.
A Detection Time is not equivalent to a Withdrawal Time.
The Withdrawal Time should be longer than a Detection Time to take into account the impact of all sources of animal variability such as age, sex, breed, and lifestyle in and those of the medicinal product actually administered such as formulation, route of administration, dosage regimen and duration of treatment.