Equine Science Update
Reports from the world of  equine research.
Detecting drugs.
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Most racing authorities, and the FEI, are determined that horses compete free from influence of medication.

In general, anything given to a horse by any route (including in the food) with the aim of influencing its performance is prohibited. This applies even if the substance is naturally present in the horse - such as testosterone and hydrocortisone. (For these substances there are internationally agreed thresholds below which no action is taken.)

Just because a drug is not yet detectable does not mean the rules can be ignored.  Some of the samples that have been declared negative are stored and may be tested again when new methods are developed.

The regulatory bodies do not want to prevent horses being treated when they need it. But they do want to prevent horses competing while any treatment they have been given might influence their performance. When competing under the Rules of Racing, medications used during training must be withdrawn at an appropriate time so that the horse does not race while under their effect.

Veterinarians are frequently called upon to advise how soon before a race a certain drug can be administered without running the risk of being detected at a post-race test. For many years it was generally accepted that allowing an interval of eight days between finishing the treatment and racing would be safe. In almost all but the most exceptional cases the horse would be free of the medication at the time of racing.

But things have changed. New drugs have become available with a longer duration of action. The methods used for detecting doping have becoming more sophisticated and sensitive.

The European Horseracing Scientific Liaison Committee (EHSLC) represents the horseracing regulatory authorities of France, Great Britain, Ireland, Italy, Germany. Its aim is to harmonise the policies and procedures for dope testing in those countries.

Recently, in response to the need for more information on the time taken for drugs to be  eliminated, the EHSLC undertook an investigation into the detection times of some commonly used medications. The first drugs to be tested were non-steroidal anti-inflammatory drugs and furosemide.

Tests were carried out at various facilities throughout Europe and in Hong Kong. Horses were tested every 24 hours after the last treatment until the drug was no longer detected. The “detection time” is the time at which the concentration of the drug (or its breakdown products) in the urine, was not detected using routine or standard methods, in all the horses in the study.

The results have been published on the Horseracing Regulatory Authority (HRA) website to help veterinarians advise their clients. However, the results must be interpreted with great care. Many factors may affect the “detection time” for a drug. Individual horses may vary in their response to drugs.

The trials were carried out on healthy horses under controlled scientific conditions, using drugs at the manufacturers’ recommended doses. Relatively small groups of horses were used for the trials. (The largest group comprised ten horses, which were used to assess the elimination of the non-steroidal anti-inflammatory drug dipyrone.)

Training and exercise programs, diet and management and disease can all affect the speed of elimination of the drug. Different formulations of a drug may affect the rate of absorption and influence the detection times.

It is interesting to note that two of the more recently developed drugs have detection times that exceed the old rule of thumb of eight days.

Eltenac had a detection time of 192 hours (8 days) after a five-day course of 0.5mg/kg by intravenous injection. Carprofen had a detection time of  264 hours (11 days) after a single intravenous injection of 0.7mg/kg.

The HRA website emphasises that detection times are not the same as “withdrawal times”. An adequate safety margin must be added to the detection time to minimise the risk of a positive result at a post-race dope test. It is the responsibility of the veterinarian overseeing the care of the horse to use their professional judgment to decide when a horse can safely compete after being given medication

For more details of the detection times, together with a full explanation of the limitations of the results, see  www.thehra.org
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