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Equine Science Update
© Equine Science Update 2001 -
Except in the USA, where many states allow the use of anti-inflammatory drugs (such as bute) and lasix (used to prevent pulmonary bleeding) most countries ban the use of drugs during racing.
Detection methods are very sensitive, and in the UK even the smallest amount of a prohibited substance detected in the blood or urine is too much. Penalties for non-compliance can be severe.
There is usually a straightforward explanation for most positive dope test results. Human error is often to blame. Treatment may be given to the wrong horse or may be given too close to the race. Contamination from other sources - such as feed buckets and mangers present another risk.
It has been suggested that if drugs are withdrawn at least eight days before competition it is unlikely that residues will be detected. However some of the newer non-steroidal anti-inflammatory drugs require a much longer withdrawal period. Procaine (which is used in some preparations of penicillin to prolong its action) may be detectable for several weeks.
Detection methods are very sensitive, and in the UK even the smallest amount of a prohibited substance detected in the blood or urine is too much. Penalties for non-
There is usually a straightforward explanation for most positive dope test results. Human error is often to blame. Treatment may be given to the wrong horse or may be given too close to the race. Contamination from other sources -
Avoiding positive dope tests
Various factors influence the rate at which drugs are removed from the body. Medications generally take longer to be cleared if given by mouth rather than being injected. A drug injected directly into the vein reaches high levels in the blood immediately and then declines. If the same drug is given mixed in food, the concentration in the blood will rise for some time as it is absorbed, before starting to fall.
Individual horses may absorb, and excrete, drugs more slowly than normal. And giving two drugs at the same time may influence the excretion rate of one or other. Topical creams that are applied to the skin may be absorbed and cause a positive test.
At a recent meeting of the Association of Racecourse Veterinary Surgeons (UK) Rob van Pelt, of the Equine Veterinary Hospital Arundel, discussed the problem of avoiding a positive dope test. He described an incident in which clenbuterol ("Ventipulmin" ®) had been detected in samples taken from a racehorse, despite the recommended withdrawal period being observed.
Was it possible that of the horse had continued to absorb clenbuterol that had been excreted into the bedding? A study was set up with the Horserace Forensic Laboratory in Newmarket. They treated a horse with a course of clenbuterol. Then they took that horse out of its stable and replaced it with another, untreated horse (without changing the bedding). Blood and urine samples were collected daily from the second horse.
One day after being put into the stable with the contaminated bedding, the second horse tested positive for clenbuterol. This continued for a further four days. The horse appeared to have absorbed the drug from the contaminated bedding.
Van Pelt emphasised the importance of being very careful with drugs that are excreted unchanged in the urine. It is not enough to simply stop administering the drug. The bedding must be completely changed as well. He pointed out that even medications being taken by the stable staff could contaminate the bedding.
Suggestions for reducing the risk of a positive dope test included:
Individual horses may absorb, and excrete, drugs more slowly than normal. And giving two drugs at the same time may influence the excretion rate of one or other. Topical creams that are applied to the skin may be absorbed and cause a positive test.
At a recent meeting of the Association of Racecourse Veterinary Surgeons (UK) Rob van Pelt, of the Equine Veterinary Hospital Arundel, discussed the problem of avoiding a positive dope test. He described an incident in which clenbuterol ("Ventipulmin" ®) had been detected in samples taken from a racehorse, despite the recommended withdrawal period being observed.
Was it possible that of the horse had continued to absorb clenbuterol that had been excreted into the bedding? A study was set up with the Horserace Forensic Laboratory in Newmarket. They treated a horse with a course of clenbuterol. Then they took that horse out of its stable and replaced it with another, untreated horse (without changing the bedding). Blood and urine samples were collected daily from the second horse.
One day after being put into the stable with the contaminated bedding, the second horse tested positive for clenbuterol. This continued for a further four days. The horse appeared to have absorbed the drug from the contaminated bedding.
Van Pelt emphasised the importance of being very careful with drugs that are excreted unchanged in the urine. It is not enough to simply stop administering the drug. The bedding must be completely changed as well. He pointed out that even medications being taken by the stable staff could contaminate the bedding.
Suggestions for reducing the risk of a positive dope test included:
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Horses should be clearly identified
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Only one or two members of staff should be involved in treating horses
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Medication should be placed directly in the manger (ie not in a bucket for distribution later)
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Staff should be aware that drugs they take could reach the horse. (ie no urinating in the stable!)
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Horses that need to be drug free should be put into stables that have clean bedding.
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Stables should be kept clean. (There have been reports of horses testing positive for isoxuprine. They had been contaminated by isoxuprine powder that had built up on cobwebs in the stable.)
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Written by Mark Andrews. Published online 2007
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Source: ARVS meeting, Newbury. UK. May 2005.
Source: ARVS meeting, Newbury. UK. May 2005.