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Trainers are reminded that the International Screening Limit (ISL) for clenbuterol of 0.1ng/ml in urine has been adopted by Harness Racing Australia (HRA) and will be implemented by Australian racing laboratories with effect from 1 April 2023.
This will have important implications for the detection of clenbuterol following its administration to racehorses and will lead to a prolongation of detection times for this substance.
The European Horserace Scientific Liaison Committee (EHSLC) has published detection time information for clenbuterol following both oral and nebulised administration. The published detection times of 13 days (oral) and 6 days (nebulised), for the stated dosage regimen and pharmaceutical preparations, are valid for the new ISL to be applied by Australian racing laboratories.
The EHSLC detection time document can be found here.
It should be noted that the revised detection times for clenbuterol are longer than the 3 - 4 days (oral) and 2 days (nebulised) previously reported, using the analytical methodology at that time, in the Australian Equine Veterinary Association (now Equine Veterinarians Australia - EVA) publication ‘Detection of Therapeutic Substances in Racing Horses’ (‘The White Book’).
Veterinarians are therefore advised that recommended withdrawal periods for treatment with clenbuterol (for example, in products including, but not limited to, Airway Gel, Claire Gel, Broncopulmin Powder, Ventipulmin Granules, Ventipulmin Injection and products in combination with trimethoprim and sulfadiazine) must be based on the published EHSLC detection times and not on previous advice provided in the ‘The White Book’, and that trainers are warned accordingly.
The EHSLC detection times appear, alongside those previously published in ‘The White Book’, in the current Equine Veterinarians Australia (EVA) publication ‘Equine Medication Detection and Withdrawal Times: A Survey of Veterinarians in Australia’.
It is important to note that a withdrawal (or withholding) period is not the same as a detection period. Any withdrawal period should be calculated based on the published detection time, with the addition of a suitable safety margin based on the circumstances of the administration, including dose, route of administration and preparation administered.
It should also be noted that none of the veterinary preparations containing clenbuterol registered for use in Australia are registered for administration by nebulisation. Such administration would therefore represents off-label use of these products.
The screening limit of 0.1ng/mL in urine for clenbuterol will come into effect on 1 April, 2023.
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