Updated: 1 August 2022
Originally Issued: 1 May 2015
AUSTRALIAN RACING BOARD NOTICE TO RACING CALENDAR
Important Notice regarding the detection of the corticosteroid drug Dexamethasone The International Screening Limit (ISL) for dexamethasone of 0.2ng/ml in urine was adopted by Racing Australia and implemented by Australian racing laboratories from 1 May, 2015.
This led to a prolongation of detection times for dexamethasone.
The ISL was applied to the analysis of samples collected during an administration trial involving a short-acting dexamethasone preparation (dexamethasone sodium phosphate) given intravenously and conducted as part of the Equine Therapeutics Research Australia (ETRA) project and published by the Rural Industries Research Development Corporation (now Agrifutures Australia). The published ETRA data sheet for dexamethasone reports a detection time of three days for the dosage regimen and pharmaceutical preparation used in the ETRA trial and is valid for the new ISL to be applied by the Australian racing laboratories.
This three-day detection time for dexamethasone sodium phosphate is longer than the detection time of 48 hours previously reported in the Australian Equine Veterinary Association (now Equine Veterinarians Australia – EVA) publication ‘Detection of Therapeutic Substances in Racing Horses’ (The White Book’), using the analytical methodology at that time.
Therefore, permitted veterinarians and trainers are advised that recommended withdrawal periods for treatment with dexamethasone sodium phosphate (for example, in products including Dexadreson, Dexapent, and Dexason) must be based on the new ETRA data sheet detection time of three (3) days and not on the previous advice provided in the EVA publication, and that trainers are warned accordingly.
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, preparation administered.
There have been no studies conducted on the detection of long-acting forms of injectable dexamethasone in relation to the ISL, and due to their long and unpredictable excretion, their use in racehorses should be avoided.