2015 ACVIM Forum Research Abstract Program

DEPLETION OF PHENYLBUTAZONE RESIDUES FROM EQUINE URINE AND TISSUES. Patricia Dowling 1 , Ron Johnson 2 , Joe Boison 3 . 1 Western College of Veterinary Medicine, Saskatoon, SK, Canada, 2 Ontario Veterinary College, Guelph, ON, Canada, 3 Canadian Food Inspection Agency, Saskatoon, SK, Canada Phenylbutazone (PBZ) is a nonsteroidal anti-inflammatory drug commonly used to treat musculoskeletal pain and inflammation in horses. It is approved for use in horses in Canada and the United States, but product labelling carries the warning "not for use in horses intended for human food". This is not a legal prohibition against the use of PBZ in horses intended for slaughter in Canada, but rather a disclaimer that there is no legal Maximum Residue Limit (MRL) established for PBZ in horse tissues, so the detection of any amount of PBZ constitutes a residue violation. Globally, the use of PBZ in horses that may eventually be used for food has been very controversial and the detection of undeclared horse meat in food products in the European Union (EU) in 2013 caused much concern that people were exposed to unsafe residues of PBZ. Because it is very effective, inexpensive and generally safe in horses, PBZ continues to be extensively used in many countries. Because of the human safety concerns and lack of residue depletion data and MRLs for PBZ, the European Union adopted the "precautionary principle" and banned PBZ for use in all food animals. Because of the valid and wide spread use of PBZ in North American horses, a lifetime ban is impractical and detrimental to equine welfare. This project was undertaken to provide information on the depletion of PBZ from urine and tissues of horses and to address concerns regarding the risk of PBZ residues in horse meat.