Bedding dope test risk

Flunixin excreted in the urine may be ingested with bedding, risking prolonging the time taken to clear the drug from the body.

Owners and trainers should be aware that horses may recycle anti-inflammatory drugs such as flunixin in the stable environment. This may prolong the time the drug is detected in the urine - thus increasing the risk of positive dope test.

Flunixin is a non-steroidal anti-inflammatory drug commonly used in horses. The rules of many disciplines prohibit its presence in the blood or urine of horses on the day of competition.

Detection times have been established for some medications to help veterinarians advise owners and trainers on how long before a competition treatment should be withdrawn to minimise the risk of the drug being found in the urine. However, research in France shows that the problem can be complicated by horses absorbing flunixin from bedding that has been contaminated by urine containing the excreted drug.

Work at the Laboratoire des Course Hippiques, found that, even if bedding is removed completely and the floor brushed out, there is still a risk of a "rebound" increase in urine flunixin levels.

Dr Marie Agnès Popot and colleagues looked at the excretion profiles of flunixin in urine collected from horses under various systems of stable management. They gave flunixin as either a single intravenous dose (1mg/kg) or as an oral paste (0.5mg/kg twice daily for 3 days).

Horses were housed in stables from which the bedding was either completely removed on a daily basis, or only "skipped out" (removing only soiled bedding on a daily basis, and cleaned completely once a week.)

The largest rebound in urine flunixin concentration was seen in those horses kept in stables that were not cleaned completely on a daily basis. However, removing all the bedding and sweeping the floor could not totally prevent rebound in flunixin levels. The only circumstance in which a rebound in urine flunixin levels did not occur was when the drug was given intravenously and the horse was moved to a clean stable after 24 hours.

"Flunixin is mainly eliminated by renal clearance and a large amount of flunixin is eliminated in urine within the first 24 hours following administration" the researchers explain in a report in the Journal of Veterinary Pharmacology and Therapeutics. "Then, for horses housed in unclean boxes, the conditions  exist for the possibility of prolonged recycling; the only way to break recycling is to move the horse in  another separate box after the first 24 hour of treatment, rendering unavailable the flunixin excreted in the urine for the first 24 hour."

They conclude that attention to stable hygiene can drastically reduce the risk of spurious drug excretion profiles for drugs such as flunixin that are mainly eliminated in the urine.

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