KY EDRC Advances Class B Classification for Levamisole

The Kentucky Equine Drug Research Council unanimously advanced the reclassification of levamisole as a Class B substance. Their recommendation, which needs approval from the Kentucky Horse Racing Commission, would put it in line with those of the Association of Racing Commissioners International and submitted-for-approval rules of the Horseracing Integrity and Safety Authority. Class B drugs have a high potential to influence equine performance but less than Class A drugs. Levamisole metabolizes to aminorex and possibly pemoline, stimulants in the more severe Class A classification. The council's recommendation comes a year after the KHRC vacated five rulings against trainer Joe Sharp related to a series of initially-called positives for the drug from races at Churchill Downs in November 2019. The trainer said his horses received those test results and later others in Louisiana, which sanctioned him on a Class B basis, from being treated with a deworming product containing levamisole. Levamisole is approved as a dewormer by the FDA for use in cattle, sheep, and goats but not in equines. It has off-label uses in horses largely for the treatment of Equine Protozoal Myelitis. The KHRC dropped levamisole from its classification schedule in August 2015 after hearing from Dr. Mary Scollay, then KHRC equine medical director, who explained it metabolizes into aminorex, which the KHRC chose to treat as a Class A substance. A 2022-presented levamisole study in equines that was partially co-authored by current KHRC equine medical directors Scollay and Dr. Bruce Howard noted that levamisole can stay in horses' systems for an extensive period of time while the presence of the metabolite aminorex tails off quickly.