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Trace level identifications of N-Ethylnicotinamide in racing horses associated with a Vitamin B3 supplement: case reports and analysis
Abstract
Nikethamide, N,N-diethyl-3-pyridinecarboxamide (Coramine®) is a central nervous system stimulant at one time used therapeutically in human medicine but no longer marketed in the US. Nikethamide is classified a Drug Class 1, Penalty Class A substance by the Association of Racing Commissioners International (ARCI) and as a Horseracing Integrity and Safety Authority (HISA) SO or banned Stimulant that lacks FDA approval. Identifications of Nikethamide or its metabolite N-Ethylnicotinamide in racing samples can result in significant penalties in horse racing. Nikethamide is rapidly metabolized to N-Ethylnicotinamide, which remains detectable in plasma and urine leading to its use as a regulatory “marker” of Nikethamide administration. N-Ethylnicotinamide is also a manufacturing impurity of nicotinamide, a form of Vitamin B3. As such, it has been identified as a trace impurity in Vitamin B3 nicotinamide supplements administered to horses. Nikethamide has also been identified in certain Corydalis plants, another potential source of trace amounts of Nikethamide and or N-Ethylnicotinamide in equines. Current LC/MS-MS technology can detect Nikethamide at 10 pg/mL concentrations in plasma, making the identification of the N-Ethylnicotinamide metabolite unnecessary in the regulatory control of Nikethamide. We now present two recent regulatory cases involving picogram/ml plasma concentrations of N-Ethylnicotinamide linked to the administration of a vitamin supplement containing low nanogram/ ml concentrations of N-Ethylnicotinamide. These cases have since been dismissed, to our knowledge based on the identified source of the N-Ethylnicotinamide being a marketed vitamin supplement.
