%0 Journal Article %A J M Frincke %A G L Henderson %T The major metabolite of fentanyl in the horse. %D 1980 %J Drug Metabolism and Disposition %P 425-427 %V 8 %N 6 %X Fentanyl, a potent, synthetic narcotic analgesic, has reportedly been used to "dope" racehorses. Urine was collected from a horse dosed with 70 mg of [3H]fentanyl, and the primary metabolite, a water-soluble, amphoteric compound, was isolated by high-pressure liquid chromatography and identified by spectroscopic analysis. This metabolite was found to be N-[1-(2-phenethyl-4-piperidinyl)] malonanilinic acid. %U https://dmd.aspetjournals.org/content/dmd/8/6/425.full.pdf