RT Journal Article SR Electronic T1 The major metabolite of fentanyl in the horse. JF Drug Metabolism and Disposition JO Drug Metab Dispos FD American Society for Pharmacology and Experimental Therapeutics SP 425 OP 427 VO 8 IS 6 A1 J M Frincke A1 G L Henderson YR 1980 UL http://dmd.aspetjournals.org/content/8/6/425.abstract AB 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.