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Lehner AF, Hughes CG, Karpiesiuk W, Harkins JD, Dirikolu L, Bosken J, Camargo F, Boyles J, Troppmann A, Woods WE, Tobin T: Development of a method for the detection and confirmation of the alpha-2 agonist amitraz and its major metabolite in horse urine. J Anal Toxicol. 2004 Oct;28(7):553-62.
Amitraz (N'-(2,4-dimethylphenyl)-N-[[(2,4-dimethylphenyl) imino] methyl]-N-methyl-me thanimidamide) is an alpha-2 adrenergic agonist used in veterinary medicine primarily as a scabicide- or acaricide-type insecticide. As an alpha-2 adrenergic agonist, it also has sedative/tranquilizing properties and is, therefore, listed as an Association of Racing Commissioners International Class 3 Foreign Substance, indicating its potential to influence the outcome of horse races. We identified the principal equine metabolite of amitraz as N-2,4-dimethylphenyl-N'-methylformamidine by electrospray ionization (+)-mass spectrometry and developed a gas chromatographic-mass spectrometric (GC-MS) method for its detection, quantitation, and confirmation in performance horse regulation. The GC-MS method involves derivatization with t-butyldimethylsilyl groups; selected ion monitoring (SIM) of m/z 205 (quantifier ion), 278, 261, and 219 (qualifier ions); and elaboration of a calibration curve based on ion area ratios involving simultaneous SIM acquisition of an internal standard m/z 208 quantifier ion based on an in-house synthesized d (6) deuterated metabolite. The limit of detection of the method is approximately 5 ng/mL in urine and is sufficiently sensitive to detect the peak urinary metabolite at 1 h post dose, following administration of amitraz at a 75-mg/horse intravenous dose. |
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