Identification of hydroxyropivacaine glucuronide in equine urine by ESI+/MS/MS.
Ropivacaine is a local anesthetic that has a high potential for abuse in racing horses. It can be recovered from urine collected after administration as a hydroxylated metabolite following beta-glucuronidase treatment of the urine. Based on these findings, it has been inferred that ropivacaine is present in equine urine as a glucuronide metabolite; however, these metabolites have never been directly identified. Using ESI+/MS/MS, the presence of a [M+H]+ molecular ion of m/z 467 was demonstrated in urine corresponding to the calculated mass of a hydroxyropivacaine glucuronide +1. The abundance of this ion diminished after glucuronidase treatment with concomitant appearance of a m/z 291 peak, which is consistent with its hydrolysis to hydroxyropivacaine. In further work, the m/z 467 material was fragmented in the MS/MS system, yielding fragments interpretable as hydroxyropivacaine glucuronide. These data are consistent with the presence of a hydroxyropivacaine glucuronide in equine urine and constitute the first direct demonstration of a specific glucuronide metabolite in equine urine.
Maxwell H Gluck Equine Research Center and the Department of Veterinary Science, University of Kentucky, Lexington 40506-0099, USA. dharkins@ca.uky.edu
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Harkins
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Karpiesiuk
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Tobin
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Dirikolu
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Lehner
D000577:Amides / Q000008:administration & dosage / Q000652:urine*; D000779:Anesthetics, Local / Q000008:administration & dosage / Q000652:urine*; D000818:Animals; D005260:Female; D020719:Glucuronides / Q000652:urine; D006736:Horses / Q000502:physiology*; D013058:Mass Spectrometry; D000077212:Ropivacaine; D019966:Substance-Related Disorders
D000577:Amides; D000779:Anesthetics, Local; D020719:Glucuronides; D000077212:Ropivacaine