Pharmacokinetics of yohimbine following intravenous administration to horses
Version of Record online: 8 JUL 2010
© 2010 Blackwell Publishing Ltd
Journal of Veterinary Pharmacology and Therapeutics
Volume 34, Issue 1, pages 58–63, February 2011
How to Cite
DiMAIO KNYCH, H. K., STEFFEY, E. P., DEUEL, J. L., SHEPARD, R. A. and STANLEY, S. D. (2011), Pharmacokinetics of yohimbine following intravenous administration to horses. Journal of Veterinary Pharmacology and Therapeutics, 34: 58–63. doi: 10.1111/j.1365-2885.2010.01194.x
- Issue online: 10 JAN 2011
- Version of Record online: 8 JUL 2010
- (Paper received 21 October 2009; accepted for publication 11 February 2010)
DiMaio Knych, H.K., Steffey, E.P., Deuel, J.L., Shepard, R.A., Stanley, S.D. Pharmacokinetics of yohimbine following intravenous administration to horses. J. vet. Pharmacol. Therap.34, 58–63.
Yohimbine is an alpha 2 adrenergic receptor antagonist used most commonly in veterinary medicine to reverse the effects of the alpha 2 receptor agonists, xylazine and detomidine. Most notably, yohimbine has been shown to counteract the CNS depressant effects of alpha 2 receptor agonists in a number of species. The recent identification of a yohimbine positive urine sample collected from a horse racing in California has led to the investigation of the pharmacokinetics of this compound. Eight healthy adult horses received a single intravenous dose of 0.12 mg/kg yohimbine. Blood samples were collected at time 0 (prior to drug administration) and at various times up to 72 h post drug administration. Plasma samples were analyzed using liquid chromatography–mass spectrometry (LC-MS) and data analyzed using both noncompartmental and compartmental analysis. Peak plasma concentration was 114.5 + 31.8 ng/mL and occurred at 0.09 + 0.03 h. Mean ± SD systemic clearance (Cls) and steady-state volume of distribution (Vdss) were 13.5 + 2.1 mL/min/kg and 3.3 + 1.3 L/kg following noncompartmental analysis. For compartmental analysis, plasma yohimbine vs. time data were best fitted to a two compartment model. Mean ± SD Cls and Vdss of yohimbine were 13.6 ± 2.0 mL/min/kg and 3.2 ± 1.1 L/kg, respectively. Mean ± SD terminal elimination half-life was 4.4 ± 0.9 h following noncompartmental analysis. Immediately following administration, two horses showed signs of sedation, while the other six appeared behaviorally unaffected. Gastrointestinal sounds were moderately increased compared to baseline while fecal consistency appeared normal.