title: Effect of yohimbine on detomidine induced changes in behavior, cardiac and blood parameters in the horse.
abstract: OBJECTIVE
  To describe selected pharmacodynamic effects of detomidine and yohimbine when administered alone and in sequence.
  
  
  METHODS
  Randomized crossover design.
  
  
  METHODS
  Nine healthy adult horses aged 9 ± 4 years and weighing 561 ± 56 kg.
  
  
  METHODS
  Three dose regimens were employed in the current study. 1) 0.03 mg kg(-1) detomidine IV, 2) 0.2 mg kg(-1) yohimbine IV and 3) 0.03 mg kg(-1) detomidine IV followed 15 minutes later by 0.2 mg kg(-1) yohimbine IV. Each horse received all three treatments with a minimum of 1 week between treatments. Blood samples were obtained and plasma analyzed for detomidine and yohimbine concentrations by liquid chromatography-mass spectrometry. Behavioral effects, heart rate and rhythm, glucose, packed cell volume and plasma proteins were monitored.
  
  
  RESULTS
  Yohimbine rapidly reversed the sedative effects of detomidine in the horse. Additionally, yohimbine effectively returned heart rate and the percent of atrio-ventricular conduction disturbances to pre-detomidine values when administered 15 minutes post-detomidine administration. Plasma glucose was significantly increased following detomidine administration. The detomidine induced hyperglycemia was effectively reduced by yohimbine administration. Effects on packed cell volume and plasma proteins were variable.
  
  
  CONCLUSIONS
  Intravenous administration of yohimbine effectively reversed detomidine induced sedation, bradycardia, atrio-ventricular heart block and hyperglycemia.
authors.affiliation: K.L. Maddy Equine Analytical Chemistry Laboratory, School of Veterinary Medicine, University of California, Davis, CA 95616, USA. hkknych@ucdavis.edu
authors.forename: Heather K
authors.initials: HK
authors.lastname: DiMaio Knych
authors.forename: Vanessa
authors.initials: V
authors.lastname: Covarrubias
authors.forename: Eugene P
authors.initials: EP
authors.lastname: Steffey
mesh_terms: D058669:Adrenergic alpha-2 Receptor Antagonists / Q000493:pharmacokinetics / Q000494:pharmacology; D000818:Animals; D001522:Behavior, Animal / Q000187:drug effects*; D018592:Cross-Over Studies; D004305:Dose-Response Relationship, Drug; D004347:Drug Interactions; D006339:Heart Rate / Q000187:drug effects; D006736:Horses / Q000097:blood* / Q000502:physiology*; D006993:Hypnotics and Sedatives / Q000493:pharmacokinetics / Q000494:pharmacology; D007093:Imidazoles / Q000008:administration & dosage / Q000493:pharmacokinetics* / Q000494:pharmacology*; D015016:Yohimbine / Q000008:administration & dosage / Q000493:pharmacokinetics*
chemical_list: D058669:Adrenergic alpha-2 Receptor Antagonists; D006993:Hypnotics and Sedatives; D007093:Imidazoles; D015016:Yohimbine; C041255:detomidine