title: Cardiopulmonary and sedative effects of the peripheral α2-adrenoceptor antagonist MK 0467 administered intravenously or intramuscularly concurrently with medetomidine in dogs.
abstract: OBJECTIVE
  To evaluate the cardiopulmonary and sedative effects of the peripheral α(2)-adrenoceptor antagonist MK 0467 when administered IM or IV concurrently with medetomidine in dogs.
  
  
  METHODS
  8 adult dogs.
  
  
  METHODS
  Dogs received 20 μg of medetomidine/kg, IM, alone or concurrently with MK 0467 (0.4 mg/kg, IM), and 10 μg of medetomidine/kg, IV, alone or concurrently with MK 0467 (0.2 mg/kg, IV), in a randomized crossover study. Sedation characteristics were scored and hemodynamic measurements and arterial and mixed-venous blood samples for blood gas analysis were obtained before (time 0; baseline) and for 90 minutes after treatment.
  
  
  RESULTS
  Heart rate (HR), mixed-venous partial pressure of oxygen (Pvo(2)), and cardiac index (CI) were significantly lower and mean arterial blood pressure (MAP), systemic vascular resistance (SVR), and oxygen extraction ratio (ER) were significantly higher after administration of medetomidine IM or IV, compared with baseline values. Administration of medetomidine and MK 0467 IM caused a significantly higher heart rate, CI, and Pvo(2) and significantly lower MAP, SVR, and ER for 60 to 90 minutes than did IM administration of medetomidine alone. Administration of medetomidine and MK 0467 IV caused a significantly higher CI and Pvo(2) and significantly lower MAP, SVR, and ER for 45 to 90 minutes than did IV administration of medetomidine alone. There was no significant difference in sedation scores among treatments.
  
  
  CONCLUSIONS
  In dogs, MK 0467 administered concurrently with medetomidine IV or IM reduced the cardiovascular effects of medetomidine but had no detectable effect on sedation scores.
authors.affiliation: Department of Clinical Studies, Ontario Veterinary College, University of Guelph, Guelph, Ontario, Canada.
authors.forename: Nicole G
authors.initials: NG
authors.lastname: Rolfe
authors.forename: Carolyn L
authors.initials: CL
authors.lastname: Kerr
authors.forename: Wayne N
authors.initials: WN
authors.lastname: McDonell
mesh_terms: D058647:Adrenergic alpha-2 Receptor Agonists / Q000008:administration & dosage*; D058669:Adrenergic alpha-2 Receptor Antagonists / Q000008:administration & dosage*; D000758:Anesthesia / Q000662:veterinary; D000818:Animals; D001784:Blood Gas Analysis / Q000662:veterinary; D018592:Cross-Over Studies; D004285:Dogs / Q000502:physiology*; D004359:Drug Therapy, Combination / Q000662:veterinary; D006339:Heart Rate / Q000187:drug effects; D006439:Hemodynamics / Q000187:drug effects; D006993:Hypnotics and Sedatives / Q000008:administration & dosage*; D007273:Injections, Intramuscular / Q000662:veterinary; D007275:Injections, Intravenous / Q000662:veterinary; D008297:Male; D020926:Medetomidine / Q000008:administration & dosage*; D011807:Quinolizines / Q000008:administration & dosage*
chemical_list: D058647:Adrenergic alpha-2 Receptor Agonists; D058669:Adrenergic alpha-2 Receptor Antagonists; D006993:Hypnotics and Sedatives; D011807:Quinolizines; C055732:vatinoxan; D020926:Medetomidine