title: Cardiovascular effects of pimobendan in healthy mature horses.
abstract: BACKGROUND
  Pimobendan is an inodilator used in dogs for the management of heart failure due to myxomatous valve disease or dilated cardiomyopathy. The lack of data regarding the effects of pimobendan in horses prevents the rational use of this drug.
  
  
  OBJECTIVE
  To determine the cardiovascular effects of pimobendan in healthy mature horses.
  
  
  METHODS
  Randomised experimental study.
  
  
  METHODS
  Five horses were fasted overnight prior to receiving i.v. pimobendan (0.25 mg/kg bwt), intragastric (i.g.) pimobendan (0.25 mg/kg bwt) or i.g. placebo with a washout period of one week between each administration. Horses were instrumented for the measurement of right ventricular (RV) minimum pressure, RV maximum pressure, RV end diastolic pressure, and maximum rate of increase and decrease in RV pressure before and 0.5, 1, 2, 4, and 8 h after drug administration. Arterial blood pressure, central venous pressure, cardiac output and heart rate were measured at the same time points. Data were expressed as a maximum percentage of change over baseline values.
  
  
  RESULTS
  There were no adverse effects associated with administration of pimobendan. The percentage increase in heart rate was significantly greater for horses given pimobendan i.g. (33 ± 4%) and i.v. (36 ± 14%) than for those given a placebo (-2 ± 7%). The percentage increase in maximum rate of increase in RV pressure (35 ± 36%) and the percentage decrease in minimum pressure (47 ± 24%) and end diastolic pressure (34 ± 13%) were significantly greater in horses given pimobendan i.v. than in those given placebo. Other variables measured were not significantly different between treatment groups.
  
  
  CONCLUSIONS
  Pimobendan administered i.v. has positive chronotropic and inotropic effects in healthy mature horses and warrants further investigation for the treatment of heart failure in horses.
authors.affiliation: Department of Large Animal Medicine, College of Veterinary Medicine, University of Georgia, Athens, USA.
authors.forename: T
authors.initials: T
authors.lastname: Afonso
authors.affiliation: Department of Large Animal Medicine, College of Veterinary Medicine, University of Georgia, Athens, USA.
authors.forename: S
authors.initials: S
authors.lastname: Giguère
authors.affiliation: Department of Small Animal Medicine and Surgery, College of Veterinary Medicine, University of Georgia, Athens, USA.
authors.forename: G
authors.initials: G
authors.lastname: Rapoport
authors.affiliation: Department of Large Animal Medicine, College of Veterinary Medicine, University of Georgia, Athens, USA.
authors.forename: M H
authors.initials: MH
authors.lastname: Barton
authors.affiliation: Department of Small Animal Medicine and Surgery, College of Veterinary Medicine, University of Georgia, Athens, USA.
authors.forename: A E
authors.initials: AE
authors.lastname: Coleman
mesh_terms: D000818:Animals; D001794:Blood Pressure / Q000187:drug effects*; D002302:Cardiac Output / Q000187:drug effects*; D002316:Cardiotonic Agents / Q000008:administration & dosage / Q000494:pharmacology*; D004333:Drug Administration Routes; D005260:Female; D006339:Heart Rate / Q000187:drug effects*; D006736:Horses / Q000502:physiology*; D011724:Pyridazines / Q000008:administration & dosage / Q000494:pharmacology*
chemical_list: D002316:Cardiotonic Agents; D011724:Pyridazines; C041648:pimobendan
keywords: contractility; horse; inotrope; myocardium