title: Preliminary investigation of concurrent administration of phenylbutazone and romifidine in healthy horses.
abstract: OBJECTIVE
  To characterize the cardiorespiratory and electrocardiographic effects of the combined administration of phenylbutazone and romifidine.
  
  
  METHODS
  Prospective four-period, four-treatment, blinded, randomized, crossover trial.
  
  
  METHODS
  Five, healthy, mixed breed horses.
  
  
  METHODS
  Prior to treatment administration, a catheter was introduced into the intra-thoracic cranial vena cava via the jugular vein and a subcutaneously located carotid artery was catheterised. All treatments were administered intravenously (IV) and consisted of saline placebo (PLC), phenylbutazone (PBZ, 4.4 mg kg(-1) ) romifidine (ROM, 80 μg kg(-1) ) and a combination of phenylbutazone (4.4 mg kg(-1) ) and romifidine (80 μg kg(-1) ). There was at least a 1 week washout period between treatments. Heart rate (HR), respiratory rate (f(R) ), systolic (SAP), diastolic (DAP) and mean (MAP) arterial pressures and central venous pressure (CVP) were recorded for baseline (prior to drug administration) and at 5 minute intervals thereafter for 30 minutes. Electrocardiographic abnormalities were recorded. Data were analyzed by anova.
  
  
  RESULTS
  For the cardiovascular variables there were no statistically significant (p>0.05) differences between horses treated with ROM and PBZ_ROM. Statistically significant (p<0.05) differences only occurred between treatments with romifidine (ROM and PBZ_ROM) and without romifidine (PLC and PBZ). Within treatments, for ROM, changes over time were statistically significant (p<0.05) for HR, SAP, DAP, MAP and CVP. For PBZ_ROM, changes over time were statistically significant (p<0.05) for CVP. Sino-atrial and atrio-ventricular blocks occurred in horses treated with ROM and PBZ_ROM.
  
  
  CONCLUSIONS
  The combined IV administration of phenylbutazone and romifidine had no statistically significant effect on cardiorespiratory variables. These limited data suggest no evidence why both agents should not be included in a preoperative medication protocol for healthy horses but do not exclude the possibility of interactions occurring in a larger population.
authors.affiliation: Department of Companion Animal Clinical Studies, Faculty of Veterinary Science, University of Pretoria, Pretoria, South Africa.
authors.forename: Karin
authors.initials: K
authors.lastname: Kruger
authors.forename: George F
authors.initials: GF
authors.lastname: Stegmann
authors.forename: Piet J
authors.initials: PJ
authors.lastname: Becker
mesh_terms: D000771:Anesthesia, Intravenous / Q000379:methods / Q000662:veterinary*; D019162:Anesthetics, Combined / Q000008:administration & dosage* / Q000494:pharmacology; D018686:Anesthetics, Intravenous / Q000008:administration & dosage* / Q000494:pharmacology; D000818:Animals; D001794:Blood Pressure / Q000187:drug effects; D006339:Heart Rate / Q000187:drug effects; D006736:Horses; D007093:Imidazoles / Q000008:administration & dosage* / Q000494:pharmacology; D010653:Phenylbutazone / Q000008:administration & dosage* / Q000494:pharmacology; D056152:Respiratory Rate / Q000187:drug effects
chemical_list: D019162:Anesthetics, Combined; D018686:Anesthetics, Intravenous; D007093:Imidazoles; C076257:romifidine; D010653:Phenylbutazone