title: Antinociceptive effects of oxymorphone-butorphanol-acepromazine combination in cats.
abstract: OBJECTIVE
  To determine the antinociceptive effects of oxymorphone, butorphanol, and acepromazine individually and in combination to a noxious visceral stimulus in cats.
  
  
  METHODS
  Randomized, blinded controlled study.
  
  
  METHODS
  Eight healthy mixed-breed cats (four male, four female) weighing 4.4 +/- 1.2 kg and aged 1 to 2 years old.
  
  
  METHODS
  A silastic balloon catheter was inserted per rectum and inflated at various pressures. Physiological parameters (respiratory rate, pulse rate, and blood pressure) were also recorded. Subjects were administered individual and combined intravenous (i.v.) doses of 0.025, 0.05, 0.10, and 0.20 mg/kg oxymorphone and 0.025, 0.05, 0.10, and 0.20 mg/kg butorphanol. A further study of various ratios of butorphanol and oxymorphone (3:1, 2:1, 1:1, 1:2, and 1:3), at a combined equivalent dose of 0.1 mg/kg, was performed in four cats per dose combination. In a separate study, four cats were administered combined i.v. doses of 0.05 mg/kg each of oxymorphone and butorphanol or 0.05 mg/kg each of oxymorphone, butorphanol, and acepromazine.
  
  
  RESULTS
  Combined doses of 0.05 and 0.10 mg/kg of oxymorphone and butorphanol showed mainly additive with some synergistic antinociceptive interactions and the combined dose of 0.2 mg/kg of each agent demonstrated additional antinociceptive effects, P < .05. Additional studies showed that various ratios of the two agents at a total combined dose of 0.10 mg/kg i.v. did not produce levels of antinociception that were significantly different from each other, P > .05. Acepromazine (ACE) significantly increased the magnitude of antinociception at 15 minutes when administered in combination with oxymorphone and butorphanol, P < .05. Also, physiological variables were unaffected by these drug combinations.
  
  
  CONCLUSIONS
  Low doses of oxymorphone and butorphanol in combination can produce greater levels of antinociception than when used individually. ACE, in conjunction with oxymorphone and butorphanol, produced even greater levels of antinociception than the two-opioid drug combination.
  
  
  CONCLUSIONS
  Oxymorphone, butorphanol, and ACE can be used in combination to produce additive or synergistic effects without adverse effects in cats. These data suggest that ACE and butorphanol at low doses given as preanesthetic medication followed by a mu opioid (eg, oxymorphone) after surgery at low doses may provide an effective method of pain management in the cat.
authors.affiliation: Department of Pharmacology and Toxicology, Michigan State University, East Lansing 48824, USA.
authors.forename: S L
authors.initials: SL
authors.lastname: Briggs
authors.forename: K
authors.initials: K
authors.lastname: Sneed
authors.forename: D C
authors.initials: DC
authors.lastname: Sawyer
mesh_terms: D000075:Acepromazine; D000698:Analgesia / Q000662:veterinary*; D000701:Analgesics, Opioid; D000818:Animals; D002077:Butorphanol; D002415:Cats / Q000502:physiology*; D018492:Dopamine Antagonists; D004305:Dose-Response Relationship, Drug; D004338:Drug Combinations; D005260:Female; D008297:Male; D010111:Oxymorphone
chemical_list: D000701:Analgesics, Opioid; D018492:Dopamine Antagonists; D004338:Drug Combinations; D000075:Acepromazine; D010111:Oxymorphone; D002077:Butorphanol