Opioid agents are widely used in veterinary medicine because of their analgesic effects. These drugs produce their effects by interacting with opioid receptors located in the CNS and in peripheral tissues, namely μ, κ, and δ receptors.1 Stimulation of μ opioid receptors is responsible for analgesia, excitatory phenomena, constipation, bradycardia, and respiratory depression, whereas a κ agonist causes some analgesic effect with less interference with gastrointestinal motility and less respiratory depression.1–4 Opioid agents have an important role in pain management in small animals. However, their use is still limited in horses because of the possibility of excitation and a clinically relevant decrease in gastrointestinal motility.3,5–8 Although opioid agonists may induce behavioral changes such as increased locomotor activity in healthy horses, pure κ opioid agonists, such as U50488H, appear to cause less interference with the normal gastrointestinal motility pattern, compared with μ agonists, such as fentanyl and morphine.3,6–8
Buprenorphine is a semisynthetic, highly lipophilic opioid agent that acts as a partial agonist at μ receptors.9 Buprenorphine has a bell-shaped dose response curve with respect to analgesia in rodents, with increasing doses resulting in less analgesia in this species.10 The effects of buprenorphine on the cardiopulmonary system are minimal in humans and dogs.11,12 Only a few reports13–15 exist on the use of buprenorphine in the equine species. Buprenorphine has been evaluated in combination with α2-adrenergic receptor agonists and with acepromazine to produce chemical restraint in horses.13,15 To our knowledge, results of the only published study14 evaluating the isolated use of buprenorphine (3 μg/kg, IV) in healthy horses and in horses with chronic obstructive pulmonary disease revealed that this drug induced an excitatory phenomenon with an increased HR and arterial blood pressure but did not induce clinically relevant changes in pulmonary function. In that study,14 however, the effects of buprenorphine on CO and gastrointestinal motility were not evaluated. In a preliminary study,a IV administration of buprenorphine at 10 μg/kg resulted in an increase in the latency period of the skin twitch reflex in response to radiant light heat directed onto the withers during a 6 hour period in comparison to control horses, providing evidence for an analgesic effect of this opioid agent in horses.
The objective of the present study was to evaluate the cardiopulmonary effects of buprenorphine in horses. In addition, the effects of this opioid agent on abdominal auscultation scores were also assessed.
Mean pulmonary artery blood pressure
Central venous pressure
Systolic arterial pressure
Diastolic arterial pressure
Mean arterial pressure
Arterial partial pressure of carbon dioxide
Arterial partial pressure of oxygen
Arterial hemoglobin saturation
Systemic vascular resistance
Carregaro AB. Estudo farmacodinâmico da buprenorfina em equinos. PhD thesis, Department of Anesthesiology, Faculdade de Medicina, São Paulo State University – UNESP, Botucatu, SP, Brazil, 2005
Xylestesin 2%, Cristália, Itapira, São Paulo, Brazil
Intro-Flex 8,5-F, Baxter Healthcare Corp, Irvine, Calif.
7-F thermodilution catheter, Baxter Healthcare Corp, Irvine, Calif
AS/3 monitor, Datex-Engstrom, Helsinki, Finland
Insyte, Becton-Dickinson, Sandy, Utah
Model PX 260, Baxter Healthcare Corp, Irvine, Calif
RapidLab 348, Chiron Diagnostics Ltd, Halstead, Essex, United Kingdom
Temgesic, Schering, São Paulo, Brazil
GraphPad Prism, version 4.00, GraphPad Software Inc, San Diego, Calif.
Yaksh TL. Pharmacology and mechanisms of opioid analgesic activity. Acta Anaesthesiol Scand 1997;41:94–111.
Kamerling S, Weckman T & Donahoe J, et al. Dose related effects of the kappa agonist U-50,488H on behaviour, nociception and autonomic response in the horse. Equine Vet J 1988;20:114–118.
Roger T, Bardon T, Ruckenbush Y. Comparative effects of mu and kappa opiate agonists on the cecocolic motility in the pony. Can J Vet Res 1994;58:163–166.
Field MJ, Carnell AJ & Gonzalez MI, et al. Enadoline, a selective kappa-opioid receptor agonist shows potent antihyperalgesic and antiallodynic actions in a rat model of surgical pain. Pain 1999;80:383–389.
Alexander F. The effect of some anti-diarrhoeal drugs on intestinal transit and faecal excretion of water and electrolytes in the horse. Equine Vet J 1978;10:229–234.
Tobin T, Combie J & Shults T, et al. The pharmacology of narcotic analgesics in the horse III. Characteristics of the locomotor effects of fentanyl and apomorphine. J Equine Med Surg 1979;3:284–288.
Tobin T, Combie J, Shults T. Pharmacology review: actions of central stimulant drugs in the horse II. J Equine Med Surg 1979;3:102–109.
Mama KR, Pascoe PJ, Steffey EP. Evaluation of the interaction of mu and kappa opioid agonists on locomotor behavior in the horse. Can J Vet Res 1993;57:106–109.
Dum JE, Herz A. In vivo receptor binding of the opiate partial agonist, buprenorphine, correlated with its agonistic and antagonistic actions. Br J Pharmacol 1981;74:627–633.
Scott DH, Arthur GR, Scott DB. Haemodynamic changes following buprenorphine and morphine. Anaesthesia 1980;35:957–961.
Martinez EA, Hartsfield SM & Melendez LD, et al. Cardiovascular effects of buprenorphine in anesthetized dogs. Am J Vet Res 1997;58:1280–1284.
Szöke MO, Blais D & Cuvelliez SG, et al. Effects of buprenorphine on cardiovascular and pulmonary function in clinically normal horses and horses with chronic obstructive pulmonary disease. Am J Vet Res 1998;59:1287–1291.
van Dijk P, Lankveld DP & Rijkenhuizen AB, et al. Hormonal, metabolic and physiological effects of laparoscopic surgery using a detomidine-buprenorphine combination in standing horses. Vet Anaesth Analg 2003;30:72–80.
Singh S, McDonell WN & Young SS, et al. The effect of glycopyrrolate on heart rate and intestinal motility in conscious horses. J Vet Anaesth 1997;24:14–19.
Muir WW, Skarda RT, Sheehan WC. Cardiopulmonary effects of narcotic agonists and a partial agonist in horses. Am J Vet Res 1978;39:1632–1635.
Kalpravidh M, Lumb WV & Wright M, et al. Effects of butorphanol, flunixim, levorphanol, morphine, and xylazine in ponies. Am J Vet Res 1984;45:217–223.
Muir WW, Robertson JT. Visceral analgesia: effects of xylazine, butorphanol, meperidine, and pentazocine in horses. Am J Vet Res 1985;46:2081–2084.
Hinchcliff KW, McKeever KH, Muir WW. Hemodynamic effects of atropine, dobutamine, nitroprusside, phenylephrine, and propranolol in conscious horses. J Vet Intern Med 1991;5:80–86.
Stephenson RB. The heart as a pump. In: Cunningham JG, ed. Veterinary physiology. 2nd ed. Philadelphia: WB Saunders Co, 1997;180–197.
Roebel LE, Cavanagh RL, Buyniski JP. Comparative gastrointestinal and biliary tract effects of morphine and butorphanol (Stadol). J Med 1979;10:225–238.
Sellon DC, Monroe VL & Roberts MC, et al. Pharmacokinetics and adverse effects of butorphanol administered by single intravenous injection or continuous intravenous infusion in horses. Am J Vet Res 2001;62:183–189.
Mircica E, Clutton RE & Kyles KW, et al. Problems associated with perioperative morphine in horses: a retrospective case analysis. Vet Anaesth Analg 2003;30:147–155.
Senior JM, Pinchbeck GL & Dugdale AH, et al. Retrospective study of the risk factors and prevalence of colic in horses after orthopaedic surgery. Vet Rec 2004;155:321–325.
Cowan A, Doxey JC, Harry EJ. The animal pharmacology of buprenorphine, an oripavine analgesic agent. Br J Pharmacol 1977;60:547–554.