Pain Control in Animals
Position
"The Canadian Veterinary Medical Association (CVMA) recommends that veterinarians do not perform surgical procedures or treat medical conditions without the appropriate use of anesthetic and analgesic drugs. The potential for pain in animals with surgical or medical conditions must always be considered, and such pain should be prevented or treated whenever possible."
Background
Nociception and the pathophysiology of pain in mammals are well described (1,2). Species-typical responses to pain are increasingly well understood. Thus the capacity of animals to experience pain is no longer a matter of debate, and absence of pain should not be surmised from the stoic behaviour that is typical of many species (3-5). Instead, a precautionary approach is required, in order to practice veterinary medicine in an ethical and humane manner.
In the case of surgically-induced pain, successful management typically requires the use of analgesic drugs preoperatively and postoperatively, in combinations that ensure intervention at more than one level of the nociceptive pathway. The concurrent use of two or more pharmacological classes of analgesic drugs (opioids, alpha-2 agonists, anti-inflammatories, local anesthetics, dissociative anesthetics) generally provides more effective pain control, with fewer side-effects, than therapy with a single drug (1,2). While sedatives (phenothiazines, benzodiazepines) and general anaesthetics (thiopental, propofol, gas anaesthetics) alter the perception of pain, they do not substantially alter nociceptive processing and should not be considered analgesic drugs.
Currently, some anesthetic and analgesic drugs are licensed for use in companion animals, but few are licensed for use in livestock or wild animals. The CVMA recognizes that there is an urgent need to approve anesthetic and analgesic drugs for species used for human consumption, and to provide veterinarians and producers with appropriate withdrawal times for these drugs. There are quality assurance programs for some livestock species that prohibit the extra-label use of anesthetic and analgesic drugs. It is unlikely that the extra-label use of anesthetic and analgesic drugs in some situations poses a significant risk to human health (i.e., young farm animals that are months away from market, or wild animals anesthetized for research or animal control purposes that are months away from legal harvest seasons). The CVMA cannot support quality assurance programs that, however unintentionally, promote inhumane treatment of any species by prohibiting the extra-label use of anesthetic and analgesic drugs.
Veterinarians are obliged to manage perioperative pain effectively, and to be aware of and treat pain associated with medical conditions (5). Performance of a painful surgical procedure (e.g., castration, ovariohysterectomy, dehorning) requires the appropriate use of anesthetic and analgesic drugs. Given the current lack of anesthetic and analgesic drugs licensed for use in companion animals, livestock, wild animals, and many species used for research, the CVMA supports the responsible extra-label use of these drugs by veterinarians to ensure the humane treatment of animals. The CVMA also urges federal regulators to develop programs that facilitate approval of both old and new species-appropriate anesthetic and analgesic drugs, or to exempt most of these drugs from restrictions that unintentionally promote the inhumane treatment of animals.
References
1. Muir WW, Woolf CJ. Mechanisms of pain and their therapeutic implications. J Am Vet Med Assoc 2001;219:1346-1356.
2. Lemke KA. Understanding the pathophysiology of perioperative pain. Can Vet J 2004;45:405-413.
3. Anand KJS, Craig KD. New perspectives on the definition of pain. Pain 1996;67:3-6.
4. Paul-Murphy J, Ludders JW, Roberston SA, Gaynor JS, Hellyer PW, Wong PL. The need for a cross-species approach to the study of pain in animals. J Am Vet Med Assoc 2004;224:692-697.
5. Stookey JM. The veterinarian's role in controlling pain in farm animals. Can Vet J 46: 453- 8, 2005.
(Adopted July 2007)