difficult choices in selecting the means by which pain and distress are controlled and how much pain and/or distress is acceptable.

Several ethical issues have been proposed for IACUC consideration when reviewing protocols involving pain and/or distress in animals (Tannenbaum, 1999):

  • Of the animal-use protocols reviewed by the IACUC, those which include pain and/or distress should be subject to a full committee review rather than review by a designated member or with an expedited review process. If necessary, the committee should involve an outside consultant to understand better the ramifications of the study.

  • The protocol should provide a compelling justification for the work, a description of the qualifications of the personnel who will perform the work and provide care for the animals, and a rationale for withholding analgesics or other pain-relieving or distress-relieving methods.

  • The protocol should contain a complete and accurate description of the severity of pain and/or distress that will potentially be experienced by the animals.

  • When it is not in conflict with the scientific goals of a well-designed study, pain relief should be provided by anesthetizing the animals; giving them analgesics; allowing them to escape or avoid the pain; or control the experimental trials.

  • A humane endpoint for the use of an animal should be determined as an element of the protocol, before work begins.

Ethically, models of persistent pain present a particular challenge because they produce pain that most guidelines for the use of animals in research state should be avoided. Scientists should demonstrate a continuing responsibility for the proper treatment of the animals involved in these experiments. Because some models produce persistent pain that the animals cannot control, it is important that investigators assess the level of pain in these animals and provide analgesic agents when they do not interfere with the purpose of the experiment. A reduction in body weight or a significant deviation from normal behavior—such as a change in normal activity patterns, social adjustment, feeding behavior, and sleep-wake patterns—suggests that an animal is in severe and possibly intolerable pain.

In animal models of inflammation and nerve injury, the IACUC should ensure that steps are taken to safeguard animal welfare. The steps may include use of fail-safe devices to avoid excessive exposure to painful stimuli (for example, monitoring stimulus intensity and duration), having in place well-established humane endpoints to deal appropriately with intractable conditions (such as self-mutilation), and postprocedure monitoring of animal well-being.

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