Pain in Laboratory Animals: The Ethical and Regulatory Imperatives

Can it ever be ethical to leave pain untreated in laboratory animals? Despite advances in the development of alternatives to using animals in research, scientists still often cite a need to use live animals in experiments. Once that need has been confirmed by funding agencies and/or the local IACUC (Institutional Animal Care and Use Committee) or other ethics committee, but before the research plans are finalized, the potential for animal pain and distress must be assessed, and plans laid to minimize animal suffering. Regulatory concern for the pain of laboratory animals is not new. In 1970, the United States Congress updated the Animal Welfare Act (AWA) in calling for “adequate veterinary care, including the appropriate use of anesthetic, analgesic or tranquilizing drugs, when such use would be proper in the opinion of the attending veterinarian” [1]. This policy is echoed in a 2009 report of the National Academy of Sciences on the pain of laboratory animals, expanding pain management to a more generalized obligation than simply an aspect of the veterinarian's duties: “Laboratory animals need not experience substantial or ongoing pain and . . . prevention and alleviation of pain is an ethical imperative” [2]. The eighth edition of the Guide for the Care and Use of Laboratory Animals similarly states that “institutions are expected to provide oversight of all research animals and ensure that pain and distress are minimized” [3]. The ethical principle underlying laboratory animal welfare policy is that causing pain and distress to sentient animals is permissible, but requires strong justification [4]. It is a nuanced norm: causing pain is not categorically prohibited; it is allowed only with the justification that a valuable scientific experiment requires that animal pain be left untreated. Taking laboratory animal pain seriously does not equate to demonstrating a zero tolerance for animal pain. Without question, present public policy allows humans to cause laboratory animals unalleviated pain. The AWA, the Guide for the Care and Use of Laboratory Animals, and current Public Health Service policy all allow for the conduct of what are often called “Category E” studies – experiments in which animals are expected to undergo significant pain or distress that will be left untreated because treatments for pain would be expected to interfere with the experiment [3], [5], [6]. One example among many would be studies of new painkillers for arthritis, in which a control cohort of animals are left untreated, while the experimental groups receive the test painkillers (which themselves may prove not to give pain relief). But how are we to determine when to allow these experiments, or what limits to set on them? To move the mandate for “pain management when possible” from platitude to real-world guidance on difficult decisions requires carefully engaging the question of Category E experiments. In this paper we assume that animal research will continue into the foreseeable future and that if regulations remain largely as they are, there will be times when scientists, veterinarians, and the local IACUC will agree that some pain will be left untreated. We discuss how that commonly happens, how things have changed over the years since the publication of Russell and Burch's seminal work, and close with some suggestions on how the process might be improved.