Global Harmonization of Pain and Distress Classification Systems: Current Analysis and Opportunity for Change

When humans suffer pain or distress, they are generally able to describe their experience to others, including doctors. Medical professionals are also able to convey the likelihood of pain and distress to humans who are voluntarily participating in clinical research trials. The same is not true for nonhuman animals. Due in great part to ethical considerations of nonhuman animals used in scientific research, many countries have developed regulations or guidelines that outline the need for the minimization or alleviation of pain and distress in laboratory animals. However, when it comes to specific regulations or guidelines issued by a country on the classification of pain and distress in research, clear and vast differences appear. This article includes a discussion of the current pain and distress classifications (or lack thereof) in 25 countries, noting similarities and differences, and examines both the barriers to, and recent trends toward, global harmonization of pain and distress classification systems for animals used in research worldwide.