Pain and analgesia: the outlook for more rational treatment.

Recent advances have been made in research on the physiology of pain, especially that focusing on the primary afferent nociceptor and endogenous analgesia systems. These advances have shed new light on the mechanisms of action of some long-used methods of managing pain, have led to the development of several methods, and have suggested new lines of investigation that may lead to more rational treatment of pain. The earlier that we can intervene in the pain-transmission pathways, the more likely we are to produce adequate and lasting control of pain. The peripheral nervous system is an important target for this therapeutic approach. The elucidation of the central neural pathways, which contain endogenous opioids and mediate the analgesia elicited by opiates, has raised the possibility of more rational use of this class of analgesics. The rationale for the use of current therapies needs to be reexamined in light of these new findings, and both current and new methods need to be tested in controlled trials.