Systemic opioid and chronic pain

Opioid analgesic drugs currently represent the most powerful choice in pain therapy. They elicit their effects by mimicking endogenous substances - opioid peptides - the natural ligands of the opioid receptors. These analgesic drugs interact with specific receptors physiologically present in the central nervous system (CNS) and in the periphery, where they serve different functions. The opioid receptors modulate well-known functions related to nociceptive transmission, but this system is also involved in the regulation of gastrointestinal, endocrine, and autonomic functions. Opioids are being prescribed more frequently for treating pain, and physicians should be able to control pain before it becomes intractable. Recent research on new endogenous opioid pathways, the development of several administration routes, and the development of new drugs with reduced ability for abuse, will allow a deeper scientific understanding, better targeted therapy, and safer use of opiate drugs for the pharmacological control of pain. The goals in this field of research are important and future knowledge will help physicians to use all analgesic drugs correctly and effectively in the treatment of pain.