Opioids and Pain

Abstract

This article reviews basic and clinical concepts on pain and mechanisms underlying opioid analgesia. It describes the structure, function, and cellular signaling of opioid receptors; endogenous and exogenous opioid receptor ligands; as well as the central and peripheral sites of opioid actions. The article also presents novel opioid-based therapeutic strategies, developed from recently gained knowledge on opioid receptor structures and signaling, pathological pain situations, and mutant mouse lines, aimed at the reduction of side effects such as respiratory depression, constipation, sedation, tolerance, or opioid-induced hyperalgesia. Lastly, the article addresses clinical problems associated with opioid use, particularly the long-term use of opioid analgesics in chronic pain.