Opioids for chronic nonmalignant and neuropathic pain

It is now two hundred years ago that theGerman pharmacist F.W. Sertürner isolated the first pure opium alkaloid (Sertürner, 1805, 1806, 1817) that he named ‘‘morphine’’. Up-to-now the later so-called opioids are still the mainstay in modern pharmacological treatment of acute and chronic pain. Driven by the growing awareness of an unacceptably widespread undertreatment of pain together with the development of new semisynthetic and synthetic drugs with opioid receptor-mediated actions, themedical use of opioids has now progressively increased throughout the world not only for the relief of acute surgical, posttraumatic and cancer-related pain, but also for the challenging group of nonmalignant chronic pain syndromes. Moreover, opioids provide an expanding field for clinical and basic sciences research, and consequently the last few years have witnessed an unmatched progress in understanding opioid drug action, the physiological role of endogenous opioids and their receptors. Much of this recent progress is reviewed in this special issue of the European Journal of Pain. Bringing together experts in basic neurosciences, pharmacology, psychology and clinical pain medicine from all parts of Europe, the fine collection of review articles in this issue of the journal provides a timely and state-of-the-art overview on current developments and breakthroughs in the field. On the basis of current knowledge and clinical experience, the present minireviews draw together experimental observations pertaining to opioid pharmacology, analgesic efficacy, tolerance, addiction and other aspects without loosing sight on the clinically relevant possibility of serious morbidity associated with opioids in special indications or patient populations. The impact of the patient s genetic background on drug action is currently being unravelled. For example, variations in the expression of drug metabolizing enzymes such as the polymorphic cytochrome P450 enzyme directly influences blood levels of the respective drug, including opioids (see Stamer, Bayerer and Stüber, this issue). To study the classical analgesic actions of