The Medical clinics of North America
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Opioids have been successfully used for the management of acute and cancer-related pain. Concerns regarding side effects, tolerance, dependence, addiction, and hyperalgesia have limited the use of opioids for the management of chronic nonmalignant pain. This article will review updated information from both clinical and preclinical studies regarding opioid-induced hyperalgesia, tolerance, and dependence. The implications of these issues in clinical opioid therapy also will be discussed.
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Opioids are extensively used in the management of all types of pain and their use is underpinned by extensive trial evidence and an abundance of practical experience. We are still amassing insight into how they achieve their pain-relieving effects, however, and this understanding becomes more complex as time progresses and shows that opioids are medications with complex and diverse central and peripheral nervous system effects. Despite the 200 years that have passed since the chemical isolation of morphine, every year brings new understanding of the mode of action, propensity to cause side effects, and appropriate clinical use of opioids. This article concentrates on this "new" evidence as disclosed by recent publications.