Adverse Effects of Spinal Opioids in Acute Pain and Their Management

Abstract

One of the most important goals in opioid research has been the separation of analgesia and adverse effects such as respiratory depression and dependence liability. A crucial milestone was the identification of multiple opioid receptors and the demonstration of high- and low-affinity binding sites in the brain and spinal cord. Each receptor subtype is believed to mediate specific pharmacological effects. Opioid analgesia is believed to be mediated at high-affinity (μ1 receptor sites and other pharmacological effects such as cardiovascular and respiratory depression at low-affinity μ2 receptor sites [1], It has also been postulated that μ-receptor agonists will decrease tidal volume while δ-receptor agonists will decrease respiratory frequency. Since the currently available opioids do not exhibit a high specificity, they are active on both receptors. Thus, analgesia and respiratory depression are dual complimentary effects involving μ and δ-receptors [2]. This suggests that pharmacological tailoring by molecular engineering may lead to the development of a drug with selective affinity to analgesic receptors. Several receptor-selective opioids including K-agonists have been evaluated in animal and human studies.KeywordsUrinary RetentionRespiratory DepressionOpioid AnalgesiaEpidural MorphineIntrathecal MorphineThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.