Opioid Induced Hyperalgesia

Introduction Pain is one of the main reasons that people seek medical attention, and it is estimated to affect tens of millions of Americans. Chronic pain management commonly includes the use of opioid type medications. This is in spite of that fact that this class of drugs has well known adverse effects including the development of dependence, tolerance, and addiction. Recently, however, a troubling clinical phenomenon known as opioid-induced hyperalgesia (OIH) is gaining more and more attention with medical providers. As a consequence, there has been a noted increase in the number of clinical studies exploring the mechanisms of action and clinical significance of OIH, although prevalence has yet to be determined. For example, one small prospective study of six opioid-naïve chronic pain patients developed hyperalgesia to cold pressor pain within 4 weeks of starting moderate doses of morphine. In another study, OIH was described in multiple patients following acute opioid exposure in a peri-operative setting. Despite the debates on clinical relevance, it is clear that OIH presents a clinical challenge in acute, chronic, and cancer pain treatment settings.