Clinical interpretation of opioid tolerance versus opioid-induced hyperalgesia

Opioid analgesics are commonly used to manage moderate to severe pain. However, the long-term use of opioids could lead to opioid tolerance (OT) and opioid-induced hyperalgesia (OIH). Distinguishing OIH from OT would impact the practice of opioid therapy because opioid dose adjustment may differentially influence OT and OIH. Currently, there are no standard criteria of OT versus OIH causing considerable ambiguity in clinical interpretation and management of these conditions. The authors designed a practitioner-based survey consisting of 20 targeted questions. Answering these questions would require responders' actual clinical experiences with opioid therapy. The survey was conducted between 2011 and 2012 through direct mails or e-mails to 1,408 physicians who are currently practicing in the United States. The authors find that certain clinical characteristics (eg, increased pain despite opioid dose escalation) are often used by practitioners to make differential diagnosis of OT and OIH despite some overlap in their clinical presentation. A key difference in clinical outcome is that OT and OIH could be improved and exacerbated by opioid dose escalation, respectively. Our survey results revealed a significant knowledge gap in some responders regarding differential diagnosis and management of OT and OIH. The results also identified several issues, such as opioid dose adjustment and clinical comorbidities related to OT and OIH, which require future patient-based studies.