Remifentanil—Acute Opioid Tolerance and Opioid-Induced Hyperalgesia

The use of opioids may seem to be a double-edged sword; they provide straight analgesic and antihyperalgesic effects initially, but subsequently are associated with the expression of acute opioid tolerance (AOT) and opioid-induced hyperalgesia (OIH) that have been reported in experimental studies and clinical observations. It has been suggested that opioids can induce an acute tolerance and hyperalgesia in dose- and/or time-dependent manners even when used within the clinically accepted doses. Recently, remifentanil has been used for pain management in clinical anesthesia and in the intensive care units because of its rapid onset and offset. We reviewed articles analyzing AOT and/or OIH by remifentanil and focused on the following issues: (1) evidence of remifentanil inducing AOT and/or OIH and (2) importance of AOT and/or OIH in considering the reduction of remifentanil dosage or adopting preventive modulations. Twenty-four experimental and clinical studies were identified using electronic searches of MEDLINE (PubMed, Ovid, Springer, and Elsevier). However, the development of AOT and OIH by remifentanil administration remains controversial. There is no sufficient evidence to support or refute the existence of OIH in humans.