ABSTRACT
Compelling evidence has accumulated over the past decade indicating that
hyperalgesia may occur in the absence of an overt, precipitated withdrawal from
opioid analgesics. This paradoxical opioid-induced hyperalgesia may be a con-
tributing factor of apparent clinical opioid tolerance, referring to the need of dose
escalation to maintain the opioid analgesic effect. Until recently, the diminished
opioid analgesic effect during a course of opioid therapy is often attributed to the
presence of pharmacological opioid tolerance (i.e., desensitization of the
responsiveness of the opioid receptor and its cellular mechanism) and/or a
worsening clinical pain condition. Accordingly, opioid dose escalation appears
to be a logical approach to restoring the lost effectiveness of opioid analgesics.
This practice should be reconsidered in light of information on opioid-induced
hyperalgesia (1).
