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The concept of opioid-induced hyperalgesia has recently gained prominence as a contributing factor for opioid tolerance and long-term treatment failure. But whereas the preclinical data for this phenomenon are strong, the mixed clinical data derive primarily from experimental pain models conducted in volunteers and heroin addicts, and nonstandardized clinical stimuli, e.g., surgery. The primary objective of this study is to delineate the effect of opioid dose and treatment duration on pain intensity and unpleasantness ratings following a standardized clinical pain stimulus.

Three hundred and fifty-five patients, on a steady regimen of analgesic medications and scheduled for an interventional procedure, received a standardized subcutaneous injection of lidocaine prior to a full dose of local anesthetic. Before and immediately following the injection, subjects were asked to rate pain …