Are Psychoactive Substance (Opioid)‐Dependent Chronic Pain Patients Hyperalgesic?

Abstract

One indirect line of evidence for opioid-induced hyperalgesia (OIH) in humans is decreased pain thresholds (PTREs) and tolerances (PTOLs) in opioid addicts on opioids. There are a number of such studies in opioid maintained addicts, but no such studies in chronic pain patients (CPPs) with current opioid addiction. The objective of this study was to determine if this group demonstrates hyperalgesia. CPPs were subdivided into those with psychoactive substance (opioid dependence) (PSOD) (n=38) (addicted) and those taking opioids but without PSOD (n=198) (not addicted). A group of opioid-free non-CPPs served as a control group (n=36). PTREs/PTOLs were determined in each group by pressure pain stimulation in both the right and left index fingers. PTREs/PTOLs were compared by analysis of variance among the three groups controlling for sex/age and by analysis of covariance between the PSOD CPPs and non-PSOD CPPs controlling for duration of pain and visual analog scale pain level over the last 24 hours. The PSOD and non-PSOD CPPs had significantly lower PTREs and PTOLs vs. the control group, ie, were hyperalgesic. However, they were not significantly different from each other. This study contributes to the human OIH literature. However, because of the potential confounders in this study, the issue of OIH in humans remains unresolved.