Quantitative Sensory Testing in Chronic Pain Patients Undergoing Opioid Treatment and Opioid Tapering

Death from drug overdoses reached a record high in 2014, with the majority involving an opioid. The United States government has labeled this an epidemic due to the progressive rise in opioid-involved deaths. In 2015, the Centers for Disease Control and Prevention determined that, on average, 650,000 opioid prescriptions are dispensed daily in the United States alone. It is well-documented and observed in clinical practice that patients on chronic opioid therapy will commonly require an escalation in opioid dose over time to maintain analgesia. The consequence of such escalations is the development of tolerance to opioids, along with other known adverse effects of opioids including respiratory depression, constipation, and potential for addiction. The drastic increase in opioid doses over the years has urged the CDC to release a report for primary care clinicians treating patients with chronic pain. This report provides a risk assessment and recommendations for prescribing opioids for non-cancer chronic pain. The guidelines state that careful reassessment of individual benefits must be considered when increasing doses to ≥50 morphine milligram equivalents (MME)/day, and that increases to ≥90 MME/day must be avoided, with recommendations for consultation with a specialist. Avoiding high opioid doses will also minimize the development of opioid-induced hyperalgesia, which is a paradoxical response to increases in opioid doses; these patients become increasingly sensitized to painful stimuli. While the precise mechanism of this condition remains to be elucidated, treatment includes reducing and tapering opioids. Interestingly, an article on patient-reported outcomes surveyed a group of 517 patients that revealed the higher opioid dose group to have greater pain intensity, poorer self-efficacy for managing pain, and more impairment in functioning and quality of life. Several studies have looked at the use of various pain testing models to investigate the effects of chronic opioid therapy and changes in pain perception. A systematic review of the literature was performed to identify clinical studies incorporating measures of hyperalgesia in patients on chronic opioid therapy. This review was aimed at finding the optimal testing modality to evaluate pain threshold and tolerance to external stimuli, including mechanical (pressure, touch, injection), thermal (cold/heat), and electrical. Although the results did not reveal any one method with sufficient power, several prospective studies evaluating hyperalgesia with heat pain ratings have shown some promising results; two studies revealing significant changes in heat responses for opioid treatment groups, and one study demonstrating lower heat pain perception values following an opioid taper. The latter study is unique in that research pertaining to changes in pain sensitivity on patients following an opioid taper is lacking. Little is known at this juncture how pain thresholds change to opioid dose reductions and following completion of a taper. The purpose of the study is to objectively measure pain threshold levels in patients without opioids, low dose opioids, high dose opioids and patients undergoing a taper from long-term opioid therapy. This study utilizes taper techniques that are commonly employed in a pain medicine practice. The innovation involves use of quantitative measures of sensitivity to evaluate patients on differing opioid doses and undergoing current taper practices.