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.

Inclusion Criteria:

- Patient age between 18 and 75

- History of chronic pain for at least 3 months

- Patients may have been selected for opioid taper by their pain physicians.

- Patients may or may not be on opioid therapy.

- They must have the ability to understand the protocol and provide voluntary, written,
informed consent.

Exclusion Criteria:

- Cancer pain

- Unstable medical conditions (including but not limited to history of myocardial
infarction within the past year, autoimmune diseases, uncontrolled diabetes with
hemoglobin A1C of greater than 10)

- Pregnancy

- Inability to adequately answer surveys

- History of substance abuse within 5 years

- Surgery within the past month

- Surgery planned during the next six months

- Use of systemic steroids.