The protocol for a randomized, sham-controlled trial of transcutaneous auricular neurostimulation for chronic pain and opioid withdrawal symptoms during a 4-day opioid taper for adults in the United States

BACKGROUND: Reducing opioid use is challenging due to limited evidence-based weaning methods and a lack of interventions to mitigate withdrawal symptoms. An emerging intervention using transcutaneous auricular neurostimulation (tAN) is being developed to reduce opioid withdrawal symptoms, but its mechanisms of action are not yet well understood. This is a clinical trial performed to investigate the mechanisms of tAN in managing pain and opioid withdrawal during opioid taper in adults with chronic pain.

METHODS: This is a single-site, randomized, double-blind, and sham-controlled superiority framework trial during an inpatient opioid taper for participants on long-term opioid therapy for chronic pain. Participants are recruited for an inpatient stay at a large, academic medical center in the United States. Included participants are adults between 18 and 75 years of age who have the presence of pain more than half of the days in the past 6 months, are prescribed opioid medication, have a willingness to taper the opioid dose by at least 10%, and have a urine drug screen positive for the prescribed opioid but negative for illicit drugs and nonprescribed opioids. Participants are excluded with a condition affecting their safety of participation (e.g., epileptic seizures, current suicidal ideation, current abuse of illicit drugs or alcohol, pregnancy), a condition that precludes fMRI assessment (implanted medical device, claustrophobia), or a status affecting pain medication intake (e.g., surgery in the past month, opioid prescription dose > 200 morphine milligram equivalents per day, history of neurological diseases or traumatic brain injury, active treatment for cancer). Participants are randomized to receive either active tAN (n = 20) or sham tAN (n = 20). Both groups undergo a mild-to-moderate opioid taper on day 1 and are maintained at the reduced level for 4 days under inpatient medical supervision. The primary outcome measure, brain functional magnetic resonance imaging (fMRI), is used to measure BOLD signals and resting functional connectivity (z-value) of pain networks. Secondary outcome measures are self- and clinician-observed opioid withdrawal scales, behavioral assessment questionnaires, and quantitative sensory testing (QST) data. The first subject enrollment was completed from July 25 to 28, 2023. The total enrollment count was set to 40 with two arms of equal ratios. Randomization stratification by gender at birth was performed. The study physician, intervention-providing staff member, and outcome-assessing study coordinator each perform recruitment, and each is blinded to treatment group assignment. Safety and harm measures of opioid withdrawal will be assessed with the Clinical and Subject-reported Opiate Withdrawal Scores. Vital signs will be assessed three times per day, and adverse events will be recorded and reported as necessary.

DISCUSSION: Understanding the mechanisms of action of tAN will lead to the development of more effective future non-pharmacologic treatments in mitigating withdrawal while gradually tapering participants off prescription opioid management.

TRIAL REGISTRATION: Clinicaltrials.gov, NCT05555485. Registered on 15 September 2022.