This study is evaluating the Sparrow Link, a wearable device that delivers gentle electrical signals to nerves in the outer ear (a technique known as transcutaneous auricular neurostimulation, or tAN). The goal is to assess whether the device is feasible to use, acceptable to patients, and may help reduce opioid withdrawal symptoms in hospitalized adults being treated for opioid use disorder (OUD). Participants will be randomly assigned to receive either the active device or a sham (inactive) version. Neither participants nor their clinical teams will know which version is used. All participants will continue receiving standard hospital care for opioid withdrawal. Researchers will collect information on how long participants use the device, whether they stop using it early, and changes in withdrawal severity. The study will also examine pain, craving, mood, anxiety, heart rate variability, and opioid use during hospitalization.

Opioid withdrawal is a major barrier to the initiation and continuation of treatment for opioid use disorder (OUD), particularly during hospitalization. Symptoms of withdrawal may lead patients to decline initiation of treatment or leave against medical advice. Neuromodulation strategies, such as transcutaneous auricular neurostimulation (tAN), are emerging as potential adjuncts to standard pharmacologic management. tAN targets cranial nerves via stimulation of the auricular branch of the vagus nerve and other nerve branches in the external ear. The Sparrow Link is a wearable tAN device intended for short-term use in clinical environments and is being evaluated in this study for its role in reducing withdrawal symptoms and enhancing the inpatient care experience.

This is a double-blind, sham-controlled, randomized pilot trial designed to evaluate the feasibility, acceptability, and preliminary effectiveness of the Sparrow Link device in hospitalized adults with OUD undergoing opioid withdrawal. The study is being conducted at UPMC Presbyterian and Montefiore hospitals with clinical oversight by the STARS (Substance Treatment and Recovery Service) addiction medicine consult team.

Eligible participants will be randomized 1:1 to receive either active or sham tAN stimulation. All participants will receive standard hospital-based opioid withdrawal management, including pharmacologic treatment as clinically indicated (e.g., methadone, buprenorphine, or full opioid agonists). The device is applied and monitored by trained research staff during daytime hours.

The study includes both implementation and effectiveness endpoints. Primary implementation outcomes include device usage consistency and early device discontinuation. The primary effectiveness outcome is change in opioid withdrawal severity, as measured by the Clinical Opiate Withdrawal Scale (COWS). The study also includes secondary measures of pain, anxiety, depressive symptoms, craving, heart rate variability, and opioid use during hospitalization. Exploratory outcomes include referral to follow-up care, intent to continue device use, and qualitative feedback from providers regarding device feasibility and integration into clinical workflow.

Inclusion Criteria:

Eligible participants must meet at least ONE of the following criteria:

1. Are continuing to experience opioid withdrawal symptoms:

   1. Despite Maximal medical therapy with methadone, buprenorphine, full agonist opioids, or non-opioid medications,

      or

   2. During tapering or detox from full agonist opioids.

   OR

2. Have chosen to decline methadone or buprenorphine but still require support for withdrawal symptoms and/or pain management.

Additionally, participants must:

• Be 18 years old or older.
• Have active history of opioid use disorder.
• Have a COWS score between 5-24 (Mild-moderate opioid withdrawal), indicating residual withdrawal symptoms.
• Be able to provide informed consent.

Exclusion Criteria:

• History of or active seizure disorder.
• Presence of a cardiac device (e.g., pacemaker, defibrillator).
• Presence of a neurostimulator (e.g., deep brain stimulator, spinal cord stimulator).
• Pregnant or lactating individuals.
• COWS score ≥ 25 (Severe Withdrawal), requiring medical stabilization.
• Abnormal ear Anatomy, ear Infections, or skin Conditions at Electrode Sites, including congenital malformations, post-surgical changes, significant scarring, open wounds, or hypersensitivity.
• Active neurological disorders, such as traumatic brain injury, stroke, multiple sclerosis, or other conditions that may interfere with neurostimulation effects or autonomic regulation as assessed at the investigator's discretion.
• Severe alcohol or benzodiazepine withdrawal that is not adequately controlled with medication, per investigator discretion.
• Known or documented allergy to hydrocolloid adhesives, as evidenced in the medical record.
• Evidence of active psychosis, as documented in the medical record or reported by clinical staff.
• Non-English speakers, whose limited English proficiency precludes informed consent or meaningful participation in study assessments validated only in English.

Individual Participant Data (IPD) from this early-phase feasibility study will not be shared due to participant confidentiality concerns, consent limitations, and the exploratory nature of the trial. Given the small sample size and potential re-identifiability of participants, especially within a high-risk inpatient population, sharing IPD could pose privacy risks. Additionally, the consent form does not explicitly authorize future data sharing, and the study's non-powered design limits generalizability of individual-level findings.