The purpose of this research is to determine if common medications for opioid use disorder (i.e., buprenorphine/naloxone, buprenorphine, methadone) and their metabolites (norbuprenorphine [a metabolite of buprenorphine], buprenorphine-3-glucuronide [B3G; a metabolite in buprenorphine], ethylidene dimethyl diphenyl pyrrolidine [EDDP; a metabolite of methadone]) can be detected in the dermal interstitial fluid (i.e., fluid extracted from the surface of the skin). Additional subjects who are not prescribed or taking any of these medications will be included in this study to act as a comparison group

This pilot study is an exploratory feasibility study that aims to determine if common medications for opioid use disorder (OUD; i.e., buprenorphine, methadone) and their metabolites (i.e., norbuprenorphine [a metabolite of buprenorphine], buprenorphine-3-glucuronide [B3G; a metabolite in buprenorphine], ethylidene dimethyl diphenyl pyrrolidine [EDDP; a metabolite for methadone]), can be detected in dermal interstitial fluid (ISF). Microliter volumes of ISF from the surface of the skin will be collected from patients with a prescription for each these medications (buprenorphine n = 10; methadone n = 10) and controls (n=2) using a microneedle patch or minimally invasive microneedle array that may be used in conjunction with a standard vacuum pump. Levels of these medications and their metabolites will then be detected and quantitated in these samples using standard and well-established instrumental analysis for comparison to blood samples.

Aim 1: Detect and quantitate buprenorphine and norbuprenorphine in ISF collected from the surface of the skin using a minimally invasive microneedle array. ISF collected from the surface of the skin will be tested for buprenorphine (i.e., Suboxone®, Subutex®), norbuprenorphine (a metabolite of buprenorphine), and B3G (a metabolite of buprenorphine) using standard instrumental analysis.

Aim 2: Detect and quantitate methadone in ISF collected from the surface of the skin using a minimally invasive microneedle array. ISF collected from the surface of the skin will be tested for methadone and EDDP using standard instrumental analysis.

Aim 3: Establish correspondence between detected medication levels in ISF and blood. Medication levels for buprenorphine and methadone detected in the ISF will be compared to medication levels measured in blood samples for the purpose of understanding the correlation between the ISF and blood levels.

Inclusion Criteria:

• Age 18-65.
• A prescription for buprenorphine at dose ≥ 16 mg/4mg, a prescription for buprenorphine/naloxone at dose ≥ 16 mg/4mg, a prescription for methadone at dose ≥ 60mg, or part of the control group.
• Taken buprenorphine, buprenorphine/naloxone, or methadone as prescribed in the last 7 days, or part of the control group

Exclusion Criteria:

• A condition preventing or complicating ISF collection. Conditions may include dermatological (skin) condition, immunodeficiency, recent blood donation, anemia, cancer, congestive heart failure, HIV, Hepatitis C [HCV], or tuberculosis [TB].
• Any active severe depression (e.g., suicidal ideation) or mania symptoms.
• Lactation, pregnancy, or intending to become pregnant during the course of the study.
• Alcohol use in the past 7 days.
• Illicit substance use in past 7 days (e.g., heroin, methamphetamines).
• Under a conservatorship.

Patients receiving medication assisted treatment for opioid use disorder and control subjects not receiving any treatment for this condition.

2 days after study blood and isf sample collection.

Difficulty recruiting subjects taking 16 mg or more of buprenorphine. Buprenorphine study group limited to 2 instead of the goal of 10 subjects. Data on buprenorphine reported as area under the curve and reading less than the level of detection for the assay reported as 0. Subject taking gabapentin 800mg 3 times a day was excluded from analysis of the correlation of blood and isf levels due to known drug-drug interaction with methadone.