Oral Buprenorphine as a Novel Low-dose Induction Strategy for Opioid Use Disorder

This is a human laboratory-based, randomized, cross-over study in which buprenorphine will be administered to healthy volunteers (n=22) in 3 separate inpatient 2-night visits, at least 1 week apart. At each visit, the participant will receive a single dose buprenorphine, either 0.15mg IV, 8mg PO, or 16mg PO. The order for the first dose administered will be fixed to the IV dose, and the subsequent doses will be randomized and counterbalanced to 8mg or 16mg PO. Participants will be given naltrexone to produce opioid blockade to eliminate the risk for opioid dependence in individuals without OUD. Timed blood samples will be collected up to 24 hours.

The approach is to conduct a randomized, cross-over trial in a controlled human laboratory setting with healthy volunteers (n=22). After obtaining informed consent, eligible participants will be scheduled for 3 separate two-night test days to receive 0.15mg IV, 8mg PO, or 16mg PO of buprenorphine. The first dose administered will be fixed to an open-label IV dose, and the subsequent doses will be randomized and counterbalanced to 8mg or 16mg PO. Visits will be scheduled at least 1 week apart to allow for washout of drug. One hour prior to receipt of the buprenorphine dose, all participants will be fed a standardized light breakfast. The IV dose will be given after establishing IV access, while the PO doses will be swallowed whole. Participants will also receive oral naltrexone 100mg 24 hours prior to each dosing to provide blockade at the mu-receptor, as well as 50mg PO at the study visit itself prior to receipt of buprenorphine. Timed blood samples will be collected in heparinized Vacutainer tubes via a catheter in the antecubital vein at baseline, and at 0.5, 1, 2, 4, 8, and 24 hours. Samples will be centrifuged and frozen until analysis.

All participants will first receive the IV arm in fixed order, in an open-label fashion. Subsequently, participants will be randomized to the two PO.

After the open-label period, the participant will receive 8mg PO, then 16mg PO will be administered in the following visit.

After the open-label period, the participant will receive 16mg PO, then 8mg PO will be administered in the following visit.

At each visit, the participant will receive a single dose of buprenorphine, either 0.15mg IV, 8mg PO, or 16mg PO. The order for the first dose administered will be fixed to the IV dose, and the subsequent doses will be randomized and counterbalanced to 8mg or 16mg PO.

The area under the plasma concentration curves (AUC) of buprenorphine will be determined. Timed blood samples will be collected in heparinized Vacutainer tubes via a catheter in the antecubital vein at baseline, and at 0.5, 1, 2, 4, 8, and 24 hours. Samples will be centrifuged and frozen until analysis.

Plasma data will be used to calculate maximum plasma concentration (Cmax) for buprenorphine, norbuprenorphine, and their glucuronides.

Plasma data will be used to calculate time to maximum plasma concentration (Tmax) for buprenorphine, norbuprenorphine, and their glucuronides.

Plasma data will be used to calculate volume of distribution (Vd) for buprenorphine, norbuprenorphine, and their glucuronides.

Plasma data will be used to calculate elimination half-life (t1/2) for buprenorphine, norbuprenorphine, and their glucuronides.

Plasma data will be used to calculate total clearance (CL) for buprenorphine, norbuprenorphine, and their glucuronides.

Pupil size will be measured through visual inspection both before and after buprenorphine dosing to confirm opioid blockade.

To confirm opioid blockade, subjective and objective opioid effects will be measured using previously validated Drug Evaluation Questionnaire (DEQ). The DEQ is a 5-item questionnaire where participants answer questions on a sliding scale from 0-100, where 0 indicates lower levels drug effects and 100 indicates higher levels of drug effects.

Inclusion Criteria: English speaking adults aged 18 years and above In good physical health as determined by routine medical screening Prior personal history of opioid use, therapeutic or non-therapeutic Exclusion Criteria: DSM-5 diagnosis of any substance use disorder excluding tobacco Presence of any alcohol, cannabis, or illicit substances on urine toxicology at any study visit Receiving treatment with opioid analgesic in last 60 days, or anticipate to require opioids during the proposed trial History of chronic pain Psychotic disorder, active suicidality or homicidality or any psychiatric condition that impair ability to provide informed consent History of hypersensitivity or allergy to buprenorphine or naltrexone Pregnant or breastfeeding Liver function test greater than 3 times upper normal limit Receiving medications that are strong or moderate CYP3A4 inducers or inhibitors in the past 30 days