This study will examine the effects of oral dronabinol tetrahydrocannabinol (THC) on withdrawal symptoms in marijuana dependent volunteers, and evaluate the safety, pharmacokinetics (PK), and cardiovascular effects of the combination of oral dronabinol and smoked marijuana to determine if there are potential significant drug interactions before conducting outpatient studies. Part One is a pilot study to characterize the cardiovascular effects/safety, subjective effects, and PK of smoked marijuana and to familiarize study staff with the conduct of controlled smoking sessions.

There will be 400 adults with moderate or severe methamphetamine use disorder randomized into this multi-site study. Eligibility will be determined during a maximum 21 day screening period. After screening is completed and eligibility is confirmed, including successful administration of a naloxone challenge, participants will begin the 12 week medication phase of the trial. Participants will be randomized to either the 1) AMC arm and receive injections of extended release naltrexone (XR-NTX; as Vivitrol®) plus once-daily oral extended-release bupropion tablets (BUP-XL) or the 2) matching placebo (PLB) arm and receive injections of placebo (iPLB) plus once-daily oral placebo (oPLB) tablets. During the course of the study, participants may be switched to another arm, as determined by the a priori adaptive aspect of the study design. Participants appearing to respond well to their original treatment assignment will not be switched. Overall, approximately 50% of the participants will receive the AMC. Injections will be administered every three weeks, in weeks 1, 4, 7, and 10. Take-home oral study medication (BUP-XL or oPLB) will be dispensed weekly for dosing on non-clinic days. Participants will be asked to attend the clinic twice weekly for observed oral medication dosing, assessments, collection of urine samples, and once-weekly medical management. On non-clinic days, participants will participate in smartphone app-based medication adherence activities. Participants will be asked to complete assessments as indicated on the schedule of assessments. Following the 12 week medication phase, participants will complete a follow-up phase, including a medication taper and post-medication phase follow-up visits during weeks 13 and 16.