Cariprazine for Comorbid Cocaine and Opioid Use Disorder

This is a phase IIa, randomized, placebo-controlled pilot study designed to examine whether low-dose cariprazine (1.5mg/d) impacts cocaine use in medically-stable OUD patients with co-occurring CocUD who have already been taking BUP-NX at a stable dose for at least one week (up to 24mg buprenorphine/6mg naloxone daily). To be eligible for this relapse-prevention study, patients will have a cocaine-negative urine at the time of study enrollment. Approximately 48 subjects will be randomized to participate in this study. At randomization, patients will be stratified on cocaine-use severity, e.g., \< 8 days cocaine use in the prior month (less severe) vs. \> 8 days cocaine use in the prior month (more severe). A subset (n=24) of participants who are fMRI-eligible will also participate in an fMRI session during the trial, examining whether cariprazine impacts the brain response to relapse-relevant probes of reward and inhibition. All fMRI-eligible patients will be offered the scanning opportunity, until 24 scans are acquired. Blinding: This pilot study will be designated as single-blind. Participants are blind to their medication status. In our single-blind studies, we also ask our clinical / patient-interacting staff to remain \"blind\" to the participants\' medication status (similar to \'double-blind\' studies), but our non-treatment (e.g., engineering) staff have access to participant group status for preliminary data examinations. After enrollment, subjects will be randomized to receive 1.5mg/d cariprazine or placebo in a 2:1 ratio. At baseline, subjects will complete several assessments, behavioral tasks and neurocognition probes monitored by fNIRS and will then begin taking cariprazine (or placebo) each day for 8 weeks. The behavioral tasks and fNIRS session will be collected again 10-17 days after taking the first dose of study medication, when plasma levels of cariprazine are likely approaching steady-state; fMRI probes will be collected at the steady-state timepoint in the fMRI-eligible subgroup. Urines will be collected 2x/weekly throughout the trial; weekly blood samples will be analyzed for buprenorphine/norbuprenorphine as an index of BUP-NX compliance, and for metabolites of cariprazine, for cariprazine compliance. Individuals will participate for approximately 11 weeks, inclusive of the screening period and follow-up visit; maximal study medication exposure for each subject is up to 8 weeks. The study has 4 distinct phases: 1. Screening (approx. 1-2 weeks) 2. Baseline (1-2 visits; includes baseline assessments, behavioral tasks/fNIRS session, and randomization) 3. Outpatient treatment (8 wks; 2 visits/wk, includes daily cariprazine (or placebo), daily BUP-NX (at the participants\' usual community treatment site), and imaging (fMRI and fNIRS)/behavioral tasks at steady-state. 4. Follow-up: A follow-up visit to assess medical and psychological status will occur approximately 1 week after the last dose of study medication.