Safety and Tolerability of Cannabidiol Among Persons With Opioid Use Disorder Receiving Methadone or Buprenorphine

Inclusion Criteria: * Men and women aged between 18 and 70 years old. * Diagnosed with OUD and currently enrolled in methadone or buprenorphine maintenance treatment. * Having chronic pain, uniformly operationalized as grade II (high-intensity) non- cancer pain for ≥ 6 months 49. * Capable of providing informed consent in English. * Compliant in opioid maintenance treatment and on a stable dose for four weeks or longer. * Not meeting DSM-5 criteria for substance use disorders other than OUD or tobacco use disorder within the last 12 months. * No current medical problems deemed contraindicated for participation by principal investigator. * For women, not pregnant as determined by pregnancy screening; not breast-feeding; using acceptable birth control methods. Acceptable contraception for women includes oral contraceptives, contraceptive depot injections, contraceptive subdermal implants, intrauterine devices, or surgical contraception methods. Acceptable contraception for men includes condoms or surgical contraception methods. Exclusion Criteria: * Other current major psychiatric disorders deemed clinically unstable by the principal investigator, such as severe depression and/or active suicidal ideation. * Having experienced major psychosocial stressors recently (≤ 6 weeks before enrollment), at the discretion of the principal investigator. * Methadone dose under 60mg or over 100mg * Buprenorphine over 24mg. * Having received inpatient psychiatric treatment recently (≤ 60 days before enrollment). * Candidates receiving products containing either THC or CBD will be excluded. * Current use regular use other prescription opioids, gabapentinoids (pregabalin, gabapentin), antidepressants (SSRIs, SNRIs, TCAs), benzodiazepines, platelet inhibitors (e.g., clopidogrel, apixaban, ticagrelor), or NSAIDs. * Current weight of less of 60 kg. * Allergy to sesame seed oil, which is an ingredient of the CBD formulation used. * Serious medical or neurological illness or treatment for a medical disorder that could interfere with study participation as determined by principal investigator. * Participants who have elevation of liver enzymes (ALT and/or AST) 2x above the normal limit or higher.