Inclusion Criteria:  Provision of signed and dated informed consent form. Stated willingness to comply with all study procedures and availability for the duration of the study (including inpatient stay and participation in video assessments and remote drug screens for the duration of the 12-week outpatient study period). Stated desire to be opioid abstinent without medications for treating opioid use disorder. Male or female, aged 18-65 years. In good general health as evidenced by medical history. Meet Diagnostic and Statistical Manual (DSM)-5 criteria for opioid use disorder (any severity level) alone or comorbid with stable medical diseases (except for certain medications below). For females of reproductive potential: use of highly effective contraception for at least 1 month prior to screening and agreement to use such a method for the duration of the study. Initiating opioid discontinuation at Isaiah House. Clinical Opiate Withdrawal Scale (COWS) total score is 13 or greater.  Exclusion Criteria:  Acute/unstable illness: conditions making it unsafe to participate. Chronic illnesses: primarily seizures and dementing illnesses, including medications for these neurological conditions. Current serious psychiatric disease: psychosis, bipolar disorder. Requiring detoxification from alcohol or benzodiazepines. Current use of anxiolytics, hypnotics (prescription and over the counter), antidepressants, anticonvulsants, sedating histamine-1 receptor subtype antihistamines (non-sedating second generation histamine-4 receptor subtype antihistamines are allowed), prescription and over the counter stimulants. Current diagnosis other than opioid use disorder requiring chronic opioid treatment. Presence of a cardiac pacemaker. Pregnancy or lactation. Females who do not agree to sexual abstinence or are heterosexually active and not using (self-report) medically approved birth control measures (sterilization, tubal ligation, oral/depot contraceptives, abstinence, intrauterine device, barrier method such as condom/foam, or a cervical cap combined with a spermicide), are not eligible. Receiving extended-release buprenorphine (Sublocade) within 300 days of enrollment.