1. Unwilling or unable to refrain from use within 24 hours of scheduled study procedures: psychoactive medications or medications that may affect study results e.g., antibiotics (must finish course at least 24 hours prior to a scheduled procedure), antidiarrheal preparations, anti-inflammatory drugs [systemic corticosteroids are exclusionary], anti-nausea, cough/cold preparations) (self-report, medical history). The following medications are allowable for entry on this study: analgesics (non-narcotic and narcotic for OUD participants); antacids; antiasthma agents that are not systemic corticosteroids; antifungal agents for topical use; antihistamines (non-sedating); H2-Blockers/PPI (proton pump inhibitors); laxatives. The use of antihyperlipidemics and/or diuretics are permitted if they have been taken for at least 1 month before procedure visits and dose has been stabilized as determined by medical history and physical exam. The episodic use of benzodiazepines such as alprazolam ((TM)Xanax), diazepam ((TM)Valium) and lorazepam ((TM)Ativan), will not exclude participants from this study unless they have been taken within the last 24 hours prior to the study.