RecruitingPhase 1Drug trialAdjunctive Effects of Psilocybin and a Formulation of BuprenorphinePrimary Aim: In participants with OUD, to characterize adverse events associated with adding two psilocybin doses to a stable buprenorphine-naloxone formulation. Secondary Aim: To evaluate the effect of psilocybin treatment on the effectiveness of a buprenorphine-naloxone maintenance therapy. Secondary Aim: To evaluate the effect of concurrent buprenorphine-naloxone use on the effects of psilocybin therapy. Descriptive Aim: To describe any changes in self-efficacy, quality of life, pain.