RecruitingPhase 1Drug trialExploration of Synaptotrophic Effects of Psilocybin in Opioid Use Disorder (OUD)This study will examine the synaptotrophic effects of psilocybin among medically healthy, detoxified OUD subjects. Eligible OUD participants will undergo pre- and post- psilocybin administration PET scans with the \[11C\]-UCB-J radiotracer while inpatient.