Psilocybin for Opioid Use Disorder in Patients on Methadone Maintenance With Ongoing Opioid Use

This randomized double-blind placebo-controlled trial will investigate whether 2 doses of psilocybin administered under supportive conditions can reduce illicit opioid use (assessed by self-report and urine toxicology) and improve quality of life as measured by World Health Organization Quality of Life (WHOQOL-BREF) in individuals with OUD in MMT who are concurrently using other opioids illicitly. In addition, the investigators will investigate secondary outcomes including whether psilocybin under supportive conditions improves mood, reduces use of tobacco and other non-opioid drugs, improves chronic pain and sleep.

Ninety-two participants aged 21-70 who meet Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5) criteria for OUD, are enrolled in a MMT program for at least 3 months, and have urine toxicology positive for methadone and another opioid will be recruited from the community and complete all study procedures. Participants will be randomized to an active group or control group (46 per group). Participants will undergo a total of 2 dosing sessions (whether psilocybin or placebo). The active group will receive 40mg psilocybin first. All participants will receive a second dosing session at three months. The active group will be further randomized, with half receiving 40mg psilocybin, and half receiving placebo at three months to test a secondary hypothesis that two doses of psilocybin are more effective in treating OUD than a single dose.