MO HB1643

Legalizes therapeutic psilocybin use for adults 21+ with end-of-life care needs, PTSD, major depressive disorder, substance use disorders, or conditions showing efficacy in FDA-registered clinical trials

Requires users to obtain physician documentation, register with the Department of Mental Health, have psilocybin tested by a state-licensed laboratory, and limit use to 150 milligrams per 12-month period

Mandates a licensed healthcare professional (physician, psychologist, therapist, or advanced practice nurse) serve as facilitator during psilocybin sessions, with at least 30 hours of APA-approved training required

Expands Missouri's "Right to Try" law to include Schedule I controlled substances and adds life-threatening and severely debilitating conditions (not just terminal illness) as qualifying conditions for investigational drugs

Provides civil and criminal liability protections for physicians, facilitators, and healthcare providers involved in psilocybin therapy or investigational drug recommendations, except in cases of gross negligence or willful misconduct