Psilocybin Efficacy With or Without Pimavanserin Pretreatment

Twenty healthy adults (≥21 years old) will be enrolled to evaluate the efficacy of a single oral dose of psilocybin (25 mg) administered with or without pretreatment using oral pimavanserin (34 mg) or placebo. Outcome assessments will occur at 1 week and 1 month following psilocybin administration. The purpose of this study is to clarify the receptor-level mechanisms underlying psilocybin's effects on mood and well-being, along with the associated neurophysiologic signatures. These mechanisms will be examined using psychometric scales, autonomic and fMRI-based neurophysiologic markers, and integrated pharmacokinetic/pharmacodynamic modeling.