Endogenous Opioid Modulation by Ketamine

This randomized, double-blind, parallel study aimed to test whether IV ketamine acutely activates endogenous µ-opioid neurotransmission in adults with treatment-resistant major depressive disorder.

Participants received a single 40-minute infusion of ketamine (0.5 mg/kg total, infused at 0.75 mg/kg/hr) or matching saline; outcomes included PET/neuroimaging measures of µ-opioid system activation and clinical depression ratings.