Ketamine Alcohol (in Treatment-Resistant Depression)

A single subanesthetic dose infusion of the N-methyl-D-aspartate (NMDA) receptor antagonist ketamine has rapid and robust antidepressant effects in patients with treatment-refractory major depressive disorder (TRD). A family history of an alcohol use disorder (Family History Positive, FHP) is one of the strongest identified predictors of an improved antidepressant response to ketamine. Like ketamine, alcohol is a functional NMDA receptor antagonist. FHP is associated with differential response to ketamine, e.g. blunted psychotomimetic side effects. One of the primary mechanistic hypotheses for ketamine's antidepressant action is the acute intrasynaptic release of glutamate from major output neurons, e.g. cortical pyramidal cells. Preliminary clinical studies have demonstrated this acute glutamate "surge" in response to subanesthetic dose ketamine. Based on these findings, the investigators hypothesize that ketamine's enhanced antidepressant efficacy in FHP TRD subjects is, at least in part, attributable to increased glutamate release relative to TRD subjects without a family history of alcohol use disorder (Family History Negative, FHN). To test this hypothesis, the investigators have designed a now two-site, open-label study of 18-55-year-old medically and neurologically healthy, currently moderately-to-severely depressed TRD patients. In total, the investigators plan to recruit 25 FHP and 25 FHN TRD subjects. All subjects must not have a current substance use disorder (except nicotine or caffeine). The experimental portion consists of two phases. The preliminary first phase is a medication taper (if needed) and psychotropic medication-free period. The experimental second phase comprises one subanesthetic dose (0.5mg/kg x 40 minute) ketamine infusion. The ketamine infusion will occur during 7T-magnetic resonance imaging (MRI), both resting-state functional MRI (rs-fMRI) and magnetic resonance spectroscopy (MRS) to detect glutamate in the ventromedial prefrontal cortex/ventral anterior cingulate cortex (vmPFC/vACC). The primary outcome measure is group mean change in Montgomery-Åsberg Depression Rating Scale (MADRS) score from pre-ketamine infusion (baseline) to one-week post-infusion, where the investigators observed ketamine's greatest antidepressant effect in FHP TRD. Additional outcome measures are vmPFC/vACC glutamate change in response to ketamine based on family history status. In summary, this study will provide key mechanistic information on ketamine's improved antidepressant efficacy in a biologically-enriched subgroup. This will contribute to the systematic development of more efficacious, personalized treatments for major depression in an effort to reduce its enormous public health burden.