Comparative metabolomic analysis in plasma and cerebrospinal fluid of humans and in plasma and brain of mice following antidepressant-dose ketamine administration.

Subanesthetic-dose racemic (R,S)-ketamine (ketamine) produces rapid, robust, and sustained antidepressant effects in major depressive disorder (MDD) and bipolar disorder (BD) and has also been shown to effectively treat neuropathic pain, complex regional pain syndrome, and post-traumatic stress disorder (PTSD). However, to date, its mechanism of action remains unclear. Preclinical studies found that (2 R,6 R;2 S,6 S)-hydroxynorketamine (HNK), a major circulating metabolite of ketamine, elicits antidepressant effects similar to those of ketamine. To help determine how (2 R,6 R)-HNK contributes to ketamine's mechanism of action, an exploratory, targeted, metabolomic analysis was carried out on plasma and CSF of nine healthy volunteers receiving a 40-minute ketamine infusion (0.5 mg/kg). A parallel targeted metabolomic analysis in plasma, hippocampus, and hypothalamus was carried out in mice receiving either 10 mg/kg of ketamine, 10 mg/kg of (2 R,6 R)-HNK, or saline. Ketamine and (2 R,6 R)-HNK both affected multiple pathways associated with inflammatory conditions. In addition, several changes were unique to either the healthy human volunteers and/or the mouse arm of the study, indicating that different pathways may be differentially involved in ketamine's effects in mice and humans. Mechanisms of action found to consistently underlie the effects of ketamine and/or (2 R,6 R)-HNK across both the human metabolome in plasma and CSF and the mouse arm of the study included LAT1, IDO1, NAD+, the nitric oxide (NO) signaling pathway, and sphingolipid rheostat.

The mental health impact of contact with COVID-19 patients on healthcare workers in the United States.

This study assessed the relationship between contact with COVID-19 patients and the mental health of healthcare workers (HCWs) in the United States (US). In a convenience sample of 957 HCWs who completed an anonymous online survey between April-May 2020, HCWs who provided direct care to confirmed or suspected COVID-19 patients reported increased depressive and posttraumatic symptoms compared to HCWs with no COVID-19 patient contact. Additionally, more frequent contact was associated with higher distress. More data drawn from diverse samples that better represent US HCWs are needed to fully assess the scope of this association.

Can 'floating' predict treatment response to ketamine? Data from three randomized trials of individuals with treatment-resistant depression.

Ketamine has rapid-acting antidepressant properties but also potentially concerning transient dissociative side effects (SEs). Recent studies noted a positive correlation between treatment response to ketamine and general dissociative SEs, as well as "floating", a depersonalization SE (a subtype of the dissociative SEs). This analysis sought to determine whether floating mediates treatment response to ketamine. Data were pooled from three double-blind, crossover, placebo-controlled ketamine clinical trials across which 82 participants with treatment-resistant depression (TRD) (44 with bipolar depression and 38 with major depressive disorder) received placebo and ketamine (0.5 mg/kg) infusions. SEs were actively solicited in a standardized fashion before and after ketamine infusion. The hypothesis that a post-infusion experience of floating would mediate antidepressant response to ketamine was assessed at 230 min post-infusion and at Day 1. Montgomery-Asberg Depression Rating Scale (MADRS) total score was the dependent variable in a linear mixed effects model. Ketamine significantly decreased MADRS scores (p < 0.0001), but no relationship was detected between floating and MADRS score at either 230 min or Day 1 post-infusion. The hypothesized mediation effect of floating was also not detected at either 230 min or Day 1 post-infusion. Taken together, the findings do not support the hypothesis that ketamine's antidepressant effects are mediated by the dissociative depersonalization subtype SE of floating.

Comprehensive assessment of side effects associated with a single dose of ketamine in treatment-resistant depression.

BACKGROUND: Concerns about ketamine for treating depression include abuse potential and the occurrence of psychotomimetic effects. This study sought to comprehensively assess side effects (SEs) associated with a single subanesthetic-dose intravenous ketamine infusion. A secondary aim was to examine the relationship between Clinician-Administered Dissociative States Scale (CADSS) scores and dissociative symptoms reported on a comprehensive, clinician-administered SE questionnaire. METHODS: Data from 188 participants were pooled from four placebo-controlled, crossover ketamine trials and one open-label study (n = 163 with either treatment-resistant major depressive disorder or bipolar disorder and 25 healthy controls). SEs were actively solicited in a standardized fashion and monitored over the time-course of each study. Statistical analyses assessed the effect of drug (ketamine, placebo) on SEs and measured the relationship between CADSS total score and SEs contemporaneously endorsed during structured interviews. RESULTS: Forty-four of 120 SEs occurred in at least 5% of participants over all trials. Thirty-three of these 44 SEs were significantly associated with active drug administration (versus placebo). The most common SE was feeling strange/weird/loopy. Most SEs peaked within an hour of ketamine administration and resolved completely by two hours post-infusion. No serious drug-related adverse events or increased ketamine craving/abuse post-administration were observed. A positive correlation was found between dissociative SEs and total CADSS score. LIMITATIONS: The post-hoc nature of the analysis; the limited generalizability of a single subanesthetic-dose ketamine infusion; and the lack of formal measures to assess ketamine's cognitive, urological, or addictive potential. CONCLUSIONS: No long-lasting significant SEs occurred over the approximately three-month follow-up period.