Oral ketamine reduces the experience of stress in people with chronic suicidality

Hippocampal subfield volumes predict treatment response to oral ketamine in people with suicidality

Ongoing stress results in hippocampal neuro-structural alterations which produce pathological consequences, including depression and suicidality. Ketamine may ameliorate stress related illnesses, including suicidality, via neuroplasticity processes. This novel study sought to determine whether oral ketamine treatment specifically affects hippocampal (whole and subfield) volumes in patients with chronic suicidality and MDD. It was hypothesised that oral ketamine treatment would differentially alter hippocampal volumes in trial participants categorised as ketamine responders, versus those who were non-responders. Twenty-eight participants received 6 single, weekly doses of oral ketamine (0.5-3 mg/kg) and underwent MRI scans at pre-ketamine (week 0), post-ketamine (week 6), and follow up (week 10). Hippocampal subfield volumes were extracted using the longitudinal pipeline in FreeSurfer. Participants were grouped according to ketamine response status and then compared in terms of grey matter volume (GMV) changes, among 10 hippocampal regions, over 6 and 10 weeks. Mixed ANOVAs were used to analyse interactions between time and group. Post treatment analysis revealed a significant main effect of group for three left hippocampal GMVs as well in the left and right whole hippocampus. Ketamine acute responders (Week 6) showed increased GMVs in both left and right whole hippocampus and in three subfields compared to acute non-responders, across all three timepoints, suggesting that pre-treatment increased hippocampal GMVs (particularly left hemisphere) may be predictive biomarkers of acute treatment response. Future studies should further investigate the potential of hippocampal volumes as a biomarker of ketamine treatment response.

Chronic oral ketamine prevents anhedonia and alters neuronal activation in the lateral habenula and nucleus accumbens in rats under chronic unpredictable mild stress

Acute injections of ketamine lead to rapid but transient antidepressant effects. Chronic oral treatment at low doses, a promising non-invasive alternative, may prolong this therapeutic effect. Here, we examine the antidepressant effects of chronic oral ketamine in rats under chronic unpredictable mild stress (CUMS), and reveal their neuronal correlates. Male Wistar rats were divided into control, ketamine, CUMS, and CUMS-ketamine groups. The CUMS protocol was applied to the latter two groups for 9 weeks, and ketamine (0.013 mg/ml) was provided ad libitum to the ketamine and CUMS-ketamine groups for 5 weeks. The sucrose consumption test, forced swim test, open field test, elevated plus maze, and Morris water maze were respectively used to assess anhedonia, behavioral despair, general locomotor activity, anxiety-like behavior and spatial reference memory. CUMS caused a reduction of sucrose consumption and impaired spatial memory, accompanied by increased neuronal activation in the lateral habenula (LHb) and paraventricular thalamic nucleus (PVT). Oral ketamine prevented behavioral despair and CUMS-induced anhedonia. Reward-triggered c-Fos immunoreactivity was decreased in the LHb and increased in the nucleus accumbens shell (NAcSh) in the CUMS-ketamine group compared to the CUMS group. Ketamine did not produce a differential effect in the OFT, EPM and MWM. These results show that chronic oral ketamine at low doses prevents anhedonia without impairing spatial reference memory. The observed neuronal activation changes in the LHb and NAcSh may be involved in the preventive effects of ketamine on anhedonia. This article is part of the Special Issue on "Ketamine and its Metabolites".

A Comparison of the Anti-Anxiety Effects of Oral Ketamine and Fluvoxamine in Children with Separation Anxiety Disorder Manifesting as School Refusal

Background

Children suffer from a high prevalence of anxiety problems that require prompt treatment. It has been demonstrated that ketamine offers rapid anti-anxiety effects. This study aimed to evaluate ketamine's anti-anxiety impact in the treatment of children with school-refusal separation anxiety disorder.

Materials and Methods

In this open-labeled randomized clinical trial, 71 children (6-10 years) diagnosed with school refusal separation anxiety disorder were randomly assigned to two groups; a case group, who received ketamine at a weekly rising dose of 0.1 to 1 mg/kg; the control group treated with Fluvoxamine (25 mg/day), which could increase to 200 mg/day if necessary. The SCARED and CATS questionnaires were used to assess anxiety before treatment, at the 8^th and 16^th weeks of intervention. The data were analyzed using repeated-measures analysis of covariance.

Results

The mean anxiety scores in the eighth week (19.7 ± 16.1) were significantly lower in the ketamine group than before (31.5 ± 10.8). Until the sixteenth week (19.4 ± 14.6), there was no further decrease in scores in the ketamine group, in the fluvoxamine group, pre-treatment scores (36.3 ± 16.5) and eighth week (36.9 ± 16.6) were not significantly different, but scores decreased significantly in a sixteenth week (26.2 ± 12.5).

Conclusion

In first eight weeks of treatment, ketamine was more successful than fluvoxamine at reducing anxiety disorder, considering the emergence of this disorder and the lack of major adverse effects of ketamine, it seems to be beneficial in early phases of treatment. Due to the quick onset of ketamine in future trials, their combination therapy is recommended during the initial weeks of treatment.

Novel ketamine and zinc treatment for anorexia nervosa and the potential beneficial interactions with the gut microbiome

Anorexia nervosa (AN) is a severe illness with diverse aetiological and maintaining contributors including neurobiological, metabolic, psychological, and social determining factors. In addition to nutritional recovery, multiple psychological and pharmacological therapies and brain-based stimulations have been explored; however, existing treatments have limited efficacy. This paper outlines a neurobiological model of glutamatergic and γ-aminobutyric acid (GABA)-ergic dysfunction, exacerbated by chronic gut microbiome dysbiosis and zinc depletion at a brain and gut level. The gut microbiome is established early in development, and early exposure to stress and adversity contribute to gut microbial disturbance in AN, early dysregulation to glutamatergic and GABAergic networks, interoceptive impairment, and inhibited caloric harvest from food (e.g., zinc malabsorption, competition for zinc ions between gut bacteria and host). Zinc is a key part of glutamatergic and GABAergic networks, and also affects leptin and gut microbial function; systems dysregulated in AN. Low doses of ketamine in conjunction with zinc, could provide an efficacious combination to act on NMDA receptors and normalise glutamatergic, GABAergic and gut function in AN.

The Effects of Acute and Repeated Administration of Ketamine on Memory, Behavior, and Plasma Corticosterone Levels in Female Mice

Ketamine is an anesthetic drug that has recently been approved for the treatment of treatment-resistant depression. Females are diagnosed with Major Depressive Disorder at higher rates than males, yet most of the pre-clinical research on ketamine has been conducted in male subjects. Additionally, the literature on the acute and long-term behavioral and cognitive effects of ketamine shows conflicting results. It is important to examine the acute and long-term cognitive and behavioral effects of ketamine exposure at lower sub-anesthetic doses, as the recreational use of the drug at higher doses is associated with cognitive and memory impairments. The current study examined the effects of acute and repeated ketamine exposure on anxiety-like behavior, novel object recognition memory, depression-like behavior, and plasma corticosterone levels in 20 adult female C57BL/6J mice. Mice were exposed acutely or repeatedly for 10 consecutive days to saline or 15 mg/kg ketamine and behavior was measured in the open field test, novel object recognition test, and the Porsolt forced swim test. Plasma corticosterone levels were measured following behavioral testing. Acute ketamine exposure decreased locomotor activity and increased anxiety-like behavior in the open field test compared to controls, while repeated ketamine exposure impaired memory in the novel object recognition test. There were no effects of acute or repeated ketamine exposure on depression-like behavior in the Porsolt forced swim test or on plasma corticosterone levels. These findings suggest that a subanesthetic dose of ketamine alters behavior and cognition in female mice and the effects are dependent on the duration of exposure.

Ketamine and esketamine in suicidal thoughts and behaviors: a systematic review

BACKGROUND

More than 2% of the general population experience suicidal ideas each year and a large number of them will attempt suicide. Evidence-based therapeutic options to manage suicidal crisis are currently limited.

OBJECTIVES

The aim of this study was to overview the findings on the use of ketamine and esketamine for the treatment of suicidal ideas and acts.

DESIGN

Systematic review.

DATA SOURCES AND METHODS

PubMed, article references, and Clinicaltrials.gov up to June 30, 2022. Meta-analyses published within the last 2 years were also reviewed.

RESULTS

We identified 12 randomized controlled trials with reduction of suicidal ideation as the primary objective and 14 trials as secondary objectives. Intravenous racemic ketamine was superior to control drugs (placebo or midazolam) within the first 72 h, in spite of large placebo effects. Adverse events were minor and transient. In contrast, intranasal esketamine did not differ from placebo in large-scale studies. Limitations, clinical considerations, and opportunities for future research include the following points: large placebo effects when studying suicidal ideation reduction; small concerns about blinding quality due to dissociative effects; no studies on the risk/prevention of suicidal acts and mortality; lack of studies beyond affective disorders; no studies in adolescents and older people; lack of knowledge of long-term side effects, notably liability for abuse; no robust predictive markers; limited understanding of the mechanisms of ketamine on suicidal ideas; need for improved assessment of suicidal ideation in clinical trials; need for studies in outpatient settings, emergency room, and liaison consultation; need for research on ketamine administration; limited knowledge on the positive and negative effects of concomitant treatments.

CONCLUSION

Overall, there is compelling evidence for a favorable short-term benefit-risk balance with intravenous racemic ketamine but not intranasal esketamine. The place of ketamine will have to be defined within a multimodal care strategy for suicidal patients. Caution remains necessary for clinical use, and pharmacovigilance will be essential.

Stress, mental disorder and ketamine as a novel, rapid acting treatment

The experience of stress is often utilised in models of emerging mental illness and neurobiological systems are implicated as the intermediary link between the experience of psychological stress and the development of a mental disorder. Chronic stress and prolonged glucocorticoid exposure have potent effects on neuronal architecture particularly in regions that modulate the hypothalamic-pituitary-adrenal (HPA) axis and are commonly associated with psychiatric disorders. This review provides an overview of stress modulating neurobiological and neurochemical systems which underpin stress-related structural and functional brain changes. These changes are thought to contribute not only to the development of disorders, but also to the treatment resistance and chronicity seen in some of our most challenging mental disorders. Reports to date suggest that stress-related psychopathology is the aetiological mechanism of these disorders and thus we review the rapid acting antidepressant ketamine as an effective emerging treatment. Ketamine, an N-methyl D-aspartate (NMDA) receptor antagonist, is shown to induce a robust treatment effect in mental disorders via enhanced synaptic strength and connectivity in key brain regions. Whilst ketamine's glutamatergic effect has been previously examined, we further consider ketamine's capacity to modulate the HPA axis and associated pathways.