Ketamine for psychotic depression: An overview of the glutamatergic system and ketamine's mechanisms associated with antidepressant and psychotomimetic effects

New drug treatments for schizophrenia: a review of approaches to target circuit dysfunction

Schizophrenia is a leading cause of global disease burden. Current drug treatments are associated with significant side-effects and have limited efficacy for many patients; highlighting the need to develop new approaches that target other aspects of the neurobiology of schizophrenia. Preclinical, in vivo imaging, post-mortem, genetic and pharmacological studies have highlighted the key role of cortical GABA-glutamatergic microcircuits and their projections to subcortical dopaminergic circuits in the pathoetiology of negative, cognitive and psychotic symptoms. Antipsychotics primarily act downstream of the dopaminergic component of this circuit. However, multiple drugs are currently in development that could target other elements of this circuit to treat schizophrenia. These include drugs for GABA or glutamatergic targets, including glycine transporters, d-amino acid oxidase, sodium channels or potassium channels. Other drugs in development are likely to primarily act on pathways that regulate the dopaminergic system such as muscarinic or trace amine receptors or serotonin 2A receptors, whilst phosphodiesterase 10 A inhibitors are being developed to modulate the downstream consequences of dopaminergic dysfunction. Our review considers where new drugs may act on this circuit and their latest clinical trial evidence in terms of indication, efficacy and side-effects. Limitations of the circuit model, including whether there are neurobiologically distinct subgroups of patients, and future directions are also considered. Several drugs based on the mechanisms reviewed have promising clinical data, with the muscarinic agonist KarXT most advanced. If they are approved for clinical use, they have the potential to revolutionise understanding of the pathophysiology and treatment of schizophrenia.

Clinical efficacy of adjunctive esketamine anesthesia in electroconvulsive therapy for major depressive disorders: A pragmatic, randomized, controlled trial

Electroconvulsive therapy (ECT) is an effective treatment for depression, and esketamine has been shown to have antidepressant effects. However, it is currently unclear whether adjunctive esketamine can enhance the clinical efficacy of ECT in real-world clinical practice. In this pragmatic clinical trial, patients with major depression were randomly assigned into two groups: patients received 0.25 mg/kg esketamine plus propofol (esketamine group) or the same volume of saline (control group) plus propofol. Results indicated that there was no difference in response and remission rates between the two groups. However, patients receiving esketamine had a higher remission rate of SI and lower psychotic scores. Patients receiving esketamine also required a lower electric dose, but the seizure duration and cognitive function were comparable between the two groups. Diastolic blood pressure increased after esketamine injection, but there was no increased risk of hypertension. Furthermore, incidence of delirium and confusion were comparable between the groups. Conclusively, adjunctive esketamine anesthesia does not provide any advantage in improving the response and remission rates of ECT. However, it can improve remission of SI and alleviate accompanying psychotic symptoms in depressive patients. With adjunctive usage, the adverse cardiovascular and neuropsychiatric events associated with esketamine appear to be tolerable.

Pharmacological treatments for psychotic depression: a systematic review and network meta-analysis

BACKGROUND

There are no recommendations based on the efficacy of specific drugs for the treatment of psychotic depression. To address this evidence gap, we did a network meta-analysis to assess and compare the efficacy and safety of pharmacological treatments for psychotic depression.

METHODS

In this systematic review and network meta-analysis, we searched ClinicalTrials.gov, CENTRAL, Embase, PsycINFO, PubMed, Scopus, and Web of Science from inception to Nov 23, 2023 for randomised controlled trials published in any language that assessed pharmacological treatments for individuals of any age with a diagnosis of a major depressive episode with psychotic features, in the context of major depressive disorder or bipolar disorder in any setting. We excluded continuation or maintenance trials. We screened the study titles and abstracts identified, and we extracted data from relevant studies after full-text review. If full data were not available, we requested data from study authors twice. We analysed treatments for individual drugs (or drug combinations) and by grouping them on the basis of mechanisms of action. The primary outcomes were response rate (ie, the proportion of participants who responded to treatment) and acceptability (ie, the proportion who discontinued treatment for any reason). We calculated risk ratios and did separate frequentist network meta-analyses by using random-effects models. The risk of bias of individual studies was assessed with the Cochrane risk-of-bias tool and the confidence in the evidence with the Confidence-In-Network-Meta-Analysis (CINeMA). This study was registered with PROSPERO, CRD42023392926.

FINDINGS

Of 6313 reports identified, 16 randomised controlled trials were included in the systematic review, and 14 were included in the network meta-analyses. The 16 trials included 1161 people with psychotic depression (mean age 50·5 years [SD 11·4]). 516 (44·4%) participants were female and 422 (36·3%) were male; sex data were not available for the other 223 (19·2%). 489 (42·1%) participants were White, 47 (4·0%) were African American, and 12 (1·0%) were Asian; race or ethnicity data were not available for the other 613 (52·8%). Only the combination of fluoxetine plus olanzapine was associated with a higher proportion of participants with a treatment response compared with placebo (risk ratio 1·91 [95% CI 1·27-2·85]), with no differences in terms of safety outcomes compared with placebo. When treatments were grouped by mechanism of action, the combination of a selective serotonin reuptake inhibitor with a second-generation antipsychotic was associated with a higher proportion of treatment responses than was placebo (1·89 [1·17-3·04]), with no differences in terms of safety outcomes. In head-to-head comparisons of active treatments, a significantly higher proportion of participants had a response to amitriptyline plus perphenazine (3·61 [1·23-10·56]) and amoxapine (3·14 [1·01-9·80]) than to perphenazine, and to fluoxetine plus olanzapine compared with olanzapine alone (1·60 [1·09-2·34]). Venlafaxine, venlafaxine plus quetiapine (2·25 [1·09-4·63]), and imipramine (1·95 [1·01-3·79]) were also associated with a higher proportion of treatment responses overall. In head-to-head comparisons grouped by mechanism of action, antipsychotic plus antidepressant combinations consistently outperformed monotherapies from either drug class in terms of the proportion of participants with treatment responses. Heterogeneity was low. No high-risk instances were identified in the bias assessment for our primary outcomes.

INTERPRETATION

According to the available evidence, the combination of a selective serotonin reuptake inhibitor and a second-generation antipsychotic-and particularly of fluoxetine and olanzapine-could be the optimal treatment choice for psychotic depression. These findings should be taken into account in the development of clinical practice guidelines. However, these conclusions should be interpreted cautiously in view of the low number of included studies and the limitations of these studies.

FUNDING

None.

Ketamine, an Old-New Drug: Uses and Abuses

Ketamine as an old-new drug has a variety of clinical implications. In the last 30 years, ketamine has become popular for acute use in humans. Ketamine in standard doses is principally utilized for the induction and maintenance of surgical procedures. Besides its use in anesthesia and analgesia, recent studies have shown that ketamine has found a place in the treatment of asthma, epilepsy, depression, bipolar affective disorders, alcohol and heroin addiction. Ketamine primarily functions as a noncompetitive antagonist targeting the N-methyl-D-aspartate (NMDA) receptor, but its mechanism of action is complex. It is generally regarded as safe, with low doses and short-term use typically not leading to significant adverse effects. Also, ketamine is known as a powerful psychostimulant. During the past decade, ketamine has been one of the commonly abused drugs.

Individual Prediction of Optimal Treatment Allocation Between Electroconvulsive Therapy or Ketamine using the Personalized Advantage Index

Introduction

Electroconvulsive therapy (ECT) and ketamine are two effective treatments for depression with similar efficacy; however, individual patient outcomes may be improved by models that predict optimal treatment assignment. Here, we adapt the Personalized Advantage Index (PAI) algorithm using machine learning to predict optimal treatment assignment between ECT and ketamine using medical record data from a large, naturalistic patient cohort. We hypothesized that patients who received a treatment predicted to be optimal would have significantly better outcomes following treatment compared to those who received a non-optimal treatment.

Methods

Data on 2526 ECT and 235 mixed IV ketamine and esketamine patients from McLean Hospital was aggregated. Depressive symptoms were measured using the Quick Inventory of Depressive Symptomatology (QIDS) before and during acute treatment. Patients were matched between treatments on pretreatment QIDS, age, inpatient status, and psychotic symptoms using a 1:1 ratio yielding a sample of 470 patients (n=235 per treatment). Random forest models were trained and predicted differential patientwise minimum QIDS scores achieved during acute treatment (min-QIDS) scores for ECT and ketamine using pretreatment patient measures. Analysis of Shapley Additive exPlanations (SHAP) values identified predictors of differential outcomes between treatments.

Results

Twenty-seven percent of patients with the largest PAI scores who received a treatment predicted optimal had significantly lower min-QIDS scores compared to those who received a non-optimal treatment (mean difference=1.6, t=2.38, q<0.05, Cohen's D=0.36). Analysis of SHAP values identified prescriptive pretreatment measures.

Conclusions

Patients assigned to a treatment predicted to be optimal had significantly better treatment outcomes. Our model identified pretreatment patient factors captured in medical records that can provide interpretable and actionable guidelines treatment selection.

The Montreal model: an integrative biomedical-psychedelic approach to ketamine for severe treatment-resistant depression

Background

Subanesthetic ketamine has accumulated meta-analytic evidence for rapid antidepressant effects in treatment-resistant depression (TRD), resulting in both excitement and debate. Many unanswered questions surround ketamine's mechanisms of action and its integration into real-world psychiatric care, resulting in diverse utilizations that variously resemble electroconvulsive therapy, conventional antidepressants, or serotonergic psychedelics. There is thus an unmet need for clinical approaches to ketamine that are tailored to its unique therapeutic properties.

Methods

This article presents the Montreal model, a comprehensive biopsychosocial approach to ketamine for severe TRD refined over 6 years in public healthcare settings. To contextualize its development, we review the evidence for ketamine as a biomedical and as a psychedelic treatment of depression, emphasizing each perspectives' strengths, weaknesses, and distinct methods of utilization. We then describe the key clinical experiences and research findings that shaped the model's various components, which are presented in detail.

Results

The Montreal model, as implemented in a recent randomized clinical trial, aims to synergistically pair ketamine infusions with conventional and psychedelic biopsychosocial care. Ketamine is broadly conceptualized as a brief intervention that can produce windows of opportunity for enhanced psychiatric care, as well as powerful occasions for psychological growth. The model combines structured psychiatric care and concomitant psychotherapy with six ketamine infusions, administered with psychedelic-inspired nonpharmacological adjuncts including rolling preparative and integrative psychological support.

Discussion

Our integrative model aims to bridge the biomedical-psychedelic divide to offer a feasible, flexible, and standardized approach to ketamine for TRD. Our learnings from developing and implementing this psychedelic-inspired model for severe, real-world patients in two academic hospitals may offer valuable insights for the ongoing roll-out of a range of psychedelic therapies. Further research is needed to assess the Montreal model's effectiveness and hypothesized psychological mechanisms.

Ketamine Evolving Clinical Roles and Potential Effects with Cognitive, Motor and Driving Ability

While driving under the influence of drugs, drivers are more likely to be involved in and cause more accidents than drivers who do not drive under the influence. Ketamine is derived from phencyclidine and acts as a noncompetitive antagonist and allosteric modulator of N-methyl-D-aspartate receptors. Ketamine has been used to treat a variety of psychiatric disorders, with the most notable being treatment-resistant depression. With the rise of at-home ketamine treatment companies, the safety of unsupervised administration remains under evaluation. A study with ketamine and a ketamine-like medication, rapasitnel, showed that those who were given ketamine experienced more sleepiness and had decreased self-reported motivation and confidence in their driving abilities. Moreover, there seem to be significant differences in the acute versus persistent effects of ketamine, as well as the anesthetic versus subanesthetic doses, both in terms of effects and outcomes. These divergent effects complicate the clinical uses of ketamine, specifically involving driving, drowsiness, and cognitive abilities. This review aims to describe not only the various clinical uses of ketamine but also the potentially detrimental effects of driving under the influence, which should be understood to help with counseling the patients who use these substances, both for their well-being and to protect public safety.

Ketamine as Add-On Treatment in Psychotic Treatment-Resistant Depression

Psychotic treatment-resistant depression is a complex and challenging manifestation of mood disorders in the clinical setting. Psychotic depression is a subtype of major depressive disorder characterized by mood-consistent hallucinations and/or delusions. Psychotic depression is often underdiagnosed and undertreated. Ketamine appears to have rapid and potent antidepressant effects in clinical studies, and the Federal Drug Agency approved the use of ketamine enantiomer esketamine-nasal spray for treatment-resistant depression pharmacotherapy in 2019. This study aimed to assess the usage of ketamine for major depressive disorder with psychotic features as an add-on treatment to the standard of care. Here we present four inpatients suffering from treatment-resistant depression with psychotic features, including one with severe suicidal crisis, all treated with 0.5 mg/kg intravenous infusion of ketamine. Subsequent monitoring revealed no exacerbation of psychotic symptoms in short and long-term observation, while stable remission was observed in all cases with imminent antisuicidal effect. Results suggest ketamine may benefit individuals with treatment-resistant depression with psychotic features.

The abuse liability of ketamine: A scoping review of preclinical and clinical studies

While ketamine has been used clinically over the past decades, it has only been recently shown to be a promising therapy for treatment-resistant depression (TRD). However, ketamine and related dissociative agents may also be misused recreationally, creating significant concerns for abuse liability when prescribed for depression. Although the abuse potential of ketamine is widely recognized, there is limited evidence on the differential abuse liability of ketamine enantiomers, (S)-ketamine and (R)-ketamine. The current scoping review aims to summarize the extant literature on the abuse liability of (R,S)-ketamine and the enantiomers. A systematic search was conducted on the Embase, Medline, and APA PsycInfo databases from 1947 to July 29, 2021. Clinical and preclinical studies that assessed the abuse potential of (R,S)-ketamine, (S)-ketamine, and (R)-ketamine were screened and assessed for eligibility by two independent reviewers. A total of 65 eligible studies were identified; 55 were preclinical studies and 10 were clinical studies. Only 4 preclinical studies evaluated the abuse liability of ketamine enantiomers. Available preclinical evidence suggests that (R,S)-ketamine and (S)-ketamine have greater risk for abuse compared to (R)-ketamine. (R)-ketamine, at the antidepressant-relevant doses in rodents, appears to be safe with minimal liability for abuse. Although the abuse potential of (R,S)-ketamine is well-established in animals, limited clinical studies indicate that single or repeated ketamine administrations in professionally controlled settings did not result in misuse, dependence, diversion and/or gateway activity in patients with TRD. However, most clinical studies were retrospective and did not systematically evaluate the abuse liability of ketamine via validated psychological scales/questionnaires. Future randomized controlled trials are warranted to ascertain the abuse liability of racemic, (S)- and (R)-ketamine in TRD population, especially among patients with comorbid substance use disorders.

Esketamine for Unipolar Major Depression With Psychotic Features: A Retrospective Chart Review and Comparison With Nonpsychotic Depression

PURPOSES/BACKGROUND

The aims of the study were to assess subanesthetic esketamine as an antidepressant for major depressive disorder with psychotic features (PMDD) and to compare posttreatment symptoms among those with PMDD to a sample of nonpsychotic depression (major depressive disorder [MDD]).

METHODS/PROCEDURES

This study is a retrospective chart review of patients with major depression and current psychotic symptoms, treated with a single parenteral 0.5-mg/kg dose of esketamine. Depression symptoms were assessed at baseline and 24-hour posttreatment with the Montgomery-Åsberg Depression Rating Scale. Individuals with PMDD were matched in a 1:2 ratio to nonpsychotic MDD patients from a randomized, noninferiority clinical trial of esketamine.

FINDINGS/RESULTS

A total of 15 individuals with PMDD were included, which had higher baseline depression scores (PMDD = 40.9, MDD = 33.6, P = 0.004). A statistically significant change in depressive symptoms was found for the PMDD sample (β = -16.20 [95% confidence interval, -23.30 to -9.10], P < 0.001), and no difference between PMDD and MDD groups was observed in the matched-sample analysis (β = -2.2 [95% confidence interval, -9.32 to 4.58], P = 0.537). Treatment-induced dissociative symptoms were present for both groups, self-contained to within 2 hours after treatment, and no exacerbation of psychotic symptoms was found in clinical assessments.

IMPLICATIONS/CONCLUSIONS

Results suggest a single 0.5-mg/kg dose of esketamine may benefit individuals with PMDD, and the symptom reduction may be comparable with esketamine's effects for MDD. Furthermore, esketamine may induce an antidepressant response in those with PMDD without complication of psychotic symptoms. Future research with controlled designs is warranted.