Oral ketamine for depression: An updated systematic review

Plasma esketamine and noresketamine levels and antidepressant response with oral esketamine treatment

OBJECTIVE

Oral esketamine has relatively low and variable bioavailability, which may complicate broader use as an antidepressant. This study aimed to investigate associations between different pharmacokinetic outcomes and change in depressive symptoms following oral esketamine administration in patients with treatment-resistant depression. Understanding such associations may inform dosing and administration strategies in clinical practice.

METHODS

Oral esketamine was administered twice weekly for six weeks using a titration approach in 17 patients. Esketamine and noresketamine serum levels were measured 30 min and 60 min after esketamine administration. Change in depression severity was plotted against the serum levels of esketamine and noresketamine, their sum and their ratios.

RESULTS

We observed high inter-individual variability in oral esketamine pharmacokinetics, and we found no association between depressive symptom change and the pharmacokinetic outcomes. The small sample size and flexible-dose regimen complicate definitive conclusions.

DISCUSSION

In the treatment of depression, clinical response may not correspond to esketamine pharmacokinetic outcomes. Individually-based titration strategies based on clinical antidepressant effects appear to be the optimal approach moving forward.

Non-response to short-term ketamine use for treatment-resistant depression

BACKGROUND

Ketamine is currently gaining attention as a rapid-acting antidepressant for treatment-resistant depression (TRD). However, many patients fail to respond, and limited data exist on predictors of non-response. This study aims to characterize the sociodemographic and clinical features associated with non-response to ketamine among TRD patients.

METHODS

This is a post-hoc analysis of a naturalistic observational study, which enrolled 40 inpatients with treatment-resistant major depressive disorder and analyzed sociodemographic and clinical features in responders and non-responders stratified per Montgomery-Åsberg Depression Rating Scale (MADRS) during short-term ketamine administration (intravenous dosage: 0,5 mg/kg and orally: 2.0 or 2.5 mg/kg) that comprise over 4 weeks.

RESULTS

In this study, 30 patients (75%) were classified as non-responders. No significant differences were detected among sociodemographic and clinical features beyond the history of substance use disorder (SUD) - only 53.3% of non-responders reported prior SUD (vs. 100%; p = 0.0075) and a lower number of psychiatric comorbidities (p = 0.0381).

CONCLUSION

This study highlights key characteristics of TRD non-responders to ketamine, including lower rates of SUD and fewer psychiatric comorbidities. These findings suggest that a higher burden of traditional TRD risk factors may not limit ketamine efficacy and could even enhance response compared to "pure" major depressive disorder. Identifying potential non-responders early can optimize treatment decisions, reduce ineffective exposure, and guide future research on improving TRD management.

Oral esketamine for patients with severe treatment-resistant depression: Effectiveness, safety, and tolerability of a six-week open-label treatment program

BACKGROUND

Oral esketamine for patients with treatment-resistant depression (TRD) could offer certain advantages over other routes, such as intravenous or intranasal, but it has not been systematically studied in a real-world setting.

AIMS

Here we present results from a relatively large naturalistic study to evaluate the effectiveness, tolerability, and safety of oral esketamine in patients with TRD.

METHODS

One hundred eighty-five adults with severe TRD (average of 8.1 antidepressant trials plus electroconvulsive therapy in 63% without beneficial outcome) received oral esketamine treatment twice-weekly for 6 weeks with individually titrated doses ranging from 0.5 to 3 mg/kg. Outcome measures included change from baseline to week 6 on the Hamilton Depression Rating Scale (HDRS17), Minimal Clinically Important Difference (MCID), response, remission, self-reported symptom improvement, functioning, and side effects.

RESULTS

Oral esketamine treatment improved depressive symptom severity on the HDRS17 from 21.2 to 15.8 (p < 0.001). MCID, response, and remission rates were 47.1%, 26.8% and 15.6% respectively. In 45.9% of participants, treatment was continued after 6 weeks to maintain initial positive effects. Side effects were reported frequently but were overall well tolerated. The drop-out rate was 7.6%. We found no significant adverse effects associated with urinary tract or cognition.

CONCLUSIONS

Repeated treatment with oral esketamine is effective in improving depressive symptom severity in highly treatment-resistant depressive patients. It is safe, well tolerated, and patient-friendly. Considering the level of treatment resistance, outcomes were in the range of studies investigating other routes of (es)ketamine administration.

Increased odds of metabolic syndrome among adults with depressive symptoms or antidepressant use

Metabolic syndrome (MetS) is a condition that includes a cluster of risk factors for cardiovascular disease. In this paper, we aimed to evaluate the association between depressive symptoms, antidepressant use, duration of antidepressant use, antidepressant type and MetS. Data from the 2005-2018 National Health and Nutrition Examination Surveys were used in this study. Adults were included if they responded to the depressive symptoms and prescription medications questionnaires and had measures of blood pressure, waist circumference, triglycerides, high-density lipoprotein, and fasting plasma glucose. Participants were categorized by their antidepressant use (yes/no), type, and duration. This study included 14,875 participants (50.45% females), with 3616 (23.45%) meeting the criteria for MetS. Participants with higher depressive symptom scores (aOR = 1.04, 95% CI: 1.02, 1.05, p < 0.001) or those with depressive symptoms (aOR = 1.42, 95% CI: 1.17, 1.73, p = 0.001) had higher odds of MetS. A similar associations was seen among those who were on antidepressants compared to those who were not on antidepressants (aOR = 1.24, 95% CI: 1.03, 1.50, p = 0.025). Duration of antidepressant use was not significantly associated with MetS. Participants on tricyclic antidepressants had greater odds of MetS compared to those not taking any antidepressants (aOR = 2.27, 95% CI: 1.31, 3.93, p = 0.004). Our study provides evidence of the association between depressive symptoms, antidepressant use, and MetS, highlighting the importance of monitoring metabolic and cardiovascular alterations in individuals of depression.

Oral Esketamine as Alternative for Maintenance Electroconvulsive Therapy in Patients With Treatment-Resistant Depression: A Case Series

OBJECTIVES

This study investigates repeated oral esketamine as a substitution strategy for maintenance electroconvulsive therapy (M-ECT) in eight patients with treatment-resistant depression (TRD).

METHODS

In a 6-week dosing phase, esketamine was titrated from 0.5 or 1.0 mg/kg to a maximum of 3.0 mg/kg twice weekly. Outcomes included 6-week change in Inventory of Depressive Symptomatology - Self-rated (IDS-SR), Hamilton Depression Rating Scale - 17 items (HDRS17), and Outcome Questionnaire 45 (OQ-45), along with esketamine treatmentcontinuation.

RESULTS

Depression severity remained stable or improved in five patients, whereas three experienced worsening symptoms and resumed M-ECT. OQ-45 scores were available for five patients, all of whom showed improvement. Currently, four patients are still receiving oral esketamine.

CONCLUSIONS

Repeated oral esketamine may be a suitable and patient-friendly alternative to M-ECT. We recommend controlled trials to compare long-term safety and efficacy.

Ketamine for treatment-resistant obsessive-compulsive disorder: Double-blind active-controlled crossover study

BACKGROUND

Obsessive-Compulsive Disorder (OCD) may respond to ketamine treatment.

AIM

To examine the responsiveness and tolerability of treatment-refractory OCD to intramuscular (IM) ketamine compared to IM fentanyl.

METHODS

This was a randomised double-blind psychoactive-controlled study with single doses of racemic ketamine 0.5 mg/kg, 1.0 mg/kg or fentanyl 50 µg (psychoactive control). Pre-dosing with 4 mg oral ondansetron provided nausea prophylaxis. Eligible participants were aged between 18 and 50 years with severe treatment-resistant OCD. The primary efficacy measure was the Yale-Brown Obsessive-Compulsive Scale (Y-BOCS). Tolerability was measured with the Clinician-Administered Dissociative States Scale (CADSS). Repeated measures analysis of variance with orthogonal polynomial trends was used to assess the effect of drug treatment on Y-BOCS and CADSS scores.

RESULTS

Twelve participants were randomised and 10 completed the study (7 females, 3 males, mean age 33 years). Two participants dropped out due to not tolerating dissociative effects associated with the study medication. The reductions in Y-BOCS scores were greater and statistically dose-related for both ketamine doses than fentanyl (dose [linear], F(1, 9) = 6.5, p = 0.031). Score changes for all treatments were maximal at 1-2 h with a steady separation of scores out to 168 h. Ketamine was associated with short-term dissociative and cardiovascular effects.

CONCLUSIONS

We provide further preliminary evidence for the efficacy and tolerability of IM ketamine in an outpatient cohort of OCD. Additional work is required to establish the optimal dosing regimen and longer-term role of ketamine for OCD. These findings are encouraging given the well-known limitations that exist for treatments in this area.

Effects of repeated intravenous esketamine administration on affective biases

OBJECTIVES

While neuropsychological effects of conventional antidepressants are well-documented, more research is needed for rapid-acting antidepressants. This study examines the effects of esketamine on emotion processing and cognitive functioning, both acutely and sub-chronically.

METHODS

Eighteen treatment-resistant depression (TRD) patients received repeated intravenous esketamine infusions. Mood state was reported daily, and the Facial Expression Recognition Task was administered 1h before and 4h after each infusion. Other assessments included the Digit Symbol Substitution Task.

RESULTS

66.7% participants who received at least five infusions (n = 12) showed significant improvement. Emotion recognition improved for all emotions except sadness, where accuracy decreased, particularly for low-intensity expressions (p = .007, d = -1.09). Misclassifications of other emotions as sad also decreased (p = .035, d = -0.79), indicating a reduced response bias towards sadness. This shift in bias emerged after the first infusion and then consolidated over time. In parallel, participants showed significant reductions in feelings of sadness (p = .015, d = -0.89) and irritability (p = .001, d = -1.35). Symptomatic improvement negatively correlated with accuracy for and misclassifications of sadness, and cognitive functioning also improved (p = .001, d = 1.62).

CONCLUSIONS

Improvement of TRD by esketamine may involve shifts in emotion processing and cognition, with the acute mood-lifting effects of esketamine being discernible from longer-lasting antidepressant response, which consolidates after repeated administration.

Personalized use of ketamine and esketamine for treatment-resistant depression

A large and disproportionate portion of the burden associated with major depressive disorder (MDD) is due to treatment-resistant depression (TRD). Intravenous (R,S)-ketamine (ketamine) and intranasal (S)-ketamine (esketamine) are rapid-acting antidepressants that can effectively treat TRD. However, there is variability in response to ketamine/esketamine, and a personalized approach to their use will increase success rates in the treatment of TRD. There is a growing literature on the precision use of ketamine in TRD, and the body of evidence on esketamine is still relatively small. The identification of reliable predictors of response to ketamine/esketamine that are easily translatable to clinical practice is urgently needed. Potential clinical predictors of a robust response to ketamine include a pre-treatment positive family history of alcohol use disorder and a pre-treatment positive history of clinically significant childhood trauma. Pre-treatment versus post-treatment increases in gamma power in frontoparietal brain regions, observed in electroencephalogram (EEG) studies, is a promising brain-based biomarker of response to ketamine, given its time of onset and general applicability. Blood-based biomarkers have shown limited usefulness, with small-effect increases in brain-derived neurotrophic factor (BDNF) being the most consistent indicator of ketamine response. The severity of treatment-emergent dissociative symptoms is typically not associated with a response either to ketamine or esketamine. Future studies should ensure that biomarkers and clinical variables are obtained in a similar manner across studies to allow appropriate comparison across trials and to reduce the signal-to-noise ratio. Most predictors of response to ketamine/esketamine have modest effect sizes; therefore, the use of multivariate predictive models will be needed.

Glutamatergic Modulators for Major Depression from Theory to Clinical Use

Major depressive disorder (MDD) is a chronic, burdensome, highly prevalent disease that is characterized by depressed mood and anhedonia. MDD is especially burdensome as approved monoamine antidepressant treatments have weeks-long delays before clinical benefit and low remission rates. In the past 2 decades, a promising target emerged to improve patient outcomes in depression treatment: glutamatergic signaling. This narrative review provides a high-level overview of glutamate signaling in synaptogenesis and neural plasticity and the implications of glutamate dysregulation in depression. Based on this preclinical evidence implicating glutamate in depression and the rapid improvement of depression with ketamine treatment in a proof-of-concept trial, a range of N-methyl-D-aspartate (NMDA)-targeted therapies have been investigated. While an array of treatments has been investigated in registered phase 2 or 3 clinical trials, the development of most of these agents has been discontinued. Multiple glutamate-targeted antidepressants are actively in development, and two are approved. Nasal administration of esketamine (Spravato®) was approved by the US Food and Drug Administration (FDA) in 2019 to treat adults with treatment-resistant depression and in 2020 for adults with MDD with acute suicidal ideation or behavior. Oral combination dextromethorphan-bupropion (AXS-05, Auvelity® extended-release tablet) was FDA approved in 2022 for the treatment of MDD in adults. These approvals bolster the importance of glutamate in depression and represent an exciting breakthrough in contemporary psychiatry, providing new avenues of treatment for patients as first-line therapy or with either poor response or unacceptable side effects to monoaminergic antidepressants.

Ketamine, Esketamine, and Arketamine: Their Mechanisms of Action and Applications in the Treatment of Depression and Alleviation of Depressive Symptoms

Research over the past years has compared the enantiomers (S)-ketamine (esketamine) and (R)-ketamine (arketamine) of the previously known racemic mixture called ketamine (R/S-ketamine). Esketamine has been found to be more potent, offering three times stronger analgesic effects and 1.5 times greater anesthetic efficacy than arketamine. It provides smoother anesthesia with fewer side effects and is widely used in clinical settings due to its neuroprotective, bronchodilatory, and antiepileptic properties. Approved by the FDA and EMA in 2019, esketamine is currently used alongside SSRIs or SNRIs for treatment-resistant depression (TRD). On the other hand, arketamine has shown potential for treating neurological disorders such as Alzheimer's, Parkinson's, and multiple sclerosis, offering possible antidepressant effects and anti-inflammatory benefits. While esketamine is already in clinical use, arketamine's future depends on further research to address its safety, efficacy, and optimal dosing. Both enantiomers hold significant clinical value, with esketamine excelling in anesthesia, and arketamine showing promise in neurological and psychiatric treatments.

At-home, telehealth-supported ketamine treatment for depression: Findings from longitudinal, machine learning and symptom network analysis of real-world data

BACKGROUND

Improving safe and effective access to ketamine therapy is of high priority given the growing burden of mental illness. Telehealth-supported administration of sublingual ketamine is being explored toward this goal.

METHODS

In this longitudinal study, moderately-to-severely depressed patients received four doses of ketamine at home over four weeks within a supportive digital health context. Treatment was structured to resemble methods of therapeutic psychedelic trials. Patients receiving a second course of treatment were also examined. Symptoms were assessed using the Patient Health Questionnaire (PHQ-9) for depression. We conducted preregistered machine learning and symptom network analyses to investigate outcomes (osf.io/v2rpx).

RESULTS

A sample of 11,441 patients was analyzed, demonstrating a modal antidepressant response from both non-severe (n = 6384, 55.8 %) and severe (n = 2070, 18.1 %) baseline depression levels. Adverse events were detected in 3.0-4.8 % of participants and predominantly neurologic or psychiatric in nature. A second course of treatment helped extend improvements in patients who responded favorably to initial treatment. Improvement was most strongly predicted by lower depression scores and age at baseline. Symptoms of Depressed mood and Anhedonia sustained depression despite ongoing treatment.

LIMITATIONS

This study was limited by the absence of comparison or control groups and lack of a fixed-dose procedure for ketamine administration.

CONCLUSIONS

At-home, telehealth-supported ketamine administration was largely safe, well-tolerated, and associated with improvement in patients with depression. Strategies for combining psychedelic-oriented therapies with rigorous telehealth models, as explored here, may uniquely address barriers to mental health treatment.

Increasing the bioavailability of oral esketamine by a single dose of cobicistat: A case study

Background

Intranasal esketamine is an approved drug for treatment‐resistant depression (TRD); however, it is costly and may result in specific adverse effects. In this single case study, we explored if oral esketamine can be a suitable alternative.

Methods

In collaboration with a 39‐year‐old female with TRD, we compared plasma concentration curves of intranasal (84 mg) and oral (1, 2 and 4 mg/kg) esketamine. Because oral esketamine has a relatively low bioavailability, it results in a different ratio between esketamine and its primary metabolite noresketamine. To increase the bioavailability of oral esketamine, we co‐administered a single dose of the cytochrome P‐450 (CYP) 3A4 inhibitor cobicistat (150 mg).

Results

For all doses administered, oral esketamine resulted in lower esketamine but higher noresketamine peak plasma concentrations compared with intranasal treatment. Using oral esketamine it was not possible to generate a similar esketamine plasma concentration curve as with the intranasal treatment, except when combined with cobicistat (esketamine 2 mg/kg plus cobicistat 150 mg).

Conclusions

Our findings demonstrate that cobicistat effectively increases the bioavailability of oral esketamine. Further research is required in a larger population, especially to investigate the clinical benefit of cobicistat as a booster drug for oral esketamine.

Protocol for a randomised controlled trial of ketamine versus ketamine and behavioural activation therapy for adults with treatment-resistant depression in the community

INTRODUCTION

Although short-term benefits follow parenteral ketamine for treatment-resistant major depressive disorder (TR-MDD), there are challenges that prevent routine use of ketamine by clinicians. These include acute dissociative effects of parenteral ketamine, high relapse rates following ketamine dosing and the uncertain role of psychotherapy. This randomised controlled trial (RCT) seeks to establish the feasibility of evaluating repeated oral doses of ketamine and behavioural activation therapy (BAT), compared with ketamine treatment alone, for TR-MDD. We also aim to compare relapse rates between treatment arms to determine the effect size of adding BAT to oral ketamine.

METHODS AND ANALYSIS

This is a prospectively registered, two-centre, single-blind RCT. We aim to recruit 60 participants with TR-MDD aged between 18 and 65 years. Participants will be randomised to 8 weeks of oral ketamine and BAT, or 8 weeks of oral ketamine alone. Feasibility will be assessed by tracking attendance for ketamine and BAT, acceptability of treatment measures and retention to the study follow-up protocol. The primary efficacy outcome measure is the Montgomery-Asberg Depression Rating Scale (MADRS) measured weekly during treatment and fortnightly during 12 weeks of follow-up. Other outcome measures will assess the tolerability of ketamine and BAT, cognition and activity (using actigraphy). Participants will be categorised as non-responders, responders, remitters and relapsed during follow-up. MADRS scores will be analysed using a linear mixed model. For a definitive follow-up RCT study to be recommended, the recruitment expectations will be met and efficacy outcomes consistent with a >20% reduction in relapse rates favouring the BAT and ketamine arm will be achieved.

ETHICS AND DISSEMINATION

Ethics approval was granted by the New Zealand Central Health and Disability Ethics Committee (reference: 2023 FULL18176). Study findings will be reported to participants, stakeholder groups, conferences and peer-reviewed publications.

TRIAL REGISTRATION NUMBER

UTN: U1111-1294-9310, ACTRN12623000817640p.

Oral prolonged-release ketamine in treatment-resistant depression - A double-blind randomized placebo-controlled multicentre trial of KET01, a novel ketamine formulation - Clinical and safety results

INTRODUCTION

We investigated the antidepressant effects of a novel oral prolonged-release formulation of racemic ketamine (KET01) in patients suffering from treatment-resistant depression (TRD) as add-on therapy.

MATERIAL AND METHODS

Patients were randomized to an additional 160 mg/day or 240 mg/day KET01 or placebo for 14 days. The primary endpoint was change in Montgomery-Åsberg Depression Rating Scale (MADRS) scores from baseline to day 15. For treatment group comparisons, we used ANOVA with pairwise least squares mean difference tests in a mixed model repeated measures analysis.

RESULTS

Twenty-seven patients completed the double-blind protocol before trial premature termination due to poor recruitment during the COVID-19 pandemic. Mean (SD) MADRS scores on day 15 were 23 (10.32) in placebo, 25 (8.28) with 160 mg/day and 17 (10.32) with 240 mg/day KET01. MADRS change was numerically larger but statistically non-significant in the 240 mg/day KET01 group vs placebo on day 7 (-5.67; p = 00.106) and day 15 was (difference: 4.99; p = 00.15). In exploratory analysis, baseline leukocyte count correlated with response to KET01 (p = 00.01). Distribution of adverse event rates were comparable between the treatment arms. Safety analysis did not identify increased risk of suicidality, dissociation, hear rate, systolic and diastolic blood pressure associated with trial treatment.

DISCUSSION

Our results suggest that adjunctive oral administration of prolonged-release ketamine at a dose of 240 mg/day shows a positive, although statistically non-significant, trend towards antidepressant efficacy, however, the benefit could not be confirmed due to premature trial termination. Given its ease of use and low side effects, further trials are warranted to investigate this route of ketamine administration as a promising potential treatment of TRD.

UK medical students' self-reported knowledge and harm assessment of psychedelics and their application in clinical research: a cross-sectional study

OBJECTIVE

To capture UK medical students' self-reported knowledge and harm assessment of psychedelics and to explore the factors associated with support for changing the legal status of psychedelics to facilitate further clinical research.

DESIGN

Cross-sectional, anonymous online survey of UK medical students using a non-random sampling method.

SETTING

UK medical schools recognised by the General Medical Council.

PARTICIPANTS

132 medical students who had spent an average of 3.8 years (SD=1.4; range: 1-6) in medical school.

RESULTS

Most students (83%) reported that they were aware of psychedelic research and only four participants (3%) said that they were not interested in learning more about this type of research. Although medical students' harm assessment of psychedelics closely aligned with that of experts, only 17% of students felt well-educated on psychedelic research. Teachings on psychedelics were only rarely encountered in their curriculum (psilocybin: 14.1 (SD=19.9), scale: 0 (never) to 100 (very often)). Time spent at medical schools was not associated with more knowledge about psychedelics (r=0.12, p=0.129). On average, this sample of medical students showed strong support for changing the legal status of psychedelics to facilitate further research into their potential clinical applications (psilocybin: 80.2 (SD=24.8), scale: 0 (strongly oppose) to 100 (strongly support)). Regression modelling indicated that greater knowledge of psychedelics (p<0.001), lower estimated harm scores (p<0.001), more time spent in medical school (p=0.024) and lower perceived effectiveness of non-pharmacological mental health treatments (p=0.044) were associated with greater support for legal status change.

CONCLUSIONS

Our findings reveal a significant interest among UK medical students to learn more about psychedelic research and a strong support for further psychedelic research. Future studies are needed to examine how medical education could be refined to adequately prepare medical students for a changing healthcare landscape in which psychedelic-assisted therapy could soon be implemented in clinical practice.

Use of ketamine for treatment resistant depression: updated review of literature and practical applications to a community ketamine program in Edmonton, Alberta, Canada

Background

Though intravenous (IV) ketamine and intranasal (IN) esketamine are noted to be efficacious for treatment-resistant depression (TRD), access to each of these treatments within healthcare systems is limited due to cost, availability, and/or monitoring requirements. IV ketamine has been offered at two public hospital sites in Edmonton, Canada since 2015. Since then, demand for maintenance ketamine treatments has grown. This has required creative solutions for safe, accessible, evidence-based patient care.

Objectives

Aims of this paper are twofold. First, we will provide a synthesis of current knowledge with regards to the clinical use of ketamine for TRD. Consideration will be given regarding; off-label racemic ketamine uses versus FDA-approved intranasal esketamine, populations treated, inclusion/exclusion criteria, dosing, assessing clinical response, concomitant medications, and tolerability/safety. Second, this paper will describe our experience as a community case study in applying evidence-based treatment. We will describe application of the literature review to our clinical programming, and in particular focus on cost-effective maintenance treatments, long-term safety concerns, routes of ketamine administration other than via intravenous, and cautious prescribing of ketamine outside of clinically monitored settings.

Methodology

We conducted a literature review of the on the use of ketamine for TRD up to June 30, 2023. Key findings are reviewed, and we describe their application to our ketamine program.

Conclusion

Evidence for the use of ketamine in resistant depression has grown in recent years, with evolving data to support and direct its clinical use. There is an increasing body of evidence to guide judicious use of ketamine in various clinical circumstances, for a population of patients with a high burden of suffering and morbidity. While large-scale, randomized controlled trials, comparative studies, and longer-term treatment outcomes is lacking, this community case study illustrates that currently available evidence can be applied to real-world clinical settings with complex patients. As cost is often a significant barrier to accessing initial and/or maintenance IV or esketamine treatments, public ketamine programs may incorporate SL or IN ketamine to support a sustainable and accessible treatment model. Three of such models are described.

Short-term ketamine use in bipolar depression: a review of the evidence for short-term treatment management

Bipolar depression constitutes a major problem in psychiatry. It correlates with high suicidality, treatment resistance, chronicity, and poor quality of life. Registered treatment for bipolar depression is limited and insufficient. There is an urgent need for implementing new therapeutic strategies. Intranasal ketamine's enantiomer-esketamine is a novel rapid-acting antidepressant with proven efficacy in treatment-resistant depression. Research on bipolar depression, although not as comprehensive, indicates that it may be a viable and safe substitute with minimal risk for mood polarity changes. Reports suggest that ketamine treatment in bipolar depression may reduce suicidal tendencies, decrease anhedonia, and alleviate anxiety. Ketamine's mood-stabilizing properties are also hypothesized. In this narrative review, we focus on ketamine use as an add-on to standard medication for the acute treatment of bipolar depression.

Sub-Chronic Ketamine Administration Increases Dopamine Synthesis Capacity in the Mouse Midbrain: a Preclinical In Vivo PET Study

PURPOSE

There is robust evidence that people with schizophrenia show elevated dopamine (DA) synthesis capacity in the striatum. This finding comes from positron emission tomography (PET) studies using radiolabelled l-3,4-dihydroxyphenylalanine (18F-DOPA). DA synthesis capacity also appears to be elevated in the midbrain of people with schizophrenia compared to healthy controls. We therefore aimed to optimise a method to quantify 18F-DOPA uptake in the midbrain of mice, and to utilise this method to quantify DA synthesis capacity in the midbrain of the sub-chronic ketamine model of schizophrenia-relevant hyperdopaminergia.

PROCEDURES

Adult male C57Bl6 mice were treated daily with either ketamine (30 mg/kg, i.p.) or vehicle (saline) for 5 days. On day 7, animals were administered 18F-DOPA (i.p.) and scanned in an Inveon PET/CT scanner. Data from the saline-treated group were used to optimise an atlas-based template to position the midbrain region of interest and to determine the analysis parameters which resulted in the greatest intra-group consistency. These parameters were then used to compare midbrain DA synthesis capacity (KiMod) between ketamine- and saline-treated animals.

RESULTS

Using an atlas-based template to position the 3.7 mm3 midbrain ROI with a T*-Tend window of 15-140 min to estimate KiMod resulted in the lowest intra-group variability and moderate test-retest agreement. Using these parameters, we found that KiMod was elevated in the midbrain of ketamine-treated animals in comparison to saline-treated animals (t(22) = 2.19, p = 0.048). A positive correlation between DA synthesis capacity in the striatum and the midbrain was also evident in the saline-treated animals (r2 = 0.59, p = 0.005) but was absent in ketamine-treated animals (r2 = 0.004, p = 0.83).

CONCLUSIONS

Using this optimised method for quantifying 18F-DOPA uptake in the midbrain, we found that elevated striatal DA synthesis capacity in the sub-chronic ketamine model extends to the midbrain. Interestingly, the dysconnectivity between the midbrain and striatum seen in this model is also evident in the clinical population. This model may therefore be ideal for assessing novel compounds which are designed to modulate pre-synaptic DA synthesis capacity.

Oral ketamine may offer a solution to the ketamine conundrum

Ketamine has received considerable attention for its rapid and robust antidepressant response over the past decade. Current evidence, in clinical populations, predominantly relates to parenterally administered ketamine, which is reported to produce significant undesirable side effects, with additional concerns regarding long-term safety and abuse potential. Attempts to produce a similar drug to ketamine, without the psychotomimetic side effects, have proved elusive. Orally administered ketamine has a different pharmacological profile to parentally administered ketamine, suggesting it may be a viable alternative. Emerging evidence regarding the efficacy and tolerability of oral ketamine suggests that it may be a favourable route of administration, as it appears to obtain similarly beneficial treatment effects, but without the cost and medical resources required in parenteral dosing. The pharmacological effects may be due to the active metabolite norketamine, which has been found to be at substantially higher levels via oral dosing, most likely due to first-pass clearance. Despite bioavailability and peak plasma concentrations both being lower than when administered parenterally, evidence suggests that low-dose oral ketamine is clinically effective in treating pain. This may also be due to the actions of norketamine and therefore, its relevance to the mental health context is explored in this narrative review.

Cherry leaf decoction inhibits NMDAR expression and thereby ameliorates CUMS- induced depression-like behaviors through downregulation of α2δ-1

Depression is a complex and prevalent mental illness. Cherry leaf is a traditional Chinese herbal medicine, which has confirmed to exert a certain antidepressant effect, but its potential neural regulation mechanism is not clear. This paper aims to investigate the improved action of cherry leaf decoction (CLD) on chronic unpredictable mild stress (CUMS) rats and its potential neural regulation mechanism by verifying the role and function of NMDAR regulatory target α2δ-1 in depression due to CUMS. Male SD rats were subjected to random stressors persisting for 5 weeks to establish the CUMS depression rat model. CLD could effectively alleviate depression-like behaviors of CUMS rats in behavioral tests including sucrose preference test, forced swimming test, tail suspension test and open field test. After the administration of the CLD, the expression of corticotropic-releasing hormone (CRH) in the hypothalamus was inhibited. Moreover, the levels of CRH, adrenal cortical hormone (ACTH) and corticosterone (CORT) in serum also decreased significantly. CUMS upregulated the expressions of α2δ-1, N-methyl-d-aspartate receptor 1 (NR1), NR2A and NR2B, and enhanced the binding ability to of α2δ-1 and NR1, which were reversed by CLD. The results demonstrated that CLD could ameliorate depression-like behaviors due to CUMS, which was related to the fact that CLD down-regulated α2δ-1 level and interfered with α2δ-1 binding to NR1, thereby reducing NMDAR expression and ultimately inhibiting HPA axis activity.

Multidisciplinary development of guidelines for ketamine treatment for treatment-resistant major depression disorder for use by adult specialist mental health services in New Zealand

BACKGROUND

The evidence base for racemic ketamine treatment for treatment-resistant major depressive disorder (TRD) continues to expand, but there are major challenges translating this evidence base into routine clinical care.

AIM

To prepare guidelines for ketamine treatment of TRD that are suitable for routine use by publicly funded specialist mental health services.

METHOD

We consulted with senior leadership, clinical pharmacy, psychiatrists, nursing, service users and Māori mental health workers on issues relating to ketamine treatment. We prepared treatment guidelines taking the evidence base for ketamine treatment and the consultation into account.

RESULTS

Ketamine treatment guidance is reported. This offers two treatment pathways, including a test of ketamine responsiveness with intramuscular ketamine and the dominant use of oral ketamine for a 3-month course to maximise the opportunity for the short-term benefits of ketamine to accumulate.

CONCLUSIONS

We have responded to the challenges of translating the evidence base for ketamine treatment into a form suitable for routine care.

Case report: Intramuscular ketamine or intranasal esketamine as a treatment in four patients with major depressive disorder and comorbid anorexia nervosa

Introduction

A comorbid diagnosis of a depressive disorder is a negative prognostic factor for individuals with AN, and novel treatments are needed to target depressive symptoms in this population. One emerging promising treatment for depressive disorders is ketamine, although there is less research investigating the use of ketamine for alleviating depression in people with AN.

Case report

This study reports on four patients with a lifetime diagnosis of AN and a comorbid diagnosis of major depressive disorder who received either intramuscular ketamine (n = 2) or intranasal esketamine (n = 2) treatment from a private psychiatric clinic. Depressive symptomatology (PHQ-9) was measured prior to (es)ketamine administration on every dosing session and adverse effects were recorded during and after dosing. All patients reported a subjective decrease in depression, although only those administered intranasal esketamine showed a reduction in PHQ-9 depression scores over time. Number of doses ranged from 3 to 23. All patients tolerated treatment well and no serious adverse effects emerged, however nausea/vomiting was experienced by one patient on one dosing session. Weight remained stable in all cases, although notably across all patients, weight at the beginning of treatment was within a "healthy" range.

Discussion

These findings suggest that (es)ketamine may reduce depressive symptoms in people with major depressive disorder and a comorbid diagnosis of AN. Future feasibility and pilot trials are warranted in order to elicit robust data on efficacy, acceptability, safety and tolerability.

Ketamine and psychotherapy for the treatment of psychiatric disorders: systematic review

BACKGROUND

Ketamine is an effective short-term treatment for a range of psychiatric disorders. A key question is whether the addition of psychotherapy to ketamine treatment improves outcomes or delays relapse.

AIM

To identify all studies combining psychotherapy with ketamine for the treatment of psychiatric disorders to summarise their effects and make recommendations for future research.

METHOD

The review protocol was prospectively registered with PROSPERO (registration number CRD42022318120). Potential studies were searched for in MEDLINE, Embase, PsycINFO, SCOPUS, the Cochrane library and Google Scholar. Eligible studies combined ketamine and psychotherapy for the treatment of psychiatric disorders and did not use case reports or qualitative designs. Key findings relating to psychotherapy type, diagnosis, ketamine protocol, sequencing of psychotherapy and study design are reported. Risk of bias was assessed using modified Joanna Briggs critical appraisal tools.

RESULTS

Nineteen studies evaluating 1006 patients were included in the systematic review. A variety of supportive individual and group, manualised and non-manualised psychotherapies were used. The majority of studies evaluated substance use disorders, post-traumatic stress disorder and treatment-resistant depression. Ketamine protocols and sequencing of ketamine/psychotherapy treatment varied substantially between studies. Outcomes were largely positive for the addition of psychotherapy to ketamine treatment.

CONCLUSION

The combination of psychotherapy and ketamine offers promise for the treatment of psychiatric disorders, but study heterogeneity prevents definitive recommendations for their integration. Larger randomised controlled trials using manualised psychotherapies and standardised ketamine protocols are recommended to clarify the extent to which the addition of psychotherapy to ketamine improves outcomes over ketamine treatment alone.