Risks Associated with Misuse of Ketamine as a Rapid-Acting Antidepressant

Efficacy and safety of peri-partum Esketamine for prevention of post-partum depression in women undergoing caesarian section: A meta-analysis and systematic review of randomized controlled trials

Postpartum depression (PPD) is a psychiatric condition affecting women post-childbirth. Medication combined with psychotherapy, is the current protocol for its treatment. A meta-analysis was conducted using RevMan 5.4 to explore the efficacy and safety of peri-partum administration of esketamine for preventing PPD. After searching several databases to retrieve the relevant RCTs, seven were included in this analysis, with dichotomous data presented as risk ratio and continuous data as mean difference. The study found a lower incidence of PPD in the esketamine group compared to the control group (RR= 0.37), with significant difference in EPDS scores between the two groups (MD= -1.23) in the first week postpartum. The esketamine group reported a lower prevalence of PPD 4-6 weeks postpartum (RR= 0.48), and no significant difference in EPDS scores after 4 weeks postpartum (MD = -0.10). The esketamine group had a significantly higher incidence of hallucination (RR= 13.85). Other adverse effects, such as dizziness (RR= 4.09), nausea (RR= 0.88), vomiting (RR=0.74), headache (RR=1.52), nightmares (RR=1.22), pruritus (RR=0.29), and drowsiness (RR=1.57) did not show significant differences between the two groups. The study found that esketamine, with manageable side effects, reduces the prevalence of post-partum depression (PPD) after one week as well as after four to six weeks. However, the findings are limited by the limited number of available RCTs, and future research should determine the ideal dosage, the most effective method of administration and the long-term safety profile of esketamine so that it may be considered as an adjunct therapy or a potential sole treatment option.

Ketamine for major depressive disorder during an inpatient psychiatric admission: Effectiveness, adverse events, and lessons learned

OBJECTIVE

Most studies examining the efficacy of ketamine for Major Depressive Disorder (MDD) have been conducted in outpatient or mixed inpatient/outpatient settings. Less is known about effectiveness and tolerability of ketamine for psychiatrically hospitalized patients. Efficacy and tolerability data from a naturalistic sample of acute inpatients may help inform institutions considering ketamine therapy for inpatient services.

METHODS

We performed a retrospective chart review of inpatients with non-psychotic MDD treated during the initial 3 years of a ketamine infusion program. Treatment effectiveness was defined using change in Montgomery Asberg Depression Rating Scale (MADRS) scores over five infusions. MDD treatment response was defined by a 50 % reduction of MADRS score, and remission was defined as MADRS score ≤ 10 at any point during the treatment. We also report the frequency of adverse events.

RESULTS

41 patients with MDD were treated and had outcome data. 19 patients (46.5 %) met criteria for response and 15 patients (26.5 %) met criteria for remission during treatment. Four patients (10 %) had adverse psychological or behavioral outcomes.

LIMITATIONS

MADRS scales were administered by psychiatrists, psychologists, and trainees in each discipline who did not undergo standardized training in scale administration. Consistent data regarding the race/ethnicity of the patients was not available.

CONCLUSION

Twice weekly racemic ketamine infusion is an effective treatment option for patients hospitalized with MDD. Unmonitored or at home ketamine therapy may pose substantial risks.

Effects of perioperative use of esketamine on postpartum depression risk in patients undergoing cesarean section: A randomized controlled trial

BACKGROUND

Postpartum depression (PPD) is a prevalent public health issue. Although ketamine has prophylactic effects on PPD in women undergoing cesarean section, the effects of esketamine on PPD remain unclear. This trial aimed to evaluate the efficacy of perioperative esketamine infusion on PPD risk by assessing Edinburgh Postnatal Depression Scale (EPDS) scores and blood biomarkers.

METHODS

A total of 150 participants undergoing elective cesarean section were randomly allocated to receive either esketamine or normal saline. Since 27 participants were excluded due to consent withdrawal or loss to follow-up, 123 patients were included. The primary outcome was the prevalence of PPD risk. Secondary outcomes included the prevalence of postpartum anxiety (PPA) risk, levels of biomarkers, postoperative pain intensity, and cumulative sufentanil consumption.

RESULTS

The prevalence of PPD and PPA risk at 3 days, 42 days, 3 months, and 6 months postpartum did not differ between the two groups. Furthermore, EPDS scores, pain intensity at rest, and during coughing on postoperative days (POD) 1 and 2 did not differ between the two groups. Sufentanil consumption during 0-12 h, 12-24 h, 0-24 h, and 0-48 h postoperatively were significantly lower in the esketamine group compared to the control group. Blood biomarkers did not differ between the two groups on POD 3.

LIMITATIONS

The sample size was small. PPD risk was simply screened, not diagnosed.

CONCLUSIONS

Perioperative administration of esketamine did not decrease the incidence of PPD risk in women after elective cesarean section. However, esketamine reduced opioid consumption.

CB1 Receptor Silencing Attenuates Ketamine-Induced Hyperlocomotion Without Compromising Its Antidepressant-Like Effects

Introduction: The antidepressant properties of ketamine have been extensively demonstrated in experimental and clinical settings. However, the psychotomimetic side effects still limit its wider use as an antidepressant. It was recently observed that endocannabinoids are inolved in ketamine induced reward properties. As an increase in endocannabinoid signaling induces antidepressant effects, this study aimed to investigate the involvement of cannabinoid type 1 receptors (CB1R) in the antidepressant and psychostimulant effects induced by ketamine. Methods: We tested the effects of genetic and pharmacological inhibition of CB1R in the hyperlocomotion and antidepressant-like properties of ketamine. The effects of ketamine (10-20 mg/kg) were assessed in the open-field and the forced swim tests (FSTs) in CB1R knockout (KO) and wild-type (WT) mice (male and female), and mice pre-treated with rimonabant (CB1R antagonist, 3-10 mg/kg). Results: We found that the motor hyperactivity elicited by ketamine was impaired in CB1R male and female KO mice. A similar effect was observed upon pharmacological blockade of CB1R in WT mice. However, genetic CB1R deletion did not modify the antidepressant effect of ketamine in male mice submitted to the FST. Surprisingly, pharmacological blockade of CB1R induced an antidepressant-like effect in both male and female mice, which was not further potentiated by ketamine. Conclusions: Our results support the hypothesis that CB1R mediate the psychostimulant side effects induced by ketamine, but not its antidepressant properties.

Ketamine for the treatment of major depression: a systematic review and meta-analysis

Background

Intranasal esketamine has received regulatory approvals for the treatment of depression. Recently a large trial of repeated dose racemic ketamine also demonstrated efficacy in severe depression. However, uncertainties remain regarding comparative efficacy, dosage, and the time course of response.

Methods

In this systematic review and meta-analysis, we searched Embase, Medline, Pubmed, PsycINFO, and CENTRAL up to April 13, 2023, for randomised controlled trials (RCTs) investigating ketamine for depression. Two investigators independently assessed study eligibility and risk of bias and extracted the data on depression severity scores, response and remission rates, and all-cause dropouts. Multivariable mixed-effects meta-regressions incorporated drug formulation (racemic (Rac) or esketamine (Esket)) and dose (Low or High) as covariates. Treatment effects were assessed: immediately following the first dose, during further repeated dosing, and follow-up after the final dose of a treatment course. This study is registered with PROSPERO (CRD42021221157).

Findings

The systematic review identified 687 articles, of which 49 RCTs were eligible for analysis, comprising 3299 participants. Standardised mean differences (95% confidence intervals) immediately following the first/single treatment were moderate-high for all conditions (Rac-High: -0.73, -0.91 to -0.56; Esket-High: -0.48, -0.75 to -0.20; Rac-Low: -0.33, -0.54 to -0.12; Esket-Low: -0.55, -0.87 to -0.24). Ongoing effects during repeated dosing were significantly greater than the control for Rac-High (-0.61; -1.02 to -0.20) and Rac-Low (-0.55, -1.09 to -0.00), but not Esket-Low (-0.15, -0.49 to 0.19) or Esket-High (-0.22, -0.54 to 0.10). At follow-up effects remained significant for racemic ketamine (-0.65; -1.23 to -0.07) but not esketamine (-0.33; -0.96 to 0.31). All-cause dropout was similar between experiment and control conditions for both formulations combined (Odds Ratio = 1.18, 0.85-1.64). Overall heterogeneity varied from 5.7% to 87.6.

Interpretation

Our findings suggested that effect sizes for depression severity, as well as response and remission rates, were numerically greater for racemic ketamine than esketamine. Higher doses were more effective than low doses. Differences were evident in initial effects, ongoing treatment, and lasting effects after the final dose.

Funding

None.

Use of ketamine for depression and suicidality in cancer and terminal patients: Review of current data

Depression and suicidality are significant challenges faced by cancer patients, particularly those in advanced stages of the disease or nearing the end of life. Conventional antidepressant therapies often have limited effectiveness or delayed onset of action, making the exploration of alternative treatments crucial. The use of ketamine as a potential treatment for depression and suicidality in cancer and terminal patients has gained considerable attention in recent years. This review article aims to provide a comprehensive analysis of the current data regarding the efficacy and safety of ketamine in this specific population. This review presents an overview of clinical trials and case studies investigating the use of ketamine in this population. It explores the effectiveness of ketamine as a standalone treatment or in combination with other interventions. Furthermore, the article addresses the limitations and future directions of research in this field. It highlights the need for larger, well-controlled studies with long-term follow-up to establish the efficacy, safety and optimal treatment parameters of ketamine for depression and suicidality in palliative care.

Predictive factors of success and failure for intravenous ketamine therapy in patients suffering from chronic neuropathic pain

Background

Intravenous (IV) ketamine is used for chronic neuropathic pain refractory to other treatments. Administration of such a medication requires high-cost services while the result is not always satisfactory with a significant percentage of failure. Success and failure are related to some factors.

Method

In this study, we aim to point the most responsive disease category to IV ketamine and the predictive factors for successful and failed treatment. Two hundred and sixty-nine patients out of 371 were included. Demographic, clinical, and therapy-related variables were retrospectively collected and then statistically analyzed using various descriptive and inferential methods. A few descriptive statistics are obtained for the variables depending on their nature (e.g., percentages for qualitative variables and means for quantitative variables). Furthermore, several inferential methods are considered to address some statistical points of interest, including, but not limited to, odds ratio interpretations via logistic regression as well as association and correlation analyses.

Results

A significant association was found between the presence of intermittent pain pattern as well as the pain of chronic primary category and favorable response to IV ketamine while the history of previous analgesic interventions was significantly associated with a negative response.

Conclusion

The identified factors can be used to prospectively study the efficacy of ketamine using selection criteria based on the observed results in our study to re-evaluate the percentage of responsiveness according to these new parameters.

Prenatal ketamine exposure impairs prepulse inhibition via arginine vasopressin receptor 1A-mediated GABAergic neuronal dysfunction in the striatum

Ketamine is a widely used anesthetic with N-methyl-D-aspartate (NMDA) receptor antagonism. Exposure to ketamine and NMDA receptor antagonists may induce psychosis. However, the mechanism underlying the effects of ketamine on the immature brain remains unclear. In this study, NMDA receptor antagonists, ketamine and methoxetamine, were administered to pregnant F344 rats (E17). These regimens induce psychosis-like behaviors in the offspring, such as hyperlocomotion induced by MK-801, a non-competitive NMDA receptor antagonist. We also observed that prepulse inhibition (PPI) was significantly reduced. Interestingly, ketamine administration increased the arginine vasopressin receptor 1A (Avpr1a) expression levels in the striatum of offspring with abnormal behaviors. Methoxetamine, another NMDA receptor antagonist, also showed similar results. In addition, we demonstrated a viral vector-induced Avpr1a overexpression in the striatum-inhibited PPI. In the striatum of offspring, ketamine or methoxetamine treatment increased glutamate decarboxylase 67 (GAD67) and δ-aminobutyric acid (GABA) levels. These results show that prenatal NMDA receptor antagonist treatment induces GABAergic neuronal dysfunction and abnormalities in sensorimotor gating via regulating Avpr1a expression in the striatum.

Characterizing brain dynamics during ketamine-induced dissociation and subsequent interactions with propofol using human intracranial neurophysiology

Ketamine produces antidepressant effects in patients with treatment-resistant depression, but its usefulness is limited by its psychotropic side effects. Ketamine is thought to act via NMDA receptors and HCN1 channels to produce brain oscillations that are related to these effects. Using human intracranial recordings, we found that ketamine produces gamma oscillations in prefrontal cortex and hippocampus, structures previously implicated in ketamine's antidepressant effects, and a 3 Hz oscillation in posteromedial cortex, previously proposed as a mechanism for its dissociative effects. We analyzed oscillatory changes after subsequent propofol administration, whose GABAergic activity antagonizes ketamine's NMDA-mediated disinhibition, alongside a shared HCN1 inhibitory effect, to identify dynamics attributable to NMDA-mediated disinhibition versus HCN1 inhibition. Our results suggest that ketamine engages different neural circuits in distinct frequency-dependent patterns of activity to produce its antidepressant and dissociative sensory effects. These insights may help guide the development of brain dynamic biomarkers and novel therapeutics for depression.

Ketamine as a therapeutic agent in major depressive disorder and posttraumatic stress disorder: Potential medicinal and deleterious effects

Major depressive disorder (MDD) and posttraumatic stress disorder (PTSD) are the most common causes of emotional distress that impair an individual's quality of life. MDD is a chronic mental illness that affects 300 million people across the world. Clinical manifestations of MDD include fatigue, loss of interest in routine tasks, psychomotor agitation, impaired ability to focus, suicidal ideation, hypersomnolence, altered psychosocial functioning, and appetite loss. Individuals with depression also demonstrate a reduced behavioral response while experiencing pleasure, a symptom known as anhedonia. Like MDD, PTSD is a prevalent and debilitating psychiatric disorder resulting from a traumatic incident such as sexual assault, war, severe accident, or natural disaster. Symptoms such as recalling event phases, hypervigilance, irritability, and anhedonia are common in PTSD. Both MDD and PTSD pose enormous socioeconomic burdens across the globe. The search for effective treatment with minimal side effects is still ongoing. Ketamine is known for its anesthetic and analgesic properties. Psychedelic and psychotropic effects of ketamine have been found on the nervous system, which highlights its toxicity. In this article, the effectiveness of ketamine as a potential therapeutic for PTSD and MDD along with its mechanisms of action, clinical trials, and possible side effects have been discussed.

The 5-HT1A receptor biased agonist, NLX-204, shows rapid-acting antidepressant-like properties and neurochemical changes in two mouse models of depression

Activation of cortical serotonin 5-HT_1A receptors may be a promising strategy to achieve rapid-acting antidepressant (RAAD) activity. NLX-204 is a selective 5-HT_1A receptor biased agonist that, in naïve mice, robustly decreases immobility in the forced swim test (FST), and preferentially phosphorylates extracellular signal-regulated kinase (ERK1/2), involved in antidepressant activity. Here, we evaluated the properties of NLX-204 in two mouse models of depression. Male CD-1 mice were subjected to unpredictable chronic mild stress (UCMS) for 4-weeks or to repeated corticosterone (CORT, 20 mg/kg s.c./day) for 3-weeks before receiving acute administration of NLX-204 (2 mg/kg, p.o.). Depressive-like behavior was assessed in the FST, anhedonia-like behavior in the sucrose preference test (SPT) and locomotor activity was also recorded. Phosphorylation of ERK1/2 (pERK1/2) and cAMP response binding element (pCREB) were measured ex vivo in hippocampus and prefrontal cortex (PFC). UCMS or CORT treatment increased immobility in the FST, elicited a sucrose preference deficit, and decreased pERK1/2 and pCREB levels in PFC and hippocampus. NLX-204 reduced depressive-like behavior in the FST in CORT and UCMS mice, and normalized sucrose preference in CORT mice, suggesting anti-anhedonic activity. NLX-204 increased pERK1/2 levels in PFC of UCMS mice. NLX-204 also increased pCREB levels in PFC of CORT mice. These data suggest that NLX-204 has RAAD-like properties not only in naïve mice, but also in mice in a "depressive-like" state, and that these involve changes in PFC and hippocampal pERK1/2 and pCREB levels. These data provide additional evidence that activation of 5-HT_1A receptors by selective biased agonists, such as NLX-204, may constitute a promising RAAD strategy.

Maintenance ketamine treatment for depression: a systematic review of efficacy, safety, and tolerability

Ketamine has rapid yet often transient antidepressant effects in patients with treatment-resistant depression. Different strategies have been proposed to prolong these effects. Maintenance ketamine treatment appears promising, but little is known about its efficacy, safety, and tolerability in depression. We searched Pubmed, Embase, and the Cochrane Library and identified three randomised controlled trials, eight open-label trials, and 30 case series and reports on maintenance ketamine treatment. We found intravenous, intranasal, oral, and possibly intramuscular and subcutaneous maintenance ketamine treatment to be effective in sustaining antidepressant effect in treatment-resistant depression. Tachyphylaxis, cognitive impairment, addiction, and serious renal and urinary problems seem uncommon. Despite the methodological limitations, we conclude that from a clinical view, maintenance ketamine treatment seems to be of therapeutic potential. We recommend both controlled and naturalistic studies with long-term follow-up and sufficient power to determine the position of maintenance ketamine treatment within routine clinical practice.

The Rapid and Long-Lasting Antidepressant Effects of Iridoid Fraction in Gardenia Jasminoides J.Ellis Are Dependent on Activating PKA-CREB Signaling Pathway

Lag periods of therapeutic efficacy cause poor compliance of patients, which has made solutions for rapid antidepressants the most urgent need in the depression study field at present. We have identified through our previous studies the rapid antidepressant effects of the traditional herb Gardenia jasminoides J.Ellis [Rubiaceae] (GJ) and its standardized fractions. Through screening different fractions of GJ, we decided to place our focus on the iridoid fraction of GJ (GJ-IF).

Methods: 1. Tail suspension test (TST), forced swimming test (FST), and novelty suppressed-feeding test (NSFT) were performed in sequence on mice after GJ-IF administration. 2. Mice in the model group were under chronic unpredictable mild stress (CUMS) for 3 w. After GJ-IF treatment, mice were placed in an open field test (OFT), Sucrose preference test (SPT), NSFT, TST, and FST. 3. Western Blot was performed to examine the expression of brain-derived neurotrophic factor (BDNF), Synapsin 1, cyclic-AMP dependent protein kinase A (PKA), phosphorylated cyclic-AMP responsive element-binding protein (p-CREB), and cAMP response element-binding protein (CREB). 4. Mice in the test group were administrated with GJ-IF after intraperitoneal injection of PKA blocker H89.

Results: 1. GJ-IF treatment significantly reduced the immobility time of TST at 1 d and FST at 26 h. 2. GJ-IF reversed the deficits induced by 3 w CUMS in SPT, TST, FST, and NSFT at 1 d and 26 h. The antidepressant effects of a single dose of iridoid fraction could also last for at least 14 d. 3. The results of molecule studies suggested that a single dose of GJ-IF activated p-CREB at 2 h and the PKA-CREB pathway at 1 d. The expression of BDNF did not significantly change from 30 min to 1 d after GJ-IF administration. 4. Blockade of PKA-CREB signaling pathway reversed the antidepressant effects of GJ-IF at 1 d, but not 30 min and 2 h.

Conclusion: GJ-IF is the crucial component in the rapid antidepressant of GJ. Rapid and sustained antidepressant effects of GJ-IF were dependent on activating the PKA-CREB signaling pathway.

Ketamine for suicidality: an umbrella review

The urgent need for appropriate treatment for suicide, the tenth leading cause of death, has led to numerous studies. This study aims to systematically identify and appraise systematic reviews with or without meta-analyses investigating ketamine in suicidal ideation and behaviors. The study protocol was published in PROSPERO (CRD42021285320). Scopus, ISI, Embase, PubMed, CINAHL, PsycINFO, Cochrane Library, Google Scholar, and two registries were searched on October 29 without any restrictions for systematic reviews investigating the efficacy of ketamine on suicidal ideation and behaviors. The primary outcome was the final inference of ketamine effectiveness. A formal narrative synthesis was conducted, and the AMSTAR-2 tool was used to evaluate the quality of the studies. No funding was received. Of 27 studies that addressed ketamine for suicidal ideation, only four reported mixed or negative results, and out of nine reviews, esketamine was significantly beneficial only in five. A transient rise in pulse rate and blood pressure, dissociation, confusion, blurred vision, nausea, and vertigo were of the most common adverse effects; however, most were mild. More than two-thirds of the included studies qualified as low or critically low quality. Preliminary evidence for the short-term efficacy of ketamine in suicidality was noted by the majority of reviews; however, long-term effects remained unknown. Due to the non-high quality of many studies and the limitations of core studies, further studies are required.

Synergistic effects of two natural compounds of iridoids on rapid antidepressant action by up-regulating hippocampal PACAP signaling

BACKGROUND AND PURPOSE

Current mainstream antidepressants have limited efficacy and a delayed onset of action. Yueju is a traditional herbal medicine conferring rapid antidepressant activity. Here we attempted to identify the effective compounds from Yueju and the underlying mechanisms.

EXPERIMENTAL APPROACH

A transcriptomic analysis was employed to discover key candidate molecules for rapid antidepressant response. The enriched compounds in Yueju were identified with HPLC. Antidepressant effects were evaluated periodically using various behavioral paradigms. The mechanistic signaling was assessed using site-directed pharmacological intervention or optogenetic manipulation.

KEY RESULTS

A transcriptomic analysis revealed that Yueju up-regulated pituitary adenylate cyclase activating polypeptide (PACAP) expression in the hippocampus. Two iridoids geniposide (GP) and shanzhiside methyl-ester (SM) were enriched in Yueju. Co-treatment of GP and SM each at an equivalent dose in Yueju synergistically increased PACAP expression and elicited rapid antidepressant effects, which were prevented by intra-hippocampal dentate gyrus (DG) infusions of a PACAP antagonist or optogenetic inactivation of PACAP-expressing neurons. GP-SM co-treatment rapidly reduced CaMKII phosphorylation and enhanced mTOR/4EBP1/P70S6k/BDNF signaling, while intra-DG infusions of a CaMKII activator blunted rapid antidepressant effects and BDNF expression up-regulation induced by GP-SM co-treatment. A single administration of GP-SM rapidly improved depression-like behaviors and up-regulated hippocampal PACAP signaling in the repeated corticosterone-induced depression model, further confirming its rapid antidepressant action and the involvement of PACAP.

CONCLUSION AND IMPLICATIONS

GP-SM co-treatment elicited a synergistic effect on rapid antidepressant effects via triggering hippocampal PACAP activity and associated CaMKII-BDNF signaling, shedding lights on the development of novel targeted antidepressants.

"Novel Management of Depression Using Ketamine in the Intensive Care Unit"

BACKGROUND

Ketamine, a dissociative anesthetic, induces improvement in depressive symptoms by antagonizing glutaminergic NMDA receptors. Ketamine has been used previously in outpatient setting for treatment-resistant depression, but we showcase its utility in depression management at the Intensive Care Unit (ICU). Research Question: Can ketamine be used for depression treatment in ICU patients? Study Design and Methods: A retrospective chart review of ICU patients was done at a tertiary center from 2018 to 2021, to assess the ketamine usage. Among the patients reviewed, ketamine was used for depression in 12, and for analgesia & sedation in 2322 patients. Ketamine was administered in doses of 0.5mg/kg & 0.75mg/kg for depression. Each course consisted of 3 doses of ketamine administered over 3 days, and 7 in 12 patients received a single course of ketamine. The rest received 3-4 courses 1 week apart. Results: Ketamine was found to improve mood and affect in most of the patients with depression. 11 in 12 patients had a positive response with better sleep. It has a major advantage over conventional anti-depressants since it takes only a few hours to induce clinical improvement. Patients who were observably withdrawn from care team and family, were administered ketamine. Conclusion: A major drawback of ketamine is that the duration of clinical improvement is short, with the response lasting only up to seven days after a single dose. Hence, all the patients in our study were weaned off ketamine with a supporting antidepressant. Ketamine has been documented to cause cardio-neurotoxicity; however, only one patient had worsening lethargy in our study. To conclude, ketamine has a marked benefit in treating depression in the ICU. Although our study was associated with positive outcomes, there is a need for prospective studies with long-term follow-up assessments.

Ketamine as a therapeutic agent for depression and pain: mechanisms and evidence

Ketamine is an anesthetic drug which is now used to treat chronic pain conditions and psychiatric disorders, especially depression. It is an N-methyl-D-aspartate (NMDA) receptor antagonist with additional effects on α-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors, hyperpolarization-activated cyclic nucleotide-gated (HCN) channels, opioid receptors, and monoaminergic receptors. This article focuses on ketamine's role in treating depression and pain, two commonly comorbid challenging conditions with potentially shared neurobiologic circuitry. Many clinical trials have utilized intravenous or intranasal ketamine for treating depression and pain. Intravenous ketamine is more bioavailable than intranasal ketamine and both are effective for acute depressive episodes. Intravenous ketamine is advantageous for post-operative analgesia and is associated with a reduction in total opioid requirements. Few studies have treated chronic pain or concurrent depression and pain with ketamine. Larger, randomized control trials are needed to examine the safety and efficacy of intravenous vs. intranasal ketamine, ideal target populations, and optimal dosing to treat both depression and pain.

Ketamine use in relation to depressive symptoms among high school seniors

BACKGROUND AND OBJECTIVES

Ketamine is efficacious in treating treatment-resistant depression in medical settings and the drug was approved for such use by the US Federal Drug Administration in 2019. However, little is known about how use outside of medical settings relates to depression. We determined whether recreational ketamine use, relative to the use of other drugs, is related to the current experience of depression among adolescents.

METHODS

We examined data from the 2016 to 2019 Monitoring the Future nationally representative survey of high school seniors in the United States (N = 15,673). We determined how past-year drug use and frequency of past-year drug use were associated with students reporting a high level of current depressive symptoms relative to other students.

RESULTS

Ketamine use was associated with highest risk for a high level of depression (aPR = 1.55, 95% confidence interval [CI]: 1.24-1.94), followed by use of cannabis (aPR = 1.29, 95% CI: 1.19-1.39), and nonmedical use of tranquilizers (aPR = 1.22, 95% CI: 1.04-1.44) and amphetamine (aPR = 1.17, 95% CI: 1.01-1.34). Alcohol use was associated with decreased risk (aPR = 0.92, 95% CI: 0.85-0.99). With respect to frequency of past-year use, more frequent use of ketamine and cannabis was associated with increased risk for a high level of depression in a dose-response-like manner, with past-year use of ketamine and cannabis ≥10 times associated with increased risk for depression by 70% and 40%, respectively.

DISCUSSION AND CONCLUSIONS

Past-year recreational ketamine use is a risk factor for reporting current depression than most other drugs.

SCIENTIFIC SIGNIFICANCE

This was the first study to compare the risk of use of various drugs in relation to depression.

Is (R)-ketamine a Potential Therapeutic Agent for Treatment-Resistant Depression with Less Detrimental Side Effects? A Review of Molecular Mechanisms Underlying Ketamine and its Enantiomers

Approximately one-third of individuals with major depressive disorder are resistant to conventional antidepressants (i.e., monoamine-based therapies), and, even among respondents, a proper therapeutic effect may require weeks of treatment. Ketamine, a racemic mixture of the two enantiomers, (R)-ketamine and (S)-ketamine, is an N-methyl-d-aspartate receptor (NMDAR) antagonist and has been shown to have rapid-acting antidepressant properties in patients with treatment-resistant depression (TRD). Although (R)-ketamine has a lower affinity for NMDAR, it presents greater potency and longer-lasting antidepressant properties, with no major side effects, than racemic ketamine or (S)-ketamine in preclinical findings. Thereby, ketamine and its enantiomers have not only an antagonistic effect on NMDAR but also a strong synaptogenic-modulatory effect, which is impaired in TRD pathophysiology. In this review, we summarize the current evidence regarding the modulation of neurotransmission, neuroplasticity, and neural network activity as putative mechanisms of these rapid-acting antidepressants, highlighting differences on intracellular signaling pathways of synaptic proteins such as mammalian target of rapamycin (mTOR), extracellular signal-regulated kinase (ERK) and brain-derived neurotrophic factor (BDNF). In addition, we discuss probable mechanisms involved in the side effects of ketamine and its enantiomers.

Effects of subanesthetic ketamine and (2R,6R) hydroxynorketamine on working memory and synaptic transmission in the nucleus reuniens in mice

RATIONALE

Acute cognitive impairment and abuse potential of ketamine incentivizes the search for alternatives to ketamine for clinical management of treatment-resistant depression. Recently, (2R,6R) hydroxynorketamine ((2R,6R)-HNK), a metabolite of ketamine, has shown promise due to its reported lack of ketamine-like reinforcing properties. Nonetheless, the effect of (2R,6R)-HNK on cognition has not been reported.

METHOD

Adult male mice were placed in a Y-maze to measure spatial working memory (SWM) 24 h after treatment with either a single or repeated subanesthetic dose of (2R,6R)-HNK or ketamine. To determine the effect of the drug regimens on synaptic mechanisms in neural circuits deemed critical for SWM, we conducted patch-clamp electrophysiological recordings from neurons in the midline thalamic nucleus reuniens (RE) in response to optogenetic stimulation of medial prefrontal cortex (mPFC) inputs in acutely prepared brain slices.

RESULTS

Single or repeated treatment with a 10 mg/kg dose of either drug did not impact performance in a Y-maze. However, single administration of a ½-log higher dose (32 mg/kg) of ketamine significantly reduced SWM. The same dose of (2R,6R)-HNK did not produce SWM deficits. Interestingly, repeated administration of either drugs at the 32 mg/kg had no effect on SWM performances. Concomitant to these effects on SWM, only single injection of 32 mg/kg of ketamine was found to increase the mPFC-driven action potential firing activity in the RE neurons. Conversely, both single and repeated administration of the 32 mg/kg dose of (2R,6R)-HNK but not ketamine, increased the input resistance of the RE neurons.

CONCLUSION

Our results indicate that acute treatment of ketamine at 32 mg/kg increases mPFC-driven firing activity of RE neurons, and this contributes to the ketamine-mediated cognitive deficit. Secondly, sub-chronic treatment with the same dose of ketamine likely induces tolerance. Although single or repeated administration of the 32 mg/kg dose of (2R,6R)-HNK can alter intrinsic properties of RE neurons, this dose does not produce cognitive deficit or changes in synaptic mechanism in the RE.

(R,S)-ketamine and (2R,6R)-hydroxynorketamine differentially affect memory as a function of dosing frequency

A single subanesthetic infusion of ketamine can rapidly alleviate symptoms of treatment-resistant major depression. Since repeated administration is required to sustain symptom remission, it is important to characterize the potential untoward effects of prolonged ketamine exposure. While studies suggest that ketamine can alter cognitive function, it is unclear to what extent these effects are modulated by the frequency or chronicity of treatment. To test this, male and female adolescent (postnatal day [PD] 35) and adult (PD 60) BALB/c mice were treated for four consecutive weeks, either daily or thrice-weekly, with (R,S)-ketamine (30 mg/kg, intraperitoneal) or its biologically active metabolite, (2R,6R)-hydroxynorketamine (HNK; 30 mg/kg, intraperitoneal). Following drug cessation, memory performance was assessed in three operationally distinct tasks: (1) novel object recognition to assess explicit memory, (2) Y-maze to assess working memory, and (3) passive avoidance to assess implicit memory. While drug exposure did not influence working memory performance, thrice-weekly ketamine and daily (2R,6R)-HNK led to explicit memory impairment in novel object recognition independent of sex or age of exposure. Daily (2R,6R)-HNK impaired implicit memory in the passive-avoidance task whereas thrice-weekly (2R,6R)-HNK tended to improve it. These differential effects on explicit and implicit memory possibly reflect the unique mechanisms by which ketamine and (2R,6R)-HNK alter the functional integrity of neural circuits that subserve these distinct cognitive domains, a topic of clinical and mechanistic relevance to their antidepressant actions. Our findings also provide additional support for the importance of dosing frequency in establishing the cognitive effects of repeated ketamine exposure.

Major depressive disorder: Validated treatments and future challenges

Depression is a prevalent psychiatric disorder that often leads to poor quality of life and impaired functioning. Treatment during the acute phase of a major depressive episode aims to help the patient reach a remission state and eventually return to their baseline level of functioning. Pharmacotherapy, especially selective serotonin reuptake inhibitors antidepressants, remains the most frequent option for treating depression during the acute phase, while other promising pharmacological options are still competing for the attention of practitioners. Depression-focused psychotherapy is the second most common option for helping patients overcome the acute phase, maintain remission, and prevent relapses. Electroconvulsive therapy is the most effective somatic therapy for depression in some specific situations; meanwhile, other methods have limits, and their specific indications are still being studied. Combining medications, psychotherapy, and somatic therapies remains the most effective way to manage resistant forms of depression.

Pharmacological and behavioral divergence of ketamine enantiomers: implications for abuse liability

Ketamine, a racemic mixture of (S)-ketamine and (R)-ketamine enantiomers, has been used as an anesthetic, analgesic and more recently, as an antidepressant. However, ketamine has known abuse liability (the tendency of a drug to be used in non-medical situations due to its psychoactive effects), which raises concerns for its therapeutic use. (S)-ketamine was recently approved by the United States' FDA for treatment-resistant depression. Recent studies showed that (R)-ketamine has greater efficacy than (S)-ketamine in preclinical models of depression, but its clinical antidepressant efficacy has not been established. The behavioral effects of racemic ketamine have been studied extensively in preclinical models predictive of abuse liability in humans (self-administration and conditioned place preference [CPP]). In contrast, the behavioral effects of each enantiomer in these models are unknown. We show here that in the intravenous drug self-administration model, the gold standard procedure to assess potential abuse liability of drugs in humans, rats self-administered (S)-ketamine but not (R)-ketamine. Subanesthetic, antidepressant-like doses of (S)-ketamine, but not of (R)-ketamine, induced locomotor activity (in an opioid receptor-dependent manner), induced psychomotor sensitization, induced CPP in mice, and selectively increased metabolic activity and dopamine tone in medial prefrontal cortex (mPFC) of rats. Pharmacological screening across thousands of human proteins and at biological targets known to interact with ketamine yielded divergent binding and functional enantiomer profiles, including selective mu and kappa opioid receptor activation by (S)-ketamine in mPFC. Our results demonstrate divergence in the pharmacological, functional, and behavioral effects of ketamine enantiomers, and suggest that racemic ketamine's abuse liability in humans is primarily due to the pharmacological effects of its (S)-enantiomer.

Post-Marketing Safety Concerns with Esketamine: A Disproportionality Analysis of Spontaneous Reports Submitted to the FDA Adverse Event Reporting System

INTRODUCTION

Esketamine nasal spray received approval for treatment-resistant depression in March 2019.

OBJECTIVE

Using the FDA Adverse Event Reporting System (FAERS) database (March 2019-March 2020), we analysed esketamine-related adverse events (AEs) to detect and characterize relevant safety signals.

METHODS

We used the consolidated case/non-case approach to estimate the reporting odds ratio (ROR) and information component (IC) with relevant confidence intervals (95% CI) for esketamine-related AEs with ≥4 counts. Comparisons between serious and non-serious AEs were performed using non-parametric tests.

RESULTS

The FAERS database contained 962 cases of esketamine-related AEs, with signals detected for several AEs, such as dissociation (ROR = 1,612.64, 95% CI = 1,354.63, 1,919.79; IC = 8.19, 95% CI = 7.96, 8.35), sedation (ROR = 238.46, 95% CI = 202.98, 280.15; IC = 7, 95% CI = 6.75, 7.18), feeling drunk (ROR = 96.17, 95% CI = 61.42, 150.57; IC = 4.84, 95% CI = 4.09, 5.36), suicidal ideation (ROR = 24.03, 95% CI = 18.72, 30.84; IC = 4.31, 95% CI = 3.9, 4.61), and completed suicide (ROR = 5.75, 95% CI = 3.18, 10.41; IC = 2.25, 95% CI = 1.23, 2.94). Signals for suicidal and self-injurious ideation, but not suicide attempt and completed suicide, remained when comparing esketamine to venlafaxine. Females and patients receiving antidepressant polypharmacy, co-medication with mood stabilizers, antipsychotics, benzodiazepines, or somatic medications were more likely to suffer from serious versus non-serious AEs (χ2 = 125.29, p < 0.001, χ2 = 9.08, p = 0.003, χ2 = 8.14, p = 0.004, χ2 = 19.48, p < 0.001, χ2 = 25.62, p < 0.001, and χ2 = 16.79, p < 0.001, respectively).

CONCLUSIONS

Esketamine may carry a clear potential for serious AEs, which deserves urgent clarification by means of further prospective studies.

Lipoxin A4 methyl ester protects PC12 cells from ketamine-induced neurotoxicity via the miR-22/BAG5 pathway

OBJECTIVE

Ketamine is an anesthetic that induces neurotoxicity when administered at high doses. In this work, we explored the protective effects of lipoxin A₄ methyl ester (LXA₄ ME) against ketamine-induced neurotoxicity and the underlying protective mechanism in pheochromocytoma (PC12) cells.

METHODS

PC12 cells were treated with 50 μM of ketamine and different LXA₄ ME concentrations of LXA4 ME (5-50 nM) for 24 h, and their viability, apoptosis, and oxidative status were assessed.

RESULTS

Quantitative real-time polymerase chain reaction experiments showed that ketamine downregulated miR-22 expression and upregulated Bcl-2-associated athanogene 5 (BAG5) in PC12 cells in a concentration-dependent manner. LXA₄ ME induced the opposite effects, thus attenuating ketamine-induced neurotoxicity. Further in vitro assays showed that miR-22 directly targeted BAG5, thus promoting cell viability by suppressing cell apoptosis and oxidative stress. Under expression miR-22 or upregulation of BAG5 antagonized the effects of LXA₄ ME.

CONCLUSION

LXA₄ ME can protect PC12 cells from ketamine-induced neurotoxicity by activating the miR-22/BAG5 signaling pathway. Thus, LXA₄ ME can be used as a protective drug against ketamine-induced neural damage.

Neurocognitive aspects of ketamine and esketamine on subjects with treatment-resistant depression: A comparative, randomized and double-blind study

The objective of this study is to evaluate cognition in patients using either ketamine or esketamine to treat TRD. We also evaluate if both ketamine and esketamine as one group influence cognition in patients with TRD. Fifty-four patients with TRD were infused with either ketamine or esketamine and were assessed at three time points: baseline, 24 h, and 7 days after infusion. We applied neuropsychological tests to evaluate executive functions, processing speed, short term memory, and auditory-verbal episodic memory. There is no cognitive difference between ketamine and esketamine, with the exception of one variable. When considered as one group, ketamine and esketamine do not impair cognition; on the contrary, they improve some neuropsychological functions such as visuospatial short-term memory, executive functions, processing speed, and several measures related to episodic verbal memory. Ketamine and esketamine do not present differing cognitive effects when used in antidepressant doses to treat TRD. Furthermore, they rapidly improve many cognitive aspects of patients with TRD at 24 h after the infusion and maintain these effects for at least 7 days.

Neurocognitive Effects of Ketamine and Esketamine for Treatment-Resistant Major Depressive Disorder: A Systematic Review

LEARNING OBJECTIVE

After participating in this activity, learners should be better able to:• Analyze the effects of ketamine and esketamine on individuals with treatment-resistant depression.

INTRODUCTION

Cognitive impairment is commonly present in individuals with treatment-resistant depression, especially in attention, memory, and executive functions. These deficits are related to symptom severity, remission rates, and functional impairments during and after the acute phase of the disorder. Ketamine, an N-methyl-D-aspartate antagonist previously used as an anesthetic, brings promising antidepressant results. This study systematically reviews the neurocognitive effects of ketamine and esketamine in patients with treatment-resistant major depressive disorder.

METHODS

Systematic searches were conducted at Embase, PubMed, and PsycINFO using the terms depression, ketamine, and cognition. Title, abstract, and full-text reading were conducted independently by two of the authors (BSM and CSL). Risk of bias, study design, neuropsychological outcomes, and neuroimaging data were recorded.

RESULTS

From a total of 997 hits, 14 articles were included. One study reported cognitive impairment after ketamine treatment for processing speed and verbal memory. Five studies reported improvements in processing speed, verbal memory, visual memory, working memory, or cognitive flexibility. The esketamine study suggested no changes to performance. Lower attention, slower processing speed, and higher working memory are reported as predictors of antidepressant response. Brain areas for emotional and reward processing, including the amygdala, insula, and orbitofrontal cortex, show a normalizing tendency after ketamine.

CONCLUSIONS

Ketamine and esketamine do not seem to exert significant deleterious neurocognitive effects in the short or long term in individuals with treatment-resistant depression. Results suggest neuropsychological functions and brain areas commonly impaired in treatment-resistant depression may especially benefit from subanesthetic ketamine infusions. Key questions that remain unanswered are discussed.

Harm related to recreational ketamine use and its relevance for the clinical use of ketamine. A systematic review and comparison study

BACKGROUNDS

Ketamine is a dissociative anesthetic that is currently considered for several new indications.

AIM

To deduce the safety of long-term ketamine treatment using the harm of heavy recreational (non-medical) ketamine use as a proxy for maximal possible harm of ketamine treatment.

METHODS

Systematic literature review according to PRISMA guidelines to identify controlled studies on ketamine-related harm in heavy recreational ketamine users. Results were compared with serious adverse events (SAEs) in patients treated with ketamine according to three systematic reviews considering dosing regimen and cumulative dose.

RESULTS

The systematic search yielded 25 studies. Heavy recreational ketamine use can escalate to ketamine dependency and was often dose-dependently associated with other SAEs, including cognitive and mental disorders, and gastrointestinal and urinary tract symptoms, which disappeared upon marked reduction of ketamine use. Heavy ketamine users have a much higher cumulative exposure to ketamine than ketamine treated patients (>90 times), which may explain why SAEs in the clinical context are mostly mild and reversible and why ketamine dependence was not reported in these patients.

CONCLUSION

Treatment of patients with ketamine is not associated with ketamine dependency or SAEs. However, caution is needed since data on long-term clinical ketamine use with a long-term follow-up is lacking.

Acute and Persistent Withdrawal Syndromes Following Discontinuation of Psychotropic Medications

Studies on psychotropic medications decrease, discontinuation, or switch have uncovered withdrawal syndromes. The present overview aimed at analyzing the literature to illustrate withdrawal after decrease, discontinuation, or switch of psychotropic medications based on the drug class (i.e., benzodiazepines, nonbenzodiazepine benzodiazepine receptor agonists, antidepressants, ketamine, antipsychotics, lithium, mood stabilizers) according to the diagnostic criteria of Chouinard and Chouinard [Psychother Psychosom. 2015;84(2):63-71], which encompass new withdrawal symptoms, rebound symptoms, and persistent post-withdrawal disorders. All these drugs may induce withdrawal syndromes and rebound upon discontinuation, even with slow tapering. However, only selective serotonin reuptake inhibitors, serotonin noradrenaline reuptake inhibitors, and antipsychotics were consistently also associated with persistent post-withdrawal disorders and potential high severity of symptoms, including alterations of clinical course, whereas the distress associated with benzodiazepines discontinuation appears to be short-lived. As a result, the common belief that benzodiazepines should be substituted by medications that cause less dependence such as antidepressants and antipsychotics runs counter the available literature. Ketamine, and probably its derivatives, may be classified as at high risk for dependence and addiction. Because of the lag phase that has taken place between the introduction of a drug into the market and the description of withdrawal symptoms, caution is needed with the use of newer antidepressants and antipsychotics. Within medication classes, alprazolam, lorazepam, triazolam, paroxetine, venlafaxine, fluphenazine, perphenazine, clozapine, and quetiapine are more likely to induce withdrawal. The likelihood of withdrawal manifestations that may be severe and persistent should thus be taken into account in clinical practice and also in children and adolescents.

Targeting the dysfunction of glutamate receptors for the development of novel antidepressants

Increasing evidence indicates that dysfunction of glutamate receptors is involved in the pathophysiology of major depressive disorder (MDD). Although accumulating efforts have been made to elucidate the applications and mechanisms underlying antidepressant-like effects of ketamine, a non-selective antagonist of N-methyl-d-aspartate receptor (NMDAR), the role of specific glutamate receptor subunit in regulating depression is not completely clear. The current review aims to discuss the relationships between glutamate receptor subunits and depressive-like behaviors. Research literatures were searched from inception to July 2020. We summarized the alterations of glutamate receptor subunits in patients with MDD and animal models of depression. Animal behaviors in response to dysfunction of glutamate receptor subunits were also surveyed. To fully understand mechanisms underlying antidepressant-like effects of modulators targeting glutamate receptors, we discussed effects of each glutamate receptor subunit on serotonin system, synaptic plasticity, neurogenesis and neuroinflammation. Finally, we collected most recent clinical applications of glutamate receptor modulators and pointed out the limitations of these candidates in the treatment of MDD.

Esketamine: a glimmer of hope in treatment-resistant depression

The motive of this article is to review the pharmacological and clinical aspects of esketamine (ESK), an NMDA-receptor antagonist approved recently by the FDA for treatment-resistant depression (TRD). PubMed/Medline database was searched using keywords 'esketamine' and 'depression', 'S-ketamine' and 'depression', and 'NMDA antagonist' and 'depression'. Individual trials were searched from ClinicalTrials.gov. We included English-language articles evaluating pharmacokinetics and pharmacodynamics of intranasal (IN) esketamine, along with clinical trial data related to its efficacy and safety in patients diagnosed with TRD. Compared to placebo, IN esketamine causes significant and rapid improvement in depression. Dizziness, vertigo, headache, increase in blood pressure are some of its common adverse effects. With the growing number of patients of TRD, additional effective and safe treatment is the need of the hour. Esketamine appears to be an effective therapy when combined with oral antidepressants in patients with TRD. It is of special value due to the rapid onset of its action. Long-term clinical studies are, however, needed to ascertain its safety profile.

Chronic Post-Surgical Pain in the Frail Older Adult

Older adults are the fastest growing segment of the population and surgical procedures in this group increase each year. Chronic post-surgical pain is an important consideration in the older adult as it affects recovery, physical functioning, and overall quality of life. It is increasingly recognized as a public health issue but there is a need to improve our understanding of the disease process as well as the appropriate treatment and prevention. Frailty, delirium, and cognition influence post-operative outcomes in older adults and have been implicated in the development of chronic post-surgical pain. Further research must be conducted to fully understand the role they play in the occurrence of chronic post-surgical pain in the older adult. Additionally, careful attention must be given to the physiologic, cognitive, and comorbidity differences between the older adult and the general population. This is critical for elucidating the proper chronic post-surgical pain treatment and prevention strategies to ensure that the older adult undergoing surgical intervention will have an appropriate and desirable post-operative outcome.

Analgesic effect of perioperative ketamine for total hip arthroplasties and total knee arthroplasties: A PRISMA-compliant meta-analysis

BACKGROUND

Total hip arthroplasties (THA) and total knee arthroplasties (TKA) are always associated with a frequent incidence of postoperative pain. Effective pain management after surgery is quite essential for surgeons and patients. The purpose of the present meta-analysis is to evaluate the analgesic effect of perioperative ketamine after THA and TKA.

METHODS

Seven online databases, Embase, Cochrane Library, Pubmed, Web of Science, China National Knowledge Infrastructure (CNKI), China Biomedical Literature Database (CBM), and Wanfang Data were searched for the related randomized controlled trials (RCT) by August 15, 2019. The qualities of the included studies were assessed based on the Cochrane Handbook for Systematic Reviews of Interventions 5.0. The visual analog scale (VAS), morphine equivalent consumption, and the side effects were used to evaluate the postoperative analgesic effect of ketamine by meta-analysis, which was performed by Review Manager version 5.3 software.

RESULTS

The VAS scores at 6 hours, 12 hours, 24 hours, and 48 hours after surgery were statistically lower in the ketamine group. The morphine equivalent consumptions in 24 hours and 48 hours after surgery were also significantly lower in the ketamine group. For the side effects, no statistical differences in odds ratio (OR) of sedation, dizziness, hallucination, sweating, pruritus, urinary retention, constipation, version trouble, nightmares, and delirium were observed between the ketamine group and the control group. But postoperative nausea and vomiting (PONV) showed lower OR in the ketamine group.

CONCLUSION

The present meta-analysis demonstrated perioperative ketamine could be used as a safe and effective analgesic agent for THA and TKA.

Chronic Pain Impairs Memory Formation via Disruption of Neurogenesis Mediated by Mesohippocampal Brain-Derived Neurotrophic Factor Signaling

BACKGROUND

Chronic pain patients often complain of their poor memory. The mechanisms underlying chronic pain-related memory impairment remain elusive, and there are few clinical therapeutic strategies available for this condition.

METHODS

In a neuropathic pain model induced by chronic constrictive injury of the sciatic nerve in male mice, we used circuit-specific electrophysiological recording, combined with chemogenetic, molecular, and pharmacologic methods, to examine the circuit and molecular mechanisms underlying chronic pain-related memory impairment.

RESULTS

Our current results show that chronic neuropathic pain impaired the acquisition of spatial memory and, meanwhile, reduced adult neurogenesis in the dentate gyrus. Experimentally reducing dentate gyrus neurogenesis mimicked this pain-induced effect on spatial memory formation in naïve mice. Furthermore, pain-associated impairments of both hippocampal neurogenesis and memory formation were rescued or mimicked by chemogenetic activation or deactivation, respectively, of the ventral tegmental area dopaminergic projection, through which ventral tegmental area-released brain-derived neurotrophic factor was required. Importantly, we found that chronic, but not acute, systematic administration of subanesthetic doses of ketamine, while without relieving pain, ameliorated chronic pain-related impairment of spatial memory formation, potentially by rescuing brain-derived neurotrophic factor-mediated dentate gyrus neurogenesis.

CONCLUSIONS

These findings provide a novel, circuit-based mechanistic link between chronic pain and memory formation deficit, and potential new therapeutic options for chronic pain-related learning deficit and memory impairment.

Ketamine metabolites, clinical response, and gamma power in a randomized, placebo-controlled, crossover trial for treatment-resistant major depression

A single, subanesthetic dose of (R,S)-ketamine (ketamine) exerts rapid and robust antidepressant effects. Several groups previously reported that (2S,6S;2R,6R)-hydroxynorketamine (HNK) had antidepressant effects in rodents, and that (2R,6R)-HNK increased cortical electroencephalographic gamma power. This exploratory study examined the relationship between ketamine metabolites, clinical response, psychotomimetic symptoms, and gamma power changes in 34 individuals (ages 18-65) with treatment-resistant depression (TRD) who received a single ketamine infusion (0.5 mg/kg) over 40 min. Plasma concentrations of ketamine, norketamine, and HNKs were measured at 40, 80, 120, and 230 min and at 1, 2, and 3 days post-infusion. Linear mixed models evaluated ketamine metabolites as mediators of antidepressant and psychotomimetic effects and their relationship to resting-state whole-brain magnetoencephalography (MEG) gamma power 6-9 h post-infusion. Three salient findings emerged. First, ketamine concentration positively predicted distal antidepressant response at Day 11 post-infusion, and an inverse relationship was observed between (2S,6S;2R,6R)-HNK concentration and antidepressant response at 3 and 7 days post-infusion. Norketamine concentration was not associated with antidepressant response. Second, ketamine, norketamine, and (2S,6S;2R,6R)-HNK concentrations at 40 min were positively associated with contemporaneous psychotomimetic symptoms; post-hoc analysis revealed that ketamine was the predominant contributor. Third, increased (2S,6S;2R,6R)-HNK maximum observed concentration (Cmax) was associated with increased MEG gamma power. While contrary to preclinical observations and our a priori hypotheses, these exploratory results replicate those of a recently published study documenting a relationship between higher (2S,6S;2R,6R)-HNK concentrations and weaker antidepressant response in humans and provide further rationale for studying gamma power changes as potential biomarkers of antidepressant response.

Ketamine's dose related multiple mechanisms of actions: Dissociative anesthetic to rapid antidepressant

Ketamine induces safe and effective anesthesia and displays unusual cataleptic properties that gave rise to the term dissociative anesthesia. Since 1970, clinicians only utilized the drug as an anesthetic or analgesic for decades, but ketamine was found to have rapid acting antidepressant effects in 1990s. Accumulated evidence exhibits NMDAR antagonism may not be the only mechanism of ketamine. The contributions of AMPA receptor, mTor signal pathway, monoaminergic system, sigma-1 receptor, cholinergic, opioid and cannabinoid systems, as well as voltage-gated calcium channels and hyperpolarization cyclic nucleotide gated channels are discussed for the antidepressant effects. Also the effects of ketamine's enantiomers and metabolites are reviewed. Furthermore ketamine's anesthetic and analgesic mechanisms are briefly revisited. Overall, pharmacology of ketamine, its enantiomers and metabolites is very unique. Insight into multiple mechanisms of action will provide further development and desirable clinical effects of ketamine.

Ketamine for depression clinical issues

Major depressive disorder (MDD) is a debilitating illness with significant morbidity and mortality, leading to attempted and completed suicides. It affects interpersonal relationships and also contributes to decreased productivity, causing financial burden to individuals and society. Patients often fail to respond to various antidepressant medication trials resulting in treatment-resistant depression (TRD). Current antidepressant medications work by modulating the monoaminergic systems and takes several weeks to establish a clinical response. Ketamine has been used extensively as an anesthetic agent since the 1970s, and more recent research has shown its rapid and robust effectiveness in TRD the subject of this review. Ketamine is a racemic mixture comprised of two enantiomers (R)-ketamine and (S)-ketamine and acts as an NMDA receptor antagonist. Most research studies have explored its antidepressant and antisuicidal effects by using it as an intravenous infusion or via the intranasal route due to increased bioavailability. Recently an intranasal esketamine spray was approved by the United States Food and Drug Administration (FDA) for TRD as an adjunct to standard antidepressant treatment in a supervised setting. Regarding its safety profile, multiple research studies have established the short-term safety and efficacy of ketamine in TRD. The cardiorespiratory and neuropsychiatric adverse events observed in these studies were mostly transient. However, ketamine is a scheduled agent with abuse potential, making its long-term use challenging and mandating further research.

Ketamina, un nuevo agente terapéutico para la depresión

Major depressive disorder affects about one in every 10 people in Mexico and is one of the first 5 causes of disability worldwide. Current treatment options are limited and only act upon some factors associated in its physiopathology. Moreover, the effects on depression are not immediate, which is a great limitation in obtaining a benefit over disability caused by this disorder and impedes a rapid action in the scenario of suicidality. Recently, ketamine (an anesthetic) has shown to have antidepressant properties by acting in the glutamate neurotransmission system (while no other current treatment acts on this level). It offers benefits in depressive symptoms in a matter of hours and has proven to be useful in patients that do not benefit from current therapeutic options. Recently, it has been approved for the treatment of depression. However, there are still many questions about its antidepressant mechanisms of action, safety, side effects, among others. Key words: Depression; antidepressants; ketamine.

Phencyclidine-induced cognitive deficits in mice are ameliorated by subsequent repeated intermittent administration of (R)-ketamine, but not (S)-ketamine: Role of BDNF-TrkB signaling

The N-methyl-d-aspartate receptor (NMDAR) antagonists including phencyclidine (PCP) and ketamine produce cognitive deficits in rodents and humans. We previously reported that (R)-ketamine produced the beneficial effects compared to (S)-ketamine in several animal models including depression. Here we compared the effects of two enantiomers of ketamine on cognitive deficits in mice after repeated administration of PCP. PCP (10 mg/kg/day for 10 days)-induced cognitive deficits were ameliorated by subsequent repeated intermittent administration of (R)-ketamine (10 mg/kg/day, twice weekly for 2-weeks), but not (S)-ketamine. Western blot analysis showed decreased levels of brain-derived neurotrophic factor (BDNF) and decreased ratio of phosphorylated-TrkB (p-TrkB) to TrkB in the prefrontal cortex (PFC) and hippocampus of PCP-treated mice. Furthermore, PCP-induced reduction of BDNF and p-TrkB/TrkB ratio in the PFC and hippocampus of PCP-treated mice was ameliorated by subsequent intermittent administration of (R)-ketamine. Interestingly, the beneficial effects of (R)-ketamine were blocked by pretreatment with TrkB inhibitor ANA-12. These findings suggest that (R)-ketamine could ameliorate PCP-induced cognitive deficits via activation of BDNF-TrkB signaling in the brain. Therefore, (R)-ketamine could be a potential therapeutic drug for cognitive impairment in patients with schizophrenia.

Esketamine for treatment resistant depression: a trick of smoke and mirrors?

In March 2019, the US Food and Drug Administration (FDA) approved a nasal spray formulation of esketamine for the treatment of resistant depression in adults. Esketamine is the S-enantiomer of ketamine, an FDA-approved anaesthetic, known to cause dissociation and, occasionally, hallucinations. While ketamine has not been approved for depression in the USA or in any other country, it has been used off-label in cases of severe depression. This commentary critically reviewed the evidence on esketamine submitted to the FDA, aiming to draw implications for clinical practice, research and regulatory science.

Contribution of skeletal muscular glycine to rapid antidepressant effects of ketamine in an inflammation-induced mouse model of depression

RATIONALE

Basic and clinical studies have reported rapid and long-lasting antidepressant effects of ketamine. Although previous studies have proposed several mechanisms underlying the antidepressant effects of ketamine, these mechanisms have not been completely elucidated.

OBJECTIVES

The present study evaluated the effects of systemically administered ketamine treatment in a lipopolysaccharide (LPS)-induced mouse model of depression.

METHODS

Non-targeted metabolomics, western blotting, and behavioral tests (locomotion, tail suspension, and forced swimming tests) were performed.

RESULT

Ketamine significantly attenuated the abnormally increased immobility time in a lipopolysaccharide (LPS)-induced mouse model of depression. Aminomalonic acid, glutaraldehyde, glycine, histidine, N-methyl-L-glutamic acid, and ribose levels in skeletal muscle were altered following ketamine administration. Furthermore, ketamine significantly decreased the LPS-induced increase in glycine receptor A1 (GlyA1) levels. However, the glycine receptor antagonist strychnine did not elicit any pharmacological effects on ketamine-induced alterations in behaviors or muscular GlyA1 levels. Exogenous glycine and L-serine significantly improved depression-like symptoms in LPS-induced mice.

CONCLUSIONS

Our findings suggest that skeletal muscular glycine contributes to the antidepressant effects of ketamine in inflammation. Effective strategies for improving skeletal muscular glycine levels may be a novel approach to depression treatment.

Antidepressant effects of ketamine on depression-related phenotypes and dopamine dysfunction in rodent models of stress

Depression, the most prevalent psychiatric disorder, is characterized by increased negative affect (i.e. depressed mood) and reduced positive affect (i.e. anhedonia). Stress is a risk factor for depression in humans, and animal models of chronic stress are typically used to study neurobehavioral alterations relevant to depression. Common behavioral outcomes in rodent models of chronic stress include anhedonia, social dysfunction and behavioral despair. For example, chronically stressed rodents exhibit reduced reward preference, as measured by a loss of preference for sucrose solutions and time spent interacting with a novel conspecific, while also exhibiting less time struggling against inescapable stressors (e.g. forced swim, tail suspension). In both humans and rodents, anhedonia is associated with dysfunction of the dopamine (DA) system. Unlike traditional antidepressants, which are limited by inadequate efficacy and delayed therapeutic response, acute ketamine administration rapidly alleviates depressive symptoms in humans and reverses stress-induced changes in animal models. These effects are partially mediated via actions on the DA system. This review summarizes the clinical effects of ketamine, the neurobiological underpinnings of depression with a focus on DA dysfunction, as well as antidepressant effects of ketamine on depression-related endophenotypes (i.e. anhedonia, despair) and ventral tegmental area (VTA) activity in rodent models of repeated stress. Moreover, we discuss evidence regarding sex differences in ketamine's antidepressant effects, wherein females appear to be more sensitive to lower dose ketamine, as well as novel findings suggesting that ketamine has prophylactic effects with regard to protection against the neurobehavioral impact of future stressors.

Molecular and cellular mechanisms underlying the antidepressant effects of ketamine enantiomers and its metabolites

Although the robust antidepressant effects of the N-methyl-D-aspartate receptor (NMDAR) antagonist ketamine in patients with treatment-resistant depression are beyond doubt, the precise molecular and cellular mechanisms underlying its antidepressant effects remain unknown. NMDAR inhibition and the subsequent α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor (AMPAR) activation are suggested to play a role in the antidepressant effects of ketamine. Although (R)-ketamine is a less potent NMDAR antagonist than (S)-ketamine, (R)-ketamine has shown more marked and longer-lasting antidepressant-like effects than (S)-ketamine in several animal models of depression. Furthermore, non-ketamine NMDAR antagonists do not exhibit robust ketamine-like antidepressant effects in patients with depression. These findings suggest that mechanisms other than NMDAR inhibition play a key role in the antidepressant effects of ketamine. Duman's group demonstrated that the activation of mammalian target of rapamycin complex 1 (mTORC1) in the medial prefrontal cortex is reportedly involved in the antidepressant effects of ketamine. However, we reported that mTORC1 serves a role in the antidepressant effects of (S)-ketamine, but not of (R)-ketamine, and that extracellular signal-regulated kinase possibly underlie the antidepressant effects of (R)-ketamine. Several lines of evidence have demonstrated that brain-derived neurotrophic factor (BDNF) and its receptor, tyrosine kinase receptor B (TrkB), are crucial in the antidepressant effects of ketamine and its two enantiomers, (R)-ketamine and (S)-ketamine, in rodents. In addition, (2R,6R)-hydroxynormetamine [a metabolite of (R)-ketamine] and (S)-norketamine [a metabolite of (S)-ketamine] have been shown to exhibit antidepressant-like effects on rodents through the BDNF-TrkB cascade. In this review, we discuss recent findings on the molecular and cellular mechanisms underlying the antidepressant effects of enantiomers of ketamine and its metabolites. It may be time to reconsider the hypothesis of NMDAR inhibition and the subsequent AMPAR activation in the antidepressant effects of ketamine.

Updates on Preclinical and Translational Neuroscience of Mood Disorders: A Brief Historical Focus on Ketamine for the Clinician

BACKGROUND

The development of new-generation antidepressants comes at a time of great clinical need when the global burden of depression, suicide, and other psychiatric conditions continues to increase. Our current treatment armamentarium is limited by the time delay needed for antidepressant effects and the significant number of patients who do not show an adequate response to antidepressants. The past 2 decades of psychiatric research has revealed that ketamine, known to be used only as an anesthetic and drug of abuse and to produce experimental models of psychosis, is effective at subanesthetic doses to ameliorate clinical depression.

METHODS

We performed a systematic search of PubMed/MEDLINE indexed reports to identify clinical and translational research done with ketamine for purposes of treating depression.

RESULTS

We will first present the rationale for investigating ketamine and other N-methyl-D-aspartate receptor antagonists as a novel class of glutamate system targeting antidepressants. We will summarize putative molecular pathways underlying mood disorders and outline a brief history of investigation into ketamine as a treatment for depression. Recent clinical/translational evidence of ketamine's rapid-acting antidepressant mechanism will be critically reviewed in detail.

CONCLUSIONS

At the end of this review, we will opine on the role of ketamine and derivatives in clinical practice.

Ketamine and depression: a narrative review

Depression is the third leading cause of disability in the world. Depressive symptoms may be reduced within several weeks after the start of conventional antidepressants, but treatment resistance concerns one-third of patients who fail to achieve recovery. Over the last 20 years, ketamine, an antagonist of the N-methyl-D-aspartate receptor, has been described to have antidepressant properties. A literature review was conducted through an exhaustive electronic search. It was restricted to Cochrane reviews, meta-analyses, and randomized controlled trials (RCTs) of ketamine for major depressive disorder and/or bipolar disorder. This review included two Cochrane reviews, 14 meta-analyses and 15 trials. Ketamine was studied versus placebo, versus other comparators and as an anesthetic adjuvant before electroconvulsive therapy. In 14 publications, ketamine provided a rapid antidepressant effect with a maximum efficacy reached at 24 hrs. Its effect lasted for 1–2 weeks after infusion, but a longer-term effect is little reported. Ketamine does not seem to improve depressive symptoms at the end of electroconvulsive sessions. Safety and tolerability profiles with ketamine at low single dose are generally good in depressed patients. However, there is a lack of data concerning ketamine with repeated administration at higher doses. The clinical use of ketamine is increasing. Intranasal (S)-ketamine has recently been approved for depression by the Food and Drug Administration. It could be a promising treatment in depressed patients with suicidal ideation. Collectively, the level of proof of efficacy remains low and more RCTs are needed to explore efficacy and safety issues of ketamine in depression.

Comparison of antidepressant and side effects in mice after intranasal administration of (R,S)-ketamine, (R)-ketamine, and (S)-ketamine

The N-methyl-d-aspartate receptor (NMDAR) antagonist (R,S)-ketamine produces rapid and sustained antidepressant effects in treatment-resistant patients with depression although intranasal use of (R,S)-ketamine in ketamine abusers is popular. In March 5, 2019, nasal spray of (S)-ketamine for treatment-resistant depression was approved as a new antidepressant by the US Food Drug Administration. Clinical study of (R)-ketamine is underway. In a chronic social defeat stress (CSDS) model, we compared the antidepressant effects of (R,S)-ketamine, (R)-ketamine, and (S)-ketamine after a single intranasal administration. Furthermore, we also compared the side effects (i.e., locomotion, prepulse inhibition (PPI), abuse liability) of these three compounds in mice. The order of potency of antidepressant effects after a single intranasal administration was (R)-ketamine > (R,S)-ketamine > (S)-ketamine. In contrast, the order of locomotor activity and prepulse inhibition (PPI) deficits after a single intranasal administration was (S)-ketamine > (R,S)-ketamine > (R)-ketamine. In the conditioned place preference (CPP) test, both (S)-ketamine and (R,S)-ketamine increased CPP scores in mice after repeated intranasal administration, in a dose dependent manner. In contrast, (R)-ketamine did not increase CPP scores in mice. These findings suggest that intranasal administration of (R)-ketamine would be a safer antidepressant than (R,S)-ketamine and (S)-ketamine.