Blood pressure safety of subanesthetic ketamine for depression: A report on 684 infusions

Effect of Continuous Infusion of Different Doses of Esketamine on the Bispectral Index During Sevoflurane Anesthesia: A Randomized Controlled Trial

Purpose

To investigate and quantify the effect of continuous esketamine infusion at different doses on the bispectral index (BIS) during sevoflurane anesthesia.

Methods

A total of 120 patients scheduled for elective laparoscopic renal surgery were randomly divided into three groups. Under steady anesthesia and surgical situations, the patient was started on continuous infusion of the study drug: 0.125 mg/kg/h esketamine (group E1), 0.25 mg/kg/h esketamine (group E2), and the same volume of saline (group C). The primary outcome was changes in BIS value after 15 min (T15), 30 min (T30), 45 min (T45), and 60 min (T60) of drug infusion. The secondary outcomes were 95% spectral edge frequency (SEF95), electromyogram (EMG), heart rate (HR), and mean arterial pressure (MAP) from T0 to T60. Furthermore, postoperative pain, postoperative recovery, and perioperative adverse events were evaluated.

Results

Compared with group C, group E1 exhibited significant BIS elevation at T30-T60 and group E2 at T15-T60 (P < 0.001). Compared with group E1, group E2 showed a more significant BIS elevation at T15-T60 (P < 0.001). The area under the curve (AUC) of BIS and SEF95 were significantly higher in group E2 than in groups C and E1 (P < 0.05). BIS value for any of the three groups was significantly correlated with SEF95 (P < 0.001). No significant differences were observed in the AUC of EMG, HR, and MAP among the three groups. Intraoperative remifentanil consumption and postoperative NRS of pain on movement were significantly reduced in group E2 compared with groups C and E1 (P < 0.05).

Conclusion

Continuous infusion of both 0.125 and 0.25 mg/kg/h of esketamine increased the BIS value during sevoflurane anesthesia, and the BIS value gradually stabilized with the prolongation of the infusion time.

Ketamine induces multiple individually distinct whole-brain functional connectivity signatures

Background

Ketamine has emerged as one of the most promising therapies for treatment-resistant depression. However, inter-individual variability in response to ketamine is still not well understood and it is unclear how ketamine's molecular mechanisms connect to its neural and behavioral effects.

Methods

We conducted a single-blind placebo-controlled study, with participants blinded to their treatment condition. 40 healthy participants received acute ketamine (initial bolus 0.23 mg/kg, continuous infusion 0.58 mg/kg/hr). We quantified resting-state functional connectivity via data-driven global brain connectivity and related it to individual ketamine-induced symptom variation and cortical gene expression targets.

Results

We found that: (i) both the neural and behavioral effects of acute ketamine are multi-dimensional, reflecting robust inter-individual variability; (ii) ketamine's data-driven principal neural gradient effect matched somatostatin (SST) and parvalbumin (PVALB) cortical gene expression patterns in humans, while the mean effect did not; and (iii) behavioral data-driven individual symptom variation mapped onto distinct neural gradients of ketamine, which were resolvable at the single-subject level.

Conclusions

These results highlight the importance of considering individual behavioral and neural variation in response to ketamine. They also have implications for the development of individually precise pharmacological biomarkers for treatment selection in psychiatry.

Funding

This study was supported by NIH grants DP5OD012109-01 (A.A.), 1U01MH121766 (A.A.), R01MH112746 (J.D.M.), 5R01MH112189 (A.A.), 5R01MH108590 (A.A.), NIAAA grant 2P50AA012870-11 (A.A.); NSF NeuroNex grant 2015276 (J.D.M.); Brain and Behavior Research Foundation Young Investigator Award (A.A.); SFARI Pilot Award (J.D.M., A.A.); Heffter Research Institute (Grant No. 1-190420) (FXV, KHP); Swiss Neuromatrix Foundation (Grant No. 2016-0111) (FXV, KHP); Swiss National Science Foundation under the framework of Neuron Cofund (Grant No. 01EW1908) (KHP); Usona Institute (2015 - 2056) (FXV).

Clinical trial number

NCT03842800.

The 5-HT1A receptor biased agonists, NLX-204 and NLX-101, display ketamine-like RAAD and anti-TRD activities in rat CMS models

OBJECTIVES

NLX-101 and NLX-204 are highly selective serotonin 5-HT1A 'biased' agonists, displaying potent and efficacious antidepressant-like activity upon acute administration in models such as the forced swim test.

METHODS

we compared the effects of repeated administration of NLX-101, NLX-204 and ketamine in the chronic mild stress (CMS) model of depression, considered to have high translational potential, on sucrose consumption (anhedonia measure), novel object recognition (NOR; working memory measure) and elevated plus maze (EPM; anxiety measure) in male Wistar and Wistar-Kyoto rats (the latter being resistant to classical antidepressants).

RESULTS

in Wistar rats, NLX-204 and NLX-101 (0.08-0.16 mg/kg i.p.), like ketamine (10 mg/kg i.p.) dose-dependently reversed CMS-induced sucrose intake deficit from treatment Day 1, with nearly full reversal observed at the higher dose at Days 8 and 15. These effects persisted for 3 weeks following treatment cessation. In the NOR test, both doses of NLX-101/NLX-204, and ketamine, rescued the deficit in discrimination index caused by CMS on Days 3 and 17; all three compounds increased time spent in open arms (EPM) but only NLX-204 achieved statistical significance on Days 2 and 16. In Wistar-Kyoto rats, all 3 compounds were also active in the sucrose test and, to a lesser extent, in the NOR and EPM. In non-stressed rats (both strains), the three compounds produced no significant effects in all tests.

CONCLUSIONS

these observations further strengthen the hypothesis that biased agonism at 5-HT1A receptors constitutes a promising strategy to achieve rapid-acting/sustained antidepressant effects combined with activity against TRD, in addition to providing beneficial effects against memory deficit and anxiety in depressed patients.

Comparing the Effects of Low-Dose Ketamine, Fentanyl, and Morphine on Hemorrhagic Tolerance and Analgesia in Humans

Hemorrhage is a leading cause of preventable battlefield and civilian trauma deaths. Ketamine, fentanyl, and morphine are recommended analgesics for use in the prehospital (i.e., field) setting to reduce pain. However, it is unknown whether any of these analgesics reduce hemorrhagic tolerance in humans. We tested the hypothesis that fentanyl (75 µg) and morphine (5 mg), but not ketamine (20 mg), would reduce tolerance to simulated hemorrhage in conscious humans. Each of the three analgesics was evaluated independently among different cohorts of healthy adults in a randomized, crossover (within drug/placebo comparison), placebo-controlled fashion using doses derived from the Tactical Combat Casualty Care Guidelines for Medical Personnel. One minute after an intravenous infusion of the analgesic or placebo (saline), we employed a pre-syncopal limited progressive lower-body negative pressure (LBNP) protocol to determine hemorrhagic tolerance. Hemorrhagic tolerance was quantified as a cumulative stress index (CSI), which is the sum of products of the LBNP and the duration (e.g., [40 mmHg x 3 min] + [50 mmHg x 3 min] …). Compared with ketamine (p = 0.002 post hoc result) and fentanyl (p = 0.02 post hoc result), morphine reduced the CSI (ketamine (n = 30): 99 [73-139], fentanyl (n = 28): 95 [68-130], morphine (n = 30): 62 [35-85]; values expressed as a % of the respective placebo trial's CSI; median [IQR]; Kruskal-Wallis test p = 0.002). Morphine-induced reductions in tolerance to central hypovolemia were not well explained by a prediction model including biological sex, body mass, and age (R2=0.05, p = 0.74). These experimental data demonstrate that morphine reduces tolerance to simulated hemorrhage while fentanyl and ketamine do not affect tolerance. Thus, these laboratory-based data, captured via simulated hemorrhage, suggest that morphine should not be used for a hemorrhaging individual in the prehospital setting.

A comparison of the safety, feasibility, and tolerability of ECT and ketamine for treatment-resistant depression

INTRODUCTION

Treatment-resistant depression (TRD) is a problematic and prevalent public health and societal concern. Although electroconvulsive therapy (ECT) is the gold standard TRD intervention, the treatment evokes apprehension due to public perceptions, feasibility, and tolerability. Despite significant medical advancements, few medications have been approved by the U.S. Food and Drug Administration for TRD. In 2019, intranasal esketamine, the S-isomer of racemic ketamine, was approved for TRD, garnering significant excitement about the potential for the drug to act as an alternative treatment to ECT.

AREAS COVERED

The goal of this narrative review is to compare the safety, efficacy, and tolerability of ketamine and ECT; clarify whether ketamine is a reasonable alternative to ECT; and to facilitate improved treatment assignment for TRD. Empirical quantitative and qualitative studies and national and international guidelines these treatments are reviewed.

EXPERT OPINION

: The field awaits the results of two ongoing large comparative effectiveness trials of ECT and IV ketamine for TRD, which should help guide clinicians and patients as to the relative risk and benefit of these interventions. Over the next five years we anticipate further innovations in neuromodulation and in drug development which broadly aim to develop more tolerable versions of ECT and ketamine, respectively.

Intravenous ketamine for depression: A clinical discussion reconsidering best practices in acute hypertension management

Ketamine is a versatile medication with an emerging role for the treatment of numerous psychiatric conditions, including treatment resistant depression. Current psychiatry guidelines for its intravenous administration to treat depression recommend regular blood pressure monitoring and an aggressive approach to potential transient hypertensive episodes induced by ketamine infusions. While this approach is aimed at ensuring patient safety, it should be updated to align with best practice guidelines in the management of hypertension. This review defines and summarizes the currently recommended approach to the hypertensive emergency, the asymptomatic hypertensive urgency, and discusses their relevance to intravenous ketamine therapy. With an updated protocol informed by these best practice guidelines, ketamine treatment for depression may be more accessible to facilitate psychiatric treatment.

Non-parenteral Ketamine for Depression: A Practical Discussion on Addiction Potential and Recommendations for Judicious Prescribing

Intravenous (IV) ketamine is increasingly used off-label at subanesthetic doses for its rapid antidepressant effect, and intranasal (IN) esketamine has been recently approved in several countries for treating depression. The clinical utility of these treatments is limited by a paucity of publicly funded IV ketamine and IN esketamine programs and cost barriers to private treatment programs, as well as the drug cost for IN esketamine itself, which makes generic ketamine alternatives an attractive option. Though evidence is limited, use of non-parenteral racemic ketamine formulations (oral, sublingual, and IN) may offer more realistic access in less rigidly supervised settings, both for acute and maintenance treatment in select cases. However, the psychiatric literature has repeatedly cautioned on the addictive potential of ketamine and raised caution for both less supervised and longer-term use of ketamine. To date, these concerns have not been discussed in view of available evidence, nor have they been discussed within a broader clinical context. This paper examines the available relevant literature and suggests that ketamine misuse risks appear not dissimilar to those of other well-established and commonly prescribed agents with abuse potential, such as stimulants or benzodiazepines. As such, ketamine prescribing should be considered in a similar risk/benefit context to balance patient access and need for treatment with concern for potential substance misuse. Our consortium of mood disorder specialists with significant ketamine prescribing experience considers prescribing of non-parenteral ketamine a reasonable clinical treatment option in select cases of treatment-resistant depression. This paper outlines where this may be appropriate and makes practical recommendations for clinicians in judicious prescribing of non-parenteral ketamine.

Beyond the Raskin Protocol: Ketamine, Lidocaine, and Other Therapies for Refractory Chronic Migraine

PURPOSE OF REVIEW

The purpose of this review is to discuss the available evidence and therapeutic considerations for intravenous drug therapy for refractory chronic migraine.

RECENT FINDINGS

In carefully monitored settings, the inpatient administration of intravenous lidocaine and ketamine can be successful in treating refractory chronic migraine. Many patients with refractory chronic migraine have experienced treatment failure with the Raskin protocol. The use of aggressive inpatient infusion therapy consisting of intravenous lidocaine or ketamine, along with other adjunctive medications, has become increasingly common for these patients when all other treatments have failed. There is a clear need for prospective studies in this population comprised of patients who have largely been excluded from other studies.

Prevention and Management of Common Adverse Effects of Ketamine and Esketamine in Patients with Mood Disorders

The emerging roles of ketamine and esketamine as effective rapid-acting antidepressants hold promise for patients suffering from treatment-resistant depression and/or major depressive disorder with suicidality. Practitioner familiarity with common tolerability/safety concerns along with pragmatic prevention and management strategies are needed to reduce patient burden and improve the acceptability and accessibility of these treatments. The most common treatment-emergent adverse events associated with ketamine/esketamine are dissociation, anxiety, nausea, increased blood pressure, and headache. The majority of side effects are mild, transient, dose dependent, and attenuate with subsequent treatments. Patient selection, baseline physical and psychiatric assessments, and an appropriate setting are critical first steps in the prevention and mitigation of adverse events. Patient education and supportive interventions play central roles in the prevention and management of select adverse events. Severe and/or clinically significant adverse effects may necessitate the judicious use of adjunctive medications. Moreover, practitioners must remain vigilant to the potential for abuse liability and long-term adverse events, for which there are insufficient data. This article succinctly reviews common treatment-emergent adverse events of ketamine and esketamine within the context of mood disorders, and provides practical suggestions for prevention and management at point-of-care.

Perspectives for therapy of treatment-resistant depression

A high proportion of depressed patients fail to respond to antidepressant drug treatment. Treatment-resistant depression (TRD) is a major challenge for the psychopharmacology of mood disorders. Only in the past decade have novel treatments, including deep brain stimulation (DBS) and ketamine, been discovered that provide rapid and sometimes prolonged relief to a high proportion of TRD sufferers. In this review, we consider the current status of TRD from four perspectives: the challenge of developing an appropriate regulatory framework for novel rapidly acting antidepressants; the efficacy of non-pharmacological somatic therapies; the development of an animal model of TRD and its use to understand the neural basis of antidepressant non-response; and the potential for rapid antidepressant action from targets (such as 5-HT_1A receptors) beyond the glutamate receptor.

Ketamine for depression

Over the last two decades, the dissociative anaesthetic agent ketamine, an uncompetitive N-Methyl-D-Aspartate (NMDA) receptor antagonist, has emerged as a novel therapy for treatment-resistant depression (TRD), demonstrating rapid and robust antidepressant effects within hours of administration. Ketamine is a racemic mixture composed of equal amounts of (S)-ketamine and (R)-ketamine. Although ketamine currently remains an off-label treatment for TRD, an (S)-ketamine nasal spray has been approved for use in TRD (in conjunction with an oral antidepressant) in the United States and Europe. Despite the promise of ketamine, key challenges including how to maintain response, concerns regarding short and long-term side-effects and the potential for abuse remain. This review provides an overview of the history of ketamine, its use in psychiatry and its basic pharmacology. The clinical evidence for the use of ketamine in depression and potential adverse effects associated with treatment are summarized. A synopsis of some of the putative neurobiological mechanisms underlying ketamine's rapid-acting antidepressant effects is provided before finally outlining future research directions, including the need to identify biomarkers for predicting response and treatment targets that may be used in the development of next-generation rapid-acting antidepressants that may lack ketamine's side-effects or abuse potential.

Synthesizing the Evidence for Ketamine and Esketamine in Treatment-Resistant Depression: An International Expert Opinion on the Available Evidence and Implementation

Replicated international studies have underscored the human and societal costs associated with major depressive disorder. Despite the proven efficacy of monoamine-based antidepressants in major depression, the majority of treated individuals fail to achieve full syndromal and functional recovery with the index and subsequent pharmacological treatments. Ketamine and esketamine represent pharmacologically novel treatment avenues for adults with treatment-resistant depression. In addition to providing hope to affected persons, these agents represent the first non-monoaminergic agents with proven rapid-onset efficacy in major depressive disorder. Nevertheless, concerns remain about the safety and tolerability of ketamine and esketamine in mood disorders. Moreover, there is uncertainty about the appropriate position of these agents in treatment algorithms, their comparative effectiveness, and the appropriate setting, infrastructure, and personnel required for their competent and safe implementation. In this article, an international group of mood disorder experts provides a synthesis of the literature with respect to the efficacy, safety, and tolerability of ketamine and esketamine in adults with treatment-resistant depression. The authors also provide guidance for the implementation of these agents in clinical practice, with particular attention to practice parameters at point of care. Areas of consensus and future research vistas are discussed.

Meta-Analysis: Hemodynamic Responses to Sub-anesthetic Doses of Ketamine in Patients With Psychiatric Disorders

Ketamine, a medication traditionally used as an anesthetic, has increasingly been recognized as an effective treatment for psychiatric disorders. At sub-anesthetic doses (defined here as ≤ 0.5 mg/kg), ketamine treatment has been studied in patients with treatment-resistant depression (TRD), obsessive-compulsive disorder (OCD), post-traumatic stress disorder (PTSD), and social anxiety disorder (SAD). Transient increases in hemodynamic activity have been reported during and after ketamine treatment, which may be desirable properties in some anesthesia settings, but are generally undesirable in psychiatric settings. While ketamine doses used in psychiatry are lower than those used in anesthesia, there are published instances of early termination of psychiatric ketamine infusions due to elevations in blood pressure and heart rate. No unifying study has been conducted to examine the impact of sub-anesthetic ketamine doses on hemodynamic parameters [systolic blood pressure (SBP), diastolic blood pressure (DBP), and heart rate (HR)] in psychiatric populations and to evaluate these changes across adult age groups. Here, data from 15 articles comprising a total N = 2,252 ketamine or esketamine treatments in adult participants were used to conduct a meta-analysis of treatment-induced hemodynamic changes. Ketamine/esketamine produced modest but significant increases in the variables of interest with an average SBP increase of 12.61 mm Hg (95% CI 10.40-14.82 mm Hg, z = 11.18, p < 0.0001), average DBP increase of 8.49 mm Hg (95% CI 6.89-10.09 mmHg, z = 10.41, p < 0.0001), and average heart rate increase of 4.09 beats per minute (95% CI 0.55-7.63 BPM), z = 2.27, p = 0.0235). Stratified subgroup analysis indicated no significant differences between ketamine and esketamine effects on blood pressure. Further analysis indicated that there was no significant effect of age on ketamine-induced changes in SBP, DBP, and HR. Taken together these data show that sub-anesthetic ketamine and esketamine induce small but significant increases in hemodynamic parameters that are transient in nature in adult psychiatric populations. While these data are reassuring, it is important for each treatment case to fully explore potential cardiovascular risks prior to initiating treatment.

Acute Effects of Ketamine Infusion on Postoperative Mood Scores in Patients Undergoing Dilation and Curettage: A Randomized Double-Blind Controlled Study

Background

Emotional and psychological effects following abortion are more common than physical side effects and can range from mild regret to more serious complications such as depression. In the last decade, it has been suggested that low dose of ketamine is a fast-acting antidepressant.

Purpose

The aim of this study was to investigate the impact of intraoperative ketamine infusion on postoperative mood score in patients undergoing Dilation and Curettage (D&C) under spinal anesthesia. We hypothesized that a single low-dose administration of ketamine infusion during D&C surgery can improve mood scores in the immediate postoperative period.

Methods

A prospective, randomized, double-blind, parallel-group, placebo-controlled trial. The study included a total of 60 patients, ≥18 years, physical status ASA II, with up to 12-week gestation undergoing elective D&C surgery. Patients were divided randomly into a ketamine group (group K) and a control group (group C). In group K, 0.4 mg/kg ketamine was given as a continuous infusion over 20 min intraoperatively. Main Outcome Measure. Profile of Mood States (POMS) was recorded preoperatively and 2 hours postoperatively.

Results

There were no differences in preoperative POMS between the two groups. Mean postoperative POMS of group K was lower than that of group C indicating mood improvement. Ketamine group patients showed higher sedation score and increased, although self-limiting, psychedelic phenomena than the control group.

Conclusion

Observed data here support an acute effect of ketamine on mood but any further claim will be speculative. Further future studies exploring postoperative mood scores after 24 hours post-infusion are needed. This trial is registered with PACTR201907779292947.

Cardiovascular effects of repeated subanaesthetic ketamine infusion in depression

BACKGROUND

Ketamine produces significant rapid-onset and robust antidepressant effects in patients with major depressive disorder. However, this drug also has transient cardiovascular stimulatory effects, and there are limited data about potential predictors of these cardiovascular effects.

METHODS

A total of 135 patients with unipolar and bipolar depression received a total of 741 ketamine infusions (0.5 mg/kg over 40 min). Blood pressure and pulse were monitored every 10 min during the infusions and 30 min after the infusions. Depressive, psychotomimetic and dissociative symptom severity was assessed at baseline and 4 hours after each infusion.

RESULTS

The maximum blood pressure and pulse values were observed at 30-40 min during infusions. The largest mean systolic/diastolic blood pressure increases were 7.4/6.0 mmHg, and the largest mean pulse increase was 1.9 beats per min. No significant change in blood pressure and pulse was found in the second to sixth infusions compared with the first infusion. Patients who were older (age⩾50 years), hypertensive and receiving infusions while exhibiting dissociative symptoms showed greater maximal changes in systolic and diastolic blood pressure than patients who were younger (age<50 years), normotensive and without dissociative symptoms (all p < 0.05). Hypertensive patients had less elevation of pulse than normotensive patients (p < 0.05). Ketamine dosage was positively correlated with changes in systolic and diastolic blood pressure (all p < 0.05).

CONCLUSIONS

Blood pressure and pulse elevations following subanaesthetic ketamine infusions are transient and do not cause serious cardiovascular events. Older age, hypertension, large ketamine dosage and dissociative symptoms may predict increased ketamine-induced cardiovascular effects.

The Canadian Network for Mood and Anxiety Treatments (CANMAT) Task Force Recommendations for the Use of Racemic Ketamine in Adults with Major Depressive Disorder: Recommandations Du Groupe De Travail Du Réseau Canadien Pour Les Traitements De L'humeur Et De L'anxiété (Canmat) Concernant L'utilisation De La Kétamine Racémique Chez Les Adultes Souffrant De Trouble Dépressif Majeur

OBJECTIVE

Patients with major depressive disorder often have limited response to first-line and second-line medications; hence, novel pharmacological treatments are needed for treatment-resistant depression (TRD). Ketamine, an N-methyl-d-aspartate (NMDA) receptor antagonist, has demonstrated rapid antidepressant effects in patients with TRD. The Canadian Network for Mood and Anxiety Treatments (CANMAT) convened a task force to review the evidence for efficacy and safety of racemic ketamine and to provide recommendations for its use in clinical practice.

METHODS

A systematic review was conducted with computerized search of electronic databases up to January 31, 2020 using combinations of search terms, inspection of bibliographies, and review of other ketamine guidelines and consensus statements. The level of evidence and lines of treatment were assigned according to CANMAT criteria. Recommendations were given in question-answer format.

RESULTS

Intravenous (IV) racemic ketamine given as a single infusion has Level 1 evidence for efficacy in adults with TRD. The evidence for multiple infusions, given as an acute series or as ongoing maintenance treatment, is limited to Level 3. Adverse events associated with ketamine infusions include behavioral (e.g., dissociative symptoms) and physiological (e.g., hypertension) events. There is only Level 3 or 4 evidence for non-IV formulations of racemic ketamine. Consensus recommendations are given for clinical administration of IV ketamine including patient selection, facility and personnel issues, monitoring, and maintaining response.

CONCLUSIONS

Single-dose IV racemic ketamine is a third-line recommendation for adults with TRD. The need for repeated and maintenance ketamine infusions should be carefully assessed on a case-by-case basis with consideration of potential risks and benefits. Because of limited evidence for efficacy and risk for misuse and diversion, the use of oral and other formulations of racemic ketamine should be limited to specialists with ketamine-prescribing expertise and affiliations with tertiary or specialized centers.

Cardiovascular Effects of Combining Subcutaneous or Intravenous Esketamine and the MAO Inhibitor Tranylcypromine for the Treatment of Depression: A Retrospective Cohort Study

BACKGROUND

(Es)ketamine and monoamine oxidase inhibitors (MAOIs), e.g., tranylcypromine, are therapeutic options for treatment-resistant major depression. Simultaneous administration is currently not recommended because of concern about hypertensive crises.

OBJECTIVE

Our objective was to evaluate whether changes in systolic blood pressure (SBP), diastolic blood pressure (DBP), and heart rate (HR) during esketamine administration differed between patients who concomitantly received tranylcypromine and those who did not.

METHODS

This was a retrospective cohort study utilizing cardiovascular monitoring data from inpatients treated for severe depression in unipolar, bipolar, and schizoaffective disorder. Primary outcomes were change in mean BP and HR during the first hour after intravenous or subcutaneous esketamine administration compared with baseline, controlled for confounders. Secondary analyses quantify differences in absolute BP during esketamine treatment and comparisons of BP peaks, temporal effects, and intraindividual comparisons before and after tranylcypromine initiation.

RESULTS

Our analysis included 509 esketamine administrations in 43 patients, 14 of whom concomitantly received tranylcypromine. Controlling for creatinine and age, mean ± standard deviation (SD) BP changes were significantly increased by concomitant tranylcypromine treatment (ΔSBP: F[1,503] = 86.73, p < 0.001; ΔDBP: F[1,503] = 55.71, p < 0.001), but HR remained unaffected. Mean SBP change during esketamine administration was 2.96 ± 18.11 mmHg in patients receiving tranylcypromine (TCP+) and -8.84 ± 11.31 mmHg in those who did not (TCP-). Changes in DBP were -2.81 ± 11.20 mmHg for TCP+ and -10.77 ± 9.13 mmHg for TCP-. Moreover, we found a significant dose-response relationship between tranylcypromine dose and BP (SBP: B = 0.35, standard error [SE] = 0.12, 95% confidence interval [CI] 0.12-0.60, p = 0.004; adjusted R² = 0.11, p = 0.008; DBP: B = 0.21, SE = 0.08, 95% CI 0.06-0.36, p = 0.007; adjusted R² = 0.08; p = 0.023).

CONCLUSIONS

Although statistically significant changes in BP were identified in patients receiving tranylcypromine and esketamine, these changes were clinically insignificant. Thus, combining esketamine and this MAOI appears to be safe at standard doses. The dose-response relationship calls for caution with higher doses of tranylcypromine.

The Cardiovascular Effects of Newer Antidepressants in Older Adults and Those With or At High Risk for Cardiovascular Diseases

Depression is common in older adults and those with cardiovascular disease. Although selective serotonin reuptake inhibitors generally have been shown to be safe to treat depression in these patients, it is important to identify additional antidepressants when selective serotonin reuptake inhibitors are not effective. This qualitative narrative review summarizes what is known about the cardiovascular side effects of some of the newer antidepressants. Twelve novel non-selective serotonin reuptake inhibitor antidepressants were identified from the literature: venlafaxine, desvenlafaxine, duloxetine, milnacipran, levomilnacipran, mirtazapine, bupropion, vilazodone, vortioxetine, agomelatine, moclobemide, and ketamine-esketamine. A search restricted to publications written in English was conducted in PubMed and Google Scholar with the following search criteria: the specific antidepressant AND (QT OR QTc OR "heart rate" OR "heart rate variability" OR "hypertension" OR "orthostatic hypotension" OR "cardiovascular outcomes" OR "arrhythmia" OR "myocardial infarction" OR "cardiovascular mortality") AND (geriatric OR "older adults" OR "late life depression" OR "cardiovascular disease" OR "hospitalized" OR "hospitalized"). The recommended use, dosing ranges, cardiovascular effects, and general advantages and disadvantages of each of the drugs are discussed. Levomilnacipran and vilazodone have not received enough study to judge their safety in older patients or in those with, or at high risk for, cardiovascular disease. There is at least some evidence for possible adverse events with each of the other newer antidepressants that could be of concern in these patients. Nevertheless, with careful administration and attention to the potential adverse reactions for each drug, these may provide safe effective alternatives for older adults and patients with cardiovascular disease who do not respond to selective serotonin reuptake inhibitor antidepressants. However, more research on the safety and efficacy of these drugs in these specific patient populations is urgently needed.

Long-term outcome in outpatients with depression treated with acute and maintenance intravenous ketamine: A retrospective chart review

BACKGROUND

Little is known about the long-term outcomes of repeated ketamine infusions for depression. We conducted a retrospective chart review to investigate outcomes of maintenance intravenous ketamine treatment at Massachusetts General Hospital.

METHODS

Eighty-five patients with treatment-resistant depression (TRD) who started intravenous ketamine from October 2018 to November 2019 were examined. Symptom severity was evaluated with the 16-item Quick Inventory of Depressive Symptomatology-Self Report scale (QIDS-SR₁₆) at every visit prior to administration. The initial ketamine dose was usually 0.5 mg/kg infused over 40 min. Intravenous ketamine was administered twice-weekly for three weeks in an induction phase, followed by maintenance with a variable administration schedule and dose. Response was defined as a ≥50% reduction in total QIDS-SR₁₆ score from baseline.

RESULTS

Forty (47.1%) of the 85 patients who started treatment discontinued during or right after the induction phase; 3 (3.5%) were still on induction at the time of this report, and 42 (49.4%) transitioned to maintenance after completing induction. Among these patients, 14 (16.5%) discontinued during maintenance and 28 (32.9%) continued on maintenance. The mean ketamine dosage during maintenance was 0.91±0.28 mg/kg. Fifteen out of 82 patients (18.3%) responded to induction treatment and 6 (7.3%) remained in responder status at the time of data analysis during maintenance. Three patients discontinued ketamine due to side-effects.

CONCLUSIONS

Despite the apparently low response rate in QIDS-SR₁₆ scores and considerable out-of-pocket costs, almost half of real-world outpatients with TRD decided to continue with maintenance ketamine treatment due to perceived significant improvement.

Low-dose ketamine affects blood pressure, but not muscle sympathetic nerve activity, during progressive central hypovolemia without altering tolerance

KEY POINTS

Haemorrhage is the leading cause of battlefield and civilian trauma deaths. Given that a haemorrhagic injury on the battlefield is almost always associated with pain, it is paramount that the administered pain medication does not disrupt the physiological mechanisms that are beneficial in defending against the haemorrhagic insult. Current guidelines from the US Army's Committee on Tactical Combat Casualty Care (CoTCCC) for the selection of pain medications administered to a haemorrhaging soldier are based upon limited scientific evidence, with the clear majority of supporting studies being conducted on anaesthetized animals. Specifically, the influence of low-dose ketamine, one of three analgesics employed in the pre-hospital setting by the US Army, on haemorrhagic tolerance in humans is unknown. For the first time in conscious males and females, the findings of the present study demonstrate that the administration of an analgesic dose of ketamine does not compromise tolerance to a simulated haemorrhagic insult. Increases in muscle sympathetic nerve activity during progressive lower-body negative pressure were not different between trials. Despite the lack of differences for muscle sympathetic nerve activity responses, mean blood pressure and heart rate were higher during moderate hypovolemia after ketamine vs. placebo administration.

ABSTRACT

Haemorrhage is the leading cause of battlefield and civilian trauma deaths. For a haemorrhaging soldier, there are several pain medications (e.g. ketamine) recommended for use in the prehospital, field setting. However, the data to support these recommendations are primarily limited to studies in animals. Therefore, it is unknown whether ketamine adversely affects physiological mechanisms responsible for maintenance of arterial blood pressure (BP) during haemorrhage in humans. In humans, ketamine has been demonstrated to raise resting BP, although it has not been studied with the concomitant central hypovolemia that occurs during haemorrhage. Thus, the present study aimed to test the hypothesis that ketamine does not impair haemorrhagic tolerance in humans. Thirty volunteers (15 females) participated in this double-blinded, randomized, placebo-controlled trial. A pre-syncopal limited progressive lower-body negative pressure (LBNP; a validated model for simulating haemorrhage) test was conducted following the administration of ketamine (20 mg) or placebo (saline). Tolerance was quantified as a cumulative stress index and compared between trials using a paired, two-tailed t test. We compared muscle sympathetic nerve activity (MSNA; microneurography), beat-to-beat BP (photoplethysmography) and heart rate (electrocardiogram) responses during the LBNP test using a mixed effects model (time [LBNP stage] × drug). Tolerance to the LBNP test was not different between trials (Ketamine: 635 ± 391 vs. Placebo: 652 ± 360 mmHg‧min, p = 0.77). Increases in MSNA burst frequency (time: P < 0.01, trial: p = 0.27, interaction: p = 0.39) during LBNP stages were no different between trials. Despite the lack of differences for MSNA responses, mean BP (time: P < 0.01, trial: P < 0.01, interaction: p = 0.01) and heart rate (time: P < 0.01, trial: P < 0.01, interaction: P < 0.01) were higher during moderate hypovolemia after ketamine vs. placebo administration (P < 0.05 for all, post hoc), but not at the end of LBNP. These data, which are the first to be obtained in conscious humans, demonstrate that the administration of low-dose ketamine does not impair tolerance to simulated haemorrhage or mechanisms responsible for maintenance of BP.

Effects of subcutaneous esketamine on blood pressure and heart rate in treatment-resistant depression

INTRODUCTION AND OBJECTIVES

The impact of multiple subcutaneous (s.c.) esketamine injections on the blood pressure (BP) and heart rate (HR) of patients with unipolar and bipolar treatment-resistant depression (TRD) is poorly understood. This study aimed to assess the cardiovascular safety of multiple s.c. doses of esketamine in patients with TRD.

METHODS

Seventy TRD patients received 394 weekly s.c. esketamine injections in conjunction with oral antidepressant therapy for up to six weeks. Weekly esketamine doses were 0.5, 0.75 or 1.0 mg/kg according to each patient's response to treatment. Participants were monitored before each treatment and every 15 minutes thereafter for 120 minutes. We assessed systolic blood pressure (SBP), diastolic blood pressure (DBP), and HR measurements for the entire treatment course.

RESULTS

BP increased after the first s.c. esketamine injection, reaching maximum mean SBP/DBP levels of 4.87/5.54 mmHg within 30-45 minutes. At the end of monitoring, 120 minutes post dose, vital signs returned to pretreatment levels. We did not detect significant differences in BP between doses of 0.5, 0.75, and 1 mg/kg esketamine. Mean HR did not differ significantly between doses or before and after s.c. esketamine injection.

CONCLUSIONS

The BP changes observed with repeated s.c. esketamine injections were mild and well tolerated for doses up to 1 mg/kg. The s.c. route is a simple and safe method of esketamine administration, even for patients with clinical comorbidities, including obesity, hypertension, diabetes, and dyslipidemia. However, 14/70 patients experienced treatment-emergent transient hypertension (SBP >180 mmHg and/or a DBP >110 mmHg). Therefore, we strongly recommend monitoring BP for 90 minutes after esketamine dosing. Since s.c. esketamine is cheap, requires less frequent dosing (once a week), and is a simpler procedure compared to intravenous infusions, it might have an impact on public health.

Lee K. Safety of Repeated Administration of Parenteral Ketamine for Depression

The objective of this study was to investigate the safety of repeated parenteral ketamine for depression. An electronic survey inquiring about the frequency of adverse events was distributed to providers of parenteral ketamine for depression. In addition, the investigators conducted a search of published studies describing six or more repeated parenteral ketamine treatments administered to individuals for depression, and extracted reported adverse events. The survey was sent to 69 providers, of which 36 responded (52% response rate); after eliminating those that were incomplete, 27 were included in the analysis. The providers in the analysis collectively reported treating 6630 patients with parenteral ketamine for depression, one-third of whom received more than 10 treatments. Only 0.7% of patients experienced an adverse effect that required discontinuation of ketamine. Psychological distress during the treatment was the most frequent cause. Other adverse events were extremely rare (such as bladder dysfunction (0.1%), cognitive decline (0.03%) and psychotic symptoms (0.03%)). Among the 20 published reports of repeated parenteral ketamine treatments, rates of significant adverse events resulting in discontinuation were low (1.2%). The rate of adverse effects reported in the survey and the published literature is low, and suggests that long-term treatment of depression with ketamine is reasonably safe.

Pilot randomized active-placebo-controlled trial of low-dose ketamine for the treatment of multiple sclerosis-related fatigue

BACKGROUND

Fatigue is the most common symptom of MS and has no effective pharmacotherapy.

OBJECTIVE

To determine the tolerability, safety, and efficacy of low-dose ketamine infusion for MS-related fatigue.

METHODS

In this double-blind, randomized, active-placebo-controlled trial, 18 subjects with multiple sclerosis (MS) and reported fatigue received a single intravenous infusion of ketamine (0.5 mg/kg) or midazolam (0.05 mg/kg). The primary outcome was change in Daily Fatigue Severity (DFS) for 7 days following the infusion. Secondary outcomes included Fatigue Severity Scale (FSS) and Modified Fatigue Impact Scale (MFIS) measured up to day 28 post-infusion. We analyzed changes in all outcomes using mixed-effect models.

RESULTS

In total, 18 participants were enrolled; 67% participants received ketamine. Side effects of ketamine were transient. No change in the DFS was observed after 7 days (-0.10 point; 95% confidence interval (CI): -0.32, 0.12; p = 0.40). We observed a trend in reduced FSS scores at 1 week (-5.2 points; 95% CI: -10.4, 0.14; p = 0.06) and a clinically and statistically significant reduction in MFIS score at day 28 (-13.5 point; 95% CI: -25.0, -1.98; p = 0.04).

CONCLUSIONS

Ketamine infusions were safe and well-tolerated. While no change in DFS after 7 days was observed, secondary analyses suggest a benefit of ketamine infusion for reduction of longer term fatigue severity in people with MS.

Current Understanding of the Neurobiology of Agitation

Introduction

Managing agitation in the clinical setting is a challenge that many practitioners face regularly. Our evolving understanding of the etiological factors involved in aggressive acts has better informed our interventions through pharmacologic and behavioral strategies. This paper reviews the literature on the neurobiological underpinnings of aggressive behaviors, linking psychopathology with proposed mechanisms of action of psychiatric medications shown to be effective in mitigating agitation.

Methods

We performed a review of the extant literature using PubMed as a primary database. Investigation focused on neurobiology of agitation and its relation to the current evidence base for particular interventions.

Results

There are well-established pathways that can lead to increased autonomic response and the potential for violence. Psychopathology and substance-induced perceptual distortions may lead to magnification and overestimation of environmental threat, heightening the potential for aggression. Additional challenges have arisen with the advent of several novel drugs of abuse, many of which lead to atypical clinical presentations and which can elude standard drug screens. Our interventions still lean on the evidence base found in Project BETA (Best Practices in Evaluation and Treatment of Agitation). Although not a new drug and not included in the Project BETA guidelines, ketamine and its use are also discussed, given its unique pharmacology and potential benefits when other protocoled interventions have failed.

Conclusion

Aggression can occur due to manifold reasons in the clinical setting. Having an informed understanding of the possible determinants of agitation can help with more tailored responses to individual patients, limiting the unnecessary use of medications or of interventions that could be deemed forceful.

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.

Cardiac Safety of Esketamine Nasal Spray in Treatment-Resistant Depression: Results from the Clinical Development Program

BACKGROUND

An intranasal formulation of esketamine, combined with an oral antidepressant, is approved in the USA and the European Union for adults with treatment-resistant depression (TRD). Transient cardiovascular stimulatory effects have been reported with ketamine.

METHODS

Cardiovascular effects of esketamine nasal spray, combined with an oral antidepressant, were evaluated in 1708 esketamine-treated adults with TRD in six trials (five double-blind, placebo-controlled (486 placebo-treated patients); one open-label) of 4-52 weeks' duration. Patients with established cardiovascular disease, including uncontrolled hypertension (> 140/> 90 mmHg), history of hypertensive crisis, or clinically significant electrocardiogram (ECG) abnormalities, were excluded from enrollment. Effects on cardiac repolarization were assessed in a phase I randomized, positive- and active-controlled thorough corrected QT (QTc) interval study. For adverse events, odds ratio (OR) [95% confidence interval] for esketamine/antidepressant versus antidepressant/placebo was calculated.

RESULTS

Adverse events related to increased BP were reported in 12.8% of all esketamine-treated patients (in double-blind trials: esketamine/antidepressant 11.6% vs. antidepressant/placebo 3.9%; OR 3.2 [1.9-5.8]). Among the patients without a history of hypertension, new antihypertensive medication was initiated by 2.1% (6/280) of patients in the esketamine/antidepressant group versus 1.2% (2/171) of patients in the antidepressant/placebo group, in the double-blinded studies. Adverse events related to abnormal heart rate were reported in 3.0% of all esketamine-treated patients (in double-blind trials: 1.6% vs. 0.8%; OR 1.9 [0.5-8.6]). Overall, three cardiovascular adverse events related to BP increase were reported as serious and severe, and there was one fatal event considered unrelated (acute cardiac failure). BP increases reached the maximum postdose value within ~ 40 min of esketamine dosing and returned to the predose range by ~ 1.5 h postdose. In two studies (4-week duration, age 18-64 years), the largest mean maximum systolic/diastolic postdose BP increases were 13.3/8.7 mmHg for esketamine/antidepressant and 6.1/4.9 mmHg for antidepressant/placebo, and in a short-term elderly study (age ≥ 65 years) were 16.0/9.5 and 11.1/6.8 mmHg, respectively. Across studies/study phases, < 2% of patients discontinued esketamine due to adverse events of increased BP and tachycardia. No clinically relevant effect on ECG parameters was observed. Therapeutic and supratherapeutic doses of esketamine did not prolong the QTcF (QT corrected by Fridericia's equation) interval (baseline-corrected values of - 2.02 to 2.16 ms, and - 3.51 to 4.89 ms, respectively).

CONCLUSIONS

BP elevations following esketamine dosing are generally transient, asymptomatic, and not associated with serious cardiovascular safety sequalae. Further evaluation of long-term cardiovascular outcomes is warranted.

Metabolic Risk Factors and Cardiovascular Safety in Ketamine Use for Treatment Resistant Depression

INTRODUCTION

Ketamine exhibits antidepressant properties in treatment-resistant depression (TRD) with some concern over its cardiovascular safety and tolerability issues. This paper reports on the cardiovascular safety in short-term intravenous ketamine treatment in TRD inpatients with major depressive disorder (MDD) and bipolar disorder (BP).

MATERIALS AND METHODS

The observational study population comprises 35 MDD and 14 BP subjects treated with intravenous ketamine.

RESULTS

Blood pressure (RR) and heart rate (HR) values returned to baseline within 1.5-hours post infusion with no sequelae for all study subjects. Six time points were analyzed for each infusion: 0', 15', 30', 45', 60' and 90' for RR and HR. After the infusion significant peaks in systolic (p = 0.004) and diastolic (p = 0.038) RR were seen. In concomitant medication with selective serotonin reuptake inhibitors (SSRIs), higher RR peaks (p = 0.020; p = 0.048) were seen as compared to other subjects. The decrease in HR was greater (p = 0.02) in the absence of concomitant medication with mood stabilizers as compared to subjects receiving mood stabilizing medication accompanied by the observation of a greater decrease in diastolic RR among those taking mood stabilizers (p = 0.009).

LIMITATIONS

The study may be underpowered due to the small sample size. The observations apply to an inhomogeneous TRD population in a single-site, pilot study, with no blinding and are limited to the acute administration.

CONCLUSION

The study demonstrates good safety and tolerability profile of intravenous ketamine as add-on intervention to current psychotropic medication in TRD, regardless of the MDD or BP type of mood disorders. The abatement of elevated RR and BP scores was observed in time with no sequelae nor harm. Still, cardiovascular risks appear to be more pronounced in subjects with comorbid arterial hypertension and diabetes mellitus.

Cortical 5-hydroxytryptamine 1A receptor biased agonist, NLX-101, displays rapid-acting antidepressant-like properties in the rat chronic mild stress model

BACKGROUND

NLX-101 (also known as F15599) is a highly selective and efficacious 'biased' agonist at cortical 5-hydroxytryptamine 1A (5-HT_1A) heteroreceptors. In rodents, it possesses marked antidepressant-like activity, potently and completely abolishing immobility in the forced swim test (FST) with extended duration of action.

METHODS

We investigated the antidepressant-like activity of NLX-101 using the rat chronic mild stress (CMS) model of depression, considered to have a higher translational potential than the FST, as it possesses construct, face and predictive validity. The effects of CMS and repeated NLX-101 treatment were tested using sucrose consumption (a measure of anhedonia), novel object recognition (NOR; a measure of working memory) and elevated plus maze (EPM; a measure of anxiety) tests.

RESULTS

NLX-101 reversed the CMS-induced decrease of sucrose intake on day 1 of testing, with full reversal observed at the dose of 0.16 mg/kg and a less pronounced but still significant effect at 0.04 mg/kg, both given twice a day intraperitoneally. The effects of NLX-101 were maintained over the 2 week treatment period and persisted for four weeks following cessation of treatment. In the NOR test, both doses of NLX-101 rescued the deficit in discrimination index caused by CMS, without any effect on locomotor activity. However, NLX-101 had no effect on the reduction of open-arms entries produced by CMS in the EPM model. In control, non-stressed rats, NLX-101 produced non-significant effects in all three models.

CONCLUSIONS

NLX-101 displayed efficacious activity in the CMS test, with more rapid (1 day) antidepressant-like effects than pharmacological compounds tested previously under the same experimental conditions. These observations suggest that biased agonist targeting of cortical 5-HT_1A receptors constitutes a promising strategy to achieve rapid-acting and sustained antidepressant effects.

Novel Aryloxyethyl Derivatives of 1-(1-Benzoylpiperidin-4-yl)methanamine as the Extracellular Regulated Kinases 1/2 (ERK1/2) Phosphorylation-Preferring Serotonin 5-HT1A Receptor-Biased Agonists with Robust Antidepressant-like Activity

Novel 1-(1-benzoylpiperidin-4-yl)methanamine derivatives were designed as "biased agonists" of serotonin 5-HT_1A receptors. The compounds were tested in signal transduction assays (ERK1/2 phosphorylation, cAMP inhibition, Ca²⁺ mobilization, and β-arrestin recruitment) which identified ERK1/2 phosphorylation-preferring aryloxyethyl derivatives. The novel series showed high 5-HT_1A receptor affinity, >1000-fold selectivity versus noradrenergic α₁, dopamine D₂, serotonin 5-HT_2A, histamine H₁, and muscarinic M₁ receptors, and favorable druglike properties (CNS-MPO, Fsp³, LELP). The lead structure, (3-chloro-4-fluorophenyl)(4-fluoro-4-(((2-(pyridin-2-yloxy)ethyl)amino)methyl)piperidin-1-yl)methanone (17, NLX-204), displayed high selectivity in the SafetyScreen44 panel (including hERG channel), high solubility, metabolic stability, and Caco-2 penetration and did not block CYP3A4, CYP2D6 isoenzymes, or P-glycoprotein. Preliminary in vivo studies confirmed its promising pharmacokinetic profile. 17 also robustly stimulated ERK1/2 phosphorylation in rat cortex and showed highly potent (MED = 0.16 mg/kg) and efficacious antidepressant-like activity, totally eliminating immobility in the rat Porsolt test. These data suggest that the present 5-HT_1A receptor-biased agonists could constitute promising antidepressant drug candidates.

Neurochemical models of near-death experiences: A large-scale study based on the semantic similarity of written reports

The real or perceived proximity to death often results in a non-ordinary state of consciousness characterized by phenomenological features such as the perception of leaving the body boundaries, feelings of peace, bliss and timelessness, life review, the sensation of traveling through a tunnel and an irreversible threshold. Near-death experiences (NDEs) are comparable among individuals of different cultures, suggesting an underlying neurobiological mechanism. Anecdotal accounts of the similarity between NDEs and certain drug-induced altered states of consciousness prompted us to perform a large-scale comparative analysis of these experiences. After assessing the semantic similarity between ≈15,000 reports linked to the use of 165 psychoactive substances and 625 NDE narratives, we determined that the N-methyl-D-aspartate (NMDA) receptor antagonist ketamine consistently resulted in reports most similar to those associated with NDEs. Ketamine was followed by Salvia divinorum (a plant containing a potent and selective κ receptor agonist) and a series of serotonergic psychedelics, including the endogenous serotonin 2A receptor agonist N,N-Dimethyltryptamine (DMT). This similarity was driven by semantic concepts related to consciousness of the self and the environment, but also by those associated with the therapeutic, ceremonial and religious aspects of drug use. Our analysis sheds light on the long-standing link between certain drugs and the experience of "dying", suggests that ketamine could be used as a safe and reversible experimental model for NDE phenomenology, and supports the speculation that endogenous NMDA antagonists with neuroprotective properties may be released in the proximity of death.

Ketamine: A Review for Clinicians

A growing series of clinical trials and case series now suggest that ketamine-originally used as an anesthetic agent-potentially offers an exciting new treatment option for severe depression. Increasing numbers of studies show that ketamine can provide prompt relief for many depressed patients, including those with severe treatment-refractory depression. Although the effects of a single treatment are commonly short-lived, multiple infusion protocols may offer sustained relief. The uniquely rapid onset of antidepressant action raises the potential for ketamine use in a variety of clinical situations, including the prevention or shortening of hospital stays, the treatment of acute suicidal ideation, and the facilitation of medication crossovers. Ketamine, in combination with other multimodal treatment approaches, including psychotherapy, may further augment response effect and duration. Promises of efficacy have led to increasingly unbridled use to treat a variety of psychiatric disorders, with diverse approaches and treatment environments, despite inadequate data demonstrating the true clinical efficacy and safety of the various protocols or a thorough understanding of mechanisms of action. This article briefly reviews the history of ketamine's development as a potential antidepressant, current hypotheses related to its mechanisms of action, and existing evidence for its safety and efficacy with a focus on clinicians' interests.

Ketamine and Ketamine Metabolite Pharmacology: Insights into Therapeutic Mechanisms

Ketamine, a racemic mixture consisting of (S)- and (R)-ketamine, has been in clinical use since 1970. Although best characterized for its dissociative anesthetic properties, ketamine also exerts analgesic, anti-inflammatory, and antidepressant actions. We provide a comprehensive review of these therapeutic uses, emphasizing drug dose, route of administration, and the time course of these effects. Dissociative, psychotomimetic, cognitive, and peripheral side effects associated with short-term or prolonged exposure, as well as recreational ketamine use, are also discussed. We further describe ketamine's pharmacokinetics, including its rapid and extensive metabolism to norketamine, dehydronorketamine, hydroxyketamine, and hydroxynorketamine (HNK) metabolites. Whereas the anesthetic and analgesic properties of ketamine are generally attributed to direct ketamine-induced inhibition of N-methyl-D-aspartate receptors, other putative lower-affinity pharmacological targets of ketamine include, but are not limited to, γ-amynobutyric acid (GABA), dopamine, serotonin, sigma, opioid, and cholinergic receptors, as well as voltage-gated sodium and hyperpolarization-activated cyclic nucleotide-gated channels. We examine the evidence supporting the relevance of these targets of ketamine and its metabolites to the clinical effects of the drug. Ketamine metabolites may have broader clinical relevance than was previously considered, given that HNK metabolites have antidepressant efficacy in preclinical studies. Overall, pharmacological target deconvolution of ketamine and its metabolites will provide insight critical to the development of new pharmacotherapies that possess the desirable clinical effects of ketamine, but limit undesirable side effects.