A review of the nonmedical use of ketamine: use, users and consequences

Ketamine induced synaptic plasticity operates independently of long-term potentiation

Synaptic plasticity occurs via multiple mechanisms to regulate synaptic efficacy. Homeostatic and Hebbian plasticity are two such mechanisms by which neuronal synapses can be altered. Although these two processes are mechanistically distinct, they converge on downstream regulation of AMPA receptor activity to modify glutamatergic neurotransmission. However, much remains to be explored regarding how these two prominent forms of plasticity interact. Ketamine, a rapidly acting antidepressant, increases glutamatergic transmission via pharmacologically-induced homeostatic plasticity. Here, we demonstrate that Hebbian plasticity mechanisms are still intact in synapses that have undergone homeostatic scaling by ketamine after either systemic injection or perfusion onto hippocampal brain slices. We also investigated this relationship in the context of stress induced by chronic exposure to corticosterone (CORT) to better model the circumstances under which ketamine may be used as an antidepressant. We found that CORT induced an anhedonia-like behavioral phenotype in mice but did not impair long-term potentiation (LTP) induction. Furthermore, corticosterone exposure does not impact the intersection of homeostatic and Hebbian plasticity mechanisms, as synapses from CORT-exposed mice also demonstrated intact ketamine-induced plasticity and LTP in succession. These results provide a mechanistic explanation for how ketamine used for the treatment of depression does not impair the integrity of learning and memory processes encoded by mechanisms such as LTP.

Ketamine for depressive symptoms: A retrospective chart review of a private ketamine clinic

Background

There is currently no published evidence demonstrating the effectiveness and safety of subanaesthetic doses of ketamine, when administered intravenously as an adjunct treatment for depressive symptoms, in a real world setting in South Africa.

Aim

This retrospective chart review reports the clinical response (change in Patient Health Questionnaire - 7 score) to an initial infusion series of ketamine added to usual treatment, and the pattern of its subsequent maintenance use, for depressive symptoms.

Setting

A private ketamine clinic in Hilton, KwaZulu-Natal.

Methods

The medical records of all patients who attended a private ketamine clinic between August 2019 and 31 May 2021 were retrospectively analysed. Depression symptoms were evaluated using the Patient Health Questionaire-9 (PHQ-9) administered immediately before and 24 h after each treatment. Response was defined as a score decrease of more than 50%.

Results

Among the 154 patients who received ketamine infusions for depression, 67 completed a six infusion initial series, with a response rate of 60.6% and remission rate of 32.4%. Of the 154, 50% no longer experienced any suicidal ideation after treatment and adverse events were uncommon, with 6.2% of infusions requiring intervention for adverse events, mostly nausea. In addition, 48.5% of those who completed the initial series continued to receive maintenance infusions, with no evidence of escalating use or abuse.

Conclusion

Incorporating intravenous ketamine into the existing treatment regimens at a private clinic was associated with reduced acuteness of depression severity and suicidal ideation. This approach appeared safe and tolerable, showing no signs of abuse or dependence.

Contribution

This is the first known naturalistic study reporting on ketamine use for depressive symptoms in South Africa.

Cellular consequences triggered by ketamine on exposure to human glioblastoma epithelial (LN-229) cells

Ketamine is generally a noncompetitive N-methyl-D-aspartate (NMDA) receptor antagonist that interrelates with various other receptors, contributing to a wide range of actions. They are mainly approved as a general anesthetic, but a low dose of ketamine is applied for pain management, depression, and as analgesics. However, there is a significant concern regarding the long-term usage as antidepressants and as an abused drug. The study mainly aims to exhibit the possible long-term side effects of ketamine as an antidepressant and in recreational users. The study explores the in vitro cytotoxicity revealed on LN-229 cells in a dose-dependent manner. According to the cell viability assays, there is a dose-dependent response toward ketamine. Morphological and nuclear integrity was changed on exposure and assessed using Giemsa, Rhodamine phalloidin, 4',6-diamidino-2-phenylindole (DAPI), and Acridine orange staining. The apoptotic cell death marked by nuclear condensation, Lactate dehydrogenase leakage, pro-inflammatory cytokine (interleukin [IL]-β) release, and inhibition of cell migration was observed. The study highlights the importance of nonanesthetic usage of ketamine, which can lead to severe adverse side effects on long-term exposure rather than a single exposure as an anesthetic agent.

The analgesic efficacy of ketamine for septorhinoplasty: a meta-analysis study

BACKGROUND

The analgesic efficacy of ketamine supplementation was not well-established for septorhinoplasty and this meta-analysis aimed to compare ketamine supplementation with placebo for the postoperative pain control of septorhinoplasty.

METHODS

We systematically searched several databases, including PubMed, EMbase, Web of science, EBSCO and Cochrane library databases, and included randomized controlled trials (RCTs) regarding the effect of ketamine supplementation versus placebo for pain control after septorhinoplasty. This meta-analysis was conducted by random effect model.

RESULTS

Five RCTs were included in this meta-analysis. In comparison with control group for septorhinoplasty, ketamine supplementation was associated with significantly decreased pain scores at 30 min (SMD = - 3.84; 95% CI = - 6.73 to - 0.96; P = 0.009), pain scores at 1 h (SMD = - 2.70; 95% CI = - 3.79 to - 1.61; P < 0.00001), pain scores at 2 h (SMD = - 1.83; 95% CI = - 3.01 to - 0.64; P = 0.003), rescue analgesics (OR = 0.08; 95% CI = 0.04 to 0.17; P < 0.00001), but unraveled no obvious impact on pain scores at 4 h (SMD = - 1.13; 95% CI = - 3.37 to 1.12; P = 0.32) or the incidence of nausea and vomiting (OR = 0.71; 95% CI = 0.30 to 1.72; P = 0.45).

CONCLUSIONS

Ketamine supplementation was effective to improve pain relief after septorhinoplasty.

Secondary Sclerosing Cholangitis After SARS-CoV2: ICU Ketamine Use or Virus-Specific Biliary Tropism and Injury in the Context of Biliary Ischemia in Critically Ill Patients?

Purpose

From the beginning of the Severe Acute Respiratory Syndrome CoronaVirus-2 (SARS-CoV2) pandemic, different cases of a cholangiopathy with features of secondary sclerosing cholangitis in critically ill patients (SSC-CIP) have been reported. Patients developing it are generally recovering from severe Coronavirus disease 19 (COVID-19) and required intensive care unit (ICU) admission and mechanical ventilation. Many of them have been administered with ketamine during their ICU stay. The pathogenesis of this novel disease is still debated, and, since prognosis is poor, efforts are needed in order to better understand it.

Patients and Methods

In this review, we focused our attention on COVID-19 SSC clinical, imaging, and histology findings in order to clarify the different pathogenetic options, particularly in regard of the ischemic-direct viral damage and ketamine-related theories, beginning with a recapitulation of SSC-CIP and ketamine-induced cholangiopathy in abusers. The research has been conducted using PubMed and Google Scholar databases. Key-words were "Secondary Sclerosing Cholangiopathy", "SSC-CIP", "Secondary Sclerosing Cholangiopathy in critically ill patients", "Ketamine and cholangiopathy", "Ketamine abusers and liver disease", "Ketamine-related cholangiopathy", "SARS-CoV2 infection and liver disease", "post Covid-19 secondary sclerosing cholangitis", "Covid-19 cholangiopathy".

Results

Many authors, based on the clinical, histological, imaging, and prognostic features of the disease, have pointed out the similarities between post COVID-19 SSC and SSC-CIP; however, peculiar features in the former were not previously observed. Therefore, a direct viral cytopathic action and SARS-CoV2-related coagulopathy are considered the most likely causes. On the other hand, ketamine, with the available data, cannot be surely linked as the main determinant cause of cholangiopathy. Moreover, ketamine-induced cholangitis (KIC) presentation is different from post COVID-19 SSC. Its role as a cofactor precipitating the disease cannot be ruled out.

Conclusion

Post COVID-19 SSC is a rare clinical entity following severe COVID-19 disease. The most accepted theory is that a sum of different insults determines the disease: biliary ischemia, direct viral damage, toxic bile, possibly worsened by ketamine and hyperinflammation due to the cytokine storm. Given the severe prognosis of the disease, with persistent cholangiopathy, organ failure, and orthotopic liver transplantation (OLT), further study on this novel clinical entity is needed.

The clinical toxicology of ketamine

INTRODUCTION

Ketamine is a pharmaceutical drug possessing both analgesic and anaesthetic properties. As an anaesthetic, it induces anaesthesia by producing analgesia with a state of altered consciousness while maintaining airway tone, respiratory drive, and hemodynamic stability. At lower doses, it has psychoactive properties and has gained popularity as a recreational drug.

OBJECTIVES

To review the epidemiology, mechanisms of toxicity, pharmacokinetics, clinical features, diagnosis and management of ketamine toxicity.

METHODS

Both OVID MEDLINE (January 1950-April 2023) and Web of Science (1900-April 2023) databases were searched using the term "ketamine" in combination with the keywords "pharmacokinetics", "kinetics", "poisoning", "poison", "toxicity", "ingestion", "adverse effects", "overdose", and "intoxication". Furthermore, bibliographies of identified articles were screened for additional relevant studies. These searches produced 5,268 non-duplicate citations; 185 articles (case reports, case series, pharmacokinetic studies, animal studies pertinent to pharmacology, and reviews) were considered relevant. Those excluded were other animal investigations, therapeutic human clinical investigations, commentaries, editorials, cases with no clinical relevance and post-mortem investigations.

EPIDEMIOLOGY

Following its introduction into medical practice in the early 1970s, ketamine has become a popular recreational drug. Its use has become associated with the dance culture, electronic and dubstep dance events.

MECHANISM OF ACTION

Ketamine acts primarily as a non-competitive antagonist on the glutamate N-methyl-D-aspartate receptor, causing the loss of responsiveness that is associated with clinical ketamine dissociative anaesthesia.

PHARMACOKINETICS

Absorption of ketamine is rapid though the rate of uptake and bioavailability is determined by the route of exposure. Ketamine is metabolized extensively in the liver. Initially, both isomers are metabolized to their major active metabolite, norketamine, by CYP2B6, CYP3A4 and CYP2C9 isoforms. The hydroxylation of the cyclohexan-1-one ring of norketamine to the three positional isomers of hydroxynorketamine occurs by CYP2B6 and CYP2A6. The dehydronorketamine metabolite occurs either by direct dehydrogenation from norketamine via CYP2B6 metabolism or non-enzymatic dehydration of hydroxynorketamine. Norketamine, the dehydronorketamine isomers, and hydroxynorketamine have pharmacological activity. The elimination of ketamine is primarily by the kidneys, though unchanged ketamine accounts for only a small percentage in the urine. The half-life of ketamine in humans is between 1.5 and 5 h.

CLINICAL FEATURES

Acute adverse effects following recreational use are diverse and can include impaired consciousness, dizziness, irrational behaviour, hallucinations, abdominal pain and vomiting. Chronic use can result in impaired verbal information processing, cystitis and cholangiopathy.

DIAGNOSIS

The diagnosis of acute ketamine intoxication is typically made on the basis of the patient's history, clinical features, such as vomiting, sialorrhea, or laryngospasm, along with neuropsychiatric features. Chronic effects of ketamine toxicity can result in cholangiopathy and cystitis, which can be confirmed by endoscopic retrograde cholangiopancreatography and cystoscopy, respectively.

MANAGEMENT

Treatment of acute clinical toxicity is predominantly supportive with empiric management of specific adverse effects. Benzodiazepines are recommended as initial treatment to reduce agitation, excess neuromuscular activity and blood pressure. Management of cystitis is multidisciplinary and multi-tiered, following a stepwise approach of pharmacotherapy and surgery. Management of cholangiopathy may require pain management and, where necessary, biliary stenting to alleviate obstructions. Chronic effects of ketamine toxicity are typically reversible, with management focusing on abstinence.

CONCLUSIONS

Ketamine is a dissociative drug employed predominantly in emergency medicine; it has also become popular as a recreational drug. Its recreational use can result in acute neuropsychiatric effects, whereas chronic use can result in cystitis and cholangiopathy.

Ketamine Induces Delirium-Like Behavior and Interferes With Endosomal Tau Trafficking

BACKGROUND

Ketamine is an intravenous anesthetic. However, whether ketamine can induce neurotoxicity and neurobehavioral deficits remains largely unknown. Delirium is a syndrome of acute brain dysfunction associated with anesthesia and surgery in patients, and tau protein may contribute to postoperative delirium. Finally, ketamine may affect the function of the endosome, the key organelle for tau release from neurons. Therefore, we set out to determine the effects of ketamine on delirium-like behavior in mice and on tau trafficking in cultured cells.

METHODS

We used the buried-food test, open-field test, and Y-maze test in adult mice to assess the presence of delirium-like behavior in mice. We quantified tau amounts in the serum of mice. We used cell fraction methods to determine the effects of ketamine on tau intracellular trafficking, extracellular release, and endosome trafficking in cultured cells.

RESULTS

Ketamine induced delirium-like behavior in mice and increased tau amounts in serum of mice. The ketamine treatments also led to increased accumulation of endosomes, as evidenced by increased endosomal markers Rab5 and Rab7. Moreover, ketamine inhibited endosome maturation, demonstrated by decreased membrane-bound but increased cytoplasm amounts of Rab5 and Rab7. Consequently, ketamine increased tau in the endosomes of cultured cells and the cell culture medium.

CONCLUSIONS

These data suggest that ketamine may interfere with intracellular tau trafficking and induce delirium-like behavior, promoting future research regarding the potential neurotoxicity of anesthetics.

Role of the mesolimbic dopamine pathway in the antidepressant effects of ketamine

Depression is a complex and highly heterogeneous disorder which diagnosis is based on an exceedingly variable set of clinical symptoms. Current treatments focus almost exclusively on the manipulation of monoamine neurotransmitter systems, but despite considerable efforts, these remain inadequate for a significant proportion of those afflicted by the disorder. The emergence of racemic (R, S)-ketamine as a fast-acting antidepressant has provided an exciting new path for the study of major depressive disorder (MDD) and the search for better therapeutics for its treatment. Previous work suggested that ketamine's mechanism of action is primarily mediated via blockaded of N-methyl-d-aspartate (NMDA) receptors, however, this is an area of active research and clinical and preclinical evidence now indicate that ketamine acts on multiple systems. The last couple of decades have cemented the mesolimbic dopamine reward pathway's involvement in the pathogenesis of MDD and related mood disorders. Exposure to negative stress dysregulates dopamine neuronal activity disrupting reward and motivational processes resulting in anhedonia (lack of pleasure), a hallmark symptom of depression. Although the mechanism(s) underlying ketamine's antidepressant activity continue to be elucidated, current evidence indicate that its therapeutic effects are mediated, at least in part, via long-lasting synaptic changes and subsequent molecular adaptations in brain regions within the mesolimbic dopamine system. Notwithstanding, ketamine is a drug of abuse, and this liability may pose limitations for long term use as an antidepressant. This review outlines the current knowledge of ketamine's actions within the mesolimbic dopamine system and its abuse potential. This article is part of the Special Issue on 'Ketamine and its Metabolites'.

Detection and discrimination of sedative-hypnotics in spiked beverage dry residues using attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy combined with chemometrics

Drugs-facilitated crimes (DFCs) involve the incapacitation of victims under the influence of drugs. Conventionally, a drug administration act is often determined through the examination of biological samples; however, dry residues from any surface, such as drinking glass if related to a DFC could be a potential source of evidence. This study was aimed to establish an attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy coupled with chemometrics for the determination of spiked sedative-hypnotics from dry residues of a drug-spiked beverage. In this study, four sedative-hypnotics, namely diazepam, ketamine, nimetazepam, and xylazine were examined using ATR-FTIR spectroscopy. Subsequently, the ATR-FTIR profiles were compared and decomposed by principal component analysis (PCA) followed by linear discriminant analysis (LDA) for their detection and discrimination. Visual comparison of ATR-FTIR profiles revealed distinct spectra among the tested drugs. An initial unsupervised exploratory PCA model indicated the separation of four main sedative-hypnotics clusters, and the proposed PCA score-LDA model had allowed for a 100% accurate classification. Discrimination of sedative-hypnotics from a dry beverage previously spiked with these drugs was also possible upon an additional extraction procedure. In conclusion, ATR-FTIR coupled with PCA score-LDA model was useful in detecting and discriminating sedative-hypnotics, including those that had been previously spiked into a beverage.

Mu Opioid Receptor Activation Mediates (S)-ketamine Reinforcement in Rats: Implications for Abuse Liability

BACKGROUND

(S)-ketamine is an NMDA receptor antagonist, but it also binds to and activates mu opioid receptors (MORs) and kappa opioid receptors in vitro. However, the extent to which these receptors contribute to (S)-ketamine's in vivo pharmacology is unknown.

METHODS

We investigated the extent to which (S)-ketamine interacts with opioid receptors in rats by combining in vitro and in vivo pharmacological approaches, in vivo molecular and functional imaging, and behavioral procedures relevant to human abuse liability.

RESULTS

We found that the preferential opioid receptor antagonist naltrexone decreased (S)-ketamine self-administration and (S)-ketamine-induced activation of the nucleus accumbens, a key brain reward region. A single reinforcing dose of (S)-ketamine occupied brain MORs in vivo, and repeated doses decreased MOR density and activity and decreased heroin reinforcement without producing changes in NMDA receptor or kappa opioid receptor density.

CONCLUSIONS

These results suggest that (S)-ketamine's abuse liability in humans is mediated in part by brain MORs.

Molecular mechanisms underlying the N-methyl-d-aspartate receptor antagonists: Highlighting their potential for transdiagnostic therapeutics

The so-called "psychedelic renaissance" has stimulated expanded interest in several classes of drugs that appear to possess transdiagnostic effects in the treatment of mental health disorders, specifically. N-methyl-d-aspartate receptor (NMDAR) antagonists are one such class with diverse therapeutic potential. NMDARs mediate excitatory postsynaptic signalling in the central nervous system (CNS) and are integral to normal neurobiological processes including neuronal development, synaptic transmission, and plasticity, and thus involved in learning and memory. However, NMDAR hyper-function is also implicated in acute CNS trauma, neuropsychiatric and neurodegenerative disorders, as well as chronic pain. The complex structure of NMDARs permits several locations for therapeutic inhibition, making these receptors a potential target for multiple drugs which modulate them in different ways. NMDAR antagonists, which may be competitive, non-competitive, or uncompetitive, either block glutamate from binding the receptor or modulate the response to glutamate binding. Despite longstanding concerns about side effects of NMDAR antagonists, recent research suggests that, when appropriately used, these agents have favourable safety profiles. Furthermore, their fast-acting mechanism of action, resulting in rapid effects compared to other therapeutic agents, makes them a promising class of drugs that may yield effective therapeutics for multiple CNS disorders.

Arylcyclohexylamine Derivatives: Pharmacokinetic, Pharmacodynamic, Clinical and Forensic Aspects

Since the 2000s, an increasing number of new psychoactive substances (NPS) have appeared on the drug market. Arylcyclohexylamine (ACH) compounds such as ketamine, phencyclidine and eticyclidine derivatives are of particular concern, given their rapidly increasing use and the absence of detailed toxicity data. First used mainly for their pharmacological properties in anesthesia, their recreational use is increasing. ACH derivatives have an antagonistic activity against the N-methyl-D-aspartate receptor, which leads to dissociative effects (dissociation of body and mind). Synthetic ketamine derivatives produced in Asia are now arriving in Europe, where most are not listed as narcotics and are, thus, legal. These structural derivatives have pharmacokinetic and pharmacodynamic properties that are sometimes very different from ketamine. Here, we describe the pharmacology, epidemiology, chemistry and metabolism of ACH derivatives, and we review the case reports on intoxication.

Neurobiological, behavioral, and cognitive effects of ketamine in adolescents: A review of human and pre-clinical research

S-ketamine is approved for treatment-resistant patients with depression and adult patients with suicide behavior. While ketamine is therapeutically beneficial in adults, there is a dearth of research on the effects of ketamine on adolescent brain function and behavior. In this review we summarize the current literature on the neurobiological and behavioral effects of adolescent ketamine exposure in preclinical animal models and humans. A search of PubMed was conducted using pre-defined criteria, resulting in the evaluation of 406 articles. A total of 39 animal studies and 7 human studies met the selection criteria. The included studies examined the effects of ketamine exposure during adolescence and excluded studies on ketamine use for pain or anesthesia and ketamine as a model of schizophrenia. Pre-clinical animal models of adolescent ketamine exposure show ketamine-induced neurotoxicity and apoptosis, and changes in locomotor activity, social behaviors, anxiety- and depression-like behaviors, and memory. There is variability in the results, and differences in ketamine dose and length of exposure appears to influence the results. Ketamine reduces symptoms of depression and anxiety and improves mood in human adolescents. Much of the literature on adolescent ketamine exposure examines the effects in males, with more limited research in females. Relatively little research has focused on adolescent ketamine exposure. Despite its effectiveness for mitigating symptoms of depression, adolescent ketamine exposure can disrupt memory and other behaviors and have deleterious effects on brain function. Further research is warranted to better define doses and dosing paradigms that are beneficial without unintended side effects in adolescence.

Ketamine plus Alcohol: What We Know and What We Can Expect about This

Drug abuse has become a public health concern. The misuse of ketamine, a psychedelic substance, has increased worldwide. In addition, the co-abuse with alcohol is frequently identified among misusers. Considering that ketamine and alcohol share several pharmacological targets, we hypothesize that the consumption of both psychoactive substances may synergically intensify the toxicological consequences, both under the effect of drugs available in body systems and during withdrawal. The aim of this review is to examine the toxicological mechanisms related to ketamine plus ethanol co-abuse, as well the consequences on cardiorespiratory, digestive, urinary, and central nervous systems. Furthermore, we provide a comprehensive discussion about the probable sites of shared molecular mechanisms that may elicit additional hazardous effects. Finally, we highlight the gaps of knowledge in this area, which deserves further research.

Esketamine inhaled as dry powder: Pharmacokinetic, pharmacodynamic and safety assessment in a preclinical study

Ketamine and its enantiomer esketamine have gained much attention in recent years as potent, fast-acting agents for the management of treatment-resistant depression. However, an alternative to oral ketamine administration is required to ensure adequate systemic exposure as the drug undergoes extensive first-pass metabolism. We propose dry powder inhalation as a new esketamine delivery route. Here, we examine the pharmacokinetics, pharmacodynamics, toxicology and safety of this novel esketamine administration method. Esketamine (10 mg/kg) and ketamine racemate (20 mg/kg) were administered to rats by dry powder inhalation, intravenous injection or intratracheal instillation and the pharmacokinetics of these treatments were compared. Analyte concentration of ketamine stereoisomers and their metabolites was assessed by LC-MS/MS method. Esketamine showed a clinically relevant pharmacokinetic profile, with high bioavailability (62%) and relatively low maximum concentration peaks. Esketamine exhibited high penetration of the blood-brain barrier, but pharmacodynamic examinations of brain homogenates showed no changes in selected protein phosphorylation or expression analyzed by the immunoblotting method. We conducted GLP-compliant 14-day and 28-day general toxicity studies in rats and dogs, respectively, subjected to dry esketamine powder inhalation. The maximum daily dosages were 46.5 mg/kg and 36.5 mg/kg, respectively. We also performed pharmacological safety studies. Esketamine inhaled as dry powder had an expected safety profile consistent with its known pharmacological action. None of its observed effects were considered toxicologically significant. The pharmacological safety studies confirmed that the observed effects were transient and that inhaled esketamine had a good safety profile. Hence, our preclinical studies demonstrated that dry powder inhalation is a highly efficacious and safe delivery route for esketamine and may be a viable alternative administration route meriting further clinical development.

Ketamine as a component of multimodal analgesia for pain management in bariatric surgery: A systematic review and meta-analysis of randomized controlled trials

Introduction

Anaesthesia in morbidly obese people is challenging with a high dose of opioid consumption. This systematic review and meta-analysis of randomised controlled trials (RCTs) summaries evidence comparing ketamine to placebo for pain management after bariatric surgery.

Methods

We used PRISMA 2020 and AMSTAR 2 guidelines to conduct this study. The random-effects model was adopted using Review Manager Version 5.3 for pooled estimates.

Results

Seven RCTs published between 2009 and 2021 were eligible, including a total of 412 patients (202 patients in the ketamine group and 210 patients in the control group). In the ketamine group total opioid consumption during the first 24 h postoperatively was reduced (mean difference, MD = −5.89; 95% CI [-10.39, −1.38], p = 0.01), lower pain score at 4 h (MD = −0.81; 95% CI [-1.52, −0.10], p = 0.03), pain score at 8 h (MD = −1.00; 95% CI [-1.21, −0.79], p < 0.01), and shorter hospital stay (MD = −0.10; 95% CI [-0.20, −0.01], p = 0.03). There was no significant difference between the two groups regarding duration of anaesthesia (MD = −3.42; 95% CI [-8.62, 1.82], p = 0.20), or sedation score (MD = −0.02; 95% CI [-0.21, 0.17], p = 0.84). As concern the postoperative complications, risks of postoperative nausea and vomiting(OR = 0.75; 95% CI [0.27, 2.04], p = 0.56), hallucinations (OR = 5.47; 95% CI [0.26, 117.23], p = 0.28), dizziness (OR = 1.05; 95% CI [0.14, 7.78], p = 0.96), and euphoria (OR = 5.77; 95% CI [0.65, 51.52], p = 0.12) were not different between the two groups either.

Conclusion

Ketamine could be an effective and safe technique for pain management following bariatric surgery. It reduces opioid consumption, postoperative pain, and hospital stay.

RegistrationThis review was registered in PROSPERO (CRD42022296484).

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This study comparing ketamine infusion or bolus with placebo when used with morphine, paracetamol or tramadol for pain management following bariatric surgery demonstrated that:

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Ketamine was associated with lower opioid consumption during the 24 h postoperatively.

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Ketamine decreased VAS scores at H4 and H8, and shorten the hospital stay.

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Ketamine ensure a similar duration of anaesthesia, postoperative sedation scores, PONV, and postoperative complications rate (hallucinations, headache, euphoria and dizziness).

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.

Long-term ketamine administration induces bladder damage and upregulates autophagy-associated proteins in bladder smooth muscle tissue

Long-term ketamine abuse can cause significant lower urinary tract symptoms in humans, termed ketamine-associated cystitis (KC). Here, we established a model of long-term (6 months) ketamine administration in wild-type (C57BL/6) mice. We elucidated the pathological effects of ketamine in the bladder and investigated changes in autophagy-associated protein expression (i.e., LC3, Beclin-1, and P62) and inflammatory cytokines (i.e., IL-6 and IL-1β) in the bladder smooth muscle tissue. Long-term ketamine administration reduced the number of layers in the bladder mucosal epithelial cells (4-5 layers in the saline group vs. 2-3 layers in the ketamine groups), but increased the number of mast cells and collagen fibers. LC3-II/LC3-I, Beclin-1, IL-6, and IL-1β protein expression in the bladder smooth muscle tissues of ketamine-treated mice was significantly increased. The mRNA and protein levels of P62 in the Ket-60 mg/kg group were also significantly increased, but not the Ket-30 mg/kg group. Our results reveal that long-term ketamine administration can cause cystitis-like pathological changes in mice, and the disordered autophagy in the bladder tissue may be involved in the persistent bladder damage following long-term administration of ketamine at 60 mg/kg.

Ketamine for the Treatment of Chronic Pain: A Comprehensive Review

Background

Chronic pain significantly worsens the quality of life. Unlike neuropathic, musculoskeletal, postoperative pain, and cancer pain, chronic primary pain cannot be explained by an underlying disease or condition, making its treatment arduous.

Objectives

This manuscript intends to provide a comprehensive review of the use of ketamine as a treatment option for specific chronic pain conditions.

Study Design

A review article.

Setting

A review of the literature.

Methods

A search was done on PubMed for relevant articles.

Results

A comprehensive review of the current understanding of chronic pain and the treatment of specific chronic pain conditions with ketamine.

Limitations

Literature is scarce regarding the use of ketamine for the treatment of chronic pain.

Conclusion

First-line treatment for many chronic pain conditions includes NSAIDs, antidepressants, anticonvulsants, and opioids. However, these treatment methods are unsuccessful in a subset of patients. Ketamine has been explored in randomized controlled trials (RCTs) as an alternative treatment option, and it has been demonstrated to improve pain symptoms, patient satisfaction, and quality of life. Conditions highlighted in this review include neuropathic pain, fibromyalgia, complex regional pain syndrome (CRPS), phantom limb pain (PLP), cancer pain, and post-thoracotomy pain syndrome. This review will discuss conditions, such as neuropathic pain, fibromyalgia, complex regional pain syndrome, and more and ketamine's efficacy and its supplementary benefits in the chronic pain patient population. As the opioid crisis in the United States continues to persist, this review aims to understand better multimodal analgesia, which can improve how chronic pain is managed.

Recreational ketamine-related deaths notified to the National Programme on Substance Abuse Deaths, England, 1997-2019

BACKGROUND

Ketamine is a phencyclidine derivative with dissociative anaesthetic properties. Increasing numbers of individuals in England take ketamine recreationally. Information on deaths arising from such use in England is presented.

METHODS

Cases were extracted on 31 January 2020 from the National Programme on Substance Abuse Deaths database, based on text searches of the cause of death, coroner's verdict and positive toxicology results for the terms 'ketamine' or 'norketamine'.

FINDINGS

During 1997-2005, there were <5 deaths p.a. in which ketamine was implicated. Numbers increased until 2009 (21), plateauing until 2016; thereafter, deaths have risen to about 30 p.a. Decedents' characteristics (N = 283): male 84.1%, mean age 31.2 (SD 10.0) years, employed 56.5%, drug use history 79.6% and living with others 60.3%. Ketamine was detected with other substances in most cases. Main (74.6%) underlying cause of death was accidental poisoning. Ketamine may have impaired judgement in other cases.

CONCLUSIONS

Although controlled, recreational ketamine use and related fatalities continue to increase. Consumers need to be more aware of the potentially fatal risks they face.

A systematic review of therapeutic ketamine use in children and adolescents with treatment-resistant mood disorders

Suicide is the second leading cause of death in the United States among individuals aged 10-24, and severe youth depression is often refractory to the current standards of care. Many studies have demonstrated the efficacy of ketamine in reducing depressive symptoms in adults with treatment-resistant mood disorders, though few studies utilizing ketamine in youth populations exist. This systematic review examines the current state of evidence for ketamine use in children with treatment-resistant mood disorders. We conducted a search utilizing two electronic databases for English-language studies investigating the therapeutic effects and side effect profile of ketamine in youth ≤ 19 years of age with a diagnosis of a treatment-resistant mood disorder. Analysis included subjects with treatment-resistant depression with and without psychotic features and with bipolar disorder. Primary outcome measures included the following scales: Montgomery-Asberg Depression Rating Scale, Children's Depression Rating Scale, Children's Depression Rating Scale Revised, Child Bipolar Questionnaire, Overt Aggression Scale, Yale-Brown Obsessive-Compulsive Scale, and Scale for Suicidal Ideation. Four published studies were identified that investigated therapeutic ketamine use in youth for the primary purpose of treating a treatment-resistant psychiatric disorder. Three additional studies that did not meet eligibility criteria were identified and discussed. Ketamine was shown in youth to generally improve depressive symptoms, decrease acute suicidality, and reduce mood lability, though a number of subjects remained resistant to its treatment. These findings substantiate the need for further longitudinal studies investigating ketamine's long-term safety, its efficacy, and abuse potential in the youth.

First-time offenders for recreational ketamine use under a new penalty system in Taiwan: incidence, recidivism and mortality in national cohorts from 2009 to 2017

BACKGROUND AND AIMS

Ketamine has become a new recreational drug of choice among young people in parts of Asia. Using national databases in Taiwan, this study aimed to (1) examine the yearly trend in the ketamine offence rate over time; (2) estimate the 3-year risk of drug-related re-offence and its correlates among the first-time offenders; and (3) estimate the 3-year standardized mortality ratio (SMR) among the first-time offenders.

DESIGN, SETTING AND PARTICIPANTS

Retrospective cohort studies of offenders for recreational ketamine use in a penalty system initiated in 2009. Offenders for recreational ketamine use were identified from the Administrative Penalty System for Schedule III/IV Substances database from 2009 to 2017, and the re-offence rate and mortality among first-time offenders were assessed via record-linkage within the database as well as with both the criminal drug offence database and the national mortality database. The cohort from 2009 to 2016 (n = 39 178) was used for the recidivism analysis and the cohort from 2009 to 2013 (n = 25 357) was used for the 3-year SMR analysis.

MEASUREMENTS

Recidivism was estimated using survival analysis of the event as re-arrest for using ketamine, more serious illicit drugs (Schedules I/II), or any illicit drugs (ketamine or Schedules I/II). SMRs were estimated for overall and cause-specific death within 3 years after the first offence for ketamine use.

FINDINGS

The age-standardized rates for both prevalent (1.38 per 1000) and first-time offenders (0.65 per 1000) peaked in 2013 and then decreased steadily. The 3-year risk of re-offence was 33.85% [95% confidence interval (CI) = 33.23-34.47%) for ketamine use and 39.52% (95% CI = 39.00-40.04%) for any illicit drug use. These first-time offenders had an SMR of 4.9 (95% CI = 4.3-5.4) for overall mortality, 2.1 (95% CI = 1.6-2.7) for natural deaths and 7.6 (95% CI = 6.7-8.6) for unnatural deaths.

CONCLUSIONS

Recreational ketamine use in Taiwan appears to lead not only to high risk for drug-related re-offence but also to excess mortality.

[History of Ketamine: An ancient molecule that is still popular today]

The history of ketamine begins in 1962, when Calvin Stevens of the pharmaceutical laboratory Parke-Davis synthesizes it from phencyclidine, a molecule with psychodysleptic, hallucinogenic and dissociative properties. Following the first administration of ketamine to humans in 1964 in Jackson prison (Michigan, USA), its dissociative effects associated with short anaesthesia were reported, and a patent for its human use was filed in 1966. In the 1990s, the discovery of opioid-induced hyperalgesia sparked interest in ketamine as an analgesic. In recent years, the human use of ketamine, and in particular its esketamine enantiomer, has shifted towards the treatment of depression. The first cases of ketamine abuse were reported in 1992 in France, leading to special surveillance by the health authorities, and its inclusion in the list of narcotic drugs in 1997. Today, ketamine has become an attractive substance for recreational use, gradually emerging from alternative techno circles to spread to more commercial party scenes. These elements represent a public health concern, associated with the risk of developing new chemically synthesized analogues, the harmful effects of which are still little known.

Chemical hemorrhagic cystitis: Diagnostic and therapeutic pitfalls (Review)

Chemical cystitis (CC) is an inflammation of the bladder caused by various chemical agents ingested intentionally or accidentally. It is linked to chemotherapeutic agents such as cyclophosphamide, therapeutic agents for diverse diseases, and anesthetic agents consumed abusively for recreational effects such as ketamine, or can be linked to environmental and surrounding factors such as soaps, gels, spermicides, and dyes. CC is a pathology with an increasing incidence that is inadequately treated due to its infectious cystitis-like symptoms. The hemorrhagic form can have a rampant evolution. Treatment options of CC and its complications are under continuous research with no accepted standardized sequence. In many situations, the treatments are difficult to obtain, administer, and follow-up. In addition, the lack of experience of the physician may pose other obstacles in delivering treatment to the patient. In conclusion, CC is a disease with an increasing incidence, challenging to diagnose, which is frequently mistreated, and has multiple treatment modalities that still require standardization in administration and sequencing.

Characteristics and circumstances of death related to the self-administration of ketamine

BACKGROUND AND AIMS

Ketamine is used for anaesthesia, sedation and the treatment of mood disorders, but is also widely used for non-medical purposes. This study aimed to: (1) determine the characteristics and circumstances of all recorded cases of self-administered ketamine-related death in Australia, 2000-19 and (2) determine the toxicology and major organ pathology of cases.

DESIGN

Retrospective study of all Australian cases in which self-administered ketamine was a mechanism contributory to death, retrieved from the National Coronial Information System.

SETTING

Australia-wide.

CASES

Sixty-eight cases, with a mean age of 35.2 years (standard deviation = 11.5, range = 16-63), 76.5% male.

MEASUREMENTS

Information was collected on cause of death, demographics, circumstances of death, toxicology and major organ pathology.

FINDINGS

Death was attributed to toxicity in 82.3% of cases (accidental, 58.8%; deliberate, 23.5%), suicide by violent means (8.8%) and traumatic accident (8.8%). In six cases the decedent had been prescribed ketamine. In 32.4% the final route of ketamine administration was by injection. The fatal incident predominantly occurred in a private environment (72.1%). Ketamine was present in the blood of 90.1% and other biomarkers in the remainder. The median blood ketamine concentration was 0.2 mg/l (0.02-6.9 mg/l). Other drugs were detected in 95.5% of cases: opioids (59.1%), hypnosedatives (57.6%), psychostimulants (50.0%), alcohol (27.3%), Δ-9-tetrahydrocannabinol (18.2%), antidepressants (28.8%) and antipsychotics (9.1%). Pulmonary oedema was present in 82.2% of cases that underwent autopsy and pneumonia in 26.7%.

CONCLUSIONS

The typical case of self-administered ketamine-related death in Australia, 2000-19, was a male in his mid-30s who had used multiple drugs, with the fatal incident most commonly occurring in a private setting. Death due to accidental drug toxicity was the most common manner of death, but suicide was highly prevalent.

Use and abuse of dissociative and psychedelic drugs in adolescence

Adolescence is a period of profound developmental changes, which run the gamut from behavioral and neural to physiological and hormonal. It is also a time at which there is an increased propensity to engage in risk-taking and impulsive behaviors like drug use. This review examines the human and preclinical literature on adolescent drug use and its consequences, with a focus on dissociatives (PCP, ketamine, DXM), classic psychedelics (LSD, psilocybin), and MDMA. It is the case for all the substances reviewed here that very little is known about their effects in adolescent populations. An emerging aspect of the literature is that dissociatives and MDMA produce mixed reinforcing and aversive effects and that the balance between reinforcement and aversion may differ between adolescents and adults, with consequences for drug use and addiction. However, many studies have failed to directly compare adults and adolescents, which precludes definitive conclusions about these consequences. Other important areas that are largely unexplored are sex differences during adolescence and the long-term consequences of adolescent use of these substances. We provide suggestions for future work to address the gaps we identified in the literature. Given the widespread use of these drugs among adolescent users, and the potential for therapeutic use, this work will be crucial to understanding abuse potential and consequences of use in this developmental stage.

Cortical Thickness Changes in Chronic Ketamine Users

Background: Previous studies have examined the effects of long-term ketamine use on gray matter volume. But it is unclear whether chronic ketamine use alters cortical thickness and whether cortical thickness changes in chronic ketamine users are associated with cognitive deficits observed in chronic ketamine users. Methods: Here, 28 chronic ketamine users and 30 healthy controls (HCs) were recruited. Cortical morphometry based on Computational Anatomy Toolbox (CAT12) was used to measure cortical thickness. Cognitive performance was measured by MATRICS Consensus Cognitive Battery (MCCB). Two-sample t-test was used to assess differences in cortical thickness and cognitive performance between the two groups. Partial correlation analysis was used for assessing correlations between cortical thickness changes and clinical characteristics, cognitive performance in chronic ketamine users. Results: Chronic ketamine users exhibited significantly reduced cortical thickness in frontal, parietal, temporal, and occipital lobes compared to HC [false discovery rate (FDR) corrected at p < 0.05]. In chronic ketamine users, the average quantity (g) of ketamine use/day was negatively correlated with cortical thickness in the left superior frontal gyrus (SFG), right caudal middle frontal gyrus (MFG), and right paracentral lobule. The frequency of ketamine use (days per week) was negatively correlated with cortical thickness in the left isthmus cingulate cortex. Duration of ketamine use (month) was negatively correlated with cortical thickness in the left precentral gyrus. The chronic ketamine users showed significantly poorer cognitive performance on the working memory (P = 0.009), visual learning (P = 0.009), speed of processing (P < 0.000), and Matrics composite (P = 0.01). There was no correlation between scores of domains of MCCB and reduced cortical thickness. Conclusion: The present study observed reduced cortical thickness in multiple brain areas, especially in the prefrontal cortex (PFC) in chronic ketamine users. Dose, frequency, and duration of ketamine use was negatively correlated with cortical thickness of some brain areas. Our results suggest that chronic ketamine use may lead to a decrease of cortical thickness. But the present study did not observe any correlation between reduced cortical thickness and decreased cognitive performance in chronic ketamine users.

Perioperative Intravenous Low-Dose Ketamine Infusion to Minimize Pain for Septorhinoplasty: A Prospective, Randomized, Double-Blind Study

OBJECTIVES

Studies investigating the effects of intravenous (IV) ketamine in pain management after septorhinoplasty is limited. This study aims to evaluate the efficacy of low-dose IV infusion of ketamine on pain scores.

METHODS

This randomized, prospective, double-blind study was conducted with 48 patients who underwent septorhinoplasty. Intravenous ketamine bolus (0.5 mg/kg) was administered to the ketamine group (group K, n = 24) at anesthesia induction, and ketamine infusion was continued (0.25 mg/kg/h) during the surgery. In the control group (group C, n = 24), the same protocol was administered using saline instead of ketamine. Furthermore, 50-mg dexketoprofen trometamol was administered to both groups 30 minutes before the end of the surgery. Then it was repeated at the 12th and 24th hours postoperatively. Pain scores were evaluated with the visual analogue scale. Consumptions intraoperative of opioid and sevoflurane, rescue opioid requirement, patient satisfaction, and side effects were recorded.

RESULTS

Pain scores were significantly lower in group K at all postoperative periods (P < .05). There was no significant difference between the groups in terms of intraoperative sevoflurane and remifentanil consumptions (P > .05). Rescue opioid analgesic requirements were significantly lower in group K than group C (0/24 vs 6/24, respectively; P  = .022). Side effects were similar between the groups (P > .05).

CONCLUSION

We recommend the administration of low-dose ketamine infusion during septorhinoplasty surgery because it reduces the requirement for rescue opioid analgesia and postoperative pain scores.

Efficacy of Psychoactive Drugs for the Treatment of Posttraumatic Stress Disorder: A Systematic Review of MDMA, Ketamine, LSD and Psilocybin

The aim of this systematic review was to examine the efficacy of MDMA, ketamine, LSD, and psilocybin for the treatment of posttraumatic stress disorder (PTSD). A search of four databases for English language, peer-reviewed literature published from inception to 18th October 2019 yielded 2,959 records, 34 of which were screened on full-text. Observational studies and RCTs which tested the efficacy of MDMA, ketamine, LSD, or psilocybin for reducing PTSD symptoms in adults, and reported changes to PTSD diagnosis or symptomatology, were included. Nine trials (five ketamine and four MDMA) met inclusion criteria. Trials were rated on a quality and bias checklist and GRADE was used to rank the evidence. The evidence for ketamine as a stand-alone treatment for comorbid PTSD and depression was ranked "very low", and the evidence for ketamine in combination with psychotherapy as a PTSD treatment was ranked "low". The evidence for MDMA in combination with psychotherapy as a PTSD treatment was ranked "moderate".

Cannabis points to the synaptic pathology of mental disorders: how aberrant synaptic components disrupt the highest psychological functions

Cannabis can elicit an acute psychotic reaction, and its long-term use is a risk factor for schizophrenia. The main active psychoactive ingredient ∆⁹-tetrahydrocannabinol (Δ⁹-THC) activates cannabinoid 1 (CB1) receptors, which are localized to the terminals of glutamate and GABA neurons in the brain. The endogenous cannabinoids are involved in information processing and plasticity at synapses in the hippocampus, basal ganglia, and cerebral cortex. Exogenously applied CB₁ receptor agonists disrupt neuronal dynamics and synaptic plasticity, resulting in cognitive deficits and impairment of the highest psychological functions. Various other pro-psychotic drugs, such as ketamine and methamphetamine, exert their effects in the same microdomain of synaptic spines as Δ⁹-THC. Additionally, many of the most robust findings in psychiatric genetics include components that localize to dendritic spines and have important roles in information processing and plasticity.


Postmortem redistribution of ketamine in ocular matrices: A study of forensic relevance

The present study evaluates the postmortem redistribution of ketamine in ocular matrices, such as vitreous humor, aqueous humor, and ocular tissues in an animal model. To understand the redistribution of ketamine and its metabolite (norketamine) in the ocular matrices, an in vivo study was performed in rabbits. The rabbits were divided into two groups: perimortem and postmortem. The postmortem samples were collected at 17 h after the administration of ketamine (40 mg/kg) intravenously. For a better understanding of the metabolism of ketamine in eyes, an ex vivo study was conducted in goat eyes after administration of ketamine intravitreally. The samples were analyzed by LC-MS/MS and the levels of ketamine and norketamine in these matrices were compared with that of whole blood and plasma. The results of the in vivo study showed a decrease in ketamine levels in whole blood and plasma while an increase in ocular matrices at postmortem. Though, in most cases, this increase/decrease was statistically insignificant. Moreover, there was an increase of norketamine level in ocular matrices. Ex vivo study also shows the presence of norketamine in ocular matrices of goat eyes. The presence of norketamine in goat eyes may be indicative of the metabolism of ketamine in the eyes.

Characteristic patterns of EEG oscillations in sheep (Ovis aries) induced by ketamine may explain the psychotropic effects seen in humans

Ketamine is a valuable anaesthetic and analgesic that in recent years has gained notoriety as a recreational drug. Recently, ketamine has also been proposed as a novel treatment for depression and post-traumatic stress disorder. Beyond its anaesthetic actions, however, the effects of ketamine on brain activity have rarely been probed. Here we examined the cortical electroencephalography (EEG) response to ketamine of 12 sheep. Following ketamine administration, EEG changes were immediate and widespread, affecting the full extent of the EEG frequency spectrum measured (0–125 Hz). After recovery from sedation during which low frequency activity dominated, the EEG was characterised by short periods (2–3 s) of alternating low (<14 Hz) and high (>35 Hz) frequency oscillation. This alternating EEG rhythm phase is likely to underlie the dissociative actions of ketamine, since it is during this phase that ketamine users report hallucinations. At the highest intravenous dose used (24 mg/kg), in 5/6 sheep we observed a novel effect of ketamine, namely the complete cessation of cortical EEG activity. This persisted for up to several minutes, after which cortical activity resumed. This phenomenon is likely to explain the ‘k-hole’, a state of oblivion likened to a near death experience that is keenly sought by ketamine abusers.

Overlap in the neural circuitry and molecular mechanisms underlying ketamine abuse and its use as an antidepressant

Ketamine, a dissociative anesthetic and psychedelic compound, has revolutionized the field of psychopharmacology by showing robust, and rapid-acting antidepressant activity in patients suffering from major depressive disorder (MDD), suicidal tendencies, and treatment-resistant depression (TRD). Ketamine's efficacy, however, is transient, and patients must return to the clinic for repeated treatment as they experience relapse. This is cause for concern because ketamine is known for its abuse liability, and repeated exposure to drugs of abuse often leads to drug abuse/dependence. Though the mechanism(s) underlying its antidepressant activity is an area of current intense research, both clinical and preclinical evidence shows that ketamine's effects are mediated, at least in part, by molecular adaptations resulting in long-lasting synaptic changes in mesolimbic brain regions known to regulate natural and drug reward. This review outlines our limited knowledge of ketamine's neurobiological and biochemical underpinnings mediating its antidepressant effects and correlates them to its abuse potential. Depression and addiction share overlapping neural circuitry and molecular mechanisms, and though speculative, repeated use of ketamine for the treatment of depression could lead to the development of substance use disorder/addiction, and thus should be tempered with caution. There is much that remains to be known about the long-term effects of ketamine, and our lack of understanding of neurobiological mechanisms underlying its antidepressant effects is a clear limiting factor that needs to be addressed systematically before using repeated ketamine in the treatment of depressed patients.

Managing Acute Agitation and Psychotic Symptoms in the Emergency Department

Background and goals:

It is fairly common for adolescents with a presenting problem of acute agitation to present to the Emergency Department. These patients present challenges with respect to both differential diagnosis and management. Furthermore, with many adolescents having extended stays in emergency departments, it is important for ED physicians to have a basic familiarity with diagnosis and treatment.

Method:

In this paper, we present a primer on the conditions underlying acute agitation and review approaches to management in the emergency department.

Discussion:

Psychotic disorders, such as schizophrenia, are distinct from other conditions presenting with psychotic symptoms, which can range from depression to substance use to non-psychiatric medical conditions. Agitation, a state of excessive verbal and physical activity, can accompany any of these conditions. Unlike the case for adults, practice guidelines do not exist, and there is no fully agreed upon expert consensus yet. Emergency physicians should have a working knowledge of antipsychotic medications and need to consider pharmacological as well as non-pharmacological treatments for optimal management.

Effects of dopamine and serotonin synthesis inhibitors on the ketamine-, d-amphetamine-, and cocaine-induced locomotor activity of preweanling and adolescent rats: sex differences

The pattern of ketamine-induced locomotor activity varies substantially across ontogeny and according to sex. Although ketamine is classified as an NMDA channel blocker, it appears to stimulate the locomotor activity of both male and female rats via a monoaminergic mechanism. To more precisely determine the neural mechanisms underlying ketamine's actions, male and female preweanling and adolescent rats were pretreated with vehicle, the dopamine (DA) synthesis inhibitor ∝-methyl-_DL-p-tyrosine (AMPT), or the serotonin (5-HT) synthesis inhibitor 4-chloro-_DL-phenylalanine methyl ester hydrochloride (PCPA). After completion of the pretreatment regimen, the locomotor activating effects of saline, ketamine, d-amphetamine, and cocaine were assessed during a 2 h test session. In addition, the ability of AMPT and PCPA to reduce dorsal striatal DA and 5-HT content was measured in male and female preweanling, adolescent, and adult rats. Results showed that AMPT and PCPA reduced, but did not fully attenuate, the ketamine-induced locomotor activity of preweanling rats and female adolescent rats. Ketamine (20 and 40 mg/kg) caused a minimal amount of locomotor activity in male adolescent rats, and this effect was not significantly modified by AMPT or PCPA pretreatment. When compared to ketamine, d-amphetamine and cocaine produced different patterns of locomotor activity across ontogeny; moreover, AMPT and PCPA pretreatment affected psychostimulant- and ketamine-induced locomotion differently. When these results are considered together, it appears that both dopaminergic and serotonergic mechanisms mediate the ketamine-induced locomotor activity of preweanling and female adolescent rats. The dichotomous actions of ketamine relative to the psychostimulants in vehicle-, AMPT-, and PCPA-treated rats, suggests that ketamine modulates DA and 5-HT neurotransmission through an indirect mechanism.

Ketamine sensitization: Influence of dose, environment, social isolation and treatment interval

Ketamine is a dissociative anesthetic first developed in the 1960s but is increasingly used at subanesthetic doses for both clinical and non-clinical purposes. There is evidence from human recreational users of compulsive use and addiction. Sensitization is an increase in an effect of a drug with repeated use that is thought to be important in the development of addiction. Research on psychomotor stimulants has shown the development of sensitization in laboratory animals to be modified by factors that influence addiction. In the current paper we describe four experiments on the development of sensitization in laboratory rats aimed at determining if ketamine sensitization is also influenced by factors thought to be important in addiction. Adult, male Sprague-Dawley rats received ketamine (5, 10, 20 or 50 mg/kg i.p.) for five or more days and the development of locomotor sensitization was followed. Experiment 1 examined the ability of low doses of ketamine to produce sensitization and found sensitization at 5, 10 and 20 mg/kg. Experiment 2 examined the influence of environmental context and found that ketamine sensitization (20 mg/kg) was greater when administration occurred in a novel environment (the experimental apparatus) than in home cages. Experiment 3 found that ketamine sensitization (20 mg/kg) did not occur when animals were housed in social isolation but occurred readily in pair-housed animals. Finally, Experiment 4 found that ketamine sensitization (20 or 50 mg/kg) was similar whether drug was administered daily or at 3-day intervals. Together, the results demonstrate that ketamine sensitization is robust and reliable, occurring under a variety of circumstances. Moreover, ketamine sensitization is influenced by factors that influence the development of addiction in humans. The current results may lead to a better understanding of ketamine abuse and addiction and may help inform clinical use of the drug.

Effects of monoamine depletion on the ketamine-induced locomotor activity of preweanling, adolescent, and adult rats: Sex and age differences

Ketamine significantly increases the locomotor activity of rodents, however this effect varies according to the sex and age of the animal being tested. To determine the role monoamine systems play in ketamine's locomotor activating effects: (a) male and female preweanling, adolescent, and adult rats were pretreated with vehicle or the monoamine depleting agent reserpine (1 or 5 mg/kg), and (b) the behavioral actions of ketamine (20 or 40 mg/kg) were then compared to d-amphetamine (2 mg/kg) and cocaine (10 or 15 mg/kg). The ability of reserpine to deplete dorsal striatal dopamine (DA) and serotonin (5-HT) in male and female rats was determined using HPLC. Ketamine caused substantial increases in the locomotion of preweanling rats and older female rats (adolescents and adults), but had only small stimulatory effects on adolescent and adult male rats. When compared to cocaine and d-amphetamine, ketamine was especially sensitive to the locomotor-inhibiting effects of monoamine depletion. Ketamine-induced locomotion is at least partially mediated by monoamine systems, since depleting DA and 5-HT levels by 87-96% significantly attenuated the locomotor activating effects of ketamine in male and female rats from all three age groups. When administered to reserpine-pretreated rats, ketamine produced a different pattern of behavioral effects than either psychostimulant, suggesting that ketamine does not stimulate locomotor activity via actions at the presynaptic terminal. Instead, our results are consistent with the hypothesis that ketamine increases locomotor activity through a down-stream mechanism, possibly involving ascending DA and/or 5-HT projection neurons.

Sex-dependent changes in ketamine-induced locomotor activity and ketamine pharmacokinetics in preweanling, adolescent, and adult rats

Although ketamine has long been known to increase locomotor activity, only recently was it realized that this behavioral effect varies according to both sex and age. The purpose of the present study was threefold: first, to measure the locomotor activating effects of ketamine in male and female rats across early ontogeny and into adulthood; second, to assess ketamine and norketamine pharmacokinetics in the dorsal striatum and hippocampus of the same age groups; and, third, to use curvilinear regression to determine the relationship between locomotor activity and dorsal striatal concentrations of ketamine and norketamine. A high dose of ketamine (80 mg/kg, i.p.) was administered in order to examine the complete cycle of locomotor responsiveness across a 280-min testing session. In separate groups of rats, the dorsal striata and hippocampi were removed at 10 time points (0-360 min) after ketamine administration and samples were assayed for ketamine, norketamine, and dopamine using HPLC. In female rats, ketamine produced high levels of locomotor activity that varied only slightly among age groups. Male preweanling rats responded like females, but adolescent and adult male rats exhibited lesser amounts of ketamine-induced locomotor activity. Ketamine and norketamine pharmacokinetics, especially peak values and area under the curve, generally mirrored age- and sex-dependent differences in locomotor activity. Among male rats and younger female rats, dorsal striatal ketamine and norketamine levels accounted for a large proportion of the variance in locomotor activity. In adult female rats, however, an additional factor, perhaps involving other ketamine and norketamine metabolites, was influencing locomotor activity.

The Special K Constellation, a Rare Presentation of Ketamine Use: A Case Report

Ketamine is commonly used in the emergency medicine setting, but also as a recreational drug. There have been many animal studies investigating ketamine, but little data on long-term clinical use of ketamine in humans. In this case presentation, a 22-year-old international male student presented with crepitus and cachexia and was found to have extensive subcutaneous emphysema, pneumorrhachis/intraspinal air, pneumomediastinum, and multiorgan failure. In this case report, we discuss how ketamine abuse is the likely cause of these findings.

Long-lasting effects of repeated ketamine administration in adult and adolescent rats

Initiation of ketamine use often occurs in adolescence, yet little is known about long-term consequences when use begins in this developmental period. The current experiments were designed to examine the effects of repeated exposure to ketamine in adolescence on behavior in adulthood. We examined locomotor activity, as well as cognitive function, in animals that received repeated administration of ketamine. Groups of adolescent and adult male rats were treated with ketamine (25 mg/kg) once daily for 10 days. Locomotor activity was assessed following the first injection, following 10 days of injection, and following 20 days of abstinence. Acute locomotor effects and locomotor sensitization were compared in adolescents and adults; cross-sensitization to dextromethorphan, another dissociative with abusive potential, was also examined. In a separate group of animals cognitive deficits were assessed following the 20 day abstinence period in spatial learning and novel object recognition tasks. The locomotor stimulant effect of ketamine was much greater in adolescents than adults. Animals that were repeatedly administered ketamine demonstrated locomotor sensitization immediately after the final injection. However, sensitization only persisted after the abstinence period in animals treated as adults. No cross-sensitization to dextromethorphan was evident. Ketamine failed to produce statistically significant cognitive deficits in either age group, although drug-treated adults showed a trend towards deficits in spatial learning. Repeated use of ketamine produces long-lasting neuroadaptations that may contribute to addiction. Mild lasting memory deficits may occur in adults, although further work is necessary to confirm these findings. The results extend the understanding of potential long-term consequences of ketamine use in adolescents and adults.

[Ketamine in the therapy of chronic pain and depression]

Although ketamine has been known and clinically applied for a long time, questions still arise around the many possible indications in which the anesthetic and analgesic substance could be used. In particular, these questions relate to new indications in which ketamine is used in low subanesthetic doses.The mechanism of action at the NMDA receptor clearly distinguishes ketamine from all other analgesics. Possible applications include the prevention of chronic postoperative pain as well as the treatment of neuropathic pain. With the treatment of refractory depression completely new therapeutic areas for ketamine could be established.

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.

p38 mitogen-activated protein kinase gene silencing rescues rat hippocampal neurons from ketamine-induced apoptosis: An in vitro study

Ketamine (KTM) is an anesthetic drug with several advantages, including the elevation of cardiac output and blood pressure. However, KTM may also induce the apoptosis of hippocampal neurons. Notably, p38 mitogen-activated protein kinase (p38MAPK) has previously been studied for its role in neuronal injury. Therefore, the present study evaluated the effect of lentivirus-mediated p38MAPK gene silencing on KTM-induced apoptosis of rat hippocampal neurons. Hippocampal neurons were extracted from neonatal Sprague-Dawley rats, and then treated with KTM, p38MAPK-short hairpin RNA or SB203580 (an inhibitor of p38MAPK). Next, the expression levels of p38MAPK and apoptosis-associated genes, including caspase-3, B-cell lymphoma 2 (Bcl-2) and Bcl-2-associated X protein (Bax), were detected. In addition, cell viability and apoptosis were determined using an MTT assay and flow cytometry, respectively. Finally, telomerase activity of hippocampal neurons was detected by ELISA. The results revealed that silencing of p38MAPK in KTM-treated cells decreased the expression levels of p38MAPK, caspase-3 and Bax, and the extent of p38MAPK phosphorylation, while it increased the expression of Bcl-2. Furthermore, silencing p38MAPK promoted cell viability, cell cycle progression and the telomerase activity of hippocampal neurons, and inhibited the apoptosis of hippocampal neurons. Taken together, the results suggested an inhibitory role of lentivirus-mediated p38MAPK gene silencing on KTM-induced apoptosis of rat hippocampal neurons. Thus, p38MAPK gene silencing may serve as a potential target for preventing the KTM-induced apoptosis of hippocampal neurons.

Ketamine induction of p53-dependent apoptosis and oxidative stress in zebrafish (Danio rerio) embryos

Ketamine is a widely used pharmaceutical that has been detected in water sources worldwide. Zebrafish embryos were used in this study to investigate the oxidative stress and apoptotic signals following a 24h exposure to different ketamine concentrations (0, 50, 70 and 90 mg L^-1). Early blastula embryos (∼2 h post fertilisation-hpf) were exposed for 24 h and analysed at 8 and 26 hpf. Reactive oxygen species and apoptotic cells were identified in vivo, at 26 hpf. Enzymatic activities (superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), lactate dehydrogenase (LDH) and acetylcholinesterase (AChE)), glutathione levels (oxidised (GSSG) and reduced (GSH)), oxidative damage (lipid peroxidation (LPO) and protein carbonyls (CO)) as well as oxidative stress (gclc, gstp1, sod1 and cat), apoptosis (casp3a, casp6, casp8, casp9, aifm1 and tp53) and cell proliferation (pcna) related-genes were evaluated at 8 and 26 hpf. Caspase (3 and 9) activity was also determined at both time-points by colorimetric methods. Superoxide dismutase (SOD), catalase (CAT), glutathione levels (GSSG), caspase-9 and reactive oxygen species (ROS) were shown to be affected by ketamine exposure while in vivo analysis showed no difference in ROS. A significant up-regulation of superoxide dismutase (sod1) and catalase (cat) genes expression was also perceived. Ketamine-induced apoptosis was observed in vivo and confirmed by the apoptotic-related genes up-regulation. The overall results suggest that ketamine induced oxidative stress and apoptosis through the involvement of p53-dependent pathways in zebrafish embryos which could be important for the evaluation of the overall risk of ketamine in aquatic environments.