Beyond the K-hole: a 3-year longitudinal investigation of the cognitive and subjective effects of ketamine in recreational users who have substantially reduced their use of the drug

Exploring ketamine's reinforcement, cue-induced reinstatement, and nucleus accumbens cFos activation in male and female long evans rats

Ketamine (KET), a non-competitive N-methyl-d-aspartate (NMDA) receptor antagonist, has rapid onset of antidepressant effects in Treatment-Resistant Depression patients and repeated infusions are required to sustain its antidepressant properties. However, KET is an addictive drug, and so more preclinical and clinical research is needed to assess the safety of recurring treatments in both sexes. Thus, the aim of this study was to investigate the reinforcing properties of various doses of KET (0-, 0.125-, 0.25-, 0.5 mg/kg/infusion) and assess KET's cue-induced reinstatement and neuronal activation in both sexes of Long Evans rats. Neuronal activation was assessed using the protein expression of the immediate early gene cFos in the nucleus accumbens (Nac), an important brain area implicated in reward, reinforcement and reinstatement to most drug-related cues. Our findings show that KET has reinforcing effects in both male and female rats, albeit exclusively at the highest two doses (0.25 and 0.5 mg/kg/infusion). Furthermore, we noted sex differences, particularly at the highest dose of ketamine, with female rats displaying a higher rate of self-administration. Interestingly, all groups that self-administered KET reinstated to drug-cues. Following drug cue-induced reinstatement test in rats exposed to KET (0.25 mg/kg/infusion) or saline, there was higher cFos protein expression in KET-treated animals compared to saline controls, and higher cFos expression in the core compared to the shell subregions of the Nac. As for reinstatement, there were no notable sex differences reported for cFos expression in the Nac. These findings reveal some sex and dose dependent effects in KET's reinforcing properties and that KET at all doses induced similar reinstatement in both sexes. This study also demonstrated that cues associated with ketamine induce comparable neuronal activation in the Nac of both male and female rats. This work warrants further research into the potential addictive properties of KET, especially when administered at lower doses which are now being used in the clinic for treating various psychopathologies.

Ketamine and the neurobiology of depression: Toward next-generation rapid-acting antidepressant treatments

Ketamine has emerged as a transformative and mechanistically novel pharmacotherapy for depression. Its rapid onset of action, efficacy for treatment-resistant symptoms, and protection against relapse distinguish it from prior antidepressants. Its discovery emerged from a reconceptualization of the neurobiology of depression and, in turn, insights from the elaboration of its mechanisms of action inform studies of the pathophysiology of depression and related disorders. It has been 25 y since we first presented our ketamine findings in depression. Thus, it is timely for this review to consider what we have learned from studies of ketamine and to suggest future directions for the optimization of rapid-acting antidepressant treatment.

Changes in social, sexual, and hedonic behaviors in rats in response to stress and restoration by a negative allosteric modulator of α5-subunit containing GABA receptor

Major depressive disorder (MDD) is a debilitating and costly human condition. Treatment for MDD relies heavily on the use of antidepressants that are slow to produce mood-related changes and are not effective in all patients, such as selective serotonin reuptake inhibitors (SSRIs). Several novel compounds, including negative allosteric modulators of GABA-A receptors containing the α5-subunit (GABA-NAMs), are under investigation for potential fast acting therapeutic use in MDD. Preclinical evidence that these compounds produce a rapid antidepressant-like response comes primarily from simple tests of escape behavior and preference for rewarding stimuli after chronic stress. To increase the ethological relevance of these compounds, we tested the hypothesis that the GABA-NAM, L-655,708, would produce an antidepressant-like response in more complex stress-sensitive social and sex behaviors, which are of relevance to the symptoms of human depression. In male rats subjected to chronic restraint stress, injection of L-655,708 increased reward in a sexual conditioned place preference task, increased male sexual activity with a receptive female, and re-established male social dominance hierarchies within 24 h. We also report increased sucrose preference in the social defeat stress (SDS) model of depression following GABA-NAM administration, demonstrating that its antidepressant-like actions are independent of the type of chronic stress administered. This work extends the impact of GABA-NAMs beyond traditional tests of anhedonia and further supports the development of alpha5 subunit-selective GABA-NAMs as a potential fast-acting therapeutic approach for treating human MDD.

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.

Neurocognitive effects of repeated ketamine infusions in comorbid posttraumatic stress disorder and major depressive disorder

BACKGROUND

The glutamate N-methyl-d-aspartate (NMDA) receptor antagonist ketamine rapidly ameliorates posttraumatic stress disorder (PTSD) and depression symptoms in individuals with comorbid PTSD and major depressive disorder (MDD). However, concerns over ketamine's potential neurocognitive side effects have yet to be assessed in this population. The current study investigated 1) changes in neurocognitive performance after a repeated ketamine dosing regimen and 2) baseline neurocognitive performance as a predictor of ketamine treatment effect.

METHOD

Veterans with comorbid PTSD and MDD (N = 15) received six infusions of 0.5 mg/kg ketamine over a 12-day period. Neurocognitive and clinical outcomes assessments occurred at baseline and within 7 days of infusion-series completion using the CogState battery.

RESULTS

Repeated ketamine infusions did not significantly worsen any measures of cognition. Rather, significant improvement was observed in working memory following completion of the infusion series. In addition, greater improvements in PTSD and MDD symptoms were associated with lower working memory, slower processing speed and faster set shifting at baseline. Lower verbal learning was also predictive of improvement in depression.

LIMITATIONS

This study applied an open-label design without a placebo control. As such, it is not known to what extent the correlations or improvement in neurocognitive performance may have occurred under placebo conditions.

CONCLUSION

This is the first study to examine the neurocognitive effects of repeated ketamine in participants with comorbid PTSD and MDD. Our findings suggest potential baseline neurocognitive predictors of ketamine response for comorbid PTSD and MDD symptoms.

Long-term safety of ketamine and esketamine in treatment of depression

INTRODUCTION

Ketamine is an NMDA receptor antagonist that can produce rapid-acting antidepressant effects. Esketamine (Spravato), the S-enantiomer of racemic ketamine, was approved by the FDA for treatment-resistant depression in 2019. Here we review what is known about the long-term safety of both racemic ketamine and esketamine as therapies for psychiatric disorders.

AREAS COVERED

In this article, we conducted a safety review of ketamine and esketamine. In looking at ketamine and esketamine long-term safety effects, we considered data available from experimental studies and several phase-three clinical trials.

EXPERT OPINION

Based on available data, the most common side effects of ketamine/esketamine are generally transient, mild, and self-limited. These include dissociation, nausea, headache, elevated heart rate, and blood pressure. Treatment with esketamine may lead to an increased risk of lower urinary tract symptoms, such as dysuria or urgency. However, severe bladder pathology has not been reported among patients receiving doses of esketamine/ketamine in line with prescribing guidelines for depression. There is considerable data that ketamine at high doses can lead to long-term impairments in cognition. However, the esketamine clinical trials found that cognition generally remains stable or improves over time, suggesting that when used appropriately, there is no increased risk of cognitive impairment.

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.

Recovery of cognitive functioning following abstinence from ketamine

BACKGROUND

Acute and adverse effects of ketamine on cognitive functioning have been documented. No longitudinal study has examined whether cognitive deficits can be reversed following ketamine abstinence although it has been suggested in some cross-sectional studies. This study aimed to investigate the changes in cognitive functioning among ketamine users following a 12-week abstinence from ketamine.

METHODS

In this longitudinal study, 114 ketamine users completed clinical and cognitive assessments at both baseline and 12-week follow-up with the following instruments: Severity of Dependence Scale, Beck Depression Inventory (BDI), Anxiety Subscale of the Hospital Anxiety Depression Scale (HADSA), and a cognitive battery.

RESULTS

BDI (p < 0.001) and HADSA (p = 0.044) scores were significantly reduced at the 12-week follow-up. Significant improvements were found in Wechsler Adult Intelligence Scale (Third edition) immediate recall (p < 0.001) and delayed recall (p < 0.001) on the Rey-Osterrieth Complex Figure Test, and in delayed recall (p < 0.001), and immediate recall (p = 0.001) on the Logical Memory component of the Wechsler Memory Scale (Third Edition) at the 12-week follow-up. Participants completed the Stroop Inference Test significantly faster (p < 0.001); and required fewer number of attempts (p < 0.001) and produced fewer perseverative errors (p < 0.001) on the Wisconsin Card Sorting Test at the 12-week follow-up.

CONCLUSION

Chronic ketamine users' verbal and visual memory and executive functions improved after 12 weeks of ketamine abstinence.

Effectiveness of a brief information, motivation and behavioral skills program on stage transitions and lapse for individuals who use ketamine

OBJECTIVE

Chronic ketamine use is a significant public health and social problem in East and South East Asia and may lead to impairments in health and cognitive functioning. The study evaluated effects of an information, motivation and behavior skills (IMB) program on changes in motivational stage and ketamine use.

METHODS

Ketamine using individuals residing in the City of Taipei were recruited (N = 395): 279 selected an IMB program consisting of a 1-day workshop of six 50-minute interactive sessions provided in small groups. The remaining 116 participants selected an education-as-usual (EAU) program consisting of a 1-day workshop of six 50-minute didactic lectures provided in a large group format. Motivational stage of change and ketamine knowledge were assessed before and after the interventions. Participants were followed one year later to assess their ketamine use status.

RESULTS

No significant difference in knowledge increase between the IMB and EAU groups (p = .59). The proportion of participants who transitioned from the contemplation to preparation motivational stages was greater in the IMB group than in the EAU group (p < .01). A significant difference in the rates of ketamine lapse during a one-year post intervention follow up was observed between the IMB (50%) and EAU (75%) groups (p < .01).

CONCLUSIONS

Interventions based on IMB principles may be more effective in supporting motivational stage transition and in prevention of lapses to ketamine use as compared to currently offered standard drug education programs. Policy makers should consider including IMB interventions in their rehabilitation programs addressing ketamine use problems.

The profile of cognitive impairments in chronic ketamine users

The aim of this study was to examine the cognitive function in chronic ketamine users. Factors correlated to cognition impairments were analyzed. Sixty-three chronic ketamine users and 65 healthy subjects were recruited. Cognitive function was assessed by using immediate/delayed visual reproduction (IVR/DVR) tasks, immediate/delayed logical memory (ILM/DLM) tasks, Stroop test, Wisconsin card sorting test (WCST), and continuous performance test (CPT). Psychopathological symptoms were assessed with the Positive and Negative Syndrome Scale (PANSS), Beck Depression Inventory (BDI) and Beck Anxiety Inventory (BAI). Ketamine users performed worse than controls on the IVR, ILM, DLM, Stroop and auditory CPT tests. IVR and DVR, color-naming and color-interference-reading scores were positively correlated with education level. In ketamine users ILM scores were negatively correlated with the negative subscale of PANSS. DLM score was positively correlated with average dose of ketamine use. Word-reading score was positively correlated with education level, and negatively correlated with duration of ketamine use. False hits in auditory CPT was positively correlated with duration of ketamine use. Number of trials to complete the first category and perseverative errors on WCST were positively correlated with the duration between the test and last ketamine use. Chronic ketamine users had cognitive impairments across multiple domains.

Cognitive profile of ketamine-dependent patients compared with methamphetamine-dependent patients and healthy controls

BACKGROUND

Ketamine has emerged as a major substance of abuse worldwide and has been listed with methamphetamine (METH) as two of the most widely available illicit substances in Taiwan. Only a few studies have examined the long-term consequences of chronic and heavy ketamine abuse. We compared the cognitive function of ketamine-dependent patients with that of METH-dependent patients and healthy controls.

METHODS

We recruited 165 participants (58 ketamine-dependent and 49 METH-dependent patients who sought treatment and 58 healthy controls) and evaluated them by using a cognitive test battery, the Brief Assessment of Cognition in Schizophrenia, with scores being estimated in reference to normative data in general population.

RESULTS

The ketamine-dependent patients had significantly poorer performance than did the controls in many cognitive tests, including verbal memory, motor speed, verbal fluency, and attention and processing speed, and the battery as a whole. METH-dependent patients exhibited poorer function in motor speed, verbal fluency, and attention and processing speed. The ketamine group performed poorer than did METH group in the domains of verbal memory, working memory, and attention and processing speed and the composite battery scores. A previous experience of ketamine-induced psychotomimetic symptoms, using higher doses of ketamine, and longer abstinence appeared to be associated with performance in some tests; however, the significance disappeared after multiple comparison correction.

CONCLUSIONS

The ketamine-dependent patients had impaired cognitive function, and METH-dependent patients exhibited intermediate performance between ketamine-dependent patients and healthy controls. Given the growing population of ketamine abusers, public education on the cognitive consequences should be provided.

Other drug use does not impact cognitive impairments in chronic ketamine users

BACKGROUND

Ketamine abuse causes cognitive impairments, which negatively impact on users' abstinence, prognosis, and quality of life.

RESULTS

of cognitive impairments in chronic ketamine users have been inconsistent across studies, possibly due to the small sample sizes and the confounding effects of concomitant use of other illicit drugs. This study investigated the cognitive impairment and its related factors in chronic ketamine users with a large sample size and explored the impact of another drug use on cognitive functions.

METHODS

Cognitive functions, including working, verbal and visual memory and executive functions were assessed in ketamine users: 286 non-heavy other drug users and 279 heavy other drug users, and 261 healthy controls. Correlations between cognitive impairment and patterns of ketamine use were analysed.

RESULTS

Verbal and visual memory were impaired, but working memory and executive functions were intact for all ketamine users. No significant cognitive differences were found between the two ketamine groups. Greater number of days of ketamine use in the past month was associated with worse visual memory performance in non-heavy other drug users. Higher dose of ketamine use was associated with worse short-term verbal memory in heavy other drug users.

CONCLUSION

Verbal and visual memory are impaired in chronic ketamine users. Other drug use appears to have no impact on ketamine users' cognitive performance.

Low serum level of epidermal growth factor in chronic ketamine users

BACKGROUND

Growth factors play an important role in brain development. Whether epidermal growth factor (EGF) plays a role in the pathophysiology of ketamine related disorders is unexplored. In this study, we examined the serum levels of EGF in chronic ketamine users as compared with healthy controls. The possible correlation between serum EGF levels with the demographic, ketamine use characteristics and psychopathological symptoms were analyzed.

METHODS

Sixty-seven chronic ketamine users and 40 healthy subjects were recruited. Serum EGF levels were measured by enzyme-linked immunosorbent assay. Psychopathological symptoms were assessed using Positive and Negative Syndrome Scale, Beck Depression Inventory and Beck Anxiety Inventory.

RESULTS

The serum level of EGF in the chronic ketamine users was significantly lower than that of healthy subjects (22.34 ± 4.81 pg/ml vs. 87.10 ± 2.96 pg/ml, F = 15.169, p < 0.01). The serum EGF level was negatively correlated with the current average dose of ketamine consumption per day of use (p = 0.015), and positively associated with the Positive and Negative Syndrome Scale positive symptom score (p = .022).

CONCLUSIONS

Serum level of EGF decreased in chronic ketamine users compared with healthy subjects, which may play a role in the pathophysiology of ketamine related disorders.

Chronic Ketamine Exposure Causes White Matter Microstructural Abnormalities in Adolescent Cynomolgus Monkeys

Acute and repeated exposures to ketamine mimic aspects of positive, negative, and cognitive symptoms of schizophrenia in humans. Recent studies by our group and others have shown that chronicity of ketamine use may be a key element for establishing a more valid model of cognitive symptoms of schizophrenia. However, current understanding on the long-term consequences of ketamine exposure on brain circuits has remained incomplete, particularly with regard to microstructural changes of white matter tracts that underpin the neuropathology of schizophrenia. Thus, the present study aimed to expand on previous investigations by examining causal effects of repeated ketamine exposure on white matter integrity in a non-human primate model. Ketamine or saline (control) was administered intravenously for 3 months to male adolescent cynomolgus monkeys (n = 5/group). Diffusion tensor imaging (DTI) experiments were performed and tract-based spatial statistics (TBSS) was used for data analysis. Fractional anisotropy (FA) was quantified across the whole brain. Profoundly reduced FA on the right side of sagittal striatum, posterior thalamic radiation (PTR), retrolenticular limb of the internal capsule (RLIC) and superior longitudinal fasciculus (SLF), and on the left side of PTR, middle temporal gyrus and inferior frontal gyrus were observed in the ketamine group compared to controls. Diminished white matter integrity found in either fronto-thalamo-temporal or striato-thalamic connections with tracts including the SLF, PTR, and RLIC lends support to similar findings from DTI studies on schizophrenia in humans. This study suggests that chronic ketamine exposure is a useful pharmacological paradigm that might provide translational insights into the pathophysiology and treatment of schizophrenia.

A Negative Allosteric Modulator for α5 Subunit-Containing GABA Receptors Exerts a Rapid and Persistent Antidepressant-Like Action without the Side Effects of the NMDA Receptor Antagonist Ketamine in Mice

New antidepressant pharmacotherapies that provide rapid relief of depressive symptoms are needed. The NMDA receptor antagonist ketamine exerts rapid antidepressant actions in depressed patients but also side effects that complicate its clinical utility. Ketamine promotes excitatory synaptic strength, likely by producing high-frequency correlated activity in mood-relevant regions of the forebrain. Negative allosteric modulators of GABA-A receptors containing α5 subunits (α5 GABA-NAMs) should also promote high-frequency correlated electroencephalogram (EEG) activity and should therefore exert rapid antidepressant responses. Because α5 subunits display a restricted expression in the forebrain, we predicted that α5 GABA-NAMs would produce activation of principle neurons but exert fewer side effects than ketamine. We tested this hypothesis in male mice and observed that the α5 GABA-NAM MRK-016 exerted an antidepressant-like response in the forced swim test at 1 and 24 h after administration and an anti-anhedonic response after chronic stress in the female urine sniffing test (FUST). Like ketamine, MRK-016 produced a transient increase in EEG γ power, and both the increase in γ power and its antidepressant effects in the forced swim test were blocked by prior administration of the AMPA-type glutamate receptor antagonist 2,3-dioxo-6-nitro-1,2,3,4-tetrahydrobenzo[f]quinoxaline-7-sulfonamide (NBQX). Unlike ketamine, however, MRK-016 produced no impairment of rota-rod performance, no reduction of prepulse inhibition (PPI), no conditioned-place preference (CPP), and no change in locomotion. α5 GABA-NAMs, thus reproduce the rapid antidepressant-like actions of ketamine, perhaps via an AMPA receptor (AMPAR)-dependent increase in coherent neuronal activity, but display fewer potential negative side effects. These compounds thus demonstrate promise as clinically useful fast-acting antidepressants.

Ketamine and Beyond: Investigations into the Potential of Glutamatergic Agents to Treat Depression

Clinical and preclinical studies suggest that dysfunction of the glutamatergic system is implicated in mood disorders such as major depressive disorder and bipolar depression. In clinical studies of individuals with major depressive disorder and bipolar depression, rapid reductions in depressive symptoms have been observed in response to subanesthetic-dose ketamine, an agent whose mechanism of action involves the modulation of glutamatergic signaling. The findings from these studies have prompted the repurposing and/or development of other glutamatergic modulators for antidepressant efficacy, both as monotherapy or as an adjunct to conventional monoaminergic antidepressants. This review highlights the evidence supporting the antidepressant effects of subanesthetic-dose ketamine as well as other glutamatergic modulators, such as D-cycloserine, riluzole, CP-101,606, CERC-301 (previously known as MK-0657), basimglurant, JNJ-40411813, dextromethorphan, nitrous oxide, GLYX-13, and esketamine.

Reliability, convergent and structural validity and cut-off score of the Severity of Dependence Scale for recreational ketamine users

BACKGROUND AND AIMS

There is a lack of instruments for measuring ketamine substance use disorders. The aims were (i) to estimate the reliability and provide evidence of validity of the Severity of Dependence Scale (SDS) in a sample of recreational users, and (ii) propose a cut-off point to determine the presence of dependence.

METHODS

We conducted a web-based cross-sectional survey with recreational users who accessed webs related to recreational drug use and harm reduction. 264 recreational ketamine users who had taken it in the past month participated in the study. The Spanish version of the SDS was used. Information on ketamine use-related problems and ketamine use patterns was also collected.

RESULTS

The reliability estimation calculated by the Cronbach's alpha coefficient was 0.776. SDS showed evidence of convergent validity based on relationships with other variables. Two comparisons were made in this study to analyze the Receiver Operating Characteristic Curve. For frequency of use in the last month the area under curve (AUC) was 0.835 (CI=0.775-0.895) with optimal discrimination at an SDS score of 3. For having been in treatment for decreasing or quitting ketamine use the AUC was 0.902 (CI=0.840-0.963) and the cut-off point was 4. Confirmatory factor analysis showed a one-dimensional structure when Items 3 and 4 were correlated.

CONCLUSIONS

This study has provided evidence of reliability and validity of the ketamine version of the SDS for recreational users. Considering that ketamine use is linked to young people and its strong potential for causing serious impairment, a cut-off of 3 is proposed as indicative of dependence.

Profiling the psychotic, depressive and anxiety symptoms in chronic ketamine users

OBJECTIVE

Although concern about chronic ketamine abuse has grown, the characteristic symptomatology of chronic ketamine users has yet to be examined. This study aims to measure the psychotic, depressive and anxiety symptoms in chronic ketamine users.

METHODS

A group of chronic ketamine users in Guangzhou, China were evaluated. The socio-demographic and drug use characteristics of subjects were documented. Symptoms of psychosis, depression, anxiety were evaluated by the Positive and Negative Syndrome Scale (PANSS), Beck Depression Inventory (BDI) and Beck Anxiety Inventory (BAI). The severity of the symptoms was identified by standard severity cutoffs.

RESULTS

The PANSS total score, positive symptom, negative symptom, general psychopathology subscale score were 45.3±8.4, 8.0±1.7, 13.2± 3.9 and 24.2± 4.9 respectively. BDI and BAI score was 13.1±6.5 and 15.7±9.6 respectively. 77.5% and 46.0% of the subjects showed moderate to severe depressive symptoms and anxiety symptoms respectively. The BDI score was positively correlated with ketamine use frequency. The BAI score was positively correlated with ketamine use frequency.

CONCLUSIONS

Depressive symptoms were commonly presented in chronic ketamine users. The higher ketamine use frequency and dosage were associated with more severe depressive symptoms.

Ketamine users have high rates of psychosis and/or depression

Ketamine has been linked to psychosis and used in the treatment of depression. However, no study has examined the prevalence of psychotic and depressive disorders in dependent ketamine users. This study aimed to examine the frequency of various psychopathologies among a series of patients seeking treatment for ketamine use in Hong Kong, China. The case records of 129 patients with a history of ketamine use receiving treatment at three substance use clinics between January 2008 and August 2012 were retrieved for data collection. Patients' demographic data, patterns of substance misuse, and comorbid psychiatric diagnoses were recorded and entered into analyses. The mean age of onset and length of ketamine use were 17.7 ± 4.4 and 8.7 ± 5.7 years, respectively. All patients were dependent on ketamine at the time of data collection. Multiple substance misuse was common. Eighty-four of the 129 (65.1%) patients were found to have comorbid psychiatric disorders, most commonly substance-induced psychotic disorder (31.8%) followed by depressive disorder (27.9%). Psychosis and/or depression were common in ketamine-dependent patients referred to a psychiatric substance use clinic. The findings provide evidence of an association between chronic ketamine use and the presence of psychosis and/or depression. The results raise the issue of safety when using ketamine in the long-term treatment of depression.

Ceftriaxone reverses ketamine-induced lasting EEG and astrocyte alterations in juvenile mice

BACKGROUND

Ketamine, an N-methyl-d-aspartate receptor antagonist, is used as a pediatric anesthetic because of its favorable safety profile. It is also being investigated as an antidepressant. Unfortunately, ketamine causes adverse reactions including hallucinations and is associated with a high prevalence of abuse among adolescents. Although chronic ketamine use has been shown to produce cognitive impairments even years following cessation, little is known about its long-term consequences on adolescents. The beta-lactam ceftriaxone has been shown to attenuate alcohol withdrawal, and alleviate early brain injury and memory impairments following subarachnoid hemorrhage. However, its ability to reverse the effects of adolescent ketamine exposure is not known. Previous data indicate that ketamine causes a reduction in the number of Excitatory Amino Acid Transporter Type 2 (EAAT2)-containing astrocytes. Additionally, the beta lactam antibiotic ceftriaxone increased expression of EAAT2. As EAAT2 is a principal mechanism of glutamate clearance from the synapse, the current study tests the hypothesis that ceftriaxone may reverse functional consequences of ketamine exposure.

METHODS

We examined the effects of chronic ketamine in juvenile mice as well as reversal by ceftriaxone using electroencephalography (EEG). Subsequently, we assessed the effects of these treatments on markers of astrocyte proliferation, using Glial Fibrillary Acidic Protein (GFAP), and function, as evidenced by EAAT2.

RESULTS

Juvenile mice exposed to chronic ketamine showed lasting alterations in EEG measurements as well as markers of astrocyte number and function. These alterations were reversed by ceftriaxone.

CONCLUSIONS

Data suggest that ceftriaxone may be able to ameliorate ketamine-induced long-term disturbances in adolescent brains.

Development of a checklist of short-term and long-term psychological symptoms associated with ketamine use

Background

Ketamine is an increasingly popular drug of abuse in China but there is currently no method for classifying the psychological effects of ketamine in individuals with ketamine dependence.

Aim

Develop a scale that characterizes the acute and long-term psychological effects of ketamine use among persons with ketamine dependence.

Methods

We developed a preliminary symptom checklist with 35 dichotomous (‘yes’ or ‘no’) items about subjective feelings immediately after ketamine use and about perceived long-term effects of ketamine use that was administered to 187 inpatients with ketamine dependence recruited from two large hospitals in Guangzhou, China. Exploratory factor analysis (EFA) was conducted on a randomly selected half of thesample to reduce the items and to identify underlying constructs. Confirmatory factor analysis (CFA) was conducted on the second half of the sample to assess the robustness of the identified factor structure.

Results

Among the 35 symptoms, the most-reported acute effects were ‘floating or circling’ (94%), ‘euphoric when listening to rousing music’ (86%), and ‘feeling excited, talkative, and full of energy’ (67%). The mostreported long-term symptoms were ‘memory impairment’ (93%), ‘personality changes’ (86%), and ‘slowed reactions’ (81%). EFA resulted in a final 22-item scale best modelled by a four-factor model: two factors representing chronic symptoms (social withdrawal and sleep disturbances), one about acute psychoticlike symptoms, and one that combined acute drug-related euphoria and longer-term decreased libido. CFA showed that these 4 factors accounted for 50% of the total variance of the final 22-item scale and that the model fit was fair (Goodness of Fit Index, GIF=83.3%; Root Mean Square Error of Approximation, RMSEA=0.072).

Conclusion

A four-factor model including social withdrawal, sleep disturbance, psychotic-like symptoms, and euphoria at the time of drug use provides a fair description of the short-term and long-term psychological symptoms associated with ketamine use. Future work on the 22-item version of the scale with larger samples is needed to confirm the validity of this 4-factor structure, to assess the scale’s test-retest reliability, and to determine whether or not it can be useful in the differential diagnosis and monitoring of treatment of individuals with ketamine dependence.

Serum level of vascular endothelial growth factor decreased in chronic ketamine abusers

AIMS

To evaluate the serum level of vascular endothelial growth factor (VEGF) in a group of chronic ketamine abusers in comparison to healthy controls.

METHODS

Eighty-one ketamine abusers who were hospitalized for the treatment of ketamine dependence and 39 healthy controls were recruited. Serum VEGF level was measured by enzyme linked immunosorbent assay (ELISA). Psychopathological symptoms were assessed using Positive and Negative Syndrome Scale (PANSS), Beck Depression Inventory (BDI) and Beck Anxiety Inventory (BAI).

RESULTS

Serum level of VEGF was significantly lower in chronic ketamine abusers compared to healthy controls (64.6±42.1 vs. 92.4±59.4pg/ml, F=7.243, p=0.008).

CONCLUSIONS

Serum level of VEGF decreased in chronic ketamine abusers compared to healthy controls.

Chronic administration of ketamine mimics the perturbed sense of body ownership associated with schizophrenia

RATIONALE

Subanaesthetic ketamine infusion in healthy volunteers induces experiences redolent of early psychosis, including changes in the experience of one's own body. It is not clear, however, whether repeated self-administration of ketamine has a sustained effect on body representation that is comparable to that found during acute administration.

OBJECTIVES

We sought to establish whether chronic ketamine use resulted in disturbances to sense of body ownership.

METHODS

Following on from our work on the effects of acute ketamine infusion, we used the rubber hand illusion (RHI) to experimentally manipulate the sense of body ownership in chronic ketamine users, compared to healthy controls.

RESULTS

Chronic ketamine users experienced the RHI more strongly and reported more body-image aberrations, even though they had not recently taken the drug.

CONCLUSIONS

These findings suggest that the chronic ketamine model for psychosis models more long-lasting changes in sense of ownership, perhaps more akin to schizophrenia.

Legal highs: staying on top of the flood of novel psychoactive substances

There has been growing clinical, public, and media awareness and concern about the availability and potential harmfulness of so-called 'legal highs', which are more appropriately called new or novel psychoactive substances (NPS). A cat-and-mouse process has emerged wherein unknown chemists and laboratories are producing new, and as yet nonproscribed, compounds for human consumption; and as soon as they are banned, which they inevitably are, slightly modified analogues are produced to circumvent new laws. This rapidly changing environment, 81 new substances were identified in 2013 alone, has led to confusion for clinicians, psychopharmacologists, and the public at large. Our difficulties in keeping up with the process has had a two-fold negative effect: the danger of ignoring what is confusing; and the problem that some of the newer synthesized compounds appear ever more potent. This review aims to circumscribe a quick moving and growing field, and to categorize NPS into five major groups based upon their 'parent' compounds: stimulants similar to cocaine, amphetamines and ecstasy; cannabinoids; benzodiazepine based drugs; dissociatives similar to ketamine and phencyclidine (PCP); and those modelled after classic hallucinogens such as LSD and psilocybin. Pharmacodynamic actions, subjective and physical effects, harmfulness, risk of dependency and, where appropriate, putative clinical potentials are described for each class. Clinicians might encounter NPS in various ways: anecdotal reportage; acute intoxication; as part of a substance misuse profile; and as a precipitant or perpetuating factor for longer-term physical and psychological ill health. Current data are overall limited, and much of our knowledge and treatment strategies are based upon those of the 'parent' compound. There is a critical need for more research in this field, and for professionals to make themselves more aware of this growing issue and how it might affect those we see clinically and try to help: a brave new world of so-called 'psychonauts' consuming NPS will also need informed 'psychotherapeutonauts'. The paper should serve as a primer for clinicians and interested readers, as well as provide a framework into which to place the new substances that will inevitably be synthesized in the future.

Novel psychoactive substances of interest for psychiatry

Novel psychoactive substances include synthetic cannabinoids, cathinone derivatives, psychedelic phenethylamines, novel stimulants, synthetic opioids, tryptamine derivatives, phencyclidine-like dissociatives, piperazines, GABA-A/B receptor agonists, a range of prescribed medications, psychoactive plants/herbs, and a large series of performance and image enhancing drugs. Users are typically attracted by these substances due to their intense psychoactive effects and likely lack of detection in routine drug screenings. This paper aims at providing psychiatrists with updated knowledge of the clinical pharmacology and psychopathological consequences of the use of these substances. Indeed, these drugs act on a range of neurotransmitter pathways/receptors whose imbalance has been associated with psychopathological conditions, including dopamine, cannabinoid CB1, GABA-A/B, 5-HT2A, glutamate, and k opioid receptors. An overall approach in terms of clinical management is briefly discussed.

Ketamine for chronic pain: risks and benefits

The anaesthetic ketamine is used to treat various chronic pain syndromes, especially those that have a neuropathic component. Low dose ketamine produces strong analgesia in neuropathic pain states, presumably by inhibition of the N-methyl-D-aspartate receptor although other mechanisms are possibly involved, including enhancement of descending inhibition and anti-inflammatory effects at central sites. Current data on short term infusions indicate that ketamine produces potent analgesia during administration only, while three studies on the effect of prolonged infusion (4-14 days) show long-term analgesic effects up to 3 months following infusion. The side effects of ketamine noted in clinical studies include psychedelic symptoms (hallucinations, memory defects, panic attacks), nausea/vomiting, somnolence, cardiovascular stimulation and, in a minority of patients, hepatoxicity. The recreational use of ketamine is increasing and comes with a variety of additional risks ranging from bladder and renal complications to persistent psychotypical behaviour and memory defects. Blind extrapolation of these risks to clinical patients is difficult because of the variable, high and recurrent exposure to the drug in ketamine abusers and the high frequency of abuse of other illicit substances in this population. In clinical settings, ketamine is well tolerated, especially when benzodiazepines are used to tame the psychotropic side effects. Irrespective, close monitoring of patients receiving ketamine is mandatory, particularly aimed at CNS, haemodynamic, renal and hepatic symptoms as well as abuse. Further research is required to assess whether the benefits outweigh the risks and costs. Until definite proof is obtained ketamine administration should be restricted to patients with therapy-resistant severe neuropathic pain.

Gender differences in subjective discontinuation symptoms associated with ketamine use

Background

Recent substance abuse research indicates gender differences in the substance-related epidemiology, biological responses, progression to dependence, medical consequences and treatments. Studies exploring human sex-different responses to ketamine are rare and there has been no systemic survey of gender differences in ketamine use. Determining whether females are more susceptible than males to ketamine withdrawal symptoms and adverse effects is important, because it associated with treatment retention and outcome in drug users.

Methods

The Taiwanese juridical system has implemented a new regulation on ketamine in the year 2009. Ketamine users who are caught by the police, are mandated to attend an educational program. We recruited ketamine offenders from February 2010 to May 2012 at the Kunming branch of the Taipei City Hospital, where the educational classes are held. A designed questionnaire was performed to gather information about demographic characteristics, discontinuation symptoms, concomitant use of other substances, and subjective experience of memory impairment or urinary discomforts, and to compare the gender differences.

Results

A total of 1,614 ketamine users were surveyed and most of them were males (83.8%), with an average age of 26.3 ± 5.4 years. Female ketamine users presented significantly more discontinuation symptoms such as anxiety, dysphoria, and tremors compared with male users. 72.4% of total ketamine users smoked cigarettes concomitantly. Male ketamine users had a higher rate of concomitant betel nut use, while female ketamine users had a higher rate of concomitant hypnotic and alcohol use. 76% of total ketamine users reported cognitive impairment and 51.6% mentioned urinary symptoms. Furthermore, female ketamine users self-reported significantly greater levels of severity in cognitive impairment and urinary discomforts compared with male users. Less than 10% of total ketamine users in our study reported the desire to transfer for medical intervention or treatment, despite the high rates of discontinuation symptoms and negative physical side effects.

Conclusions

Gender differences were noted in the subjective experience of discontinuation symptoms, concomitant substance use, and severity of impairment related to ketamine use. However, the probable cause of the gender differences found in this study requires further investigation. We hoped our study will stimulate further research in this field.

Glutamate receptor antagonists as fast-acting therapeutic alternatives for the treatment of depression: ketamine and other compounds

The N-methyl-D-aspartate (NMDA) receptor antagonist ketamine has rapid and potent antidepressant effects in treatment-resistant major depressive disorder and bipolar depression. These effects are in direct contrast to the more modest effects seen after weeks of treatment with classic monoaminergic antidepressants. Numerous open-label and case studies similarly validate ketamine's antidepressant properties. These clinical findings have been reverse-translated into preclinical models in an effort to elucidate ketamine's antidepressant mechanism of action, and three important targets have been identified: mammalian target of rapamycin (mTOR), eukaryotic elongation factor 2 (eEF2), and glycogen synthase kinase-3 (GSK-3). Current clinical and preclinical research is focused on (a) prolonging/maintaining ketamine's antidepressant effects, (b) developing more selective NMDA receptor antagonists free of ketamine's adverse effects, and (c) identifying predictor, mediator/moderator, and treatment response biomarkers of ketamine's antidepressant effects.

Psychiatric morbidity in ketamine users attending counselling and youth outreach services

BACKGROUND

No study has examined ketamine users' psychiatric morbidity using structured diagnostic instruments. The aim of this study was thus to determine the psychiatric comorbidity of community-based ketamine users using the Structured Clinical Interview for DSM-IV (Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition), Axis I Disorders (SCID).

METHODS

A convenience sample of 200 frequent ketamine users was recruited from community organizations in Hong Kong. Participants were screened with the Severity of Dependence Scale (SDS), Beck Depression Inventory (BDI), Anxiety subscale of the Hospital Anxiety Depression Scale (HADSA), and SCID psychotic symptoms. Those who scored above the threshold (cutoff point of 8/9 on the BDI and 4/5 on HADSA) or displayed evidence of psychotic symptoms were referred for a structured clinical interview conducted by a psychiatrist.

RESULTS

One hundred and seventy participants scored above the cutoff point on 1 or more of the scales, and 115 participants attended the SCID interview. Fifty-one of these 115 participants received a psychiatric diagnosis of 1 or more comorbidities for the month preceding the interview. Mood disorders accounted for 80.4% of the diagnoses, anxiety disorders for 33.3%, and psychotic disorders for 7.8%.

CONCLUSIONS

Female gender and history of psychiatric/psychological clinic attendance were significantly associated with comorbid psychiatric disorders, whereas ketamine dependence had a borderline association.

Ketamine: an update on its abuse

Ketamine is a dissociative anesthetic and substance of abuse. Numerous effects can result from the abuse of ketamine. Death from acute direct toxicity is rare. Ketamine can alter numerous functions in the brain including color perception, memory, attention, cognition, reaction time, and sense of time and can produce psychological addiction. Chronic ketamine abuse can produce toxicity to the gastrointestinal and urinary tract. Gastrointestinal changes include epigastric pain, hepatic dysfunction, and impaired gallbladder activity. The most common urological condition from ketamine is cystitis but renal failure has been reported.

Are sexes affected differently by ketamine? An exploratory study in ketamine users

One hundred primary ketamine users and 100 controls were recruited in Hong Kong between December 2009 and December 2011. Cognitive assessment included general intelligence, working, verbal, and visual memory, and executive functions. A Univariate General Linear Model was used to compare cognitive performance between the male and female ketamine users and controls. The female users appeared to have a higher risk of visual memory impairment than their male counterparts. Further studies are warranted to clarify the mechanism of the sex-specific effect of ketamine on cognitive functions.

Pharmacokinetic drug interactions between drugs of abuse and antiretroviral medications: implications and management for clinical practice

Substance abuse and HIV/AIDS are two of the most serious, yet treatable diseases worldwide. Global access to HIV treatment continues to expand. In settings where both active illicit drug use and HIV treatment are concurrent, potentional problematic pharmacokinetic drug interactions may arise and complicate therapy. Clinical case series and carefully controlled pharmacokinetic interaction studies have been conducted between only a few drugs of abuse and approved antiretroviral therapies. Important pharmacokinetic drug interactions have been described for benzodiazepines, 3,4-methylenedioxymethamphetamine, methadone and buprenorphine; however, most have not been studied and few well-controlled studies have been conducted to adequately address the clinical implications of these interactions. The metabolism of drugs of abuse, description of the known interactions, and clinical implications and management of these interactions are reviewed. Certain interactions between drugs of abuse and antiretroviral therapies are known and others are likely based upon shared metabolic pathways. These may result in important clinical consequences. To optimize care, clinicians must be alert, knowledgeable about known and possible interactions and equipped to clinically manage the medical consequences. Moreover, there is considerable need for carefully controlled studies in this important and emerging area.

Long-Term Heavy Ketamine Use is Associated with Spatial Memory Impairment and Altered Hippocampal Activation

Ketamine, a non-competitive N-methyl-d-aspartate receptor antagonist, is rising in popularity as a drug of abuse. Preliminary evidence suggests that chronic, heavy ketamine use may have profound effects on spatial memory but the mechanism of these deficits is as yet unclear. This study aimed to examine the neural mechanism by which heavy ketamine use impairs spatial memory processing. In a sample of 11 frequent ketamine users and 15 poly-drug controls, matched for IQ, age, years in education. We used fMRI utilizing an ROI approach to examine the neural activity of three regions known to support successful navigation; the hippocampus, parahippocampal gyrus, and the caudate nucleus during a virtual reality task of spatial memory. Frequent ketamine users displayed spatial memory deficits, accompanied by and related to, reduced activation in both the right hippocampus and left parahippocampal gyrus during navigation from memory, and in the left caudate during memory updating, compared to controls. Ketamine users also exhibited schizotypal and dissociative symptoms that were related to hippocampal activation. Impairments in spatial memory observed in ketamine users are related to changes in medial temporal lobe activation. Disrupted medial temporal lobe function may be a consequence of chronic ketamine abuse and may relate to schizophrenia-like symptomatology observed in ketamine users.

Abnormalities in white matter microstructure associated with chronic ketamine use

Ketamine is an N-methyl-D-aspartate (NMDA) receptor antagonist that has been found to induce schizophrenia-type symptoms in humans and is a potent and fast-acting antidepressant. It is also a relatively widespread drug of abuse, particularly in China and the UK. Acute administration has been well characterized, but the effect of extended periods of ketamine use-on brain structure in humans-remains poorly understood. We measured indices of white matter microstructural integrity and connectivity in the brain of 16 ketamine users and 16 poly-drug-using controls, and we used probabilistic tractography to quantify changes in corticosubcortical connectivity associated with ketamine use. We found a reduction in the axial diffusivity profile of white matter in a right hemisphere network of white matter regions in ketamine users compared with controls. Within the ketamine-user group, we found a significant positive association between the connectivity profile between the caudate nucleus and the lateral prefrontal cortex and dissociative experiences. These findings suggest that chronic ketamine use may be associated with widespread disruption of white matter integrity, and white matter pathways between subcortical and prefrontal cortical areas may in part predict individual differences in dissociative experiences due to ketamine use.

Cognitive impairments in poly-drug ketamine users

RATIONALE

Cognitive impairment has been found to be reversible in people with substance abuse, particularly those using ketamine. Ketamine users are often poly-substance users. This study compared the cognitive functions of current and former ketamine users who were also abusing other psychoactive substances with those of non-users of illicit drugs as controls.

METHODS

One hundred ketamine poly-drug users and 100 controls were recruited. Drug users were divided into current (n = 32) and ex-users (n = 64) according to the duration of abstinence from ketamine (>30 days). The Beck Depression Inventory (BDI), the Hospital Anxiety Depression Scale (HADSA) and the Severity of Dependence Scale (SDS) were used to evaluate depression and anxiety symptoms and the severity of drug use, respectively. The cognitive test battery comprised verbal memory (Wechsler Memory Scale III: Logic Memory and Word List), visual memory (Rey-Osterrieth Complex Figure, ROCF), executive function (Stroop, Wisconsin Card Sorting Test, and Modified Verbal Fluency Test), working memory (Digit Span Backward), and general intelligence (Information, Arithmetic and Digit-Symbol Coding) tests.

RESULTS

Current users had higher BDI and HADSA scores than ex-users (p < 0.001 for BDI and p = 0.022 for HADSA) and controls (p < 0.001 for BDI and p = 0.002 for HADSA). Ex-users had higher BDI (p = 0.006) but equal HADSA scores (p = 1.000) compared to controls. Both current and ex-users had lower scores on Logical Memory delayed recall (p = 0.038 for current users and p = 0.032 for ex-users) and ROCF delayed recall (p = 0.033 for current users and p = 0.014 for ex-users) than controls. Current users also performed worse on ROCF recognition than controls (p = 0.002). No difference was found between the cognitive functions of current and ex-users.

CONCLUSIONS

Ketamine poly-drug users displayed predominantly verbal and visual memory impairments, which persisted in ex-users. The interactive effect of ketamine and poly-drug use on memory needs further investigation.

From "Special K" to "Special M": the evolution of the recreational use of ketamine and methoxetamine

This article reviews the recreational use of ketamine ("Special K"; KET) and explores the recent diffusion of its new derivative methoxetamine ("Special M"; MXE). The literature search on the nonclinical/recreational use of KET and MXE was carried out in a range of medical databases. Considering the limitations of peer-reviewed information, data were integrated with a qualitative assessment of a range of websites, drug fora, and other online resources including e-newsgroups, chat rooms, mailing lists, e-newsletters, and bulletin boards. The recreational use of KET has started since its discovery in 1962. This was due to its rapid onset, short duration of action, and peculiar psychotropic effects ("K-hole"). The latter effect ranges from confusion to dissociation and depersonalization (near-death experience). However, KET abuse is often associated with physical and psychological side effects, of which the worst is urological/bladder toxicity. Recently, MXE has emerged as a legal and "bladder-friendly" KET alternative. MXE presents with the same dissociative effect of KET, but with slower onset and longer duration of action. However, MXE seems to be associated with worse side effects than KET, ranging from mood disturbances/suicidal attempts to acute cerebellar toxicity. After 50 years of its discovery, KET has led to the emergence of MXE. However, this latter derivative does not appear to be a safer alternative to KET itself.

Effects of chronic ketamine use on frontal and medial temporal cognition

BACKGROUND

Recreational ketamine use has been on the rise worldwide. Previous studies have demonstrated that it disrupts various memory systems, but few studies have examined how it affects learning and frontal functioning. The present study investigates the effects of repeated ketamine self-administration on frontal fluency, attention, learning, and memory along the verbal/nonverbal axis.

METHODS

Twenty-five ketamine users and 30 healthy controls took a battery of neuropsychological tests. Frontal fluency was measured by the Verbal Fluency Test for semantic organization ability and the Figural Fluency Test for nonverbal executive functioning. Learning and memory were measured with the Chinese Auditory-Verbal Learning Test for acquisition and retention abilities of verbal information, as well as with the Continuous Visual Memory Test for nonverbal information. Participants also took several tests tapping subdomains of attention. To test for the potential effects of other drug use, 10 polydrug controls were included for comparison with the ketamine users and healthy controls.

RESULTS

Ketamine users had impaired verbal fluency, cognitive processing speed, and verbal learning. Verbal learning impairment was strongly correlated with estimated lifetime ketamine use. Ketamine users showed no impairments in figural fluency, sustained attention, selective attention, visual learning, or verbal/nonverbal memory. However, heavier lifetime ketamine use was significantly correlated with deficits in verbal memory (both immediate recall and delayed recall) and visual recognition memory. Deficits in cognitive processing speed and verbal learning persisted even after polydrug controls were included in the control group, but their inclusion did make the impairment in verbal fluency barely reach statistical significance.

CONCLUSIONS

This study suggests that repeated ketamine use causes differential impairment to multiple domains of frontal and medial temporal functioning, possibly specific to verbal information processing.

Neuropsychological effects associated with recreational cocaine use

RATIONALE

Recent evidence suggests that recreational cocaine use is on the increase, with the UK reporting one of the highest levels of use in the EU (EMCDDA 2010). Nevertheless, very few studies have addressed the neuropsychological effects associated with non-dependent recreational cocaine use.

OBJECTIVES

The current study aimed to assess whether recreational cocaine users show neuropsychological deficits on a battery of tests, previously shown to be sensitive to cocaine-dependent and psychosis-prone individuals. Schizotypal traits were also measured.

METHODS

Recreational cocaine users (n = 17) were compared with controls (n = 24) on drug use patterns, the General Health Questionnaire, the Brief Schizotypal Personality Questionnaire (SPQ-B) and four neuropsychological tasks: spatial working memory, intra/extra-dimensional set shifting, the Stocking of Cambridge and the rapid visual processing.

RESULTS

Relative to controls, recreational cocaine users produced significantly more errors on the intra/extra-dimensional set shift task and completed fewer stages, made significantly more six box stage errors on the spatial working memory task, and made significantly more errors and fewer hits, with overall poorer detection rates on the rapid visual processing task. Recreational cocaine users reported significantly higher scores on the cognitive perceptual and disorganised thinking SPQ-B subscales and total SPQ-B scores compared to controls.

CONCLUSIONS

Recreational cocaine users displayed impairments on tasks tapping sustained attention, attentional shifting and spatial memory and reported higher schizotypal trait expression. These findings are consistent with the emerging literature suggesting subtle cognitive deficits, putatively reflecting underlying dopaminergic dysfunction, in non-dependent, recreational cocaine users.

HIV and club drugs in emerging adulthood

PURPOSE OF REVIEW

To evaluate the incidence of club drug use in pediatric patients, especially those aged 13-25, and how it relates to the spread of HIV.

RECENT FINDINGS

Transmission of HIV among younger patients has become largely associated with risky sexual behaviors, as the rate of transmission from vertical infection and intravenous drug use has decreased. Use of club drugs in emerging adult populations contributes to the HIV epidemic through a combination of decreased inhibitions as well as physiological effects that increase high-risk sexual practices. Robust data exists linking the use of club drugs by the men who have sex with men population with spread of HIV, but this data in other at-risk populations (e.g. African Americans) is not as robust. Additional research is needed to identify the rates of transmission among adolescents and emerging adults, as well as knowledge, attitudes, beliefs, and practices that affect HIV transmission in this population.

SUMMARY

Use of club drugs by adolescents and emerging adults contributes to the current rate of HIV transmission among this age group.

Ketamine for treatment-resistant unipolar depression: current evidence

Currently available drugs for unipolar major depressive disorder (MDD), which target monoaminergic systems, have a delayed onset of action and significant limitations in efficacy. Antidepressants with primary pharmacological targets outside the monoamine system may offer the potential for more rapid activity with improved therapeutic benefit. The glutamate system has been scrutinized as a target for antidepressant drug discovery. The purpose of this article is to review emerging literature on the potential rapid-onset antidepressant properties of the glutamate NMDA receptor antagonist ketamine, an established anaesthetic agent. The pharmacology of ketamine and its enantiomer S-ketamine is reviewed, followed by examples of its clinical application in chronic, refractory pain conditions, which are commonly co-morbid with depression. The first generation of studies in patients with treatment-resistant depression (TRD) reported the safety and acute efficacy of a single subanaesthetic dose (0.5 mg/kg) of intravenous ketamine. A second generation of ketamine studies is focused on testing alternate routes of drug delivery, identifying methods to prevent relapse following resolution of depressive symptoms and understanding the neural basis for the putative antidepressant actions of ketamine. In addition to traditional depression rating endpoints, ongoing research is examining the impact of ketamine on neurocognition. Although the first clinical report in MDD was published in 2000, there is a paucity of adequately controlled double-blind trials, and limited clinical experience outside of research settings. Given the potential risks of ketamine, safety considerations will ultimately determine whether this old drug is successfully repositioned as a new therapy for TRD.

Cannabis use and cognitive function: 8-year trajectory in a young adult cohort

AIM

  To evaluate the relationship between change in cannabis use and changed cognitive performance over 8 years.

DESIGN

  We used survey methodology with a cohort design.

SETTING AND PARTICIPANTS

  An Australian community sample aged 20-24 years at baseline.

MEASURES

  We assessed cognitive performance with the California Verbal Learning Test (CVLT) (immediate and delayed), Spot-the-Word test (STW), Symbol Digit Modality test (SDMT) and Digit Backwards (DB). Groups of cannabis users were defined from self-reports across three waves as: 'never' (n= 420) 'remain light' (n= 71), 'former light' (n= 231), 'remain heavy' (n= 60), 'former heavy' (n= 60) and 'always former' (since start of study) (n= 657). Planned contrasts within mixed model repeated-measures analysis of variance was used for longitudinal analysis with an adjusted alpha of 0.01.

FINDINGS

  Data were obtained from 2404 participants with 1978 (82.3%) completing wave 3. At baseline there were significant differences between cannabis groups on CVLT (immediate and delayed) and SDMT. However, after controlling for education, gender, gender × group and gender × wave, there were no significant between-group differences and only CVLT immediate recall reached adjusted statistically significant longitudinal change associated with changed cannabis use (group × wave P= 0.007). Specifically, former heavy users improved their performance relative to remaining heavy users (estimated marginal means: former heavy 6.1-7.5: remain heavy 6.4-6.6).

CONCLUSIONS

  Cessation of cannabis use appears to be associated with an improvement in capacity for recall of information that has just been learned. No other measures of cognitive performance were related to cannabis after controlling for confounds.

To use or not to use: an update on licit and illicit ketamine use

Ketamine, a derivative of phencyclidine that was developed in the 1960s, is an anesthetic and analgesic with hallucinogenic effects. In this paper, the pharmacological and toxicological effects of ketamine are briefly reviewed. Ketamine possesses a wide safety margin but such a therapeutic benefit is somewhat offset by its emergence phenomenon (mind-body dissociation and delirium) and hallucinogenic effects. The increasing abuse of ketamine, initially predominantly in recreational scenes to experience a “k-hole” and other hallucinatory effects but more recently also as a drug abused during the workday or at home, has further pushed governments to confine its usage in many countries. Recently, urinary tract dysfunction has been associated with long-term ketamine use. In some long-term ketamine users, such damage can be irreversible and could result in renal failure and dialysis. Although ketamine has not yet been scheduled in the United Nations Conventions, previous studies using different assessment parameters to score the overall harms of drugs indicated that ketamine may cause more harm than some of the United Nations scheduled drugs. Some countries in Southeast and East Asia have reported an escalating situation of ketamine abuse. Dependence, lower urinary tract dysfunction, and sexual impulse or violence were the most notable among the ketamine-associated symptoms in these countries. These results implied that the danger of ketamine may have been underestimated previously. Therefore, the severity levels of the ketamine-associated problems should be scrutinized more carefully and objectively. To prevent ketamine from being improperly used and evolving into an epidemic, a thorough survey on the prevalence and characteristics of illicit ketamine use is imperative so that suitable policy and measures can be taken. On the other hand, recent findings that ketamine could be useful for treating major depressive disorder has given this old drug a new impetus. If ketamine is indeed a remedy for treating depression, more research on the risks and benefits of its clinical use will be indispensable.