N-acetylcysteine for treating cocaine addiction - A systematic review

Heroin Self-Administration and Extinction Increase Prelimbic Cortical Astrocyte-Synapse Proximity and Alter Dendritic Spine Morphometrics That Are Reversed by N-Acetylcysteine

Clinical and preclinical studies indicate that adaptations in corticostriatal neurotransmission significantly contribute to heroin relapse vulnerability. In animal models, heroin self-administration and extinction produce cellular adaptations in both neurons and astrocytes within the nucleus accumbens (NA) core that are required for cue-induced heroin seeking. Specifically, decreased glutamate clearance and reduced association of perisynaptic astrocytic processes with NAcore synapses allow glutamate release from prelimbic (PrL) cortical terminals to engage synaptic and structural plasticity in NAcore medium spiny neurons. Normalizing astrocyte glutamate homeostasis with drugs like the antioxidant N-acetylcysteine (NAC) prevents cue-induced heroin seeking. Surprisingly, little is known about heroin-induced alterations in astrocytes or pyramidal neurons projecting to the NAcore in the PrL cortex (PrL-NAcore). Here, we observe functional adaptations in the PrL cortical astrocyte following heroin self-administration (SA) and extinction as measured by the electrophysiologically evoked plasmalemmal glutamate transporter 1 (GLT-1)-dependent current. We likewise observed the increased complexity of the glial fibrillary acidic protein (GFAP) cytoskeletal arbor and increased association of the astrocytic plasma membrane with synaptic markers following heroin SA and extinction training in the PrL cortex. Repeated treatment with NAC during extinction reversed both the enhanced astrocytic complexity and synaptic association. In PrL-NAcore neurons, heroin SA and extinction decreased the apical tuft dendritic spine density and enlarged dendritic spine head diameter in male Sprague-Dawley rats. Repeated NAC treatment during extinction prevented decreases in spine density but not dendritic spine head expansion. Moreover, heroin SA and extinction increased the co-registry of the GluA1 subunit of AMPA receptors in both the dendrite shaft and spine heads of PrL-NAcore neurons. Interestingly, the accumulation of GluA1 immunoreactivity in spine heads was further potentiated by NAC treatment during extinction. Finally, we show that the NAC treatment and elimination of thrombospondin 2 (TSP-2) block cue-induced heroin relapse. Taken together, our data reveal circuit-level adaptations in cortical dendritic spine morphology potentially linked to heroin-induced alterations in astrocyte complexity and association at the synapses. Additionally, these data demonstrate that NAC reverses PrL cortical heroin SA-and-extinction-induced adaptations in both astrocytes and corticostriatal neurons.

Glutamate dynamics in the dorsolateral striatum of rats with goal-directed and habitual cocaine-seeking behavior

The shift from drug abuse to addiction is considered to arise from the transition between goal-directed and habitual control over drug behavior. Habitual responding for appetitive and skill-based behaviors is mediated by potentiated glutamate signaling in the dorsolateral striatum (DLS), but the state of the DLS glutamate system in the context of habitual drug-behavior remains undefined. Evidence from the nucleus accumbens of cocaine-experienced rats suggests that decreased transporter-mediated glutamate clearance and enhanced synaptic glutamate release contribute to the potentiated glutamate signaling that underlies the enduring vulnerability to relapse. Preliminary evidence from the dorsal striatum of cocaine-experienced rats suggests that this region exhibits similar alterations to glutamate clearance and release, but it is not known whether these glutamate dynamics are associated with goal-directed or habitual control over cocaine-seeking behavior. Therefore, we trained rats to self-administer cocaine in a chained cocaine-seeking and -taking paradigm, which yielded goal-directed, intermediate, and habitual cocaine-seeking rats. We then assessed glutamate clearance and release dynamics in the DLS of these rats using two different methods: synaptic transporter current (STC) recordings of patch-clamped astrocytes and the intensity-based glutamate sensing fluorescent reporter (iGluSnFr). While we observed a decreased rate of glutamate clearance in STCs evoked with single-pulse stimulation in cocaine-experienced rats, we did not observe any cocaine-induced differences in glutamate clearance rates from STCs evoked with high frequency stimulation (HFS) or iGluSnFr responses evoked with either double-pulse stimulation or HFS. Furthermore, GLT-1 protein expression in the DLS was unchanged in cocaine-experienced rats, regardless of their mode of control over cocaine-seeking behavior. Lastly, there were no differences in metrics of glutamate release between cocaine-experienced rats and yoked-saline controls in either assay. Together, these results suggest that glutamate clearance and release dynamics in the DLS are largely unaltered by a history of cocaine self-administration on this established cocaine seeking-taking paradigm, regardless of whether the control over the cocaine seeking behavior was habitual or goal directed.

The Potential of N-acetyl Cysteine in Behavioral Addictions and Related Compulsive and Impulsive Behaviors and Disorders: a Scoping Review

Purpose of Review

Behavioral addictions (also termed disorders due to addictive behaviors) contain impulsive and compulsive features and have been shown to involve glutamate dysregulation. N-acetylcysteine (NAC), a well-tolerated cysteine pro-drug and antioxidant, may reduce addictive behaviors by restoring glutamate homeostasis. The current review details and discusses the use of NAC in behavioral addictions and related impulsive and compulsive behaviors, including gambling disorder, problematic use of the internet, problematic video gaming, compulsive sexual behavior, problematic shopping/buying, problematic stealing, repetitive self-injurious behavior, and binge eating disorder.

Recent Findings

Preliminary results have indicated the usefulness of NAC in gambling disorder, self-injurious behaviors, and compulsive sexual behaviors. Preclinical studies indicate that NAC is effective in improving binge eating behavior, but clinical trials are limited to a small open-label trial and case report. Studies are lacking on the efficacy of NAC in problematic use of the internet, problematic video gaming, problematic stealing, and problematic shopping/buying.

Summary

NAC demonstrates potential for use in behavioral addictions and compulsive behaviors, particularly in gambling disorder and self-injury. However, more studies are needed to assess the effectiveness of NAC in other behavioral addictions and the mechanisms by which NAC improves these conditions.

Prefrontal Cortical Control of Activity in Nucleus Accumbens Core Is Weakened by High-Fat Diet and Prevented by Co-Treatment with N-Acetylcysteine: Implications for the Development of Obesity

A loss of neuroplastic control on nucleus accumbens (NAc) neuronal activity exerted by the medial prefrontal cortex (mPFC) through long-term depression (LTD) is involved in triggering drug-seeking behavior and relapse on several substances of abuse due to impaired glutamate homeostasis in tripartite synapses of the nucleus accumbens (NAc) core. To test whether this maladaptive neuroplastic mechanism underlies the addiction-like behavior induced in young mice by a high-fat diet (HFD), we utilized 28-days-old male mice fed HFD ad-libitum over 2 weeks, followed by 5 days of HFD abstinence. Control groups were fed a regular diet. HFD fed mice showed increased ΔFosB levels in the NAc core region, whereas LTD triggered from the mPFC became suppressed. Interestingly, LTD suppression was prevented by an i.p. injection of 100 mg/kg N-acetylcysteine 2.5 h before inducing LTD from the mPFC. In addition, excessive weight gain due to HFD feeding was diminished by adding 2mg/mL N-acetylcysteine in drinking water. Those results show a loss of neuroplastic mPFC control over NAc core activity induced by HFD consumption in young subjects. In conclusion, ad libitum consumption of HFD can lead to neuroplastic changes an addiction-like behavior that can be prevented by N-acetylcysteine, helping to decrease the rate of excessive weight gain.

A dual mechanism fully blocks ethanol relapse: Role of vagal innervation

Previous studies showed that vagotomy markedly inhibits alcohol self-administration. Present studies hypothesised that vagotomy significantly adds to the inhibition of alcohol relapse induced by drugs that reduce the alcohol-induced hyperglutamatergic state (e.g., N-acetylcysteine + acetylsalicylic acid). The alcohol relapse paradigm tested gauges the elevated alcohol intake observed in animals that had consumed ethanol chronically, were subjected to a prolonged alcohol deprivation and are subsequently allowed ethanol re-access. Ethanol-drinker rats (UChB) were exposed to 10% and 20% ethanol and water concurrently for 4 months, were alcohol deprived for 14 days and were thereafter allowed re-access to the ethanol solutions. An initial binge-like drinking episode is observed upon ethanol re-access, followed by a protracted elevated ethanol intake that exceeds the predeprivation intake baseline. Prior to ethanol re-access, animals were (i) administered N-acetylcysteine (40 mg/kg/day) + acetylsalicylic acid (15 mg/kg/day), (ii) were bilaterally vagotomised, (iii) were exposed to both treatments or (iv) received no treatments. The initial binge-like relapse intake and a protracted elevated ethanol intake observed after repeated ethanol deprivations/re-access cycles were inhibited by 50%-70% by the administration of N-acetylcysteine + acetylsalicylic acid and by 40%-70% by vagotomy, while the combined vagotomy plus N-acetylcysteine + acetylsalicylic acid treatment inhibited both the initial binge-like intake and the protracted ethanol intake by >95% (p < 0.001), disclosing a dual mechanism of ethanol relapse and subsequent inhibition beyond that induced by either treatment alone. Future exploration into the mechanism by which vagal activity contributes to ethanol relapse may have translational promise.

Addiction of High Dose of Benzodiazepine: Verona Detox Approach With Flumazenil

INTRODUCTION

Since the 1990s there has been evidence of the significant role Flumazenil (FLU) has in benzodiazepines (BZD) detoxes. The Verona Detox approach has been developed for high dose BZD and Z-drug detoxification via continuous subcutaneous infusion of FLU, a selective BZD receptor antagonist acting on the BZD subunit of the GABA-A receptor. Flumazenil is licensed in the United Kingdom and other countries to treat only BZD overdose although numerous studies have demonstrated its effectiveness in rapidly resetting GABA-A receptors, quickly reducing tolerance and dependence from BZD, and providing a safe and rapid detox from benzodiazepines.

OBJECTIVE

The aim of this article is to provide all healthcare professional who are interested in BZD detoxification with an approach and clear practical information on how to administer FLU.

METHOD

In this article we outline the approach in detail, describing all medical and nursing procedures day by day. This detox treatment is indicated for patients abusing from at least 5 Defined Daily Dose (DDD) of BZDs or Z-drugs. The process lasts 7 days, and is conducted under medical supervision (daily reviews) and continuous nursing (24/7). During this period, 7mg of FLU is administered (1 mg/24) through an elastomeric pump, via continuous subcutaneous infusion.

CONCLUSION

To this day, the largest database of FLU detoxification was published by our group, showing how this treatment is safe, with very little side effects even in patients with significant medical comorbidities.

N-acetylcysteine reduces addiction-like behaviour towards high-fat high-sugar food in diet-induced obese rats

Compulsive forms of eating displayed by some obese individuals share similarities with compulsive drug-taking behaviour, a hallmark feature of substance use disorder. This raises the possibility that drug addiction treatments may show utility in the treatment of compulsive overeating. N-Acetylcysteine (NAC) is a cysteine pro-drug which has experienced some success in clinical trials, reducing cocaine, marijuana and cigarette use, as well as compulsive behaviours such as gambling and trichotillomania. We assessed the impact of NAC on addiction-like behaviour towards highly palatable food in a rat model of diet-induced obesity. Adult male Sprague-Dawley rats were placed on a high-fat high-sugar diet for 8 weeks and then assigned to diet-induced obesity-prone (DIO) or diet-induced obesity-resistant (DR) groups based on weight gain. DIO and DR rats were subjected to an operant conditioning paradigm whereby rats could lever press for high-fat high-sugar food pellets. This alternated with periods of signalled reward unavailability. Before treatment DIO rats ate more in their home cage, earned more food pellets in operant sessions, and responded more during periods that signalled reward unavailability (suggestive of compulsive-like food seeking) compared with DR rats. This persistent responding in the absence of reward displayed by DIO rats was ameliorated by daily injections of NAC (100 mg/kg, i.p.) for 14 days. By the end of the treatment period, lever-pressing by NAC-treated DIO rats resembled that of DR rats. These findings suggest that NAC reduces addiction-like behaviour towards food in rats and supports the potential use of this compound in compulsive overeating.

Effectiveness of N-acetylcysteine in Treating Clinical Symptoms of Substance Abuse and Dependence: A Meta-analysis of Randomized Controlled Trials

Objective

Treatment with N-acetylcysteine (NAC) is believed to reduce the clinical symptoms among individuals with substance abuse or dependence. We conducted a meta-analysis of randomized controlled trials to evaluate the effectiveness of NAC in treating substance abuse and dependence.

Methods

PubMed, EMBASE, ClinicalTrials.gov registry, and the Cochrane Library were searched for trials published before June 2020.

Results

A total of 16 trials were analyzed. The treatment effectiveness domains assessed in this study were craving and depressive symptoms, withdrawal syndrome, adverse events, and smoking frequency. Standardized mean difference (SMD), weighted mean difference (WMD), and odds ratio (OR) were used for evaluation where appropriate. A significant decrease in craving symptoms was observed in the NAC treatment group compared with the control group (SMD, −0.67; 95% confidence interval [CI], −1.21 to 0.21). When withdrawal and depressive symptoms were considered as a single domain, the NAC treatment group demonstrated a significantly higher overall improvement than the control group (SMD, −0.35; 95% CI, −0.64 to −0.06). No between-group differences in term of the OR of adverse events (OR, 1.18; 95% CI, 0.68 to 2.06) and a non-significant trend toward reduction in smoking frequency was observed in the NAC treatment group compared with the control group (WMD, −3.09; 95% CI, −6.50 to 0.32).

Conclusion

NAC provides certain noticeable benefits in attenuating substance craving and might help alleviate depressive symptoms and withdrawal syndrome. Precautious measures should be considered when using NAC although no difference in adverse effects was found between NAC treatment and control group.

N-Acetylcysteine causes analgesia in a mouse model of painful diabetic neuropathy

N-Acetylcysteine, one of the most prescribed antioxidant drugs, enhances pain threshold in rodents and humans by activating mGlu2 metabotropic glutamate receptors. Here, we assessed the analgesic activity of N-acetylcysteine in the streptozotocin model of painful diabetic neuropathy and examined the effect of N-acetylcysteine on proteins that are involved in mechanisms of nociceptive sensitization. Mice with blood glucose levels ≥250 mg/dl in response to a single intraperitoneal (i.p.) injection of streptozotocin (200 mg/kg) were used for the assessment of mechanical pain thresholds. Systemic treatment with N-acetylcysteine (100 mg/kg, i.p., either single injection or daily injections for seven days) caused analgesia in diabetic mice. N-acetylcysteine-induced analgesia was abrogated by the Sxc− inhibitors, sulfasalazine (8 mg/kg, i.p.), erastin (30 mg/kg, i.p.), and sorafenib (10 mg/kg, i.p.), or by the mGlu2/3 receptor antagonist, LY341495 (1 mg/kg, i.p.). Repeated administrations of N-acetylcysteine in diabetic mice reduced ERK1/2 phosphorylation in the dorsal region of the lumbar spinal cord. The analgesic activity of N-acetylcysteine was occluded by the MEK inhibitor, PD0325901 (25 mg/kg, i.p.), the TRPV1 channel blocker, capsazepine (40 mg/kg, i.p.), or by a cocktail of NMDA and mGlu5 metabotropic glutamate receptor antagonists (memantine, 25 mg/kg, plus MTEP, 5 mg/kg, both i.p.). These findings offer the first demonstration that N-acetylcysteine relieves pain associated with diabetic neuropathy and holds promise for the use of N-acetylcysteine as an add-on drug in diabetic patients.

The Promise of Automated Home-Cage Monitoring in Improving Translational Utility of Psychiatric Research in Rodents

Large number of promising preclinical psychiatric studies in rodents later fail in clinical trials, raising concerns about the efficacy of this approach to generate novel pharmacological interventions. In this mini-review we argue that over-reliance on behavioral tests that are brief and highly sensitive to external factors play a critical role in this failure and propose that automated home-cage monitoring offers several advantages that will increase the translational utility of preclinical psychiatric research in rodents. We describe three of the most commonly used approaches for automated home cage monitoring in rodents [e.g., operant wall systems (OWS), computerized visual systems (CVS), and automatic motion sensors (AMS)] and review several commercially available systems that integrate the different approaches. Specific examples that demonstrate the advantages of automated home-cage monitoring over traditional tests of anxiety, depression, cognition, and addiction-like behaviors are highlighted. We conclude with recommendations on how to further expand this promising line of preclinical research.

N-Acetylcysteine and Acetylsalicylic Acid Inhibit Alcohol Consumption by Different Mechanisms: Combined Protection

Chronic ethanol intake results in brain oxidative stress and neuroinflammation, which have been postulated to perpetuate alcohol intake and to induce alcohol relapse. The present study assessed the mechanisms involved in the inhibition of: (i) oxidative stress; (ii) neuroinflammation; and (iii) ethanol intake that follow the administration of the antioxidant N-acetylcysteine (NAC) and the anti-inflammatory acetylsalicylic acid (ASA) to animals that had consumed ethanol chronically. At doses used clinically, NAC [40 mg/kg per day orally (p.o.)] and ASA (15 mg/kg per day p.o.) significantly inhibited chronic alcohol intake and relapse intake in alcohol-preferring rats. The coadministration of both drugs reduced ethanol intake by 65% to 70%. N-acetylcysteine administration: (a) induced the Nrf2-ARE system, lowering the hippocampal oxidative stress assessed as the ratio of oxidized glutathione (GSSG)/reduced glutathione (GSH); (b) reduced the neuroinflammation assessed by astrocyte and microglial activation by immunofluorescence; and (c) inhibited chronic and relapse ethanol intake. These effects were blocked by sulfasalazine, an inhibitor of the xCT transporter, which incorporates cystine (precursor of GSH) and extrudes extracellular glutamate, an agonist of the inhibitory mGlu2/3 receptor, which lowers the synaptic glutamatergic tone. The inhibitor of mGlu2/3 receptor (LY341495) blocked the NAC-induced inhibition of both relapse ethanol intake and neuroinflammation without affecting the GSSG/GSH ratio. Unlike N-acetylcysteine, ASA inhibited chronic alcohol intake and relapse via lipoxin A4, a strong anti-inflammatory metabolite of arachidonic acid generated following the ASA acetylation of cyclooxygenases. Accordingly, the lipoxin A4 receptor inhibitor, WRW4, blocked the ASA-induced reduction of ethanol intake. Overall, via different mechanisms, NAC and ASA administered in clinically relevant doses combine their effects inhibiting ethanol intake.

Potential of Glial Cell Modulators in the Management of Substance Use Disorders

The pervasive and devastating nature of substance use disorders underlies the need for the continued development of novel pharmacotherapies. We now know that glia play a much greater role in neuronal processes than once believed.  The various types of glial cells (e.g., astrocytes, microglial, oligodendrocytes) participate in numerous functions that are crucial to healthy central nervous system function. Drugs of abuse have been shown to interact with glia in ways that directly contribute to the pharmacodynamic effects responsible for their abuse potential. Through their effect upon glia, drugs of abuse also alter brain function resulting in behavioral changes associated with substance use disorders. Therefore, drug-induced changes in glia and inflammation within the central nervous system (neuroinflammation) have been investigated to treat various aspects of drug abuse and dependence. This article presents a brief overview of the effects of each of the major classes of addictive drugs on glia. Next, the paper reviews the pre-clinical and clinical studies assessing the effects that glial modulators have on abuse-related behavioral effects, such as pleasure, withdrawal, and motivation. There is a strong body of pre-clinical literature demonstrating the general effectiveness of several glia-modulating drugs in models of reward and relapse. Clinical studies have also yielded promising results, though not as robust. There is still much to disentangle regarding the integration between addictive drugs and glial cells. Improved understanding of the relationship between glia and the pathophysiology of drug abuse should allow for more precise exploration in the development and testing of glial-directed treatments for substance use disorders.

Treatment of stimulant use disorder: A systematic review of reviews

AIMS

Stimulant use disorder contributes to a substantial worldwide burden of disease, although evidence-based treatment options are limited. This systematic review of reviews aims to: (i) synthesize the available evidence on both psychosocial and pharmacological interventions for the treatment of stimulant use disorder; (ii) identify the most effective therapies to guide clinical practice, and (iii) highlight gaps for future study.

METHODS

A systematic database search was conducted to identify systematic reviews and meta-analyses. Eligible studies were those that followed standard systematic review methodology and assessed randomized controlled trials focused on the efficacy of interventions for stimulant use disorder. Articles were critically appraised using an assessment tool adapted from Palmeteer et al. and categorized for quality as 'core' or 'supplementary' reviews. Evidence from the included reviews were further synthesized according to pharmacological or non-pharmacological management themes.

RESULTS

Of 476 identified records, 29 systematic reviews examining eleven intervention modalities were included. The interventions identified include: contingency management, cognitive behavioural therapy, acupuncture, antidepressants, dopamine agonists, antipsychotics, anticonvulsants, disulfiram, opioid agonists, N-Acetylcysteine, and psychostimulants. There was sufficient evidence to support the efficacy of contingency management programs for treatment of stimulant use disorder. Psychostimulants, n-acetylcysteine, opioid agonist therapy, disulfiram and antidepressant pharmacological interventions were found to have insufficient evidence to support or discount their use. Results of this review do not support the use of all other treatment options.

CONCLUSIONS

The results of this review supports the use of contingency management interventions for the treatment of stimulant use disorder. Although evidence to date is insufficient to support the clinical use of psychostimulants, our results demonstrate potential for future research in this area. Given the urgent need for effective pharmacological treatments for stimulant use disorder, high-quality primary research focused on the role of psychostimulant medications for the treatment of stimulant use disorder is needed.

[Addictive behaviors: Clinical facts]

Malgré les fréquentes comorbidités psychiatriques, le trouble de l’usage de substance doit être appréhendé comme une pathologie autonome par ses déterminants, sa sémiologie et ses modalités évolutives spontanées ou sous traitement. De multiples produits de synthèse sont désormais accessibles via internet : associé à la créativité des chimistes cela a participé à l’émergence de pratiques inédites allant du chemsex au purple drank. Les conduites addictives résultent d’un ensemble de facteurs individuels (vulnérabilités biologique et psychique) et contextuels (disponibilité et banalisation du toxique dans l’environnement). Les pathologies mentales autres sont des facteurs de vulnérabilité à la pathologie addictive, tout comme les conduites addictives peuvent révéler une pathologie émotionnelle ou psychotique. Le médecin se doit d’entendre l’impuissance du malade face au besoin irrépressible de consommer (craving) et proposer une thérapeutique qui peut être chimique (y compris traitement de substitution) et psychologique. Dans la majorité des cas, un accompagnement social s’impose pour corriger les effets désocialisants du trouble de l’usage de substances ou des comportements addictifs.

Can cocaine-induced neuroinflammation explain maladaptive cocaine-associated memories?

Persistent and intrusive memories define a number of psychiatric disorders, including posttraumatic stress disorder and substance use disorder. In the latter, memory for drug-paired cues plays a critical role in sustaining compulsive drug use as these are potent triggers of relapse. As with many drugs, cocaine-cue associated memory is strengthened across presentations as cues become reliable predictors of drug availability. Recently, the targeting of cocaine-associated memory through disruption of the reconsolidation process has emerged as a potential therapeutic strategy; reconsolidation reflects the active process by which memory is re-stabilized after retrieval. In addition, a separate line of work reveals that neuroinflammatory markers, regulated by cocaine intake, play a role in memory processes. Our review brings these two literatures together by summarizing recent findings on cocaine-associated reconsolidation and cocaine-induced neuroinflammation. We discuss the interactions between reconsolidation processes and neuroinflammation following cocaine use, concluding with a new perspective on treatment to decrease risk of relapse to cocaine use.

The effect of N-acetylcysteine and working memory training on neural mechanisms of working memory and cue reactivity in regular cocaine users

The current study investigated the combined effects of N-acetylcysteine and working memory (WM) training on behavioral and neural mechanisms of cue reactivity and WM in cocaine users in a randomized, double-blind design. Twenty-four of 38 cocaine-using men completed a 25-day treatment with either 2400 mg/day NAC or placebo. Both groups performed WM-training. During pre- and post-test lab-visits, neural mechanisms of cue reactivity and WM, and cue-induced craving and WM performance were assessed. Additionally, exploratory whole brain analyses were performed. Overall, the hypotheses were not confirmed, possibly due to small sample size, low WM-training adherence and/or ongoing substance use.

Medical and Dietary Uses of N-Acetylcysteine

N-acetylcysteine (NAC), a plant antioxidant naturally found in onion, is a precursor to glutathione. It has been used as a drug since the 1960s and is listed on the World Health Organization (WHO) Model List of Essential Medicines as an antidote in poisonings. There are numerous other uses or proposed uses in medicine that are still in preclinical and clinical investigations. NAC is also used in food supplements and cosmetics. Despite its abundant use, there are projections that the NAC global market will grow in the next five years; therefore, the purpose of this work is to provide a balanced view of further uses of NAC as a dietary supplement. Although NAC is considered a safe substance, the results among clinical trials are sometimes controversial or incomplete, like for many other antioxidants. More clinical trials are underway that will improve our understanding of NAC applicability.

Drug addiction: a curable mental disorder?

Drug addiction is a chronic, relapsing brain disorder. Multiple neural networks in the brain including the reward system (e.g., the mesocorticolimbic system), the anti-reward/stress system (e.g., the extended amygdala), and the central immune system, are involved in the development of drug addiction and relapse after withdrawal from drugs of abuse. Preclinical and clinical studies have demonstrated that it is promising to control drug addiction by pharmacologically targeting the addiction-related systems in the brain. Here we review the pharmacological targets within the dopamine system, glutamate system, trace amine system, anti-reward system, and central immune system, which are of clinical interests. Furthermore, we discuss other potential therapies, e.g., brain stimulation, behavioral treatments, and therapeutic gene modulation, which could be effective to treat drug addiction. We conclude that, although drug addiction is a complex disorder that involves complicated neural mechanisms and psychological processes, this mental disorder is treatable and may be curable by therapies such as gene modulation in the future.

N-Acetylcysteine for the Treatment of Psychiatric Disorders: A Review of Current Evidence

N-acetylcysteine, a sulphur-containing amino acid for the treatment of paracetamol overdose and chronic obstructive pulmonary disease, is a widely available off-the-shelf oral antioxidant supplement in many countries. With the potential to modulate several neurological pathways, including glutamate dysregulation, oxidative stress, and inflammation that can be beneficial to the brain functions, N-acetylcysteine is being explored as an adjunctive therapy for many psychiatric conditions. This narrative review synthesises and presents the current evidence from systematic reviews, meta-analyses, and latest clinical trials on N-acetylcysteine for addiction and substance abuse, schizophrenia, obsessive-compulsive and related disorders, and mood disorders. Good evidence exists to support the use of N-acetylcysteine as an adjunct treatment to reduce the total and negative symptoms of schizophrenia. N-acetylcysteine also appears to be effective in reducing craving in substance use disorders, especially for the treatment of cocaine and cannabis use among young people, in addition to preventing relapse in already abstinent individuals. Effects of N-acetylcysteine on obsessive-compulsive and related disorders, as well as on mood disorders, remain unclear with mixed reviews, even though promising evidence does exist. Larger and better-designed studies are required to further investigate the clinical effectiveness of N-acetylcysteine in these areas. Oral N-acetylcysteine is safe and well tolerated without any considerable adverse effects. Current evidence supports its use as an adjunctive therapy clinically for psychiatric conditions, administered concomitantly with existing medications, with a recommended dosage between 2000 and 2400 mg/day.

Clinical neuropsychiatric considerations regarding nonsubstance or behavioral addictions

Over the past several decades, non-substance-use behaviors like gambling, gaming, and sex have received greater consideration as possible foci of addictions. In this article, I will review the recent history and current status of non-substance or behavioral addictions. A main focus will involve gambling and gambling disorder, given that the latter is currently the sole non-substance addictive disorder described in the main text of the current (fifth) edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM-5). Internet gaming disorder, currently in the DSM-5 section addressing conditions that may need additional research, will also be considered, as will the concept of Internet addiction. Compulsive sexual behaviors (including problematic pornography use) will be considered, particularly with respect to how behavioral addictions may be considered in the forthcoming 11th edition of the International Classification of Diseases (ICD-11).

Normal glutathione levels in autopsied brain of chronic users of heroin and of cocaine

BACKGROUND

Animal studies suggest that exposure to either of the two widely used drugs of abuse, heroin or cocaine, causes depletion of the antioxidant, reduced glutathione, a hallmark of oxidative stress, in the brain. However, the relevance of the animal findings to the human is uncertain and clinical trials with the antioxidant GSH precursor n-acetylcysteine have produced mixed results in cocaine dependence.

METHODS

Our major objective was to compare glutathione levels, determined by an HPLC-coulometric procedure, in autopsied brain of chronic heroin (n = 11) and cocaine users (n = 9), who were positive for the drugs in the brain, to those of matched controls (n = 16). Six brain regions were examined, including caudate, hippocampus, thalamus and frontal, temporal and insular cortices.

RESULTS

In contrast to experimental animal findings, we found no statistically significant difference between mean levels of reduced or oxidized glutathione in the drug user vs. control groups. Moreover, no correlation was found between levels of drugs in the brain and those of glutathione.

CONCLUSIONS

Acknowledging the many generic limitations of an autopsied human brain study and the preliminary nature of the findings, our data nevertheless suggest that any oxidative stress caused by heroin or cocaine in chronic users of the drugs might not be sufficient to cause substantial loss of stores of glutathione in the human brain, at least during early withdrawal. These findings, requiring replication, might also have some relevance to future clinical trials employing glutathione supplement therapy as an anti-oxidative strategy in chronic users of the two abused drugs.

Reprint of The effect of N-acetylcysteine and working memory training on cocaine use, craving and inhibition in regular cocaine users: correspondence of lab assessments and Ecological Momentary Assessment

INTRODUCTION

Effective treatment for cocaine use disorder should dampen hypersensitive cue-induced motivational processes and/or strengthen executive control. Using a randomized, double-blind, placebo-controlled intervention, the primary aim of this study was to investigate the effect of N-Acetylcysteine (NAC) and working memory (WM)-training to reduce cocaine use and craving and to improve inhibition assessed in the laboratory and during Ecological Momentary Assessment (EMA). The second aim was to examine correspondence between laboratory and EMA data.

METHODS

Twenty-four of 38 cocaine-using men completed a 25-day intervention with 2400mg/day NAC or placebo and WM-training as well as two lab-visits assessing cocaine use, craving and inhibition (Stop Signal task). Additionally, cocaine use, craving and cognition (Stroop task) were assessed using EMA during treatment, with 26 participants completing 819 assessments.

RESULTS

Cocaine problems according to the Drug Use Disorder Identification Test (DUDIT) decreased more after NAC than after placebo, and the proportion of cocaine-positive urines at lab-visit 2 was lower in the NAC group. No NAC effects were found on craving. For cocaine use and craving, results from the lab data were generally similar to EMA results. NAC also showed some effects on cognitive control: improved inhibition assessed with the Stop Signal task in the lab, and decreased classic Stroop performance during EMA. There were no significant effects of number of completed WM-training sessions.

CONCLUSIONS

Overall this study revealed mixed findings regarding the treatment of cocaine use disorders with NAC and WM-training. The effect of NAC on inhibition should be further investigated.

The effect of N-acetylcysteine and working memory training on cocaine use, craving and inhibition in regular cocaine users: correspondence of lab assessments and Ecological Momentary Assessment

INTRODUCTION

Effective treatment for cocaine use disorder should dampen hypersensitive cue-induced motivational processes and/or strengthen executive control. Using a randomized, double-blind, placebo-controlled intervention, the primary aim of this study was to investigate the effect of N-Acetylcysteine (NAC) and working memory (WM)-training to reduce cocaine use and craving and to improve inhibition assessed in the laboratory and during Ecological Momentary Assessment (EMA). The second aim was to examine correspondence between laboratory and EMA data.

METHODS

Twenty-four of 38 cocaine-using men completed a 25-day intervention with 2400mg/day NAC or placebo and WM-training as well as two lab-visits assessing cocaine use, craving and inhibition (Stop Signal task). Additionally, cocaine use, craving and cognition (Stroop task) were assessed using EMA during treatment, with 26 participants completing 819 assessments.

RESULTS

Cocaine problems according to the Drug Use Disorder Identification Test (DUDIT) decreased more after NAC than after placebo, and the proportion of cocaine-positive urines at lab-visit 2 was lower in the NAC group. No NAC effects were found on craving. For cocaine use and craving, results from the lab data were generally similar to EMA results. NAC also showed some effects on cognitive control: improved inhibition assessed with the Stop Signal task in the lab, and decreased classic Stroop performance during EMA. There were no significant effects of number of completed WM-training sessions.

CONCLUSIONS

Overall this study revealed mixed findings regarding the treatment of cocaine use disorders with NAC and WM-training. The effect of NAC on inhibition should be further investigated.

The effect of N-acetylcysteine or bupropion on methamphetamine self-administration and methamphetamine-triggered reinstatement of female rats

N-acetylcysteine and bupropion are two promising candidate medications for treatment of substance use disorder. The effects of N-acetylcysteine or bupropion on methamphetamine self-administration of female rats are not well understood. To fill this gap, this study assessed the effects of N-acetylcysteine (0, 30, 60, or 120 mg/kg) and bupropion (0, 10, 30, and 60 mg/kg) on methamphetamine self-administration of female rats across the natural estrous cycle. Following a completed dose-response curve, responding for methamphetamine self-administration was extinguished and the effects of N-acetylcysteine or bupropion on methamphetamine-triggered reinstatement was evaluated in separate experiments. N-acetylcysteine did not decrease responding maintained by methamphetamine or methamphetamine-triggered reinstatement. Bupropion significantly decreased methamphetamine self-administration and methamphetamine-triggered reinstatement in female rats with highest dose (60 mg/kg) also significantly decreasing general chamber activity. In a companion experiment, testing the effect of bupropion on responding maintained by sucrose, we confirmed non-specificity of bupropion's effects as bupropion also decreased responding for sucrose. Considered together, our findings suggest that while N-acetylcysteine has considerable promise for treatment of cocaine dependence it may not generalize to other stimulants like methamphetamine. Furthermore, although bupropion has been shown to effectively decrease methamphetamine self-administration, and presently methamphetamine-triggered reinstatement, its locomotor and reward suppressing effects warrant further investigation including both sexes.

Effects of the Usage of l-Cysteine (l-Cys) on Human Health

This review summarizes recent knowledge about the use of the amino acid l-Cysteine (l-Cys) through diet, nutritional supplements or drugs with the aim to improve human health or treat certain diseases. Three databases (PubMed, Scopus, and Web of Science) and different keywords have been used to create a database of documents published between 1950 and 2017 in scientific journals in English or Spanish. A total of 60,885 primary publications were ultimately selected to compile accurate information about the use of l-Cys in medicine and nutritional therapies and to identify the reported benefits of l-Cys on human health. The number of publications about the use of l-Cys for these purposes has increased significantly during the last two decades. This increase seems to be closely related to the rise of nutraceutical industries and personalized medicine. The main evidence reporting benefits of l-Cys usage is summarized. However, the lack of accurate information and studies based on clinical trials hampers consensus among authors. Thus, the debate about the role and effectiveness of supplements/drugs containing l-Cys is still open.

Glutamate Transport: A New Bench to Bedside Mechanism for Treating Drug Abuse

Drug addiction has often been described as a "hijacking" of the brain circuits involved in learning and memory. Glutamate is the principal excitatory neurotransmitter in the brain, and its contribution to synaptic plasticity and learning processes is well established in animal models. Likewise, over the past 20 years the addiction field has ascribed a critical role for glutamatergic transmission in the development of addiction. Chronic drug use produces enduring neuroadaptations in corticostriatal projections that are believed to contribute to a maladaptive deficit in inhibitory control over behavior. Much of this research focuses on the role played by ionotropic glutamate receptors directly involved in long-term potentiation and depression or metabotropic receptors indirectly modulating synaptic plasticity. Importantly, the balance between glutamate release and clearance tightly regulates the patterned activation of these glutamate receptors, emphasizing an important role for glutamate transporters in maintaining extracellular glutamate levels. Five excitatory amino acid transporters participate in active glutamate reuptake. Recent evidence suggests that these glutamate transporters can be modulated by chronic drug use at a variety of levels. In this review, we synopsize the evidence and mechanisms associated with drug-induced dysregulation of glutamate transport. We then summarize the preclinical and clinical data suggesting that glutamate transporters offer an effective target for the treatment of drug addiction. In particular, we focus on the role that altered glutamate transporters have in causing drug cues and contexts to develop an intrusive quality that guides maladaptive drug seeking behaviors.