Naltrexone: A Pan-Addiction Treatment?

Neuroprotective effects of naltrexone in a mouse model of post-traumatic seizures

Traumatic Brain Injury (TBI) induces neuroinflammatory response that can initiate epileptogenesis, which develops into epilepsy. Recently, we identified anti-convulsive effects of naltrexone, a mu-opioid receptor (MOR) antagonist, used to treat drug addiction. While blocking opioid receptors can reduce inflammation, it is unclear if post-TBI seizures can be prevented by blocking MORs. Here, we tested if naltrexone prevents neuroinflammation and/or seizures post-TBI. TBI was induced by a modified Marmarou Weight-Drop (WD) method on 4-week-old C57BL/6J male mice. Mice were placed in two groups: non-telemetry assessing the acute effects or in telemetry monitoring for interictal events and spontaneous seizures both following TBI and naltrexone. Molecular, histological and neuroimaging techniques were used to evaluate neuroinflammation, neurodegeneration and fiber track integrity at 8 days and 3 months post-TBI. Peripheral immune responses were assessed through serum chemokine/cytokine measurements. Our results show an increase in MOR expression, nitro-oxidative stress, mRNA expression of inflammatory cytokines, microgliosis, neurodegeneration, and white matter damage in the neocortex of TBI mice. Video-EEG revealed increased interictal events in TBI mice, with 71% mice developing post-traumatic seizures (PTS). Naltrexone treatment ameliorated neuroinflammation, neurodegeneration, reduced interictal events and prevented seizures in all TBI mice, which makes naltrexone a promising candidate against PTS, TBI-associated neuroinflammation and epileptogenesis in a WD model of TBI.

Current Understanding of Compulsive Sexual Behavior Disorder and Co-occurring Conditions: What Clinicians Should Know about Pharmacological Options

Compulsive sexual behavior disorder (CSBD) has recently been recognized as a psychiatric disorder. Pharmacological treatments for CSBD have received little study and thus have limited empirical support. The main objective of the present work is to review existing literature on the efficacy of different drugs on the symptomatology of CSBD, including the subtype of problematic pornography use (PPU). The main pharmacological approaches to treating CSBD have included opioid antagonists (naltrexone and nalmefene), selective serotonin reuptake inhibitors (paroxetine, citalopram, fluoxetine, and sertraline), mood stabilizers (topiramate), tricyclic antidepressants (clomipramine), serotonin antagonist and reuptake inhibitors (nefazodone), and N-acetylcysteine. Since people with CSBD may experience different co-occurring disorders, these should be considered when choosing the best pharmacological treatment. Pharmacological therapy for CSBD/PPU has been suggested as an adjunct to psychological therapies, which, for the moment, have the most empirical evidence. However, to evaluate the efficacy of most of the drugs presented in this narrative review, data to date have only been available from case studies. Thus, empirical support is scant and generalizability of results is limited, highlighting the need for more research in this area.

Pharmacological management of gambling disorder: an update of the literature

INTRODUCTION

Gambling disorder (GD) is a mental health condition characterized by persistent and problematic betting behavior. GD generates distress and impairment, and treatment options include psychological and pharmacological interventions.

AREAS COVERED

This narrative review explores existing pharmacological treatments for GD. The following classes of medications were considered: opioid-receptor antagonists (e.g. naltrexone and nalmefene), serotonin reuptake inhibitors (e.g. fluvoxamine, paroxetine, sertraline, escitalopram, and citalopram), glutamatergic agents (e.g. N-acetylcysteine (NAC), acamprosate, and memantine), mood stabilizers (e.g. topiramate, carbamazepine, lithium), and other medications (e.g. modafinil, nefazodone, olanzapine, haloperidol, tolcapone, and bupropion).

EXPERT OPINION

Due to the limitations of the studies reviewed, solid conclusions regarding the optimal choice of pharmacotherapy for individuals with GD are challenging to draw at this time. Despite some medications, such as naltrexone and nalmefene, showing promising results, efficacy has varied across studies. The review highlights current gaps/limitations, including small sample sizes, limited diversity in participant demographics, the need for exploring different gambling subtypes and treatment responses, high placebo response rates, lack of longer-term longitudinal information, limited investigation of neurobiological correlates and co-occurring disorders, and the importance of implementation research. Further research is needed to address these gaps and explore additional medications, as well as interventions like neuromodulation.

Treatment Approaches for Problematic Pornography Use: A Systematic Review

Problematic pornography use (PPU) is an emerging condition associated with several negative psychological and sexual outcomes. This study aimed to systematically review treatment approaches for PPU. Potentially eligible studies were searched for in PubMed/MEDLINE, Embase, PsycINFO, and Web of Science up to April 1, 2023. The quality of the evidence was assessed with the use of the Joanna Briggs Institute's checklists, the Cochrane risk-of-bias tools, and the GRADE approach. A total of 8936 references were retrieved, and 28 studies were included in the systematic review (n = 500 participants). Included studies were case reports (k = 16), case series (k = 1), quasi-experimental investigations (k = 7), and randomized clinical trials (k = 4). The majority of included studies presented overall low quality and significant risk of bias, with all interventions receiving a low or very low rating according to the GRADE approach. Most studies investigated psychological interventions, with the predominance of second and third wave cognitive behavioral therapy interventions. Pharmacological treatments included opioid antagonists (naltrexone in most cases) and antidepressants, while one study investigated a protocol that included rTMS. Several investigations described the combination of psychological and pharmacological approaches. Most studies did not report on side effects, with online and self-help interventions presenting significant issues in terms of treatment adherence. Even though there are promising options that may have efficacy for the treatment of patients with PPU, the literature in the topic still presents significant limitations that compromise the reaching of more definitive conclusions.

Screening and Treatment for Co-occurring Gambling and Substance Use: A Scoping Review

There is a high prevalence of gambling harms co-occurring with substance use harms. Where harms are co-occurring, they may be experienced as more severe. However, there is little evidence that services are systematically screening for such co-occurring harms in treatment-seeking populations. Furthermore, treatment modalities remain relatively under-developed, with treatment usually addressing only one source of harm.This scoping review looks at the current literature on screening and therapeutic interventions for co-occurring gambling and substance use harms to understand how co-occurring harms may be managed in a treatment setting. It draws together available data on the intersections of substance use harms and gambling related harms, in a treatment context.This research identifies a range of potentially useful validated tools for clinicians in substance use treatment settings to screen for gambling harms. For workers in gambling treatment settings who are seeking validated tools to screen for co-occurring substance use harms, the literature provides less guidance.The validated toolbox of therapeutic interventions for those experiencing co-occurring substance use and gambling harms is relatively sparse. Psychosocial interventions appear to offer the best outcomes on gambling measures for those experiencing co-occurring substance use harms. Further research is needed to establish the benefits of different combinations of treatment and treatment types in achieving reductions across both substance use and gambling harms, when these harms are experienced concurrently.

Treatment of Acute Pain in Patients on Naltrexone: A Narrative Review

PURPOSE OF REVIEW

The tissue damage and trauma associated with surgery almost always result in acute postoperative pain. The intensity of postoperative pain can range from mild to severe. Naltrexone is suitable for patients who do not wish to be on an agonist treatment such as methadone or buprenorphine. However, naltrexone has been shown to complicate postoperative pain management.

RECENT FINDINGS

Multiple studies have found that the use of naltrexone can increase the opioid requirement for postoperative pain control. Other modalities exist that can help outside of opioids such as ketamine, lidocaine/bupivacaine, duloxetine, and non-pharmacological management can help manage pain. Multimodal pain regiments should also be employed in patients. In addition to traditional methods for postoperative pain management, other methods of acute pain control exist that can help mitigate opioid dependence and help control pain in patients who use naltrexone for their substance use disorders.

Is there a therapeutic potential in combining bupropion and naltrexone in schizophrenia?

INTRODUCTION

A sustained-release tablet composed of a combination of the dopamine and norepinephrine reuptake inhibitor bupropion (BUP) and the µ-opioid receptor antagonist naltrexone (NAT) is marketed under the brand name Contrave by Orexigen Therapeutics for appetite control. Minimal literature is available regarding the use of combination bupropion and naltrexone (BUPNAT) in individuals with schizophrenia.

AREAS COVERED

In this review, we propose a theoretical model where BUPNAT may have a therapeutic effect in the treatment of schizophrenia. We explore the pathways targeted by the constituent drugs BUP and NAT and summarize the literature on their efficacy and possible adverse effects. We then look at the potential use of BUPNAT in schizophrenia.

EXPERT OPINION

Research has hinted that BUP's dopaminergic properties affect the same striatal pathways involved in schizophrenia. NAT, via opioid receptor antagonism, indirectly increases striatal dopamine release by disinhibiting nicotinic acetylcholine receptors. As such, we hypothesize that BUPNAT can have a therapeutic effect in schizophrenia, particularly on negative symptoms. We also suggest that it may ameliorate comorbidities frequently seen in this group of patients, including obesity, smoking, and substance use. Further research and clinical data are needed to elucidate the potential clinical benefits of BUPNAT in the treatment of schizophrenia.

Naltrexone promotes mechanical allodynia in humans and rats

Mechanical allodynia has been studied in chronic naltrexone-treated people (N.T.P.) and rats (N.T.R.). After persistent naltrexone administration, patients acquired static and dynamic mechanical allodynia, as measured by von Frey filament (vFf) and brush stimulations. Pregabalin and levodopa administrations in N.T.P. significantly reduced allodynic behaviour, albeit these molecules did not completely stop it. As evidenced by the deployment of the vFf, subchronic treatment with Naltrexone delivered peripherally or intrathecally induced allodynic behaviour in rats. Increased expressions of two pain markers, pERK1/2 and PKCγ, in the spinal dorsal horn laminae were associated with naltrexone-induced allodynic behaviour. After vFf stimulation, pERK1/2 expression was substantially higher (p < 0.001) in superficial spinal dorsal horn laminae than in non-stimulated or naive non-stimulated rats. In addition, when compared to control rats, N.T.R. showed a substantial (p < 0.001) increase in PKCγ expression. PKCγ expression was found to be strong in lamina IIi and laminae III-IV. A cellular mechanism is proposed for the naltrexone effect. In both people and rats, Naltrexone induces static mechanical allodynia, according to this study.

Intranasal as needed naloxone in the treatment of gambling disorder: A randomised controlled trial

BACKGROUND

Gambling disorder (GD) is a global phenomenon affecting millions of people. GD can result in severe social and financial difficulties and efficacious treatments are warranted. Psychosocial treatments form the basis of treatment. Opioid antagonists (OAs) have however shown promise in previous studies. In a recent imaging study intranasal naloxone was found to rapidly and fully occupy brain μ-opioid receptors. This trial investigates the effect and safety of as needed naloxone in the treatment of gambling disorder.

METHODS

This was a 12-week double blind, randomised control trial comparing intranasal naloxone to placebo. The primary endpoint was gambling urge measured by the Gambling symptom Assessment Scale (G-SAS). Secondary outcome measures were gambling severity measures (PGSI) as well as quality of life (WHO:EUROHIS-8), alcohol consumption (AUDIT), depression (MARDS) and internet use (IDS-9SF). In addition, safety of treatment was assessed. Both treatment groups received psychosocial support.

RESULTS

126 participants were randomised to treatment groups in a 1:1 ratio. 106 patients completed the study. Gambling urge (GSAS) and other gambling related measured improved in both groups, but no statistically significant difference could be found. Intranasal naloxone was well tolerated, no subjects discontinued the study due to adverse events. No serious adverse drug reactions were observed.

CONCLUSIONS

This study found no difference between the as-needed administration of intranasal naloxone and placebo in reducing gambling urge in persons with GD. Intranasal naloxone was safe and well tolerated.

Assessing Naltrexone Prescribing and Barriers to Initiation for Alcohol Use Disorder: A Multidisciplinary, Multisite Survey

OBJECTIVE

To survey barriers in prescribing naltrexone for alcohol use disorder.

METHODS

A 12-question survey related to naltrexone prescribing patterns, perceptions, and knowledge was sent to 770 prescribers in the departments of internal medicine, family medicine, and psychiatry across a health system with sites in Arizona, Florida, and Minnesota.

RESULTS

Responses were obtained and included for 146/770 prescribers (19.0% response rate). Most respondents were in the department of internal medicine (n = 94, 64.4%), but the departments of psychiatry (n = 22, 15.1%) and family medicine (n = 30, 20.5%) were also represented. Only 34 (23.3%) respondents indicated they had prescribed naltrexone in the previous 3 months. The most common reasons for not prescribing naltrexone were "unfamiliarity with naltrexone for treatment of alcohol use disorder" and "patients do not have appropriate follow-up or are not in a formal treatment program." Compared with those representing internal/family medicine, psychiatry respondents were more likely to prescribe naltrexone and answer knowledge questions correctly.

CONCLUSION

In this survey among primarily non-addiction-trained prescribers, a disparity was shown for prescribing naltrexone and in knowledge barriers between staff in internal/family medicine and psychiatry. There exist opportunities for education and quality improvement that promote the prescribing of naltrexone for alcohol use disorder by non-addiction specialists.

Understanding the genetics and neurobiological pathways behind addiction (Review)

The hypothesis issued by modern medicine states that many diseases known to humans are genetically determined, influenced or not by environmental factors, which is applicable to most psychiatric disorders as well. This article focuses on two pending questions regarding addiction: Why do some individuals become addicted while others do not? along with Is it a learned behavior or is it genetically predefined? Recent data suggest that addiction is more than repeated exposure, it is the synchronicity between intrinsic factors (genotype, sex, age, preexisting addictive disorder, or other mental illness), extrinsic factors (childhood, level of education, socioeconomic status, social support, entourage, drug availability) and the nature of the addictive agent (pharmacokinetics, path of administration, psychoactive properties). The dopamine-mesolimbic motivation-reward-reinforcement cycle remains the most coherent physiological theory in addiction. While the common property of addictive substances is that they are dopamine-agonists, each class has individual mechanisms, pharmacokinetics and psychoactive potentials.

Successive treatment with naltrexone induces epithelial-mesenchymal transition and facilitates the malignant biological behaviors of bladder cancer cells

Naltrexone is widely used for alleviating opioid-related side effects in cancer patients. However, the effects of naltrexone on cancer progression are controversial in the literature. The present study was carried out to investigate the effects of successive treatment with clinically relevant doses of naltrexone on the malignant biological behaviors of bladder cancer cells. The human bladder cancer T24 cells and mouse bladder cancer MB49 cells were treated with naltrexone. Cell proliferation, migration, and invasion abilities were analyzed. Morphological changes of the cells were confirmed by F-actin immunofluorescence staining. Epithelial-mesenchymal transition (EMT)-related markers and transcriptional factors, as well as activation of the phosphatidylinositol 3 kinase (PI3K)/AKT signaling pathway, were analyzed. Results showed that, compared with the control group, successive treatment with naltrexone significantly promoted the proliferation and decreased the apoptosis of bladder cancer cells, together with increase in cell migration and invasion ability. Continuous treatment with naltrexone also significantly reduced the expression of epithelial markers (E-cadherin and cytokeratin 19), increased the expression of mesenchymal markers (N-cadherin and vimentin) and EMT-inducing transcription factors (Snail and Slug), and further shifted the morphological phenotype of bladder cancer cells to a mesenchymal phenotype. The PI3K/AKT signaling pathway was activated by successive treatment with naltrexone. Notably, incubation with the specific PI3K inhibitor LY294002 together with naltrexone reversed the naltrexone-induced EMT progression. In conclusion, successive treatment with naltrexone may be favorable for the progression of bladder tumors by activating the PI3K/AKT signaling pathway and inducing EMT. Long-term exposure to naltrexone should be used cautiously in patients with bladder cancer.

Bupropion and Naltrexone in Methamphetamine Use Disorder

BACKGROUND

The use of naltrexone plus bupropion to treat methamphetamine use disorder has not been well studied.

METHODS

We conducted this multisite, double-blind, two-stage, placebo-controlled trial with the use of a sequential parallel comparison design to evaluate the efficacy and safety of extended-release injectable naltrexone (380 mg every 3 weeks) plus oral extended-release bupropion (450 mg per day) in adults with moderate or severe methamphetamine use disorder. In the first stage of the trial, participants were randomly assigned in a 0.26:0.74 ratio to receive naltrexone-bupropion or matching injectable and oral placebo for 6 weeks. Those in the placebo group who did not have a response in stage 1 underwent rerandomization in stage 2 and were assigned in a 1:1 ratio to receive naltrexone-bupropion or placebo for an additional 6 weeks. Urine samples were obtained from participants twice weekly. The primary outcome was a response, defined as at least three methamphetamine-negative urine samples out of four samples obtained at the end of stage 1 or stage 2, and the weighted average of the responses in the two stages is reported. The treatment effect was defined as the between-group difference in the overall weighted responses.

RESULTS

A total of 403 participants were enrolled in stage 1, and 225 in stage 2. In the first stage, 18 of 109 participants (16.5%) in the naltrexone-bupropion group and 10 of 294 (3.4%) in the placebo group had a response. In the second stage, 13 of 114 (11.4%) in the naltrexone-bupropion group and 2 of 111 (1.8%) in the placebo group had a response. The weighted average response across the two stages was 13.6% with naltrexone-bupropion and 2.5% with placebo, for an overall treatment effect of 11.1 percentage points (Wald z-test statistic, 4.53; P<0.001). Adverse events with naltrexone-bupropion included gastrointestinal disorders, tremor, malaise, hyperhidrosis, and anorexia. Serious adverse events occurred in 8 of 223 participants (3.6%) who received naltrexone-bupropion during the trial.

CONCLUSIONS

Among adults with methamphetamine use disorder, the response over a period of 12 weeks among participants who received extended-release injectable naltrexone plus oral extended-release bupropion was low but was higher than that among participants who received placebo. (Funded by the National Institute on Drug Abuse and others; ADAPT-2 ClinicalTrials.gov number, NCT03078075.).

Monitoring and Improving Naltrexone Adherence in Patients with Substance Use Disorder

OBJECTIVE

Naltrexone is an opioid antagonist used for the treatment of patients with opioid use disorder and alcohol use disorder. This population often presents problems of follow-up and therapeutic efficacy related to adherence to treatment. The purpose of our study is to provide an exhaustive summary of the current evidence regarding naltrexone adherence in people with substance use disorders and to identify possible variables that may influence adherence to naltrexone.

METHODS

Two searches were performed in bibliographic databases (PubMed, Embase), and studies included in the systematic review were those published from January 1, 2011 to September 2020, with participants over 18 years of age, evaluating treatment with naltrexone in alcohol use disorder and opioid use disorder. From the total of 133 articles initially selected, 36 were included and analyzed in the systematic review.

RESULTS

Naltrexone has not demonstrated superiority over other available treatments in terms of adherence and abstinence, although reinforcement systems have obtained favorable results as an additional strategy to improve adherence.

CONCLUSION

It is necessary to study other psychosocial variables involved in improving adherence, in addition to taking patient preferences into account in order to improve the external validity of the results.

A Case-Control Study on Behavioral Addictions and Neurocognition: Description of the BANCO and BANCO2 Protocols

INTRODUCTION

Only two behavioral addictions (BAs) are currently recognized in international classifications (gambling disorder: GbD; gaming disorder: GmD), while some of them await further investigation (food addiction: FA; sexual addiction: SA). Neurocognitive functioning is considered a risk factor for BAs. Research is quite abundant for GbD and highlights specific deficits in several cognitive functions. Nevertheless, grey areas still exist. The aim of this research programme is to investigate the neurocognitive profiles of patients presenting with various BAs and to establish parallels between different forms of BA to achieve a common addiction concept.

METHODS AND ANALYSIS

This research program is composed of two studies sharing the same methodology but focusing on different samples: the BANCO study aims to include 30 individuals with a GbD, whereas the BANCO2 study aims to include 30 individuals with a GmD, 30 with a SA, and 30 with a FA. Moreover, for each BA group, 30 healthy controls will be recruited, matched by sex, age and education level. Several cognitive tasks will be completed by participants. Cue reactivity and physiological responses, as well as clinical data regarding addiction characteristics and personality, will also be investigated. A composite score based on the cognitive tasks will be computed using principal component analysis (PCA). Overall cognitive performance and detailed performance on the different cognitive tasks will be compared between individuals with BAs and their matched healthy controls using linear models with random effects. Comparisons will also be made between BA groups to investigate specific alterations associated with each disorder.

DISCUSSION

The results of this research programme will impact both research and clinical areas by (i) providing new knowledge for discussions regarding the inclusion of BAs under the spectrum of addictive disorders; (ii) improving understanding of addiction mechanisms in general; (iii) providing clarity in the grey areas in neurocognitive research on BAs and improving the understanding of less studied BAs, (iv) guiding clinicians to propose therapeutic alternatives and complementary programmes.

TRIAL REGISTRATION

BANCO study (ClinicalTrials.gov NCT03202290); BANCO2 study (ClinicalTrials.gov NCT03967418).

Acceptability and efficacy of naltrexone for criminal justice-involved individuals with opioid use disorder: a systematic review and meta-analysis

BACKGROUND AND AIMS

Criminal justice-involved individuals carry a disproportionately higher burden of opioid use disorder (OUD) than those not involved with the criminal justice system, and are often unable to access opioid agonist therapies such as methadone and buprenorphine. The opioid receptor antagonist naltrexone (NTX) is effective for the prevention of relapse to OUD and may be more acceptable in criminal justice settings. The objectives of this review were to: (1) provide an overall summary effect across studies for the efficacy and acceptability of oral and injectable NTX for the treatment of OUD among criminal justice-involved individuals and (2) examine systematic variations in study results to explain heterogeneity among study-specific effects.

METHODS

Systematic review and meta-analysis of 1045 patients across 11 studies (10 randomized controlled trials, one quasi-experimental study). All available outcomes were pooled using random-effects meta-analysis. Subgroup analyses were conducted for oral and injectable naltrexone; meta-regression analyses were conducted for socio-demographic and study-level characteristics.

RESULTS

NTX improved retention in treatment [risk ratio (RR) = 1.31; 95% confidence interval (CI) = 1.05, 1.63], reduced rates of re-incarceration (RR = 0.70, 95% CI = 0.54-0.92), reduced opioid relapse (RR = 0.63, 95% CI = 0.53-0.76) and improved opioid abstinence (RR = 1.38, 95% CI = 1.16-1.65). While NTX was associated with a greater burden of adverse events overall (RR = 1.49, 95% CI = 1.13-1.95), the findings were inconclusive as to whether or not a difference was present for the number of serious adverse events or overdoses.

CONCLUSIONS

Naltrexone appears to be efficacious and acceptable for the treatment of opioid use disorder among criminal justice-involved individuals; however, the risk for adverse events must be weighed against the potential benefits.

Naltrexone Use in Treating Hypersexuality Induced by Dopamine Replacement Therapy: Impact of OPRM1 A/G Polymorphism on Its Effectiveness

Hypersexuality is a well-known adverse side effect of dopamine replacement therapy (DRT), and anti-craving drugs could be an effective therapeutic option. Our aim was to update the knowledge on this issue, particularly on the influence of an Opioid Receptor Mu 1 (OPRM1) genetic polymorphism. A systematic review was conducted according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement. We also analyzed a case of iatrogenic hypersexuality that occurred in a patient treated with DRT. An analysis of the OPRM1 gene was performed on said patient. Our search identified 597 publications, of which only 7 were included in the final data synthesis. All seven publications involved naltrexone use. Five of them were case reports. None of the publications mentioned DRT side effects, nor did they report genetic data. Regarding our case report, the introduction of naltrexone corresponded with the resolution of the patient’s hypersexuality. Moreover, the patient carried the A/G genotype, which has been reported to be associated with a stronger response to naltrexone for patients with an alcohol use disorder. Although studies are inconclusive so far, naltrexone could be an interesting therapeutic option for resistant hypersexuality due to DRT. Carrying the A/G genotype could help explain a good response to treatment.

Case Study: Naltrexone for the Treatment of Nitrous Oxide Use

BACKGROUND

Using a clinical case example, we describe and discuss the use of oral naltrexone as a novel treatment strategy for nitrous oxide use. Nitrous oxide is an inhalant drug that is readily available and legally obtained. Though frequency of reported cases of substance use disorder for nitrous oxide is low, previous case reports have described severe neurological and psychiatric harms associated with chronic use. Despite this, evidence for pharmacotherapy is currently lacking. Clinical studies have shown variable efficacy for naltrexone across a number of substances including alcohol, nicotine, and stimulants.

CASE

We present here a case of a 41-year-old man with a substance use disorder for nitrous oxide who was reportedly using of up to four hundred 8 g canisters of nitrous oxide per day. Oral naltrexone was initiated at 50 mg daily in an attempt to decrease cravings. The dose was subsequently titrated to 100 mg daily, resulting in a decrease in nitrous oxide use to less than sixty 8 g canisters per week over a 1-month timeframe.

DISCUSSION

Previous literature surrounding naltrexone provides both a plausible mechanism of action for craving reduction as well as a precedent for its use across a number of substances. To our knowledge, use of naltrexone for nitrous oxide use has not been previously described. While clinical studies are currently lacking, this case highlights naltrexone as a possible treatment strategy for nitrous oxide use, with potential to reduce significant harms associated with chronic use.

Managing Pain in the Setting of Opioid Use Disorder

SPECIFIC CLINICAL ISSUE

Healthcare providers are challenged with managing pain and minimizing morbidity and mortality associated with opioid use disorder.

MAJOR PRACTICE RECOMMENDATIONS BASED ON BEST EVIDENCE

The purpose of this article is to guide acute and ambulatory care clinicians in managing pain in patients with opioid use disorder. Included in this article is a review of medications used for opioid use disorder, a discussion of the management of patients with active opioid use disorder and acute or chronic pain, and a discussion of the management of acute and chronic pain in people in recovery both on and off medications for opioid use disorder.

Opioid receptors: drivers to addiction?

Drug addiction is a worldwide societal problem and public health burden, and results from recreational drug use that develops into a complex brain disorder. The opioid system, one of the first discovered neuropeptide systems in the history of neuroscience, is central to addiction. Recently, opioid receptors have been propelled back on stage by the rising opioid epidemics, revolutions in G protein-coupled receptor research and fascinating developments in basic neuroscience. This Review discusses rapidly advancing research into the role of opioid receptors in addiction, and addresses the key questions of whether we can kill pain without addiction using mu-opioid-receptor-targeting opiates, how mu- and kappa-opioid receptors operate within the neurocircuitry of addiction and whether we can bridge human and animal opioid research in the field of drug abuse.

The Use of Naltrexone in Dermatology. Current Evidence and Future Directions

Naltrexone is a competitive opioid receptor antagonist approved as supportive treatment in alcohol dependence and opioid addiction. At a dose of 50-100 mg daily, naltrexone is used off-label in dermatology for the treatment of trichotillomania and different types of pruritus. At a dose as low as 1- 5 mg per day, naltrexone demonstrates immunomodulatory action i.e. modulates Toll-like receptors signaling, decreases release of proinflammatory cytokines (tumor necrosis factor, interleukin-6, interleukin- 12), inhibits T lymphocyte proliferation, down-regulates the expression of chemokine receptors and adhesion molecules. The efficacy of standard and low doses of naltrexone in a variety of dermatological disorders has been reported. These include diseases such as familial benign chronic pemphigus (Hailey-Hailey disease), dermatomyositis, systemic sclerosis, psoriasis and lichen planopilaris. Optimistic preliminary findings, low cost of therapy and good tolerance make naltrexone a promising alternative therapy or adjunct drug in dermatology.

Online Porn Addiction: What We Know and What We Don't-A Systematic Review

In the last few years, there has been a wave of articles related to behavioral addictions; some of them have a focus on online pornography addiction. However, despite all efforts, we are still unable to profile when engaging in this behavior becomes pathological. Common problems include: sample bias, the search for diagnostic instrumentals, opposing approximations to the matter, and the fact that this entity may be encompassed inside a greater pathology (i.e., sex addiction) that may present itself with very diverse symptomatology. Behavioral addictions form a largely unexplored field of study, and usually exhibit a problematic consumption model: loss of control, impairment, and risky use. Hypersexual disorder fits this model and may be composed of several sexual behaviors, like problematic use of online pornography (POPU). Online pornography use is on the rise, with a potential for addiction considering the "triple A" influence (accessibility, affordability, anonymity). This problematic use might have adverse effects in sexual development and sexual functioning, especially among the young population. We aim to gather existing knowledge on problematic online pornography use as a pathological entity. Here we try to summarize what we know about this entity and outline some areas worthy of further research.

Pharmacological and Behavioral Treatment of Opioid Use Disorder

Objective:

Opioid use disorder (OUD) in the United States has surged, with an estimated 2.5 million needing treatment. The aim of this article is to provide a clinical overview of the key pharmacological and behavioral treatments for OUD.

Methods:

A nonsystematic review of the literature was conducted to investigate OUD treatments, including their mechanism of action, efficacy, clinical guidelines in the United States, and consideration of frequently occurring comorbid conditions.

Results:

Food and Drug Administration (FDA)–approved pharmacotherapies for OUD include methadone, buprenorphine, and naltrexone, each of which has different actions on opioid receptors. Although these medications all show efficacy in some dosages and formulations, barriers to accessibility may be most pronounced for methadone, whereas treatment retention poses greater challenges for naltrexone and, to a lesser extent, buprenorphine. Lofexidine, an α₂‐adrenergic agonist, has recently been approved by the FDA for treatment of opioid withdrawal symptoms. OUD is commonly treated with medication‐assisted treatment (MAT), which offers pharmacotherapy in the context of counseling and/or behavioral treatments. Behavioral therapies, rarely offered as stand‐alone treatments for OUD, are generally used in the context of MAT, in structured settings or to prevent relapse after detoxification and stabilization. The aim of behavioral interventions is to improve medication compliance and target problems not addressed with medication alone. Individuals with OUD commonly have other comorbid psychiatric and substance use conditions, which are not exclusionary for initiating MAT but should be carefully evaluated and monitored because they may reduce treatment effectiveness.

Conclusions:

MAT is the first‐line treatment for patients with OUD and should be provided in combination with behavioral interventions. Treatment retention remains challenging in this population. Future studies should focus on approaches that will serve the complex needs of patients with OUD, including those with comorbid psychiatric and substance use conditions.

Opioid Antagonists for Pharmacological Treatment of Gambling Disorder: Are they Relevant?

Background:

To date, no drugs have been approved for gambling disorder. Numerous publications have described the value of opioid antagonists. Indeed, the mesocorticolimbic dopaminergic pathway has been suggested as the underlying cause of reward-seeking behaviour, and it is modulated by the opioid system.

Objective:

This study aims to evaluate the relevance of opioid antagonists for treating GD.

Method:

A systematic literature review was conducted. A search of the PubMed electronic database, PsycINFO and the Cochrane Systematic Review Database without any limits was performed.

Results:

There is little information concerning the effects of opioid antagonists on GD. The total search with “nalmefene and gambling” without any limits revealed only 11 articles. The search with “naltrexone and gambling” without any limits gener-ated 47 articles. Nevertheless, the best available data support the use of opioid antagonists, particularly in individuals with a history of alcohol use disorder or strong gambling urges.

Conclusion:

Future trials are still needed. Indeed, opioid antagonists effectiveness has been investigated in only a limited number of patients, clinical trials do not reflect the heterogeneity of GD and there is little knowledge of the predictive factors of response to treatments. Moreover, differential affinity to nalmefene for kappa receptors may be associated with a particular effect in a yet to be defined addiction phenotype. Head to head comparisons between naltrexone and nalmefene would be helpful in combining other medication or psychotherapy. The identification of subgroups of patients that are more likely to benefit from opioid antagonists should be a goal

The use of naltrexone in pathological and problem gambling: A UK case series

BACKGROUND AND AIMS

To investigate the potential indications and adverse effects of using the opioid antagonist naltrexone to treat problem gamblers.

CASE PRESENTATION

The files of the 1,192 patients who were referred to the National Problem Gambling Clinic between January 2015 and June 2016 were audited. Seventeen patients were considered appropriate for treatment with naltrexone, having attended and failed to respond to psychological therapies at the clinic. Fourteen patients were placed on a regimen of 50 mg/day naltrexone.

DISCUSSION

Of the 14 patients who were treated with naltrexone, there were 10 for whom sufficient follow-up existed to analyze the treatment efficacy and side effects of naltrexone. Patients showed significant decreases in their craving to gamble and the majority (60%) were able to abstain completely from gambling in the treatment period, with a further 20% reducing their gambling to almost nothing. The reported side effects from the naltrexone included: loss of appetite, gastrointestinal pain, headaches, sedation, dizziness, and vivid dreams. Two patients with concurrent alcohol-use disorder relapsed during the treatment. One patient relapsed after the treatment period.

CONCLUSIONS

The study showed significant outcomes in reducing gambling cravings for the sample set. Given the design of the study as a case series, there was no control group, and a number of patients were on other psychotropic medications. We recommend care when prescribing to those suffering from concurrent alcohol-use disorder.

Caenorhabditis elegans Show Preference for Stimulants and Potential as a Model Organism for Medications Screening

The nematode Caenorhabditis elegans (C. elegans) is a popular invertebrate model organism to study neurobiological disease states. This is due in part to the intricate mapping of all neurons and synapses of the entire animal, the wide availability of mutant strains, and the genetic and molecular tools that can be used to manipulate the genome and gene expression. We have shown that, C. elegans develops a conditioned preference for cues that had previously been paired with either cocaine or methamphetamine exposure that is dependent on dopamine neurotransmission, similar to findings using place conditioning with rats and mice. In the current study, we show C. elegans also display a preference for, and self-exposure to, cocaine and nicotine. This substance of abuse (SOA) preference response can be selectively blocked by pretreatment with naltrexone and is consistent with the recent discovery of an opioid receptor system in C. elegans. In addition, pre-exposure to the smoking cessation treatment varenicline also inhibits self-exposure to nicotine. Exposure to concentrations of treatments that inhibit SOA preference/self-exposure did not induce any significant inhibition of locomotor activity or affect food or benzaldehyde chemotaxis. These data provide predictive validity for the development of high-throughput C. elegans behavioral medication screens. These screens could enable fast and accurate generation of data to identify compounds that may be effective in treating human addiction. The successful development and validation of such models would introduce powerful and novel tools in the search for new pharmacological treatments for substance use disorders, and provide a platform to study the mechanisms that underlie addictions.

The role of prevention strategies in achieving HCV elimination in Canada: what are the remaining challenges?

BACKGROUND

The worldwide economic, health, and social consequences of drug use disorders are devastating. Injection drug use is now a major factor contributing to hepatitis C virus (HCV) transmission globally, and it is an important public health concern.

METHODS

This article presents a narrative review of scientific evidence on public health strategies for HCV prevention among people who inject drugs (PWID) in Canada.

RESULTS

A combination of public health strategies including timely HCV detection and harm reduction (mostly needle and syringe programmes and opioid substitution therapy) have helped to reduce HCV transmission among PWID. The rising prevalence of pharmaceutical opioid and methamphetamine use and associated HCV risk in several Canadian settings has prompted further innovation in harm reduction, including supervised injection facilities and low-threshold opioid substitution therapies. Further significant decreases in HCV incidence and prevalence, and in corresponding disease burden, can only be accomplished by reducing transmission among high-risk persons and enhancing access to HCV treatment for those at the greatest risk of disease progression or viral transmission. Highly effective and tolerable direct-acting antiviral therapies have transformed the landscape for HCV-infected patients and are a valuable addition to the prevention toolkit. Curing HCV-infected persons, and thus eliminating new infections, is now a real possibility.

CONCLUSIONS

Prevention strategies have not yet ended HCV transmission, and sharing of injecting equipment among PWID continues to challenge the World Health Organization goal of eliminating HCV as a global public health threat by 2030. Future needs for research, intervention implementation, and uptake in Canada are discussed.

Orphan neuropeptides and receptors: Novel therapeutic targets

Neuropeptides are the largest class of intercellular signaling molecules, contributing to a wide variety of physiological processes. Neuropeptide receptors are therapeutic targets for a broad range of drugs, including medications to treat pain, addiction, sleep disorders, and nausea. In addition to >100 peptides with known functions, many peptides have been identified in mammalian brain for which the cognate receptors have not been identified. Similarly, dozens of "orphan" G protein-coupled receptors have been identified in the mammalian genome. While it would seem straightforward to match the orphan peptides and receptors, this is not always easily accomplished. In this review we focus on peptides named PEN and big LEN, which are among the most abundant neuropeptides in mouse brain, and their recently identified receptors: GPR83 and GPR171. These receptors are co-expressed in some brain regions and are able to interact. Because PEN and big LEN are produced from the same precursor protein and co-secreted, the interaction of GPR83 and GPR171 is physiologically relevant. In addition to interactions of these two peptides/receptors, PEN and LEN are co-localized with neuropeptide Y and Agouti-related peptide in neurons that regulate feeding. In this review, using these peptide receptors as an example, we highlight the multiple modes of regulation of receptors and present the emerging view that neuropeptides function combinatorially to generate a network of signaling messages. The complexity of neuropeptides, receptors, and their signaling pathways is important to consider both in the initial deorphanization of peptides and receptors, and in the subsequent development of therapeutic applications.

The assessment and treatment of adult heterosexual men with self-perceived problematic pornography use: A review

Self-Perceived Problematic Porn Use (SPPPU) refers to an individual who self-identifies as addicted to porn because they feel they are unable to regulate their porn consumption, and that use interferes with everyday life. Although porn addiction has not been formally classified as its own distinct behavioral addiction, therapists and clinicians are advised to educate themselves on the current state of literature pertaining to pornography consumption given the widespread availability and consumption of sexually explicit material online. This review article begins with a general overview of pornography and porn use so that therapists and researchers can discern between non-intrusive and problematic pornography consumption patterns within their practice and understand the common characteristics of those that most commonly present with SPPPU. Thereafter, an overview and examination of therapeutic interventions for SPPPU will be identified and analysed. Finally, the review concludes with recommendations for therapists, clinicians, and future research.

Focusing on the Opioid System for Addiction Biomarker Discovery

Substance use disorders (SUD) and behavioral addictions are devastating conditions that impose a severe burden on all societies, and represent difficult challenges for clinicians. Therefore, biomarkers are urgently needed to help predict vulnerability, clinical course, and response to treatment. Here, we elaborate on the potential for addiction biomarker discovery of the opioid system, particularly within the emerging framework aiming to probe opioid function in peripheral tissues. Mu, delta, and kappa opioid receptors all critically regulate neurobiological and behavioral processes that define addiction, and are also targeted by major pharmacotherapies used in the management of patients with SUD. We propose that opioid biomarkers may have the potential to improve and guide diagnosis and therapeutic decisions in the addiction field.

Pharmacotherapies for decreasing maladaptive choice in drug addiction: Targeting the behavior and the drug

Drug addiction can be conceptualized as a disorder of maladaptive decision making in which drugs are chosen at the expense of pro-social, nondrug alternatives. The study of decision making in drug addiction has focused largely on the role of impulsivity as a facilitator of addiction, in particular the tendency for drug abusers to choose small, immediate gains over larger but delayed outcomes (i.e., delay discounting). A parallel line of work, also focused on decision making in drug addiction, has focused on identifying the determinants underlying the choice to take drugs over nondrug alternatives (i.e., drug vs. nondrug choice). Both tracks of research have been valuable tools in the development of pharmacotherapies for treating maladaptive decision making in drug addiction, and a number of common drugs have been studied in both designs. However, we have observed that there is little uniformity in the administration regimens of potential treatments between the designs, which hinders congruence in the development of single treatment strategies to reduce both impulsive behavior and drug choice. The current review provides an overview of the drugs that have been tested in both delay-discounting and drug-choice designs, and focuses on drugs that reduced the maladaptive choice in both designs. Suggestions to enhance congruence between the findings in future studies are provided. Finally, we propose the use of a hybridized, experimental approach that may enable researchers to test the effectiveness of therapeutics at decreasing impulsive and drug choice in a single design.

Preclinical Studies of Cannabinoid Reward, Treatments for Cannabis Use Disorder, and Addiction-Related Effects of Cannabinoid Exposure

Cannabis use has become increasingly accepted socially and legally, for both recreational and medicinal purposes. Without reliable information about the effects of cannabis, people cannot make informed decisions regarding its use. Like alcohol and tobacco, cannabis can have serious adverse effects on health, and some people have difficulty discontinuing their use of the drug. Many cannabis users progress to using and becoming addicted to other drugs, but the reasons for this progression are unclear. The natural cannabinoid system of the brain is complex and involved in many functions, including brain development, reward, emotion, and cognition. Animal research provides an objective and controlled means of obtaining information about: (1) how cannabis affects the brain and behavior, (2) whether medications can be developed to treat cannabis use disorder, and (3) whether cannabis might produce lasting changes in the brain that increase the likelihood of becoming addicted to other drugs. This review explains the tactics used to address these issues, evaluates the progress that has been made, and offers some directions for future research.

Introducing care management to Brazil's alcohol and substance use disorder population

Brazil has a sizable alcohol and substance use disorder (ASUD) population, yet there are considerable gaps in treatment access and retention. ASUD, a chronic medical condition, is highly comorbid with medical and behavioral health disorders. This indicates a need for more targeted interventions in order to achieve health care integration (a major goal of Brazil's health care system). Care management - that is, the organization of patient care by an institution - is a viable strategy to engage individuals with ASUD who might benefit from treatment but are not aware of or do not use the available resources, as well as to help maintain patients in treatment. Care management is considered an essential supplement to the treatment of chronic disease. The objective of this article is to discuss the applicability of care management for the treatment of ASUD within the public health care system in Brazil. We describe models of care management that have been adopted internationally and identify the feasibility and advantages for its adoption in Brazil.

Naltrexone in the Treatment of Broadly Defined Behavioral Addictions: A Review and Meta-Analysis of Randomized Controlled Trials

INTRODUCTION

Broadly defined behavioral addiction is a conceptual framework including behaviors characterized by loss of control and continuation despite significant negative consequences. Broadly defined behavioral addictions share many similarities with substance use disorders. As naltrexone is one of the most studied treatment for substance use disorders, we conducted a meta-analysis of randomized placebo-controlled trials (RCT) assessing the effectiveness of naltrexone in the treatment of broadly defined behavioral addictions.

METHOD

We conducted a literature search and selection, up to January 1, 2017, according to previously set inclusion criteria. The selected trials underwent a quality assessment before data extraction and statistical analysis, which used fixed and random effects models. Standardized mean differences (SMD) were calculated using Hedge's adjusted g.

RESULTS

A total of 6 RCTs (n = 356) were included. Of these, 3 assessed naltrexone effectiveness in the treatment of pathological gambling, and 3 tested its benefits in broadly defined behavioral addictions other than pathological gambling (kleptomania, trichotillomania, and impulsive compulsive disorders). The meta-analysis of the whole sample resulted in a statistically significant score improvement under naltrexone versus placebo (fixed effect model: SMD = -0.27, 95% CI [-0.51 to -0.03], z = 2.23; p = 0.025).

CONCLUSION

The results of our meta-analysis suggest a beneficial effect of naltrexone in the treatment of broadly defined behavioral addictions.