Neural correlates of adherence to extended-release naltrexone pharmacotherapy in heroin dependence

Common and Distinct Drug Cue Reactivity Patterns Associated with Cocaine and Heroin: An fMRI Meta-Analysis

Substance use and substance use disorders represent ongoing major public health crises. Specifically, the use of substances such as cocaine and heroin are responsible for over 50,000 drug related deaths combined annually. We used a comparative meta-analysis procedure to contrast activation patterns associated with cocaine and heroin cue reactivity, which may reflect substance use risk for these substances. PubMed and Google Scholar were searched for studies with within-subject whole brain analyses comparing drug to neutral cues for users of cocaine and heroin published between 1995 and 2022. A total of 18 studies were included, 9 in each subgroup. Voxel-based meta-analyses were performed using seed-based d mapping with permuted subject images (SDM-PSI) for subgroup mean analyses and a contrast meta-regression comparing the two substances. Mean analysis results indicated that users of heroin showed more widespread activation in the nucleus accumbens, right inferior and left middle temporal gyrus, the right thalamus, and the right cerebellum while cocaine use was associated with recruitment of dorsolateral prefrontal cortex. Direct comparison of cue reactivity studies in heroin relative to cocaine users revealed greater activation in dopaminergic targets for users of heroin compared to users of cocaine. Differential activation patterns between substances may underlie differences in the clinical characteristics observed across users of cocaine and heroin, including seeking mood numbing effects in users of heroin. More consistent research methodology is needed to provide adequate studies for stringent meta-analyses examining common and distinct neural activation patterns across substances and moderation by clinically relevant factors.

Investigating brain dynamics and their association with cognitive control in opioid use disorder using naturalistic and drug cue paradigms

Objectives

Opioid use disorder (OUD) impacts millions of people worldwide. The prevalence and debilitating effects of OUD present a pressing need to understand its neural mechanisms to provide more targeted interventions. Prior studies have linked altered functioning in large-scale brain networks with clinical symptoms and outcomes in OUD. However, these investigations often do not consider how brain responses change over time. Time-varying brain network engagement can convey clinically relevant information not captured by static brain measures.

Methods

We investigated brain dynamic alterations in individuals with OUD by applying a new multivariate computational framework to movie-watching (i.e., naturalistic; N=76) and task-based (N=70) fMRI. We further probed the associations between cognitive control and brain dynamics during a separate drug cue paradigm in individuals with OUD.

Results

Compared to healthy controls (N=97), individuals with OUD showed decreased variability in the engagement of recurring brain states during movie-watching. We also found that worse cognitive control was linked to decreased variability during the rest period when no opioid-related stimuli were present.

Conclusions

These findings suggest that individuals with OUD may experience greater difficulty in effectively engaging brain networks in response to evolving internal or external demands. Such inflexibility may contribute to aberrant response inhibition and biased attention toward opioid-related stimuli, two hallmark characteristics of OUD. By incorporating temporal information, the current study introduces novel information about how brain dynamics are altered in individuals with OUD and their behavioral implications.

Hippocampal volume loss in individuals with a history of non-fatal opioid overdose

Incidence of opioid-related overdoses in the United States has increased dramatically over the past two decades. Despite public emphasis on overdose fatalities, most overdose cases are not fatal. Although there are case reports of amnestic syndromes and acute injury to the hippocampus following non-fatal opioid overdose, the effects of such overdoses on brain structure are poorly understood. Here, we investigated the neuroanatomical correlates of non-fatal opioid overdoses by comparing hippocampal volume in opioid use disorder (OUD) patients who had experienced an opioid overdose (OD; N = 17) with those who had not (NOD; N = 32). Voxel-based morphometry showed lower hippocampal volume in the OD group than in the NOD group, which on post hoc analysis was evident in the left but not the right hippocampus. These findings strengthen the evidence that hippocampal injury is associated with non-fatal opioid overdose, which is hypothesized to underlie overdose-related amnestic syndrome.

Association between body mass index and treatment completion in extended-release naltrexone-treated patients with opioid dependence

Background

Excessive consumption of opioids is associated with impaired metabolic function including increased body mass index (BMI). Opioid antagonist naltrexone (NTX) is an effective treatment for opioid use disorder (OUD) that has the potential to mitigate such metabolic disturbances. Understanding the relationship between treatment adherence and BMI in NTX-treated OUD patients may provide valuable insights into optimizing clinical outcomes.

Methods

Patients with opioid dependence were offered up to three monthly injections of extended-release (XR) NTX. Treatment completers (n = 41) were defined as those who had received all three XR-NTX injections, and non-completers (n = 20) as those missing at least one injection. Logistic regression was performed to examine the association between pre-treatment BMI and treatment completion.

Results

BMI was positively associated with treatment completion. This association remained significant after adjusting for potentially confounding variables.

Conclusion

Our findings suggest that baseline BMI may serve as a potential predictor of XR-NTX treatment adherence in patients with OUD and could help healthcare providers and policy makers alike in developing strategies to improve retention and tailor interventions for specific patient subgroups.

Potential biomarker of brain response to opioid antagonism in adolescents with eating disorders: a pilot study

Background

Eating Disorders (ED) affect up to 5% of youth and are associated with reward system alterations and compulsive behaviors. Naltrexone, an opioid antagonist, is used to treat ED behaviors such as binge eating and/or purging. The presumed mechanism of action is blockade of reward activation; however, not all patients respond, and the optimal dose is unknown. Developing a tool to detect objective drug response in the brain will facilitate drug development and therapeutic optimization. This pilot study evaluated neuroimaging as a pharmacodynamic biomarker of opioid antagonism in adolescents with ED.

Methods

Youth aged 13-21 with binge/purge ED completed functional magnetic resonance imaging (fMRI) pre- and post-oral naltrexone. fMRI detected blood oxygenation-level dependent (BOLD) signal at rest and during two reward probes (monetary incentive delay, MID, and passive food view, PFV) in predefined regions of interest associated with reward and inhibitory control. Effect sizes for Δ%BOLD (post-naltrexone vs. baseline) were estimated using linear mixed effects modeling.

Results

In 12 youth (16-21 years, 92% female), BOLD signal changes were detected following naltrexone in the nucleus accumbens during PFV (Δ%BOLD -0.08 ± 0.03; Cohen's d -1.06, p = 0.048) and anterior cingulate cortex during MID (Δ%BOLD 0.06 ± 0.03; Cohen's d 1.25, p = 0.086).

Conclusion

fMRI detected acute reward pathway modulation in this small sample of adolescents with binge/purge ED. If validated in future, larger trials, task-based Δ%BOLD detected by fMRI may serve as a pharmacodynamic biomarker of opioid antagonism to facilitate the development of novel therapeutics targeting the reward pathway, enable quantitative pharmacology trials, and inform drug dosing.

Clinical trial registration

https://clinicaltrials.gov/ct2/show/NCT04935931, NCT#04935931.

Addicted to green: priming effect of menthol cigarette packaging on brain response to smoking cues

INTRODUCTION

Mentholated tobacco cigarettes are believed to be more addictive than non-menthol ones. Packaging of most menthol cigarette brands includes distinctive green hues, which may act as conditioned stimuli (ie, cues) and promote menthol smoking. To examine the cue properties of menthol cigarette packaging, we used a priming paradigm to assess the effect of packaging on the neural substrates of smoking cue reactivity. We hypothesised that menthol packaging will exert a specific priming effect potentiating smoking cue reactivity in menthol compared with non-menthol smokers.

METHODS

Forty-two menthol and 33 non-menthol smokers underwent functional MRI while viewing smoking and neutral cues. The cues were preceded (ie, primed) by briefly presented images of menthol or non-menthol cigarette packages. Participants reported craving for cigarettes in response to each cue.

RESULTS

Menthol packaging induced greater frontostriatal and occipital smoking cue reactivity in menthol smokers than in non-menthol smokers. Menthol packaging also enhanced the mediation by neural activity of the relationship between cue exposure and cigarette craving in menthol but not non-menthol smokers. Dynamic causal modelling showed stronger frontostriatal-occipital connectivity in response to menthol packaging in menthol compared with non-menthol smokers. The effects of non-menthol packaging did not differ between categories of smokers.

CONCLUSIONS

Our findings demonstrate heightened motivational and perceptual salience of the green-hued menthol cigarette packaging that may exacerbate menthol smokers' susceptibility to smoking cues. These effects could contribute to the greater addiction severity among menthol smokers and could be considered in the development of science-based regulation and legal review of tobacco product marketing practices.

A review of functional brain differences predicting relapse in substance use disorder: Actionable targets for new methods of noninvasive brain stimulation

Neuroimaging studies have identified a variety of brain regions whose activity predicts substance use (i.e., relapse) in patients with substance use disorder (SUD), suggesting that malfunctioning brain networks may exacerbate relapse. However, this knowledge has not yet led to a marked improvement in treatment outcomes. Noninvasive brain stimulation (NIBS) has shown some potential for treating SUDs, and a new generation of NIBS technologies offers the possibility of selectively altering activity in both superficial and deep brain structures implicated in SUDs. The goal of the current review was to identify deeper brain structures involved in relapse to SUD and give an account of innovative methods of NIBS that might be used to target them. Included studies measured fMRI in currently abstinent SUD patients and tracked treatment outcomes, and fMRI results were organized with the framework of the Addictions Neuroclinical Assessment (ANA). Four brain structures were consistently implicated: the anterior and posterior cingulate cortices, ventral striatum and insula. These four deeper brain structures may be appropriate future targets for the treatment of SUD using these innovative NIBS technologies.

Baseline- and treatment-associated pain in the X:BOT comparative effectiveness study of extended-release naltrexone versus buprenorphine-naloxone for OUD

Chronic pain is highly prevalent among patients with opioid use disorder (OUD). However, little is known about how pharmacological treatments for OUD, for example, extended-release naltrexone (XR-NTX) and buprenorphine-naloxone (BUP-NX), affect pain. To begin addressing this question, we performed a secondary analysis of pain data on a large prospective 24-week, open-label, randomized-controlled comparative effectiveness trial of XR-NTX versus BUP-NX (X:BOT trial). Participants' pain status was measured by the EuroQol (EQ-5D). Based on their responses to the pain question at baseline, participants were dichotomized into "Pain" versus "No Pain" categories. Participant's pain status was evaluated every 4 weeks. A mixed effects longitudinal logistic regression model was fitted to examine the differential effect of XR-NTX versus BUP-NX on pain, modelling pain at all available follow-up assessments, adjusted for age, sex, and baseline pain. A total of 474 individuals who were successfully inducted onto their assigned medications were included in this analysis. Among participants endorsing pain at baseline, substantial reductions in pain were observed over the course of the study in both treatment groups. Howecver reduction in pain was slightly greater in the group treated with XR-NTX than the one treated with BUP-NX (OR = 1.60 [95% CI: 1.07-2.40], P = 0.023). Future research using instruments and design specifically focused on pain could extend the present observations and evaluate their clinical significance.

Are There Neural Overlaps of Reactivity to Illegal Drugs, Tobacco, and Alcohol Cues? With Evidence From ALE and CMA

Abuses of most illegal drugs, including methamphetamine, marijuana, cocaine, heroin, and polydrug, are usually in conjunction with alcohol and tobacco. There are similarities and associations between the behavior, gene, and neurophysiology of such abusers, but the neural overlaps of their cue-reactivity and the correlation of neural overlap with drug craving still needs to be further explored. In this study, an Activation Likelihood Estimation (ALE) was performed on brain activation under legal (tobacco, alcohol) and illegal drug cues, for identifying the similarities in brain functions between different craving states. A Comprehensive meta-analysis (CMA) on the correlation coefficient between brain activation and craving scores in the selected literatures with subjective craving reports explained the degree of the craving via brain imaging results. In ALE, co-activation areas of the three cue-reactivity (posterior cingulate, caudate, and thalamus) suggest that the three cue-reactivity may all arouse drug-use identity which is a predictor of relapse and generation of conditioned reflexes under reward memory, thus leading to illegal drug relapses. In CMA, the brain activation was significantly correlated with subjective craving, with a correlation coefficient of 0.222. The neural overlap of tobacco, alcohol and most of the prevalent illegal drug cues not only further helps us understand the neural mechanism of substance co-abuse and relapse, but also provides implications to detoxification. Furthermore, the correlation between brain activation and craving is low, suggesting the accuracy of craving-based quantitative evaluation by neuroimaging remains unclear.

A systematic review of addiction substitution in recovery: Clinical lore or empirically-based?

This systematic review synthesized the literature examining addiction substitution during recovery from substance use or behavioral addictions. A total of 96 studies were included with sample sizes ranging from 6 to 14,885. The most common recovery addictions were opioids (30.21%), followed by cannabis (20.83%), unspecified use (17.71%), nicotine (12.50%), alcohol (12.50%), cocaine (4.17%), and gambling (2.08%). Statistical results were provided by 70.83% of the studies. Of these, 17.65% found support for addiction substitution, whereas 52.94% found support for concurrent recovery. A total of 19.12% found no statistical changes and 10.29% found both significant increases and decreases. The remaining 29.17% of studies provided descriptive data, without statistical tests. Predictors of addiction substitution were provided by 22.92% of the studies and 11.46% included information on impact of addiction substitution on treatment outcomes. Overall, male gender, younger age, greater substance use severity, and presence of mental health disorders were associated with addiction substitution. Addiction substitution was associated with poorer treatment outcomes. A limitation of the present systematic review is the use of significance counting for the quantitative synthesis. More research examining changes in addiction during recovery would aid in the development of more effective treatments for addictive disorders and prevent addiction substitution.

Multivariate pattern analysis links drug use severity to distributed cortical hypoactivity during emotional inhibitory control in opioid use disorder

Opioid use disorder (OUD) is characterized by emotional and cognitive impairements that are associated with poor treatment outcomes. The present study investigated the neural mechanism underlying emotion evaluation and inhibitory control using an affective go/no-go (AGN) task and its association with drug use severity and craving in patients with OUD. Twenty-six recently detoxified patients with OUD underwent functional magnetic resonance imaging (fMRI) while performing the AGN task that required response to frequently presented appetitive stimuli ("go") and inhibition of response to infrequently presented aversive stimuli ("no-go"). The fMRI session was immediately followed by an injection of extended-release opioid antagonist naltrexone (XR-NTX). Participants' opioid craving was assessed immediately before fMRI and 10 ± 2 days after XR-NTX injection. Multivariate pattern analysis (MVPA) showed that drug use severity was associated with distributed brain hypoactivity in response to aversive no-go stimuli, with particularly large negative contributions from the cognitive control and dorsal attention brain networks. While drug use severity and its associated MVPA brain response pattern were both correlated with opioid craving at baseline, only the brain response pattern predicted craving during XR-NTX treatment. Our findings point to widespread functional hypoactivity in the brain networks underlying emotional inhibitory control in OUD. Such a distributed pattern is consistent with the multifaceted nature of OUD, which affects multiple brain networks. It also highlights the utility of the multivariate approach in uncovering large-scale cortical substrates associated with clinical severity in complex psychiatric disorders and in predicting treatment response.

Dissociable neural substrates of opioid and cocaine use identified via connectome-based modelling

Opioid use disorder is a major public health crisis. While effective treatments are available, outcomes vary widely across individuals and relapse rates remain high. Understanding neural mechanisms of treatment response may facilitate the development of personalized and/or novel treatment approaches. Methadone-maintained, polysubstance-using individuals (n = 53) participated in fMRI scanning before and after substance-use treatment. Connectome-based predictive modeling (CPM)-a recently developed, whole-brain approach-was used to identify pretreatment connections associated with abstinence during the 3-month treatment. Follow-up analyses were conducted to determine the specificity of the identified opioid abstinence network across different brain states (cognitive vs. reward task vs. resting-state) and different substance use outcomes (opioid vs. cocaine abstinence). Posttreatment fMRI data were used to assess network changes over time and within-subject replication. To determine further clinical relevance, opioid abstinence network strength was compared with healthy subjects (n = 38). CPM identified an opioid abstinence network (p = 0.018), characterized by stronger within-network motor/sensory connectivity, and reduced connectivity between the motor/sensory network and medial frontal, default mode, and frontoparietal networks. This opioid abstinence network was anatomically distinct from a previously identified cocaine abstinence network. Relationships between abstinence and opioid and cocaine abstinence networks replicated across multiple brain states but did not generalize across substances. Network connectivity measured at posttreatment related to abstinence at 6-month follow-up (p < 0.009). Healthy comparison subjects displayed intermediate network strengths relative to treatment responders and nonresponders. These data indicate dissociable anatomical substrates of opioid vs. cocaine abstinence. Results may inform the development of novel opioid-specific treatment approaches to combat the opioid epidemic.

The role of withdrawal in mesocorticolimbic drug cue reactivity in opioid use disorder

Opioid use disorder (OUD) is characterized by heightened cognitive, physiological, and neural responses to opioid-related cues that are mediated by mesocorticolimbic brain pathways. Craving and withdrawal are key symptoms of addiction that persist during physiological abstinence. The present study evaluated the relationship between the brain response to drug cues in OUD and baseline levels of craving and withdrawal. We used functional magnetic resonance imaging (fMRI) to examine brain responses to opioid-related pictures and control pictures in 29 OUD patients. Baseline measures of drug use severity, opioid craving, and withdrawal symptoms were assessed prior to cue exposure and correlated with subsequent brain responses to drug cues. Mediation analysis was conducted to test the indirect effect of drug use severity on brain cue reactivity through craving and withdrawal symptoms. We found that baseline drug use severity and opioid withdrawal symptoms, but not craving, were positively associated with the neural response to drug cues in the nucleus accumbens, orbitofrontal cortex, and amygdala. Withdrawal, but not craving, mediated the effect of drug use severity on the nucleus accumbens' response to drug cues. We did not find similar effects for the neural responses to stimuli unrelated to drugs. Our findings emphasize the central role of withdrawal symptoms as the mediator between the clinical severity of OUD and the brain correlates of sensitization to opioid-related cues. They suggest that in OUD, baseline withdrawal symptoms signal a high vulnerability to drug cues.

Assessing effect of long-term abstinence on coupling of three core brain networks in male heroin addicts: A resting-state functional magnetic resonance imaging study

Abstinence is one of the important measures for heroin addiction. However, it is unknown whether long-term abstinence (LA) would improve the coupling among three core brain networks (salience, default mode, and executive control) and decrease craving in treated heroin addicts. Forty-three heroin addicts with LA, 27 heroin addicts with short-term abstinence (SA), and 46 demographically matched healthy controls (HC) participated in the resting-state functional magnetic resonance imaging study. The authors compared the functional connectivity among the three groups and examined how the coupling among salience, default mode, and executive control networks related to duration of abstinence and craving before and after drug cue exposure among heroin addicts. Compared with the SA group, with a tendency toward the HC group, the LA group showed lower drug cue-induced craving, stronger connectivity between the dorsal anterior cingulate cortex (a key node of salience network) and left dorsolateral prefrontal cortex and right posterior parietal cortex (key nodes of executive control network), and stronger connectivity between the right dorsolateral prefrontal cortex and precuneus (a key node of default mode network). Meanwhile, the right dorsolateral prefrontal cortex-precuneus connectivity positively correlated with duration of abstinence. The LA and SA groups demonstrated lower connectivity between the left anterior insula (a key node of salience network) and dorsolateral prefrontal cortex and lower connectivity within the left dorsolateral prefrontal cortex, compared with the HC group. Our findings revealed that LA is associated with lower drug cue induced craving and improve the coupling among the three core brain networks in heroin addicts.

Early Life Stress and Risks for Opioid Misuse: Review of Data Supporting Neurobiological Underpinnings

A robust body of research has shown that traumatic experiences occurring during critical developmental periods of childhood when neuronal plasticity is high increase risks for a spectrum of physical and mental health problems in adulthood, including substance use disorders. However, until recently, relatively few studies had specifically examined the relationships between early life stress (ELS) and opioid use disorder (OUD). Associations with opioid use initiation, injection drug use, overdose, and poor treatment outcome have now been demonstrated. In rodents, ELS has also been shown to increase the euphoric and decrease antinociceptive effects of opioids, but little is known about these processes in humans or about the neurobiological mechanisms that may underlie these relationships. This review aims to establish a theoretical model that highlights the mechanisms by which ELS may alter opioid sensitivity, thereby contributing to future risks for OUD. Alterations induced by ELS in mesocorticolimbic brain circuits, and endogenous opioid and dopamine neurotransmitter systems are described. The limited but provocative evidence linking these alterations with opioid sensitivity and risks for OUD is presented. Overall, the findings suggest that better understanding of these mechanisms holds promise for reducing vulnerability, improving prevention strategies, and prescribing guidelines for high-risk individuals.

A Novel Precision Approach to Overcome the "Addiction Pandemic" by Incorporating Genetic Addiction Risk Severity (GARS) and Dopamine Homeostasis Restoration

This article describes a unique therapeutic precision intervention, a formulation of enkephalinase inhibitors, enkephalin, and dopamine-releasing neuronutrients, to induce dopamine homeostasis for detoxification and treatment of individuals genetically predisposed to developing reward deficiency syndrome (RDS). The formulations are based on the results of the addiction risk severity (GARS) test. Based on both neurogenetic and epigenetic evidence, the test evaluates the presence of reward genes and risk alleles. Existing evidence demonstrates that the novel genetic risk testing system can successfully stratify the potential for developing opioid use disorder (OUD) related risks or before initiating opioid analgesic therapy and RDS risk for people in recovery. In the case of opioid use disorders, long-term maintenance agonist treatments like methadone and buprenorphine may create RDS, or RDS may have been in existence, but not recognized. The test will also assess the potential for benefit from medication-assisted treatment with dopamine augmentation. RDS methodology holds a strong promise for reducing the burden of addictive disorders for individuals, their families, and society as a whole by guiding the restoration of dopamine homeostasisthrough anti-reward allostatic neuroadaptations. WC 175.

Gray matter alteration in heroin-dependent men: An atlas-based magnetic resonance imaging study

Previous imaging studies on heroin addiction have reported brain morphological alterations. However, the effects of heroin exposure on gray matter volume varied among different studies due to different factors such as substitution treatment or mandatory abstinence. Meanwhile, the relationship between gray matter and heroin use history remains unknown. Thirty-three male heroin-dependent (HD) individuals who are not under any substitution treatment or mandatory abstinence and 40 male healthy controls (HC) were included in this structural magnetic resonance imaging study. With an atlas-based approach, gray matter structures up to individual functional area were delineated, and the differences in their volumes between the HD and HC groups were analyzed. In addition, the relationship between gray matter volume and duration of heroin use was explored. The HD group demonstrated significantly lower cortical volume mainly in the prefrontal cortex and mesolimbic dopaminergic regions across different parcellation levels, whereas several visual and somatosensory cortical regions in the HD group had greater volume relative to the HC group at a more detailed parcellation level. The duration of heroin use was negatively correlated with the gray matter volume of prefrontal cortex. These findings suggest that heroin addiction be related to gray matter alteration and might be related to damage/maladaption of the inhibitory control, reward, visual, and somatosensory functions of the brain, although cognitive correlates are warranted in future study. In addition, the atlas-based morphology analysis is a potential tool to help researchers search biomarkers of heroin addiction.

Multi-View Cluster Analysis with Incomplete Data to Understand Treatment Effects

Multi-view cluster analysis, as a popular granular computing method, aims to partition sample subjects into consistent clusters across different views in which the subjects are characterized. Frequently, data entries can be missing from some of the views. The latest multi-view co-clustering methods cannot effectively deal with incomplete data, especially when there are mixed patterns of missing values. We propose an enhanced formulation for a family of multi-view co-clustering methods to cope with the missing data problem by introducing an indicator matrix whose elements indicate which data entries are observed and assessing cluster validity only on observed entries. In comparison with the simple strategy of removing subjects with missing values, our approach can use all available data in cluster analysis. In comparison with common methods that impute missing data in order to use regular multi-view analytics, our approach is less sensitive to imputation uncertainty. In comparison with other state-of-the-art multi-view incomplete clustering methods, our approach is sensible in the cases of missing any value in a view or missing the entire view, the most common scenario in practice. We first validated the proposed strategy in simulations, and then applied it to a treatment study of heroin dependence which would have been impossible with previous methods due to a number of missing-data patterns. Patients in a treatment study were naturally assessed in different feature spaces such as in the pre-, during-and post-treatment time windows. Our algorithm was able to identify subgroups where patients in each group showed similarities in all of the three time windows, thus leading to the recognition of pre-treatment (baseline) features predictive of post-treatment outcomes.

Reduced cigarette smoking during injectable extended-release naltrexone treatment for opioid use disorder

BACKGROUND

The prevalence of tobacco cigarette smoking in the US has declined to approximately 15%, yet, it remains over 90% among individuals with opioid use disorder regardless of whether they are currently using opioids illicitly or as opioid substitution therapy. This disparity raises the question of whether opioids facilitate smoking among individuals with opioid use disorder and whether opioid antagonists may reduce it.

OBJECTIVES

Determine whether injectable extended-release naltrexone (XR-NTX) treatment of opioid use disorder patients is associated with a spontaneous smoking reduction. We hypothesized that treatment with XR-NTX for would lead to a reduction in smoking in tobacco cigarette smokers with opioid use disorder.

METHODS

We analyzed data from 64 tobacco cigarette smokers (38% female) with opioid use disorder who were induced on XR-NTX for prevention of relapse to opioids. The number of cigarettes smoked per day and opioid-related craving and withdrawal were assessed at baseline and during treatment.

RESULTS

Smoking was reduced from 14.4 ± 1.0 to 9.8 ± 1.0(p < 0.001) cigarettes per day after one month and 8.6 ± 1.1 cigarettes per day after two months of treatment. Daily cigarette consumption was positively correlated with the pre-treatment frequency of opioid use and opioid-related craving during the XR-NTX treatment.

CONCLUSIONS

XR-NTX treatment in smokers with opioid use disorder was associated with a 29% decline in daily cigarette consumption. Together with prior evidence of increased smoking during opioid agonist therapy, our finding suggests a pharmacodynamic interaction between nicotine and opioid systems that could influence treatment choices in this population. Our findings merit confirmation in a prospective controlled study. (NCT02324725 and NCT01587196).

Opioid use and dropout from extended-release naltrexone in a controlled trial: implications for mechanism

BACKGROUND AND AIMS

Extended-release formulations of naltrexone have emerged as effective treatment options for opioid use disorder. This post-hoc analysis examined the temporal relationship between episodes of opioid use and subsequent dropout in a placebo-controlled trial of extended-release injection naltrexone (XR-NTX) to draw inferences about the mechanism by which extended blockade of opioid receptors translates into clinical effectiveness.

DESIGN

This was a 24-week multiple-site, double-blind, randomized trial of monthly XR-NTX versus placebo injections. We analyzed time to dropout from treatment using survival analysis with an extended Cox model as a function of treatment (XR-NTX versus placebo) and with weekly urine drug test (UDT) results for opioids at each week as a time-dependent covariate.

SETTING

Thirteen addiction treatment programs in Russia, 2008-09.

PARTICIPANTS

A total of 250 adults with opioid use disorder who had completed in-patient detoxification.

INTERVENTION

XR-NTX injection or placebo injection every 4 weeks with weekly clinic visits and biweekly counseling.

MEASUREMENTS

Urine toxicology for opioids measured weekly and week of dropout from treatment.

FINDINGS

The Cox model yielded a significant interaction of time-dependent urine toxicology by treatment (P = 0.024). Among patients receiving placebo, a positive UDT in a given week increased the risk for dropout from treatment in the subsequent week [hazard ratio (HR) = 6.25; 95% confidence interval (CI) = 3.6-10.0], whereas among patients receiving XR-NTX, a positive UDT result showed no significant effect on risk for dropout (HR = 1.67; 95% CI = 0.6-4.5). The proportion of patients who completed all 24 weeks without any positive UDT result was 31% on XR-NTX compared with 20% on placebo (P = 0.051).

CONCLUSIONS

Extended-release injection naltrexone was effective at reducing the risk of dropout from opioid use disorder treatment after an episode of opioid use. Just under a third of patients (31%) on XR-NTX had no opioid-positive urine tests across the trial, but the hypothesis that this would differ from placebo (20%) was not confirmed.

Cingulo-hippocampal effective connectivity positively correlates with drug-cue attentional bias in opioid use disorder

Individuals with opioid use disorder (OUD) often relapse when exposed to opioid-related cues. Previous functional magnetic resonance imaging (fMRI) studies have identified neuronal corticolimbic changes related to drug cue reactivity in OUD. However, the corresponding manner in which brain regions interact is still unclear. Effective (directional) connectivity was analyzed using dynamic causal modeling of fMRI data acquired from 27 OUD participants (13 with OUD and 14 with OUD and cocaine use disorder [OUD+CUD]), while performing an opioid-word Stroop task. Participants were shown opioid and neutral words presented in different colors and were instructed to indicate word color but ignore word meaning. The effects of opioid words relative to neutral words on effective connectivity and on behavioral reaction time were defined as modulatory change and attentional bias, respectively. For all the 27 participants, left anterior cingulate cortex (ACC) to right hippocampus effective connectivity exhibited the largest modulatory change, which was positively correlated with attentional bias. The findings for the ACC to hippocampus EC were consistent across OUD and CUD found in a previous study.

Behavioral and Accumbal Responses During an Affective Go/No-Go Task Predict Adherence to Injectable Naltrexone Treatment in Opioid Use Disorder

Adherence is a major factor in the effectiveness of the injectable extended-release naltrexone as a relapse prevention treatment in opioid use disorder. We examined the value of a variant of the Go/No-go paradigm in predicting extended-release naltrexone adherence in 27 detoxified opioid use disorder patients who were offered up to 3 monthly extended-release naltrexone injections. Before extended-release naltrexone, participants performed a Go/No-go task that comprised positively valenced Go trials and negatively valenced No-go trials during a functional magnetic resonance imaging scan. Errors of commission and neural responses to the No-go vs Go trials were independent variables. Adherence, operationalized as the completion of all 3 extended-release naltrexone injections, was the outcome variable. Fewer errors of commission and greater left accumbal response during the No-go vs Go trials predicted better adherence. These findings support the clinical potential of the behavioral and neurophysiological correlates of response inhibition in the prediction of extended-release naltrexone treatment outcomes in opioid use disorder.

Forging Neuroimaging Targets for Recovery in Opioid Use Disorder

The United States is in the midst of an opioid epidemic and lacks a range of successful interventions to reduce this public health burden. Many individuals with opioid use disorder (OUD) consume drugs to relieve physical and/or emotional pain, a pattern that may increasingly result in death. The field of addiction research lacks a comprehensive understanding of physiological and neural mechanisms instantiating this cycle of Negative Reinforcement in OUD, resulting in limited interventions that successfully promote abstinence and recovery. Given the urgency of the opioid crisis, the present review highlights faulty brain circuitry and processes associated with OUD within the context of the Three-Stage Model of Addiction (1). This model underscores Negative Reinforcement processes as crucial to the maintenance and exacerbation of chronic substance use together with Binge/Intoxication and Preoccupation/Anticipation processes. This review focuses on cross-sectional as well as longitudinal studies of relapse and treatment outcome that employ magnetic resonance imaging (MRI), functional near-infrared spectroscopy (fNIRs), brain stimulation methods, and/or electroencephalography (EEG) explored in frequency and time domains (the latter measured by event-related potentials, or ERPs). We discuss strengths and limitations of this neuroimaging work with respect to study design and individual differences that may influence interpretation of findings (e.g., opioid use chronicity/recency, comorbid symptoms, and biological sex). Lastly, we translate gaps in the OUD literature, particularly with respect to Negative Reinforcement processes, into future research directions involving operant and classical conditioning involving aversion/stress. Overall, opioid-related stimuli may lessen their hold on frontocingulate mechanisms implicated in Preoccupation/Anticipation as a function of prolonged abstinence and that degree of frontocingulate impairment may predict treatment outcome. In addition, longitudinal studies suggest that brain stimulation/drug treatments and prolonged abstinence can change brain responses during Negative Reinforcement and Preoccupation/Anticipation to reduce salience of drug cues, which may attenuate further craving and relapse. Incorporating this neuroscience-derived knowledge with the Three-Stage Model of Addiction may offer a useful plan for delineating specific neurobiological targets for OUD treatment.

Can neuroimaging help combat the opioid epidemic? A systematic review of clinical and pharmacological challenge fMRI studies with recommendations for future research

The current opioid epidemic is an urgent public health problem, with enormous individual, societal, and healthcare costs. Despite effective, evidence-based treatments, there is significant individual variability in treatment responses and relapse rates are high. In addition, the neurobiology of opioid-use disorder (OUD) and its treatment is not well understood. This review synthesizes published fMRI literature relevant to OUD, with an emphasis on findings related to opioid medications and treatment, and proposes areas for further research. We conducted a systematic literature review of Medline and Psychinfo to identify (i) fMRI studies comparing OUD and control participants; (ii) studies related to medication, treatment, abstinence or withdrawal effects in OUD; and (iii) studies involving manipulation of the opioid system in healthy individuals. Following application of exclusionary criteria (e.g., insufficient sample size), 45 studies were retained comprising data from ~1400 individuals. We found convergent evidence that individuals with OUD display widespread heightened neural activation to heroin cues. This pattern is potentiated by heroin, attenuated by medication-assisted treatments for opioids, predicts treatment response, and is reduced following extended abstinence. Nonetheless, there is a paucity of literature examining neural characteristics of OUD and its treatment. We discuss limitations of extant research and identify critical areas for future neuroimaging studies, including the urgent need for studies examining prescription opioid users, assessing sex differences and utilizing a wider range of clinically relevant task-based fMRI paradigms across different stages of addiction.

Extended-release injectable naltrexone for opioid use disorder: a systematic review

AIMS

To review systematically the published literature on extended-release naltrexone (XR-NTX, Vivitrol^® ), marketed as a once-per-month injection product to treat opioid use disorder. We addressed the following questions: (1) how successful is induction on XR-NTX; (2) what are adherence rates to XR-NTX; and (3) does XR-NTX decrease opioid use? Factors associated with these outcomes as well as overdose rates were examined.

METHODS

We searched PubMed and used Google Scholar for forward citation searches of peer-reviewed papers from January 2006 to June 2017. Studies that included individuals seeking treatment for opioid use disorder who were offered XR-NTX were included.

RESULTS

We identified and included 34 studies. Pooled estimates showed that XR-NTX induction success was lower in studies that included individuals that required opioid detoxification [62.6%, 95% confidence interval (CI) = 54.5-70.0%] compared with studies that included individuals already detoxified from opioids (85.0%, 95% CI = 78.0-90.1%); 44.2% (95% CI = 33.1-55.9%) of individuals took all scheduled injections of XR-NTX, which were usually six or fewer. Adherence was higher in prospective investigational studies (i.e. studies conducted in a research context according to a study protocol) compared to retrospective studies of medical records taken from routine care (6-month rates: 46.7%, 95% CI = 34.5-59.2% versus 10.5%, 95% CI = 4.6-22.4%, respectively). Compared with referral to treatment, XR-NTX reduced opioid use in adults under criminal justice supervision and when administered to inmates before release. XR-NTX reduced opioid use compared with placebo in Russian adults, but this effect was confounded by differential retention between study groups. XR-NTX showed similar efficacy to buprenorphine when randomization occurred after detoxification, but was inferior to buprenorphine when randomization occurred prior to detoxification.

CONCLUSIONS

Many individuals intending to start extended-release naltrexone (XR-NTX) do not and most who do start XR-NTX discontinue treatment prematurely, two factors that limit its clinical utility significantly. XR-NTX appears to decrease opioid use but there are few experimental demonstrations of this effect.

Regional cerebral blood flow predictors of relapse and resilience in substance use recovery: A coordinate-based meta-analysis of human neuroimaging studies

BACKGROUND

Predicting relapse vulnerability can inform level-of-care and personalized substance use treatment. Few reliable predictors of relapse risk have been identified from traditional clinical, psychosocial, and demographic variables. However, recent neuroimaging findings highlight the potential prognostic import of brain-based signals, indexing the degree to which neural systems have been perturbed by addiction. These proposed "neuromarkers" forecast the likelihood, severity, and timing of relapse but the reliability and generalizability of such effects remains to be established.

METHODS

Activation likelihood estimation was used to conduct a preliminary quantitative, coordinate-based meta-analysis of the addiction neuroprediction literature; specifically, studies wherein baseline measures of regional cerebral blood flow were prospectively associated with substance use treatment outcomes. Consensus patterns of activation associated with relapse vulnerability (greater activation predicts poorer outcomes) versus resilience (greater activation predicts improved outcomes) were specifically investigated.

RESULTS

Twenty-four eligible studies yielded 134 foci, representing 923 subjects. Consensus activation was identified in right putamen and claustrum (p < .05, cluster-corrected) in relation to positive and negative treatment outcomes - likely reflecting variability in measurement context (e.g., task, sample characteristics) across datasets. A single cluster in rostral-ventral anterior cingulate cortex (rACC) was associated with relapse resilience, specifically (p < .05, cluster-corrected); no significant vulnerability-related clusters were identified.

CONCLUSIONS

Right putamen activation has been associated with relapse vulnerability and resilience, while increased baseline rACC activation has been consistently associated with improved treatment outcomes. Methodological heterogeneity within the existing literature, however, limits firm conclusions and future work will be necessary to confirm and clarify these results.

Effects of extended-release naltrexone on the brain response to drug-related stimuli in patients with opioid use disorder

BACKGROUND

Heightened response to drug-related cues is a hallmark of addiction. Extended-release naltrexone (XR-NTX) is a US Food and Drug Administration-approved pharmacotherapy for relapse prevention in patients with opioid use disorder (OUD). In these patients, XR-NTX has been shown to reduce brain responses to opioid-related visual stimuli. To assess the biomarker potential of this phenomenon, it is necessary to determine whether this effect is limited to opioid-related stimuli and whether it is associated with key OUD symptoms.

METHODS

Using functional MRI (fMRI), we measured the brain responses to opioid-related and control (i.e., sexual and aversive) images in detoxified patients with OUD before, during and after XR-NTX treatment. Craving and withdrawal severity were evaluated using clinician- and self-administered instruments during each session.

RESULTS

We included 24 patients with OUD in our analysis. During XR-NTX treatment, we found reduced responses to opioid-related stimuli in the nucleus accumbens (NAcc) and medial orbitofrontal cortex (mOFC). The reduction in mOFC response was specific to the opioid-related stimuli. The reduced NAcc and mOFC opioid cue reactivity was correlated with reduction in clinician-assessed and self-reported withdrawal symptoms, respectively.

LIMITATIONS

The study was not placebo-controlled owing to ethical, safety and feasibility concerns.

CONCLUSION

Extended-release naltrexone reduces the NAcc and mOFC cue reactivity in patients with OUD. This effect is specific to opioid-related stimuli in the mOFC only. The reduction in neural response to opioid-related stimuli is more robust in patients with greater decline in withdrawal severity. Our results support the clinical utility of mesocorticolimbic cue reactivity in monitoring the XR-NTX treatment outcomes and highlight the link between opioid withdrawal symptomatology and neural opioid cue reactivity.

Open-label Study of Injectable Extended-release Naltrexone (XR-NTX) in Healthcare Professionals With Opioid Dependence

OBJECTIVES

Healthcare professionals (HCPs) with opioid dependence are at risk for relapse and death, particularly in the first year of recovery; however, maintenance treatment with opioid agonists is controversial in this safety-sensitive group. We evaluated long-term safety, tolerability, and treatment outcomes of injectable, intramuscular, extended-release naltrexone (XR-NTX) in opioid-dependent HCPs.

METHODS

This single-arm, multisite, open-label study was conducted in opioid-dependent HCPs who had been detoxified from opioids for at least 2 weeks. Subjects received monthly XR-NTX injections for up to 24 months, combined with counseling via intensive outpatient substance abuse treatment programs. Assessments included monthly urine opioid drug tests and routine safety assessments, along with a trimonthly short form (36) Health Survey, opioid craving questionnaire, and Treatment Satisfaction Questionnaire for Medication.

RESULTS

Of 49 opioid-dependent HCPs screened, 38 enrolled and received at least 1 XR-NTX injection. Most were female (n = 31) and nurses or nursing assistants (n = 30). More than half (n = 21; 55.3%) received at least 12 injections. Seven discontinued due to adverse events (3 anxiety, 2 headache, 1 injection-site mass, 1 derealization). None experienced relapses to opioid dependence necessitating detoxification, overdose, or death during treatment. At 24 months, mean opioid craving fell by 45.2%, and short form (36) mental component scores improved by 31.1% from baseline and approached normal levels. Of 22 unemployed subjects at baseline, 45.5% improved employment status at 24 months.

CONCLUSIONS

Long-term (2 years) XR-NTX was associated with no new safety concerns, and, compared with shorter-term studies in the general population, similar or better rates of retention, opioid-negative urines, opioid craving reduction, mental health functional quality of life improvement, and re-employment.

Toward biomarkers of the addicted human brain: Using neuroimaging to predict relapse and sustained abstinence in substance use disorder

The ability to predict relapse is a major goal of drug addiction research. Clinical and diagnostic measures are useful in this regard, but these measures do not fully and consistently identify who will relapse and who will remain abstinent. Neuroimaging approaches have the potential to complement these standard clinical measures to optimize relapse prediction. The goal of this review was to survey the existing drug addiction literature that either used a baseline functional or structural neuroimaging phenotype to longitudinally predict a clinical outcome, or that examined test-retest of a neuroimaging phenotype during a course of abstinence or treatment. Results broadly suggested that, relative to individuals who sustained abstinence, individuals who relapsed had (1) enhanced activation to drug-related cues and rewards, but reduced activation to non-drug-related cues and rewards, in multiple corticolimbic and corticostriatal brain regions; (2) weakened functional connectivity of these same corticolimbic and corticostriatal regions; and (3) reduced gray and white matter volume and connectivity in prefrontal regions. Thus, beyond these regions showing baseline group differences, reviewed evidence indicates that function and structure of these regions can prospectively predict - and normalization of these regions can longitudinally track - important clinical outcomes including relapse and adherence to treatment. Future clinical studies can leverage this information to develop novel treatment strategies, and to tailor scarce therapeutic resources toward individuals most susceptible to relapse.

Disrupted coupling of large-scale networks is associated with relapse behaviour in heroin-dependent men

BACKGROUND

It is unknown whether impaired coupling among 3 core large-scale brain networks (salience [SN], default mode [DMN] and executive control networks [ECN]) is associated with relapse behaviour in treated heroin-dependent patients.

METHODS

We conducted a prospective resting-state functional MRI study comparing the functional connectivity strength among healthy controls and heroin-dependent men who had either relapsed or were in early remission. Men were considered to be either relapsed or in early remission based on urine drug screens during a 3-month follow-up period. We also examined how the coupling of large-scale networks correlated with relapse behaviour among heroin-dependent men.

RESULTS

We included 20 controls and 50 heroin-dependent men (26 relapsed and 24 early remission) in our analyses. The relapsed men showed greater connectivity than the early remission and control groups between the dorsal anterior cingulate cortex (key node of the SN) and the dorsomedial prefrontal cortex (included in the DMN). The relapsed men and controls showed lower connectivity than the early remission group between the left dorsolateral prefrontal cortex (key node of the left ECN) and the dorsomedial prefrontal cortex. The percentage of positive urine drug screens positively correlated with the coupling between the dorsal anterior cingulate cortex and dorsomedial prefrontal cortex, but negatively correlated with the coupling between the left dorsolateral prefrontal cortex and dorsomedial prefrontal cortex.

LIMITATIONS

We examined deficits in only 3 core networks leading to relapse behaviour. Other networks may also contribute to relapse.

CONCLUSION

Greater coupling between the SN and DMN and lower coupling between the left ECN and DMN is associated with relapse behaviour. These findings may shed light on the development of new treatments for heroin addiction.

Sustained opioid antagonism modulates striatal sensitivity to baby schema in opioid use disorder

BACKGROUND

Chronic opioid misuse is associated with reduced sensitivity to natural rewards and social motivation deficits that include impaired caregiving. The neurobiological mechanisms underlying these deficits and their response to treatment are not well understood. Baby schema (Kindchenschema) is a set of juvenile physical features, which is perceived as "cute" and triggers motivation for caregiving. Recent studies suggest that the "baby schema effect" is mediated by the brain "reward" network. We studied the impact of opioid antagonist treatment on the baby schema response in patients with opioid use disorder.

METHODS

Forty-seven (24 F) recently detoxified patients with opioid use disorder underwent functional magnetic resonance imaging (fMRI) while viewing infant portraits that were parametrically manipulated for baby schema content and rating them for cuteness, at baseline and during treatment with the injectable extended release opioid antagonist naltrexone (XRNTX). The study was not placebo-controlled.

RESULTS

The behavioral effect of baby schema, indexed by "cuteness" ratings, was present and unaffected by XRNTX. The brain response to baby schema was absent at baseline, but present in the bilateral ventral striatum after two weeks of XRNTX treatment. The decline in self-reported craving for opioids was positively correlated with the brain fMRI response to baby schema in the bilateral ventral striatum.

CONCLUSIONS

Opioid antagonist treatment modulated the brain reward system response to a marker of caregiving motivation in patients with opioid use disorder. Neural response to baby schema may offer a novel probe of social motivation and affiliative behaviors in this population.

Effects of incentives for naltrexone adherence on opiate abstinence in heroin-dependent adults

AIM

To test whether an incentive-based intervention that increased adherence to naltrexone also increased opiate abstinence.

DESIGN

Post-hoc combined analysis of three earlier randomized controlled trials that showed individually that incentives for adherence to oral and to extended-release injection naltrexone dosing schedules increased naltrexone adherence, but not opiate abstinence.

SETTING

Out-patient therapeutic work-place in Baltimore, MD, USA.

PARTICIPANTS

One hundred and forty unemployed heroin-dependent adults participating from 2006 to 2010.

INTERVENTIONS

Participants were hired in a model work-place for 26 weeks and randomized to a contingency (n = 72) or prescription (n = 68) group. Both groups were offered naltrexone. Contingency participants were required to take scheduled doses of naltrexone in order to work and earn wages. Prescription participants could earn wages independent of naltrexone adherence.

MEASURES

Thrice-weekly and monthly urine samples tested for opiates and cocaine and measures of naltrexone adherence (percentage of monthly urine samples positive for naltrexone or percentage of scheduled injections received). All analyses included pre-randomization attendance, opiate use and cocaine use as covariates. Additional analyses controlled for cocaine use and naltrexone adherence during the intervention.

FINDINGS

Contingency participants had more opiate abstinence than prescription participants (68.1 versus 52.9% opiate-negative thrice-weekly urine samples, respectively; and 71.9 versus 61.7% opiate-negative monthly urine samples, respectively) based on initial analyses [thrice-weekly samples, odds ratio (OR) = 3.3, 95% confidence interval (CI) = 1.7-6.5, P < 0.01; monthly samples, OR = 2.6, 95% CI = 1.0-7.1, P = 0.06] and on analyses that controlled for cocaine use (thrice-weekly samples, OR = 3.9, 95% CI = 3.3-4.5, P < 0.01; monthly samples, OR = 3.4, 95% CI = 1.1-11.1, P = 0.04), which was high and associated with opiate use. The difference in opiate abstinence rates between contingency and prescription participants was reduced when controlling for naltrexone adherence (monthly samples, OR = 1.1, 95% CI = 0.7-1.7, P = 0.84).

CONCLUSIONS

Incentives for naltrexone adherence increase opiate abstinence in heroin-dependent adults, an effect that appears to be due to increased naltrexone adherence produced by the incentives.