CLINICAL PREDICTORS OF RESPONSE TO NALTREXONE IN ALCOHOLIC PATIENTS: WHO BENEFITS MOST FROM TREATMENT WITH NALTREXONE?

Hazardous drinking and alcohol use disorders

Alcohol is one of the most widely consumed psychoactive drugs globally. Hazardous drinking, defined by quantity and frequency of consumption, is associated with acute and chronic morbidity. Alcohol use disorders (AUDs) are psychiatric syndromes characterized by impaired control over drinking and other symptoms. Contemporary aetiological perspectives on AUDs apply a biopsychosocial framework that emphasizes the interplay of genetics, neurobiology, psychology, and an individual's social and societal context. There is strong evidence that AUDs are genetically influenced, but with a complex polygenic architecture. Likewise, there is robust evidence for environmental influences, such as adverse childhood exposures and maladaptive developmental trajectories. Well-established biological and psychological determinants of AUDs include neuroadaptive changes following persistent use, differences in brain structure and function, and motivational determinants including overvaluation of alcohol reinforcement, acute effects of environmental triggers and stress, elevations in multiple facets of impulsivity, and lack of alternative reinforcers. Social factors include bidirectional roles of social networks and sociocultural influences, such as public health control strategies and social determinants of health. An array of evidence-based approaches for reducing alcohol harms are available, including screening, pharmacotherapies, psychological interventions and policy strategies, but are substantially underused. Priorities for the field include translating advances in basic biobehavioural research into novel clinical applications and, in turn, promoting widespread implementation of evidence-based clinical approaches in practice and health-care systems.

Clinical moderators of response to nalmefene in a randomized-controlled trial for alcohol dependence: An exploratory analysis

BACKGROUND

Nalmefene is the only medication marketed to reduce the consumption of alcohol in patients with alcohol dependence, but it remains unclear which patients could most benefit from it. This study aimed to identify clinical moderators that affect treatment response to nalmefene in patients with alcohol dependence.

METHODS

In a multicenter, randomized, controlled, double-blind, phase 3 study of nalmefene on Japanese patients with alcohol dependence, the relationship between the reduction of heavy drinking days (HDD) and total alcohol consumption (TAC) at 12 and 24 weeks of treatment and baseline variables of the participants were analyzed in a linear regression and multiple adjusted analysis.

RESULTS

Age < 65, no family history of problem drinking, age at onset of problem drinking ≥ 25, and not currently smoking were possible positive moderators. Nalmefene showed a significant HDD reduction in patients with age < 65 or no family history of problem drinking, and a significant TAC reduction in patients with age at onset of problem drinking ≥ 25 or who were not currently smoking. After multiple adjusted analyses, age < 65 (p = .028), no family history of problem drinking (p = .047), and age at onset of problem drinking ≥ 25 (p = .030) were statistically significant. Not currently smoking (p = .071) was marginally significant. In combination, these moderators indicated synergistic effects.

CONCLUSIONS

Alcohol-dependent patients with favorable prognostic factors such as non-smoking status, no family history of problem drinking, and a late-onset of problem drinking selectively benefit from nalmefene. Further research is needed to validate these exploratory results.

Occupancy of the kappa opioid receptor by naltrexone predicts reduction in drinking and craving

The efficacy of naltrexone to treat alcohol use disorder (AUD) is modest. A better understanding of the neurobiology underlying naltrexone effects could optimize treatments. We evaluated the occupancy of the kappa opioid receptor (KOR) by naltrexone measured with [¹¹C]-LY2795050 positron emission tomography (PET) as a predictor of response to naltrexone. Response to naltrexone was defined as the difference in craving and the difference between the number of drinks consumed during an alcohol drinking paradigm (ADP) before and after 1 week of supervised 100 mg daily oral naltrexone. Forty-four (14 F) nontreatment seeking heavy drinkers meeting criteria for AUD were enrolled. Participants drank 47 ± 16 drinks per week and were balanced in family history of alcoholism (FH, 26 positive). High KOR occupancy (92 ± 1%) was achieved. Occupancy was negatively associated with number of years drinking (YOD) in FH positive, but not FH negative, participants (t_3,42 = 4.00, p = 0.0003). Higher KOR occupancy by naltrexone was associated with higher alcohol craving during the ADP (F_1,81 = 4.88, p = 0.030). The reduction in drinking after naltrexone was negatively associated with KOR occupancy, with significant effects of FH status (t_1,43 = -2.08, p = 0.044). A logistic regression model including KOR occupancy, YOD, and FH variables achieved an 84% prediction accuracy for ≥50% reduction in drinking. These results confirm that naltrexone binds at the KOR site and suggest that KOR occupancy by naltrexone may be related to clinical response. Based on our results, we propose that differential affinities for the mu and KOR could explain why lower doses of naltrexone can have greater clinical efficacy.

Interventions to Improve Post-Detoxification Treatment Engagement and Alcohol Recovery: Systematic Review of Intervention Types and Effectiveness

AIMS

Most inpatient alcohol detoxification patients do not seek treatment post-discharge, which increases the risk of relapse and re-hospitalization. To date, there have been no efforts to synthesize the evidence supporting the broad range of available interventions for this critical transition. The current study is a systematic review and evaluation of interventions designed to promote treatment engagement and recovery following alcohol detoxification.

METHODS

The initial literature search yielded 6419 articles, published since 1999, from PubMed, CINAHL, PsycINFO, Psychology & Behavioral Sciences Collection and PsycARTICLES databases, 49 of which were eligible for full review. Data extraction included in-depth evaluation of intervention types, study and research design features, reported outcomes and study quality/bias indicators. All articles were coded by independent raters and final results were obtained through consensus.

RESULTS

Interventions included medical/medication, psychological/psychosocial, technological, mutual-help and combined approaches. On average, medical/medication interventions were less, and psychological/psychosocial and technological interventions were more likely to demonstrate efficacy with respect to treatment engagement and recovery. There was significant variability in study quality/bias but no significant differences across intervention types. Studies differed considerably across measured outcomes, internal and external validity, in/exclusion criteria and documentation of co-occurring psychiatric disorders.

CONCLUSION

Over half of studies reviewed reported empirical support for the intervention(s) evaluated. Although findings slightly favor non-medical interventions, the variability in study design and quality/bias requires more rigorous follow-up research. Recommendations from this review may guide future implementation and intervention development, which are critically needed to improve post-detoxification care and outcomes for patients with alcohol use disorder.

Predictive factors of long-term follow-up in treatment of Korean alcoholics with naltrexone or acamprosate

Medication is integral in treating alcohol use disorder. However, because of the small to medium effect size, much effort is being exerted to identify predicting factors for effective pharmacological treatment in alcohol abuse disorder. Rather than focusing on abstinence days, alcohol craving, or frequency of drinking, which has been the focus of previous studies. Recently, there have been several studies which focused on follow-up length as an indicator of pharmacological treatment effe ctiveness. The purpose of this study was to investigate the predicting factors of long-term follow-up in treating Korean alcoholics with naltrexone or acamprosate. A retrospective study was conducted. Medical records of all patients diagnosed from November 2008 to May 2017 with alcohol abuse or alcohol dependence at psychiatric clinics at PNUYH were reviewed. We examined total days of which naltrexone or acamprosate were prescribed, and investigated if there were predicting factors maintaining follow-up at least 180 days or more. With these data, logistic regression analysis was conducted. In naltrexone long group compared to naltrexone short group, factors of having medical comorbidities [odds ratio (OR) = 5.477, P = 0.012] showed higher OR. In acamprosate long group, factors of age (OR = 1.083, P = 0.030), and use of more than four psychotropic medications (OR = 7.107, P = 0.030), showed higher OR. In both medications, predicting factors were different from the other. Further study to investigate the reasons would provide us with a new insight.

Reward, Relief and Habit Drinking: Initial Validation of a Brief Assessment Tool

AIMS

Alcohol use disorder is highly heterogeneous. One approach to understanding this heterogeneity is the identification of drinker subtypes. A candidate classification consists of reward and relief subtypes. The current study examines a novel self-report measure of reward, relief, and habit drinking for its clinical correlates and subjective response (SR) to alcohol administration.

METHODS

Non-treatment-seeking heavy drinkers (n = 140) completed the brief reward, relief, habit drinking scale (RRHDS). A subset of this sample (n = 67) completed an intravenous alcohol administration. Individuals were classified into drinker subtypes. A crowdsourced sample of heavy drinkers (n = 187) completed the RRHDS and a validated reward relief drinking scale to compare drinking classification results.

RESULTS

The majority of the sample was classified as reward drinkers (n = 100), with fewer classified as relief (n = 19) and habit (n = 21) drinkers. Relief and habit drinkers reported greater tonic alcohol craving compared to reward drinkers. Reward drinkers endorsed drinking for enhancement, while relief drinkers endorsed drinking for coping. Regarding the alcohol administration, the groups differed in negative mood, such that relief/habit drinkers reported a decrease in negative mood during alcohol administration, compared to reward drinkers. The follow-up crowdsourcing study found a 62% agreement in reward drinker classification between measures and replicated the tonic craving findings.

CONCLUSIONS

Our findings suggest that reward drinkers are dissociable from relief/habit drinkers using the brief measure. However, relief and habit drinkers were not successfully differentiated, which suggests that these constructs may overlap phenotypically. Notably, measures of dysphoric mood were better at detecting group differences than measures capturing alcohol's rewarding effects.

The effects of nalmefene on emotion processing in alcohol use disorder - A randomized, controlled fMRI study

Nalmefene is a µ- and δ-opioid receptor antagonist and a partial κ-opioid receptor agonist. The drug is suggested to reduce the craving for, and the consumption of alcohol effectively, also alleviating anxiety and anhedonia. The present fMRI study is the first to investigate the processing of emotions as a possible mechanism of action of nalmefene in humans. Fifteen non-treatment-seeking participants suffering from alcohol use disorder (AUD) (24-66 years; 5 females) finished this randomized, placebo controlled, double blind study. Following a cross over design, participants received either a single dose nalmefene or a placebo, with an interval of one week between sessions. Using fMRI, we investigated neural reactivity during the presentation of emotional faces picture sets. Additionally, we performed a visual dot-probe task to detect nalmefene's effects on attentional bias. We detected an increase in the response to emotional faces in the supramarginal gyrus, the angular gyrus as well as the putamen in the nalmefene vs. placebo condition. However, contradictory to our initial hypotheses, amygdala activation was not altered significantly in the placebo condition - a limitation, which might be associated with a lack of activation in the placebo condition maybe due to the small sample size. Attentional bias analyses revealed an interaction effect by trend, which was driven by a significant effect in a sub-analysis showing increased attentional shift towards happy compared to fearful facial expressions under nalmefene. Nalmefene increased brain activation in areas responsible for empathy, social cognition and behavior, which might help alleviating the reinforcing properties of alcohol.

Testosterone modulation of ethanol effects on the �‑opioid receptor kinetics in castrated rats

The present investigation was conducted to evaluate the effects of testosterone on ethanol-induced alterations of µ-opioid receptor binding kinetics in specific brain regions of castrated rats. Male Sprague Dawley rats (100-124 g) adapted to a 12-h light/dark cycle were used. Animals were castrated under pentobarbital anesthesia. After a recovery period of 14 days, ethanol [3 g/kg as 22.5% solution in saline via intraperitoneal injection (i.p.)], testosterone [2.5 mg in 0.2 ml of olive oil via subcutaneous injection (s.c.) in the dorsal neck region] or the combination of ethanol and testosterone were administered to rats at 9:00 a.m. The control group was injected i.p. with 2 ml saline and s.c. with 0.2 ml olive oil for 7 days. Animals were sacrificed by decapitation at 2 h after the final injection. The brains were immediately removed, and the cortex, hippocampus, hypothalamus and midbrain were dissected. In an attempt to elucidate the mechanism involved in the hormonal modulation of the effects of ethanol and testosterone on the endogenous opioid system, the binding kinetics of the µ-opioid receptors were determined. The results obtained in the present study assisted in identifying the regulatory role of testosterone on ethanol-induced changes on µ-opioid receptor binding kinetics.

Neuroimaging findings from an experimental pharmacology trial of naltrexone in heavy drinkers of East Asian descent

BACKGROUND

Despite known genetic variation across races, studies examining pharmacogenetics of a single nucleotide polymorphism (SNP) of the mu-opioid receptor gene (OPRM1) on clinical response to naltrexone have been conducted in predominantly Caucasian samples. Evidence is mixed for pharmacogenetic OPRM1 and naltrexone effects on neural responses to alcohol cues. The current study tests the pharmacogenetic effects of naltrexone and OPRM1 on neural responses to alcohol taste cues in heavy drinkers of East Asian descent.

METHODS

Participants (N = 41) completed two double-blinded and counterbalanced functional magnetic resonance imaging (fMRI) sessions: one after taking naltrexone (50 mg/day) for four days and one after taking placebo for four days. Following titration, participants completed an fMRI alcohol taste-cues task. Analyses tested effects of naltrexone, OPRM1, and their interaction in whole-brain and region of interest (ROI) analyses of functional activation and functional connectivity in response to alcohol versus water taste cues.

RESULTS

We found no effects of naltrexone orOPRM1 on neural activation in whole-brain and ROI analyses, which included left and right ventral striatum (VS), anterior cingulate cortex (ACC), and orbitofrontal cortex (OFC). Naltrexone increased functional connectivity between left VS and clusters in medial prefrontal cortex, posterior cingulate gyrus, as well as right VS and occipital cortex, compared to placebo.

CONCLUSIONS

Naltrexone treatment enhanced functional connectivity in a key reinforcement-related pathway during alcohol versus water taste cues, corroborating neuroimaging work with other substances. Null medication and pharmacogenetics effects on functional activation add to a mixed naltrexone literature and may underscore the modest size of these effects in East Asians.

Naltrexone Acutely Enhances Connectivity Between the Ventromedial Prefrontal Cortex and a Left Frontoparietal Network

BACKGROUND

Naltrexone, an opioid receptor antagonist that is Food and Drug Administration approved for treating alcohol use disorder (AUD), reduces alcohol craving and intake. Despite known pharmacological properties, little is known regarding the effects of naltrexone on neural circuit function. Thus, a data-driven examination of the neural effects of naltrexone in human subjects may offer novel insight into its treatment mechanisms.

METHODS

Twenty-one alcohol using males (22 to 39) participated in a double-blind, placebo-controlled crossover study of the effects of naltrexone on brain voxel-wise functional connectivity (FC) using intersubject FC correlation mapping. We first cross-correlated the time series from each gray matter voxel to produce a 6,356 × 6,356 FC matrix for each subject and session. We then subtracted the placebo FC matrix from the naltrexone FC matrix. To identify brain regions demonstrating significant reconfiguration of whole-brain FC patterns following naltrexone treatment, we statistically quantified the consistency of patterns of voxel FC changes across subjects. Permutation testing identified significant clusters of voxels undergoing significant reconfiguration. Using the identified clusters in a seed-based FC analysis, we then compared the FC patterns of affected brain areas on placebo versus naltrexone in a paired t-test. Ridge regression analyses identified self-report measures, including substance use, that significantly predicted individual differences in FC among naltrexone-modulated regions.

RESULTS

Two clusters in the rostral anterior cingulate cortex (rACC)/ventromedial prefrontal cortex (vmPFC) demonstrated significant modulation of FC by naltrexone. Using these 2 proximal clusters as a single seed, specific FC changes were identified in regions associated with a left frontoparietal network (increasing), as well as visual and motor regions (decreasing). Stronger FC between the rACC/vmPFC and this set of regions on placebo was associated with more external locus of control, whereas weaker connectivity was associated with greater substance use problems. Naltrexone strengthened these connections most among individuals who reported greater drinking to cope.

CONCLUSIONS

Enhancing connectivity between the rACC/vmPFC, implicated in alcohol craving, and components of a left frontoparietal network involved in executive control may represent an effective strategy for the treatment of AUD.

Cost-Effectiveness Analysis of Genotype-Guided Treatment Allocation in Patients with Alcohol Use Disorders Using Naltrexone or Acamprosate, Using a Modeling Approach

Alcohol use disorders (AUD) are a major contributor to the global burden of disease, and have huge societal impact. Some studies show that AUD patients carrying the G-allele of the OPRM1 variant c.118A>G respond better to naltrexone, resulting in reduced relapse rates compared to carriers of the AA genotype. Genotype-guided treatment allocation of these patients carrying a G-allele to naltrexone could potentially improve the treatment outcome. However, cost-effectiveness of this strategy should be investigated before considering clinical implementation. We, therefore, evaluated costs and Quality-Adjusted Life-Years (QALYs), using a modelling approach, from an European perspective, of genotype-guided treatment allocation (G-allele carriers receiving naltrexone; AA homozygotes acamprosate or naltrexone) compared to standard care (random treatment allocation to acamprosate or naltrexone), by using a Markov model. Genotype-guided treatment allocation resulted in incremental costs of EUR 66 (95% CI -28 to 149) and incremental effects of 0.005 QALYs (95% CI 0.000-0.011) per patient (incremental cost-effectiveness ratio of EUR 13,350 per QALY). Sensitivity analyses showed that the risk ratio to relapse after treatment allocation had the largest impact on the cost-effectiveness. Depending on the willingness to pay for a gain of one QALY, probabilities that the intervention is cost-effective varies between 6 and 79%. In conclusion, pharmacogenetic treatment allocation of AUD patients to naltrexone, based on OPRM1 genotype, can be a cost-effective strategy, and could have potential individual and societal benefits. However, more evidence on the impact of genotype-guided treatment allocation on relapse is needed to substantiate these conclusions, as there is contradictory evidence about the effectiveness of OPRM1 genotyping.

Pharmacogenetic Effects of Naltrexone in Individuals of East Asian Descent: Human Laboratory Findings from a Randomized Trial

BACKGROUND

Genetic variation in the endogenous opioid system has been identified as 1 potential source of individual variability in naltrexone treatment outcomes. The majority of naltrexone pharmacogenetic studies have focused on a particular single nucleotide polymorphism (SNP) of the mu-opioid receptor gene (OPRM1; rs1799971; commonly known as the Asn40Asp SNP) in Caucasian samples with decidedly mixed results. The goal of this study was to test the pharmacogenetic effects of naltrexone on subjective response to alcohol and self-administration of alcohol in individuals of East Asian descent. We hypothesized that naltrexone, compared with placebo, would potentiate the aversive and sedative effects of alcohol and reduce alcohol self-administration to a greater extent in Asp40 carriers.

METHODS

Participants (N = 77; Asn40Asn, n = 29; Asn40Asp, n = 34, and Asp40Asp, n = 14) completed 2 double-blinded and counterbalanced experimental sessions: one after taking naltrexone (50 mg/d) for 5 days and one after taking matched placebo for 5 days. In each experimental session, participants received a priming dose of intravenous alcohol up to the breath alcohol concentration target of 0.06 g/dl which was immediately followed by an alcohol self-administration period (1 hour).

RESULTS

There were no pharmacogenetic effects observed for alcohol-induced stimulation, sedation, craving for alcohol, or alcohol self-administration in the laboratory. During the self-administration period, Asp40 carriers consumed fewer drinks and had a longer latency to first drink as compared to Asn40 homozygotes.

CONCLUSIONS

These findings in East Asians add to the mixed literature on naltrexone pharmacogenetics from predominantly Caucasian samples and highlight the complexity of these effects and their overall limited replicability. It is plausible that a consistent pharmacogenetic effect in tightly controlled preclinical and experimental medicine models "fades" in more complex and heterogeneous settings and samples.

Review article: pharmacotherapy for alcohol dependence - the why, the what and the wherefore

BACKGROUND

The development of alcohol dependence is associated with significant morbidity and mortality. For the majority of affected people the most appropriate goal, in terms of drinking behaviour, is abstinence from alcohol. Psychosocial intervention is the mainstay of the treatment but adjuvant pharmacotherapy is also available and its use recommended.

AIM

To provide an updated analysis of current and potential pharmacotherapeutic options for the management of alcohol dependence. In addition, factors predictive of therapeutic outcome, including compliance and pharmacogenetics, and the current barriers to treatment, including doctors' unwillingness to prescribe these agents, will be explored.

METHODS

Relevant papers were selected for review following extensive, language- and date-unrestricted, electronic and manual searches of the literature.

RESULTS

Acamprosate and naltrexone have a substantial evidence base for overall efficacy, safety and cost-effectiveness while the risks associated with the use of disulfiram are well-known and can be minimised with appropriate patient selection and supervision. Acamprosate can be used safely in patients with liver disease and in those with comorbid mental health issues and co-occurring drug-related problems. A number of other agents are being investigated for potential use for this indication including: baclofen, topiramate and metadoxine.

CONCLUSION

Pharmacotherapy for alcohol dependence has been shown to be moderately efficacious with few safety concerns, but it is substantially underutilised. Concerted efforts must be made to remove the barriers to treatment in order to optimise the management of people with this condition.

Predictors of Continued Use of Extended-Released Naltrexone (XR-NTX) for Opioid-Dependence: An Analysis of Heroin and Non-Heroin Opioid Users in Los Angeles County

Extended-release naltrexone (XR-NTX) is associated with an increased number of opioid-free days, improved adherence rates in substance use disorder treatment programs, and reduced cravings and drug-seeking behaviors. There is little evidence on the predictive associations between baseline characteristics of opioid-dependent patients and XR-NTX utilization. Some studies have demonstrated better pharmacotherapy adherence and/or retention rates among non-heroin opioid users compared to heroin users. This study examines predictive associations between characteristics of patients and XR-NTX utilization, as well as participants' urge to use opiates. Our findings suggest that XR-NTX may contribute to decreases in urges to use among both heroin and non-heroin opioid users. Non-heroin opioid users and heroin users were retained in XR-NTX treatment for comparable periods of time. However, those who identified as homeless, injected opioids (regardless of opioid-type), or were diagnosed with a mental illness were less likely to be retained in treatment with XR-NTX.

Effects of naltrexone on neural and subjective response to alcohol in treatment-seeking alcohol-dependent patients

BACKGROUND

Positively reinforcing properties of alcohol are in part mediated by activation of the ventral striatum (VS). Alcohol-induced release of endogenous opioids is thought to contribute to this response. Preclinical studies show that the opioid antagonist naltrexone (NTX) can block this cascade, but its ability to do so in treatment-seeking alcoholics has not been examined. Our objective was to study the effects of NTX on alcohol-induced VS activation and on amygdala response to affective stimuli in treatment-seeking alcohol-dependent inpatients.

METHODS

Sixty-three treatment-seeking alcoholics were randomized to receive NTX (50 mg) or placebo (PLC) daily. On Day 7, participants underwent an alcohol cue reactivity session, and craving was measured using the Penn Alcohol Craving Scale. On Day 9, participants received a saline infusion followed by an alcohol infusion and also viewed affective stimuli in a magnetic resonance scanner.

RESULTS

Irrespective of medication treatment condition, the alcohol infusion did not activate the VS in the alcohol-dependent patients. Unexpectedly, VS activation was greater in NTX treated patients than in the PLC group. NTX treated patients also reported increased craving in response to alcohol cue exposure, and increased subjective response to alcohol ("high" and "intoxicated") compared to PLC subjects. No significant effects of alcohol infusion on brain response to affective stimuli were in the NTX or PLC groups.

CONCLUSIONS

Unlike previous findings in social drinkers, a moderate level of intoxication did not activate the VS in treatment-seeking alcoholics. This is likely to reflect tolerance to the positively reinforcing properties of alcohol in this clinical population. Our findings may help explain the efficacy of NTX to reduce heavy drinking, but not to maintain abstinence.

Pharmacotherapy for alcohol dependence: A stratified approach

Alcohol dependence is a common disorder in many societies worldwide, and remains difficult to identify and treat. It is also a risk factor for many secondary non-communicable diseases. Pharmacotherapy is one available treatment option, but appears to be underutilised in practice. Major barriers to use of medications in this area include lack of clinical guidance and questionable efficacy. However, for each medication there appears to be a subpopulation that responds positively, and understanding the moderating factors to treatment efficacy is an important research goal. Thus, this review provides a narrative regarding potential stratification techniques in pharmacological treatment of alcohol dependence, with a specific focus on typologies and pharmacogenetics. In addition, we discuss the basic background of stratified medicine and recent studies on genetic predisposition to alcohol dependence. A growing repository of data exists for both approved and non-approved pharmacotherapies, but failure to replicate findings, inadequate sample sizes, and insufficient funding has resulted in a translational gap. Implementing evidence-based stratified/personalised therapy and identifying new therapeutic agents may lead to improved clinical outcomes and reduced financial burden. Despite some promising findings to date, much work is still required.

Inhibition of alcohol self-administration by positive allosteric modulators of the GABAB receptor in rats: lack of tolerance and potentiation of baclofen

RATIONALE

Treatment with positive allosteric modulators (PAMs) of the GABAB receptor (GABAB PAMs) inhibits several alcohol-motivated behaviors in rodents, including operant, oral alcohol self-administration.

OBJECTIVES

The present study assessed the effects of (a) repeated administration of the GABAB PAMs, GS39783, and rac-BHFF and (b) a combination of an ineffective dose of either GS39783, or rac-BHFF, and an ineffective dose of the prototypic GABAB receptor agonist, baclofen, on operant, oral alcohol self-administration.

METHODS

Studies were conducted using selectively bred Sardinian alcohol-preferring (sP) rats exposed to a standard procedure of fixed ratio (FR) 4 (FR4) schedule of reinforcement for 15 % (v/v) alcohol.

RESULTS

Repeated treatment with GS39783 (50 mg/kg, i.g.) or rac-BHFF (50 mg/kg, i.g.) produced an initial 40 % reduction in number of lever responses for alcohol and amount of self-administered alcohol that was maintained unaltered throughout the 10-day period of the GS39783 treatment and increased throughout the 5-day period of the rac-BHFF treatment. Combination of per se ineffective doses of GS39783 (5 mg/kg, i.g.), or rac-BHFF (5 mg/kg, i.g.), and baclofen (1 mg/kg, i.p.) reduced, by 35-45 %, both number of lever responses for alcohol and amount of self-administered alcohol.

CONCLUSIONS

GS39783 and rac-BHFF (a) reduced alcohol reinforcing properties when given repeatedly, with no development of tolerance, and (b) potentiated baclofen effect. Both sets of data possess translational interest, as they suggest potential effectiveness of GABAB PAMs under chronic treatment and selective potentiation of baclofen effect.

Effects of systemic opioid receptor ligands on ethanol- and sucrose seeking and drinking in alcohol-preferring (P) and Long Evans rats

The endogenous opioid system has been implicated in mediating the reinforcing effects of ethanol (EtOH). Naltrexone (NTX), an opioid antagonist with concentration-dependent selectivity for the mu receptor, naltrindole (NTI), a selective delta receptor antagonist, and U50,488H, a selective kappa receptor agonist were examined in both alcohol-preferring (P) and nonselected (Long Evans (LE)) rats to determine whether they differentially affected the seeking and consumption of EtOH and sucrose. Using the sipper-tube model, rats reinforced with either 2% sucrose or 10% EtOH were injected with vehicle and either NTI (2.5, 5.0, or 10.0 mg/kg), U50 (2.5, 5.0, or 10.0 mg/kg), low-dose NTX (0.1, 0.3, or 1.0 mg/kg), or high-dose NTX (1.0, 3.0, or 10.0 mg/kg). Subsequent intakes (consummatory) or lever responses (seeking) were assessed. Overall, NTI, U50, and NTX attenuated intake and responding for sucrose and EtOH, with EtOH-reinforced P rats being the most sensitive to the effects of NTI on intake and seeking. U50 treatment decreased intake and seeking in both P and LE rats but did not selectively reduce EtOH intake or seeking in either line. P rats were more sensitive than LE rats to lower doses of NTX, and these doses more selectively attenuated responding for EtOH than sucrose. Higher doses of NTX suppressed intake and responding across both lines and reinforcers. These results suggest that drugs selective for the opioid receptors may be good pharmacotherapeutic targets, particularly in those with an underlying genetic predisposition for greater EtOH preference/intake.

Clinical and biological moderators of response to naltrexone in alcohol dependence: a systematic review of the evidence

AIM

The goal of this systematic review was to identify moderators of naltrexone efficacy in the treatment of alcohol dependence.

METHODS

We searched Pubmed, CINHAL, Embase, PsycINFO and the Cochrane Library from 1990 to April 2012 and reference lists of pertinent review articles, which yielded 622 trial, pooled analysis and review articles. Using pre-established eligibility criteria, two reviewers independently determined whether abstracts contained evidence of demographic or biological characteristics, i.e. moderators, influencing naltrexone response in alcohol dependence. We assessed each publication for risk of bias and evaluated the strength of the body of evidence for each moderator.

RESULTS

Twenty-eight publications (on 20 studies) met criteria for data synthesis. These included 26 publications from 12 randomized, placebo-controlled trials, three non-randomized, non-placebo studies and one randomized, non-placebo study. In addition, there were two publications from pooled analyses of four randomized, placebo-controlled trials. Family history of alcohol problems and the Asn40Asp polymorphism of the μ-opioid receptor gene showed a positive association with efficacy in four of five and three of five studies, respectively. Other moderators reported to be associated with efficacy included male sex (two of five studies), pre-treatment drinking (two of two studies) and high craving (two of five studies). However, the overall risk of bias in the published literature is high.

CONCLUSIONS

The identification of naltrexone-responsive alcohol-dependent patients is still in development. Studies to date point to two potential moderators-family history and presence of the OPRM1 Asn40Asp polymorphism-as having the strongest evidence. However, the data to date is still insufficient to recommend that any moderator be used in determining clinical treatment.

Improving clinical outcomes for naltrexone as a management of problem alcohol use

Despite being a relatively effective and safe treatment, the clinical management of alcohol abuse/dependence by oral naltrexone can be compromised due to the patient's non-compliance with daily use of this medication. Over the past decade an increasing body of research has suggested that the use of sustained release depot naltrexone preparations can overcome this issue and deliver improved clinical outcomes. However, at the same time, research findings from diverse areas of pharmacogenetics, neurobiology and behavioural psychology have also been converging to identify variables including genetic markers, patient psychosocial characteristics and drug use history differences, or clusters of these variables that play a major role in mediating the response of alcohol abuse/dependent persons to treatment by naltrexone. While this article does not attempt to review all available data pertaining to an individual alcohol dependent patient's response to treatment by naltrexone, it does identify relevant research areas and highlights the importance of data arising from them. The characterization of clinical markers, to identify those patients who are most likely to benefit from naltrexone and to tailor a more individual naltrexone treatment, will ultimately provide significant benefit to both patients and clinicians by optimizing treatment outcome.

Targeted opioid receptor antagonists in the treatment of alcohol use disorders

In 1994, the US Food and Drug Administration approved the μ-opioid receptor antagonist naltrexone to treat alcohol dependence. However, treatments requiring daily administration, such as naltrexone, are inconsistently adhered to in substance abusing populations, and constant medication exposure can increase risk of adverse outcomes, e.g., hepatotoxicity. This has fostered a 'targeted' or 'as needed' approach to opioid receptor antagonist treatment, in which medications are used only in anticipation of or during high-risk situations, including times of intense cravings. Initial studies of the ability of targeted naltrexone to reduce drinking-related outcomes were conducted in problem drinkers and have been extended into larger, multi-site, placebo-controlled investigations with positive results. Another μ-opioid receptor antagonist, nalmefene, has been studied on an 'as-needed' basis to reduce heavy drinking in alcohol-dependent individuals. These studies include three large multi-site trials in Europe of up to 1 year in duration, and serve as the basis for the recent approval of nalmefene by the European Medicines Agency as an 'as-needed' adjunctive treatment for alcohol dependence. We review potential moderators of opioid receptor antagonist treatment response including subjective assessments, objective clinical measures and genetic variants. In sum, the targeted or 'as-needed' approach to treatment with opioid antagonists is an efficacious harm-reduction strategy for problem drinking and alcohol dependence.

The μ-opioid receptor and treatment response to naltrexone

AIMS

To evaluate the pharmacogenetic evidence relating to the use of opioid antagonists (in particular naltrexone) in treating patients with alcohol abuse problems.

METHODS

Narrative review of pre-clinical and clinical published research regarding genetic modulation of psychotropic effects produced by alcohol and the therapeutic effects of opioid antagonists.

RESULTS

Alcohol activates brain reward pathways, leading to positive reinforcement of alcohol seeking and consumption. Thus, the underlying biological mechanisms may be targets for treatment, particularly in the early stages of addiction development. Alcohol reward is in part mediated by endogenous opioids. A single-nucleotide polymorphism (SNP) within the OPRM1 gene, A118G, leading to an amino acid change (Asn40Asp) in the extracellular portion of the receptor, has been implicated in alcoholism as well as in drug addiction, pain sensitivity and stress response, and in animal and human studies relates to the alcohol-dependent phenotype as well as to the treatment response to the µ-opioid antagonist naltrexone.

CONCLUSION

The effect size reported in naltrexone clinical studies is often small, which may be due to heterogeneity among patients. Pharmacogenetic approaches may help guide us in the search for the appropriate treatment optimal for one patient's need.

Cigarette smoking predicts differential benefit from naltrexone for alcohol dependence

BACKGROUND

Identifying factors that modify responsiveness to pharmacotherapies for alcohol dependence is important for treatment planning. Cigarette smoking predicts more severe alcohol dependence and poorer treatment response in general. Nevertheless, there is limited research on cigarette smoking as a potential predictor of differential response to pharmacological treatment of alcoholism.

METHODS

We examined the association between cigarette smoking and drinking outcomes in the COMBINE (Combined Pharmacotherapies and Behavioral Interventions for Alcohol Dependence) study, a randomized, double-blind placebo-controlled 16-week trial comparing combinations of medications (i.e., acamprosate and naltrexone) and behavioral interventions (i.e., medical management, combined behavioral therapy) in 1383 alcohol-dependent individuals.

RESULTS

Smokers (i.e., more than one half the sample) significantly differed from nonsmokers on several demographic and drinking-related variables at baseline and generally had poorer treatment outcomes than nonsmokers. However, smokers who received naltrexone had better drinking outcomes than smokers who received placebo, whereas alcohol use among nonsmokers did not vary by naltrexone assignment. This pattern of findings occurred independent of whether patients received combined behavioral intervention or medical management and remained after controlling for alcoholism typology and baseline demographic differences. Approximately 9% of smokers quit smoking, and an additional 10% reduced their cigarette intake during treatment. Reductions in smoking did not vary by treatment assignment.

CONCLUSIONS

These results suggest that naltrexone might be particularly beneficial for improving alcohol use outcomes in alcohol-dependent smokers.

Personalized treatment of alcohol dependence

Pharmacogenetic and adaptive treatment approaches can be used to personalize care for alcohol-dependent patients. Preliminary evidence shows that variation in the gene encoding the μ-opioid receptor moderates the response to naltrexone when used to treat alcohol dependence. Studies have also shown moderating effects of variation in the gene encoding the serotonin transporter on response to serotonergic treatment of alcohol dependence. Adaptive algorithms that modify alcohol treatment based on patients' progress have also shown promise. Initial response to outpatient treatment appears to be a particularly important in the selection of optimal continuing care interventions. In addition, stepped-care algorithms can reduce the cost and burden of treatment while maintaining good outcomes. Finally, matching treatment to specific problems present at intake or that emerge during treatment can also improve outcomes. Although all of these effects require replication and further refinement, the future of personalized care for alcohol dependence appears bright.

Neuropeptides as mediators of the early-life impact on the brain; implications for alcohol use disorders

The brain is constantly exposed to external and internal input and to function in an ever-changing environment we are dependent on processes that enable the brain to adapt to new stimuli. Exposure to postnatal environmental stimuli can interfere with vital adaption processes and cause long-term changes in physiological function and behavior. Early-life alterations in brain function may result in impaired ability to adapt to new situations, in altered sensitivity to challenges later in life and thereby mediate risk or protection for psychopathology such as alcohol use disorders (AUD). In clinical research the studies of mechanisms, mediators, and causal relation between early environmental factors and vulnerability to AUD are restricted and attempts are made to find valid animal models for studies of the early-life influence on the brain. This review focuses on rodent models and the effects of adverse and naturalistic conditions on peptide networks within the brain and pituitary gland. Importantly, the consequences of alcohol addiction are not discussed but rather neurobiological alterations that can cause risk consumption and vulnerability to addiction. The article reviews earlier results and includes new data and multivariate data analysis with emphasis on endogenous opioid peptides but also oxytocin and vasopressin. These peptides are vital for developmental processes and it is hypothesized that early-life changes in peptide networks may interfere with neuronal processes and thereby contribute the individual vulnerability for AUD. The summarized results indicate a link between early-life rearing conditions, opioids, and ethanol consumption and that the ethanol-induced effects and the treatment with opioid antagonists later in life are dependent on early-life experiences. Endogenous opioids are therefore of interest to further study in the early-life impact on individual differences in vulnerability to AUD and treatment outcome.

BAP updated guidelines: evidence-based guidelines for the pharmacological management of substance abuse, harmful use, addiction and comorbidity: recommendations from BAP

The British Association for Psychopharmacology guidelines for the treatment of substance abuse, harmful use, addiction and comorbidity with psychiatric disorders primarily focus on their pharmacological management. They are based explicitly on the available evidence and presented as recommendations to aid clinical decision making for practitioners alongside a detailed review of the evidence. A consensus meeting, involving experts in the treatment of these disorders, reviewed key areas and considered the strength of the evidence and clinical implications. The guidelines were drawn up after feedback from participants. The guidelines primarily cover the pharmacological management of withdrawal, short- and long-term substitution, maintenance of abstinence and prevention of complications, where appropriate, for substance abuse or harmful use or addiction as well management in pregnancy, comorbidity with psychiatric disorders and in younger and older people.

Association of µ-opioid receptor (OPRM1) gene polymorphism with response to naltrexone in alcohol dependence: a systematic review and meta-analysis

Previous studies have suggested that the effect of naltrexone in patients with alcohol dependence may be moderated by genetic factors. In particular, the possession of the G allele of the A118G polymorphism of the µ-opioid receptor gene (OPRM1) has been associated with a better response to naltrexone, although controversial results have been reported. The aim of this paper is to combine previous findings by means of a systematic review and a meta-analysis. We retrieved studies on the relationship between A118G polymorphism in OPRM1 gene and response to treatment with naltrexone in patients with alcohol dependence by means of electronic database search. A meta-analysis was conducted using a random-effects model. Calculations of odds ratio (OR) and their confidence intervals (CI) and tests for heterogeneity of the results have been performed. Six previous studies have analyzed the role of A118G polymorphism in response to naltrexone for alcohol dependence. After meta-analysis, we found that naltrexone-treated patients carrying the G allele had lower relapse rates than those who were homozygous for the A allele (OR: 2.02, 95% CI 1.26-3.22; P = 0.003). There were no differences in abstinence rates. Our results support the fact that the G allele of A118G polymorphism of OPRM1 moderates the effect of naltrexone in patients with alcohol dependence. This genetic marker may therefore identify a subgroup of individuals more likely to respond to this treatment.

The genetics of the opioid system and specific drug addictions

Addiction to drugs is a chronic, relapsing brain disease that has major medical, social, and economic complications. It has been established that genetic factors contribute to the vulnerability to develop drug addiction and to the effectiveness of its treatment. Identification of these factors may increase our understanding of the disorders, help in the development of new treatments and advance personalized medicine. In this review, we will describe the genetics of the major genes of the opioid system (opioid receptors and their endogenous ligands) in connection to addiction to opioids, cocaine, alcohol and methamphetamines. Particular emphasis is given to association and functional studies of specific variants. We will provide information on the sample populations and the size of each study, as well as a list of the variants implicated in association with addiction-related phenotypes, and with the effectiveness of pharmacotherapy for addiction.

Comparison of the effect of the GABAΒ receptor agonist, baclofen, and the positive allosteric modulator of the GABAB receptor, GS39783, on alcohol self-administration in 3 different lines of alcohol-preferring rats

BACKGROUND

Administration of the GABA(B) receptor agonist, baclofen, and positive allosteric modulator, GS39783, has been repeatedly reported to suppress multiple alcohol-related behaviors, including operant oral alcohol self-administration, in rats. This study was designed to compare the effect of baclofen and GS39783 on alcohol self-administration in 3 lines of selectively bred, alcohol-preferring rats: Indiana alcohol-preferring (P), Sardinian alcohol-preferring (sP), and Alko Alcohol (AA).

METHODS

Rats of each line were initially trained to respond on a lever, on a fixed ratio (FR) 4 (FR4) schedule of reinforcement, to orally self-administer alcohol (15%, v/v) in daily 30-minute sessions. Once responding reached stable levels, rats were exposed to a sequence of experiments testing baclofen (0, 1, 1.7, and 3 mg/kg; i.p.) and GS39783 (0, 25, 50, and 100 mg/kg; i.g.) on FR4 and progressive ratio (PR) schedules of reinforcement. Finally, to assess the specificity of baclofen and GS39783 action, rats were slightly food-deprived and trained to lever-respond for food pellets.

RESULTS

The rank of order of the reinforcing and motivational properties of alcohol was P>sP>AA rats. Under both FR and PR schedules of reinforcement, the rank of order of potency and efficacy of baclofen and GS39783 in suppressing alcohol self-administration was P>sP>AA rats. Only the highest dose of baclofen reduced lever-responding for food pellets; this effect was common to all 3 rat lines. Conversely, no dose of GS39783 altered lever-responding for food in any rat line.

CONCLUSIONS

These results suggest that: (i) the strength of the reinforcing and motivational properties of alcohol differ among P, sP, and AA rats; (ii) the reinforcing and motivational properties of alcohol in P, sP, and AA rats are differentially sensitive to treatment with baclofen and GS39783; (iii) the heterogeneity in sensitivity to baclofen and GS39783 of alcohol self-administration in P, sP, and AA rats may resemble the differential effectiveness of pharmacotherapies among the different typologies of human alcoholics; and (iv) the GABA(B) receptor is part of the neural substrate mediating the reinforcing and motivational properties of alcohol.

Pharmacogenetic approaches to the treatment of alcohol addiction

Addictive disorders are partly heritable, chronic, relapsing conditions that account for a tremendous disease burden. Currently available addiction pharmacotherapies are only moderately successful, continue to be viewed with considerable scepticism outside the scientific community and have not become widely adopted as treatments. More effective medical treatments are needed to transform addiction treatment and address currently unmet medical needs. Emerging evidence from alcoholism research suggests that no single advance can be expected to fundamentally change treatment outcomes. Rather, studies of opioid, corticotropin-releasing factor, GABA and serotonin systems suggest that incremental advances in treatment outcomes will result from an improved understanding of the genetic heterogeneity among patients with alcohol addiction, and the development of personalized treatments.

Predictors for the efficacy of naltrexone treatment in alcohol dependence: sweet preference

AIMS

To analyse the possible associations between sweet preference and the efficacy of naltrexone treatment of alcohol dependence.

METHODS

The preference for different concentrations of sucrose was evaluated in 78 participants diagnosed with alcohol dependence after treatment for 32 weeks with naltrexone or placebo without prior detoxification.

RESULTS

A significant difference between naltrexone and placebo groups was found in the association between the preference for higher sucrose concentrations and relapses to heavy drinking. Higher sweet preference was significantly related to successful treatment measures in the naltrexone group but not in the placebo group.

CONCLUSION

Sweet preference has a strong correlation to treatment outcomes with naltrexone, and sweet preference might be used as a predictor for better treatment results in alcoholics. Our study offers one possible new explanation of the clinical observation that naltrexone is not effective for every patient.

Opioid antagonists for alcohol dependence

BACKGROUND

Alcohol dependence belongs to the globally leading health risk factors. Therapeutic success of psychosocial programs for relapse prevention is moderate and could be increased by an adjuvant treatment with the opioid antagonists naltrexone and nalmefene.

OBJECTIVES

To determine the effectiveness and tolerability of opioid antagonists in the treatment of alcohol dependence.

SEARCH STRATEGY

We searched the Cochrane Drugs and Alcohol Group (CDAG) Specialized Register, PubMed, EMBASE and CINAHL in January 2010 and inquired manufacturers and researchers for unpublished trials.

SELECTION CRITERIA

All double-blind randomised controlled trials (RCTs) which compare the effects of naltrexone or nalmefene with placebo or active control on drinking-related outcomes.

DATA COLLECTION AND ANALYSIS

Two authors independently extracted outcome data. Trial quality was assessed by one author and cross-checked by a second author.

MAIN RESULTS

Based on a total of 50 RCTs with 7793 patients, naltrexone reduced the risk of heavy drinking to 83% of the risk in the placebo group RR 0.83 (95% CI 0.76 to 0.90) and decreased drinking days by about 4%, MD -3.89 (95% CI -5.75 to -2.04). Significant effects were also demonstrated for the secondary outcomes of the review including heavy drinking days, MD - 3.25 (95% CI -5.51 to -0.99), consumed amount of alcohol, MD - 10.83 (95% CI -19.69 to -1.97) and gamma-glutamyltransferase, MD - 10.37 (95% CI -18.99 to -1.75), while effects on return to any drinking, RR 0.96 (95 CI 0.92 to 1.00) missed statistical significance. Side effects of naltrexone were mainly gastrointestinal problems (e.g. nausea: RD 0.10; 95% CI 0.07 to 0.13) and sedative effects (e.g. daytime sleepiness: RD 0.09; 95% CI 0.05 to 0.14). Based on a limited study sample, effects of injectable naltrexone and nalmefene missed statistical significance. Effects of industry-sponsored studies, RR 0.90 (95% CI 0.78 to 1.05) did not significantly differ from those of non-profit funded trials, RR 0.84 (95% CI 0.77 to 0.91) and the linear regression test did not indicate publication bias (P = 0.765).

AUTHORS' CONCLUSIONS

Naltrexone appears to be an effective and safe strategy in alcoholism treatment. Even though the sizes of treatment effects might appear moderate in their magnitudes, these should be valued against the background of the relapsing nature of alcoholism and the limited therapeutic options currently available for its treatment.

Translating the neuroscience of alcoholism into clinical treatments: from blocking the buzz to curing the blues

Understanding the pathophysiology of addictive disorders is critical for development of new treatments. A major focus of addiction research has for a long time been on systems that mediate acute positively reinforcing effects of addictive drugs, most prominently the mesolimbic dopaminergic (DA) system and its connections. This research line has been successful in shedding light on the physiology of both natural and drug reward, but has not led to therapeutic breakthroughs. The role of classical reward systems is perhaps least clear in alcohol addiction. Here, recent work is summarized that points to some clinically important conclusions. First, important pharmacogenetic differences exist with regard to positively reinforcing effects of alcohol and the ability of this drug to activate classical reward pathways. This offers an opportunity for personalized treatment approaches in alcoholism. Second, brain stress and fear systems become pathologically activated in later stages of alcoholism and their activation is a major influence in escalation of alcohol intake, sensitization of stress responses, and susceptibility to relapse. These findings offer a new category of treatment mechanisms. Corticotropin-releasing hormone (CRH) signaling through CRH1 receptors is a major candidate target in this category, but recent data indicate that antagonists for substance P (SP) neurokinin 1 (NK1) receptors may have a similar potential.

Suppression of alcohol preference by naltrexone in the rhesus macaque: a critical role of genetic variation at the micro-opioid receptor gene locus

BACKGROUND

The role of a nonsynonymous A118G polymorphism of the human micro-opioid receptor gene (OPRM1) for alcohol reward and therapeutic efficacy of naltrexone remains controversial. A functionally equivalent OPRM1 C77G polymorphism in rhesus macaques allows this to be addressed under controlled experimental conditions.

METHODS

Twenty-one rhesus macaques (13 female rhesus macaques, 8 male rhesus macaques) were genotyped for OPRM1 C77G and studied during 1-hour sessions for preference between an aspartame-sweetened alcohol solution (8.4% vol/vol) and a nonalcoholic control fluid in a baseline session followed by naltrexone (1 mg/kg) and vehicle treatment in a counterbalanced within-subject design.

RESULTS

Mixed-model analysis of variance controlling for baseline and sex showed a highly significant (p = .003) interaction between genotype and treatment. Post hoc analysis showed that vehicle-treated 77G carriers had markedly higher alcohol preference than 77C homozygous subjects (p = .001). Following naltrexone administration, 77G carriers decreased their preference (p = .002) and no longer differed from 77C homozygous subjects. In contrast, the latter group was unaffected by treatment and, in fact, showed a trend-level increase of preference following naltrexone.

CONCLUSIONS

These results support a critical pharmacogenetic role of OPRM1 variation for therapeutic efficacy of naltrexone.

Pharmacogenetics of alcohol and alcohol dependence treatment

In this article, we review studies of genetic moderators of the response to medications to treat alcohol dependence, the acute response to alcohol, and the response to the psychotherapeutic treatment of heavy drinking. We consider four neurotransmitter systems: opioidergic, dopaminergic, GABAergic, and glutamatergic and focus on one receptor protein in each: OPRM1 (the &#micro;-opioid receptor gene), DRD4 (the D(4) dopamine receptor gene), GABRA2 (GABA(A) receptor alpha-2 subunit gene), and GRIK1 (the kainite receptor GluR5 subunit gene). We conclude that because parallel developments in alcoholism treatment and the genetics of alcohol dependence are beginning to converge, using genotypic information, it may be possible to match patients with specific treatments. Of greatest clinical relevance is the finding that the presence of an Asp40 allele in OPRM1 modestly predicts a better response to naltrexone treatment. Promising findings include the observations that a polymorphism in GABRA2 predicts the response to specific psychotherapies; a polymorphism in DRD4 predicts the effects of the antipsychotic olanzapine on craving for alcohol and drinking behavior; and a polymorphism in GRIKI predicts adverse events resulting from treatment with the anticonvulsant topiramate. Although variants in other genes have been associated with the risk for alcohol dependence, they have not been studied as moderators of the response either to treatment or acute alcohol administration. We recommend that, whenever possible, treatment trials include the collection of DNA samples to permit pharmacogenetic analyses, and that such analyses look broadly for relevant genetic variation.

Sweet liking phenotype, alcohol craving and response to naltrexone treatment in alcohol dependence

AIMS

To investigate the relationship between the sweet liking/sweet disliking phenotype (a putative probe of brain opioid function), craving for alcohol and response to treatment with naltrexone in individuals with alcohol dependence.

METHODS

Forty individuals with alcohol dependence were enrolled in a 12-week open-label study of 50 mg of naltrexone with four sessions of motivational enhancement therapy. Prior to treatment, individuals completed a sweet preference test and the Penn Alcohol Craving Scale. Subjects were categorized as sweet liking (SL), n = 15, or sweet disliking (SDL), n = 25, via a standard sweet tasting paradigm. The sweet tasting results were blinded to the subjects and to treatment staff. SL status, pretreatment craving and their interaction were examined as predictors of frequency of abstinent days and heavy drinking days during treatment with naltrexone.

RESULTS

SL and SDL subjects achieved similar reductions in percent heavy drinking days with treatment. During treatment, SDL subjects had 48% abstinent days compared to 30% for SL subjects (P = 0.034). Pretreatment craving did not predict % heavy drinking days or % abstinent days. An interaction effect was found between the SL/SDL phenotype and pretreatment craving such that SL subjects with high craving demonstrated higher rates of percent abstinent days whereas SDL subjects with high craving demonstrated lower rates of percent abstinent days, P < 0.001.

CONCLUSIONS

These findings indicate that the SL/SDL phenotype may predict variation in response to naltrexone and/or counseling treatment. Furthermore, the SL/SDL phenotype may interact with craving to provide a more robust prediction of outcome with naltrexone or counseling.

Effects of opioid receptor gene variation on targeted nalmefene treatment in heavy drinkers

BACKGROUND

Recent studies examining the moderating effects of polymorphic variation in opioid receptor genes have yielded conflicting results. We examined opioid receptor gene polymorphisms as moderators of the therapeutic effects of the opioid antagonist nalmefene.

METHODS

Participants (n = 272) were subjects who consented to the pharmacogenetic analysis of a multi-site, randomized, placebo-controlled trial of targeted nalmefene for the reduction of heavy drinking. We genotyped two single nucleotide polymorphisms (SNPs) in OPRM1 (including A118G, a commonly studied SNP that encodes an Asn40Asp amino acid substitution), two SNPs in OPRD1, and one SNP in OPRK1, which encode the mu-, delta-, and kappa-opioid receptors, respectively. Regression analysis served to examine the moderating effects of these SNPs on medication response.

RESULTS

As previously described by Karhuvaara et al. (2007), nalmefene significantly reduced the number of heavy drinking and very heavy drinking days per week, compared with placebo. There were no main or moderating effects of the genotypes examined on these outcomes.

CONCLUSIONS

Our finding that the therapeutic effects of targeted nalmefene were not moderated by polymorphic variation in opioid receptor genes is consistent with two recent reports showing that variation in opioid receptor genes does not moderate the response to naltrexone. However, these findings contrast with those from two other studies, in which the Asn40Asp polymorphism in OPRM1 moderated the naltrexone treatment response. Additional research is needed to clarify the role of variation in opioid receptor genes on the response to opioid antagonist treatment of alcoholism.

Effects of alcoholism typology on response to naltrexone in the COMBINE study

BACKGROUND

This study investigated whether subgroups of alcohol-dependent patients responded differently to naltrexone versus placebo in the NIAAA COMBINE study. In particular, the A versus B and the Early Onset versus Late Onset typologies were examined. Relative to Type A alcoholics, Type B alcoholics are characterized by greater severity, earlier onset, stronger family history, more childhood risk factors (e.g., conduct disorder), and greater frequency of comorbid psychiatric and substance use disorders.

METHODS

COMBINE study participants were categorized as Type A or Type B using k-means cluster analysis and variables from 5 domains that have been shown to replicate the original Babor typology efficiently. Early Onset was defined as alcohol dependence beginning before age 25. For the planned analyses, the sample was reduced to the 618 participants receiving naltrexone alone or placebo, either with medical management (MM) alone or with MM plus the Combined Behavioral Intervention (CBI). The a priori primary outcome was percent heavy drinking days during treatment in the groups receiving MM without CBI.

RESULTS

Among those receiving MM without CBI, Type A alcoholics had better drinking outcomes with naltrexone than placebo, whereas medication condition did not influence outcomes significantly in the Type Bs. Age of onset was not significantly related to outcome. For those receiving CBI, no significant effects were found for either typology.

CONCLUSIONS

In this sample, the beneficial effects of opioid antagonism were limited to Type A alcoholics receiving treatment in a MM model. Future studies should investigate the relationship between clinically relevant genotypes, phenotypes such as typologies, and treatment response. More work is also needed to develop practical algorithms for phenotypic assignment.

Naltrexone alone and with sertraline for the treatment of alcohol dependence in Alaska natives and non-natives residing in rural settings: a randomized controlled trial

BACKGROUND

Access to specialty alcoholism treatment in rural environments is limited and new treatment approaches are needed. The objective was to evaluate the efficacy of naltrexone alone and in combination with sertraline among Alaska Natives and other Alaskans living in rural settings. An exploratory aim examined whether the Asn40Asp polymorphism of the mu-opioid receptor gene (OPRM1) predicted response to naltrexone, as had been reported in Caucasians.

METHODS

Randomized, controlled trial enrolling 101 Alaskans with alcohol dependence, including 68 American Indians/Alaska Natives. Participants received 16 weeks of either (1) placebo (placebo naltrexone + placebo sertraline), (2) naltrexone monotherapy (50 mg naltrexone + sertraline placebo) and (3) naltrexone + sertraline (100 mg) plus nine sessions of medical management and supportive advice. Primary outcomes included Time to First Heavy Drinking Day and Total Abstinence.

RESULTS

Naltrexone monotherapy demonstrated significantly higher total abstinence (35%) compared with placebo (12%, p = 0027) and longer, but not statistically different, Time to First Heavy Drinking Day (p = 0.093). On secondary measures, naltrexone compared with placebo demonstrated significant improvements in percent days abstinent (p = 0.024) and drinking-related consequences (p = 0.02). Combined sertraline and naltrexone did not differ from naltrexone alone. The pattern of findings was generally similar for the American Indian/Alaska Native subsample. Naltrexone treatment response was significant within the group of 75 individuals who were homozygous for OPRM1 Asn40 allele. There was a small number of Asp40 carriers, precluding statistical testing of the effect of this allele on response.

CONCLUSIONS

Naltrexone can be used effectively to treat alcoholism in remote and rural communities, with evidence of benefit for American Indians and Alaska Natives. New models of care incorporating pharmacotherapy could reduce important health disparities related to alcoholism.

Cloninger's typology and treatment outcome in alcohol-dependent subjects during pharmacotherapy with naltrexone

Naltrexone is an opiate receptor antagonist mainly at the micro-receptor that is thought to reduce the positively reinforcing, pleasurable effects of alcohol and to reduce craving. An increase in time to first relapse to heavy drinking has been the most consistent finding obtained with naltrexone, although not all trials including two of the largest have been positive. Inconsistent outcome data suggest that effectiveness varies among different subgroups of patients. This paper re-evaluates recent data on the effectiveness of naltrexone in subjects differentiated according to Cloninger Type I and II. Moreover, it combines and cross-validates results of two recent European studies that found naltrexone treatment more beneficial in alcohol-dependent patients with early age at onset of drinking problems (Cloninger Type II). It is discussed whether especially these subjects should be targeted for pharmacological relapse prevention treatment with naltrexone.

Moderators of naltrexone's effects on drinking, urge, and alcohol effects in non-treatment-seeking heavy drinkers in the natural environment

BACKGROUND

Naltrexone (NTX) has proven to be effective with alcoholics in treatment, with most controlled clinical trials showing beneficial effects on heavy drinking rates. However, little is known about the behavioral mechanisms underlying the effects of NTX on drinking, or about patient characteristics that may moderate NTX's effects on drinking. In this study, ecological momentary assessment (EMA) techniques were used to investigate some of the putative mechanisms of naltrexone's effects on drinking in heavy drinkers who were not seeking treatment for alcohol problems. Polymorphisms in the D4 dopamine receptor (DRD4) gene and the mu-opiate receptor (OPRM1) gene, family history of alcohol problems, age of onset of alcoholism and gender were explored as potential moderators of NTX's effects.

METHODS

After a 1-week placebo lead-in period, heavy drinkers (n = 180), 63% of whom were alcohol-dependent, were randomized to 3 weeks of daily naltrexone (50 mg) or placebo. Throughout the study, participants used EMA on palm-pilot computers to enter, in real time, drink data, urge levels, and subjective effects of alcohol consumption.

RESULTS

Naltrexone reduced percentage drinking days in all participants and reduced percent heavy drinking days in DRD4-L individuals; NTX decreased urge levels in participants with younger age of alcoholism onset; NTX increased time between drinks in participants who had more relatives with alcohol problems; and NTX reduced the stimulating effects of alcohol in women. OPRM1 status did not moderate any of NTX's effects.

CONCLUSIONS

These results confirm earlier findings of NTX's effects on drinking and related subjective effects, and extend them by describing individual difference variables that moderate these effects in the natural environment, using data collected in real time.

Family history of alcoholism influences naltrexone-induced reduction in alcohol drinking

BACKGROUND

The purpose of this study was to examine the interactive effects of family history of alcoholism (FH+, FH-) and naltrexone dose (0, 50, 100 mg/day) on alcohol drinking.

METHODS

Ninety-two, non-treatment-seeking alcohol-dependent participants received naltrexone daily for 6 days. On the 6th day, they participated in a laboratory paradigm involving exposure to a priming dose of alcohol followed by a 2-hour drinking period in which they made choices between consuming alcoholic drinks and receiving money.

RESULTS

Total number of drinks consumed during the drinking period was significantly decreased by the 100-mg dose of naltrexone in FH+ drinkers. Secondary analyses in male drinkers (n = 70) indicated that 100 mg of naltrexone significantly decreased drinking in FH+ participants and increased drinking in FH- drinkers.

CONCLUSIONS

These results suggest that family history of alcoholism might be a significant clinical predictor of response to naltrexone and that FH+ men are more likely to benefit from naltrexone therapy for alcohol drinking.

Opioid receptor gene (OPRM1, OPRK1, and OPRD1) variants and response to naltrexone treatment for alcohol dependence: results from the VA Cooperative Study

BACKGROUND

Pharmacotherapy of alcohol dependence (AD) is at an early stage of development; currently available medications have limited efficacy. It would be clinically valuable to identify, before initiation of a course of treatment, those patients who, based on genetic markers, are most likely to respond to a specific pharmacotherapy. A previous report suggested that a functional variant at the genetic locus encoding the mu opioid receptor (Asn40Asp) is such a marker, in short-term (3-month) treatment with the opioid-blocking drug naltrexone (NTX).

METHODS

We studied polymorphic variants at each of the 3 opioid receptor genes--OPRM1, OPRD1, and OPRK1, which encode the mu, delta, and kappa opioid receptors, respectively--including the OPRM1 Asn40Asp variant--as predictors of response to NTX or placebo in 215 alcohol-dependent male subjects who participated in Veterans Affairs Cooperative Study 425, "Naltrexone in the Treatment of Alcohol Dependence."

RESULTS

At the 3-month time point, treatment condition, age, and the pretreatment number of drinks per drinking day were all significant (p<0.05) predictors of the rate of relapse and time to relapse. Although NTX had no significant effect on relapse to heavy drinking in the overall sample in CSP 425, it significantly reduced relapse in the subgroup that provided DNA for analysis (i.e., the present study sample). There were no significant interactions between any individual single nucleotide polymorphisms studied and NTX treatment response.

CONCLUSIONS

These results do not support association of the OPRM1 Asn40Asp polymorphism with NTX treatment response for AD.

Naltrexone in patients with bipolar disorder and alcohol dependence

Bipolar disorder is associated with very high rates of substance abuse. However, few clinical trials are reported in this population. Naltrexone is effective for alcohol dependence, but its safety and efficacy are not established in patients with bipolar disorder and alcohol dependence. A 16-week, open-label, add-on pilot study of naltrexone was conducted in 34 outpatients with bipolar disorder and alcohol dependence. Assessments included the 17-item Hamilton Rating Scale for Depression (HRSD-17), Young Mania Rating Scale (YMRS), Brief Psychiatric Rating Scale (BPRS), and an alcohol craving scale. Alcohol use was quantified. Significant improvement was observed in the HRSD-17 and YMRS, and days of alcohol use and craving decreased significantly. Naltrexone was well tolerated. Controlled trials are warranted.

Effects of Conditioned Reward and Nonreward Cues on the Heart Rate Response to Alcohol Intoxication in Male Social Drinkers

BACKGROUND

An exaggerated heart rate (HR) increase following alcohol intoxication has been suggested to reflect sensitivity to alcohol-induced reward. The goal of this study is to verify whether pairing alcohol ingestion with conditioned reward and nonreward cues can influence HR responses to alcohol in previously identified individuals with a low and a high HR response.

METHODS

Fifty-six male social drinkers participated in a 2-day study. On day 1, participants consumed 0.75 g/kg of body weight of pure ethanol. A median split of the alcohol-induced HR responses identified groups of low and high HR responders. On day 2, both groups participated while sober in a computer task where distinct auditory and visual cues were paired either with monetary reward or no monetary reward. Subsequently, participants were randomly assigned to an alcohol challenge, which occurred while they were exposed to either the conditioned cues of reward or to the nonreward cues.

RESULTS

The physiological response to alcohol intoxication on day 2 was compared with alcohol-induced HR responses on day 1 (neutral alcohol challenge) for both low and high HR responders. Paired t-tests showed that high HR responders had significantly decreased alcohol-induced HR responses on day 2 in the nonreward condition when compared with day 1. No other relationships between cardiac responses to alcohol and cue conditions were obtained.

CONCLUSIONS

The rewarding nature of alcohol can be altered by the context in which it is consumed in a subset of individuals who are sensitive to alcohol's stimulating properties.