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

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.

Identifying and Characterizing Subpopulations of Heavy Alcohol Drinkers Via a Sucrose Preference Test: A Sweet Road to a Better Phenotypic Characterization?

Aims

Sweet preference in individuals with alcohol use disorder (AUD) has been associated with family history of AUD and personality traits. Therefore, testing sweet preference may help identify subpopulations of AUD individuals.

Short summary

Sweet preference has been associated with family history of AUD and personality traits. We compared heavy drinkers based on their sweet liker status and using two cutoffs. Our findings support the role of sweet preference in heavy drinkers and point to the importance of how sweet likers are defined.

Methods

This study aimed at describing and comparing heavy drinkers based on their sweet liker status, through demographic, neuroendocrine, inflammatory, behavioral and drinking characteristics. Participants rated the pleasantness and intensity of sucrose solutions (0.05, 0.10, 0.21, 0.42 and 0.83 M). Two cutoffs were used to identify likers versus dislikers: Grouping A likers preferred 0.83 M and Grouping B likers preferred 0.83 or 0.42 M; the rest were dislikers.

Results

Sweet likers were 36% (n = 20) using Grouping A and 58.2% (n = 32) using Grouping B. Grouping B, but not Grouping A, sweet likers had higher BMI (P = 0.01). In Grouping B, sweet likers had higher plasma leptin and insulin concentrations and higher insulin resistance (P's < 0.05). C-reactive protein concentrations were higher in sweet likers in Grouping A (P = 0.0015) and at a trend level in Grouping B (P = 0.07). Grouping A sweet likers had higher alcohol craving (P = 0.0004). Sweet likers preferred spirits compared to nonspirits (wine and beer) across both grouping (P's < 0.05).

Conclusions

These results provide further support for the role of sweet liking phenotype in identifying subpopulations of AUD individuals. These findings also point to the importance of how sweet likers are defined, therefore highlighting the need for further research.

Spicy Food Preference and Risk for Alcohol Dependence in Korean

OBJECTIVE

Previous studies have reported that both preference for spicy food and drinking behavior are associated with the activity of the opioid system in the central nervous system. The relationship between the preference for spicy food and the risk of alcohol dependence by comparing spicy food preference in alcohol-dependent patients vs. healthy controls was investigated. Also the association between the preference for spicy food and OPRM1 A118G was studied.

METHODS

A total of 150 Korean male patients with alcohol dependence and 100 normal male control subjects were included in this study. Preference for spicy food was measured using the Food Preference Scale (FPS). DNA analysis was conducted to detect the A118G polymorphism.

RESULTS

The mean FPS score was significantly higher in the alcohol-dependent patients (61.2±24.2) than in the normal control subjects (53.0±22.0). FPS scores differed significantly between alcohol-dependent patients and normal control subjects who had the G allele in OPRM1 A118G, but not between the two groups with the AA genotype.

CONCLUSION

A strong preference for spicy food can be assumed to be a risk factor for alcohol dependence, particularly in those carrying the G allele in OPRM1 A118G.

The importance of nutrition in aiding recovery from substance use disorders: A review

BACKGROUND

Nutrition is a prerequisite for health; yet, there is no special nutritional assessment or guidance for drug and alcohol dependent individuals, despite the fact that their food consumption is often very limited, risking malnutrition. Further, the premise is examined that malnutrition may promote drug seeking and impede recovery from substance use disorders (SUD).

METHOD

A narrative review addressed the relationship between substance use disorders and nutrition, including evidence for malnutrition, as well as their impact on metabolism and appetite regulation. The implications of the biopsychology of addiction and appetite for understanding the role of nutrition in SUD were also considered.

RESULTS

The literature overwhelmingly finds that subjects with alcohol use disorder (AUD) and drug use disorder (DUD) typically suffer from nutrient deficiencies. These nutrient deficiencies may be complicit in the alcoholic myopathy, osteopenia and osteoporosis, and mood disorders including anxiety and depression, observed in AUD and DUD. These same individuals have also been found to have altered body composition and altered hormonal metabolic regulators. Additionally, brain processes fundamental for survival are stimulated both by food, particularly sweet foods, and by substances of abuse, with evidence supporting confusion (addiction transfer) when recovering from SUD between cravings for a substance and craving for food.

CONCLUSION

Poor nutritional status in AUD and DUD severely impacts their physical and psychological health, which may impede their ability to resist substances of abuse and recover their health. This review contributes to a better understanding of interventions that could best support individuals with substance use disorders.

The opioid system majorly contributes to preference for fat emulsions but not sucrose solutions in mice

Rodents show a stronger preference for fat than sucrose, even if their diet is isocaloric. This implies that the preference mechanisms for fat and sucrose differ. To compare the contribution of the opioid system to the preference of fat and sucrose, we examined the effects of mu-, delta-, kappa-, and non-selective opioid receptor antagonists on the preference of sucrose and fat, assessed by a two-bottle choice test and a licking test, in mice naïve to sucrose and fat ingestion. Administration of non-selective and mu-selective opioid receptor antagonists more strongly inhibited the preference of fat than sucrose. While the preference of fat was reduced to the same level as water by the antagonist administration that of sucrose was still greater than water. Our results suggest that the preference of fat relies strongly on the opioid system, while that of sucrose is regulated by other mechanisms in addition to the opioid system.

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.

Difference of the naltrexone's effects in social drinkers by spicy food preference

The purpose of this study was to investigate the differences in subjective acute effects of alcohol and naltrexone among those who prefer spicy food to varying degrees. Acute biphasic alcohol effects scale (BAES), visual analogue scale for craving (VAS-C), blood alcohol concentration (BAC) and food preference scale were measured in 26 men. Repeated measures ANOVA (2 preference groups×4 time blocks) on the stimulative subscale of BAES revealed a significant group by block interaction in naltrexone condition (N+) (P<0.001), but not in non-naltrexone condition (N-). Furthermore, repeated measures ANOVA (2 drug groups×4 time blocks) on the stimulative subscale of BAES revealed a significant group by block interaction in strong preference for spicy food (SP) (P<0.001), but not in lesser preference for spicy food (LP). The paired t-test revealed that significant suppression of the stimulative subscale of BAES was observed at 15 min (P<0.001) and 30 min (P<0.001) after drinking when N+ compared with N- in SP. For those who prefer spicy food, the stimulative effect of acute alcohol administration was suppressed by naltrexone. This result suggests that the effect of naltrexone may vary according to spicy food preference.

Intact Hedonic Responses to Sweet Tastes in Autism Spectrum Disorder

The Sweet Taste Test (STT) is a standardized measure designed to index the ability to detect differences in sweet tastes (sweet taste sensitivity) and hedonic responses to sweet tastes (sweet taste liking). Profiles of response on the STT suggest enhanced hedonic responses to sweet tastes in psychiatric disorders characterized by dysfunctional reward processing systems, including binge-eating disorders and substance use disorders, and a putative mechanism governing STT responses is the brain opioid system. The present study examined STT responses in 20 adults with autism spectrum disorder (ASD) and 38 healthy control adults. There were no differences in sweet taste sensitivity or hedonic response to sweet tastes between the ASD and control groups. Within the ASD sample, ASD symptom severity was associated with sweet taste sensitivity, but not hedonic response to sweet taste. Results may ultimately shed light on brain opioid system functioning in ASD.

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.

Cocaine self-administration punished by i.v. histamine in rat models of high and low drug abuse vulnerability: effects of saccharin preference, impulsivity, and sex

A key feature of substance use disorders is continued drug consumption despite aversive consequences. This has been modeled in the animal laboratory by pairing drug self-administration with electric shock, thereby punishing drug intake (Deroche-Gamonet et al. 2004). In the present experiments, we examined the effects of punishment on i.v. cocaine self-administration by adding histamine to the cocaine solution with three different animal models of high and low vulnerability to drug abuse: rats selectively bred for high (HiS) and low (LoS) saccharin consumption, rats selected for high (HiI) and low (LoI) impulsivity, and sex differences. Animals were allowed to self-administer cocaine (0.4 mg/kg/infusion) to establish a baseline of operant responding. Histamine (4.0mg/kg/infusion) was then added directly into the cocaine solution and its consequent effects on self-administration were compared to baseline. The histamine+cocaine solution was then replaced with a cocaine-only solution, and the rats' operant responding was again compared to baseline. Concurrent histamine exposure was effective in reducing cocaine consumption in all groups of rats; however, LoS and female rats took longer to return to baseline levels of cocaine consumption after histamine was removed compared to HiS and male rats. These data suggest that the reduction of drug self-administration by aversive consequences may differ in groups that vary in drug use vulnerability . Such results may inform pharmacological strategies that enhance the negative aspects of drug consumption.

Opiate agonists and antagonists modulate taste perception in opiate-maintained and recently detoxified subjects

Heroin addicts consume large quantities of refined sugars. This study investigated the effect of opiate use and antagonism on sweet taste in opiate-maintained drug users and detoxified former chronic opiate users, using a within-subject design. Seven opiate users received methadone and seven buprenorphine maintenance. Six detoxified subjects received naltrexone. Sucrose recognition thresholds and measurements of pleasantness and intensity were determined before and four hours after 1) a single dose of methadone or buprenorphine or 2) naltrexone. Control data were taken from a cohort of healthy volunteers including smokers. All measures of sweet and salt taste perception were significantly greater in opiate users and recently detoxified subjects compared to control subjects, with the exception of sweet pleasantness, which returned to control level after detoxification. Acute methadone administration reduced salt thresholds and unpleasantness to control levels. Increased sweet thresholds and salt unpleasantness in detoxified subjects were reversed by acute opioid antagonism, returning to control levels. These results suggest that opiate use and antagonism alters taste perception. Some of the alterations reverse on detoxification (sweet pleasantness), and others can be reversed by opioid antagonism (sweet threshold, salt unpleasantness). Changes in taste perception may underlie altered consumption of refined sugars in opiate users.

The contribution of brain reward circuits to the obesity epidemic

One of the defining characteristics of the research of Ann E. Kelley was her recognition that the neuroscience underlying basic learning and motivation processes also shed significant light upon mechanisms underlying drug addiction and maladaptive eating patterns. In this review, we examine the parallels that exist in the neural pathways that process both food and drug reward, as determined by recent studies in animal models and human neuroimaging experiments. We discuss contemporary research that suggests that hyperphagia leading to obesity is associated with substantial neurochemical changes in the brain. These findings verify the relevance of reward pathways for promoting consumption of palatable, calorically dense foods, and lead to the important question of whether changes in reward circuitry in response to intake of such foods serve a causal role in the development and maintenance of some cases of obesity. Finally, we discuss the potential value for future studies at the intersection of the obesity epidemic and the neuroscience of motivation, as well as the potential concerns that arise from viewing excessive food intake as an "addiction". We suggest that it might be more useful to focus on overeating that results in frank obesity, and multiple health, interpersonal, and occupational negative consequences as a form of food "abuse".

Endogenous opiates and behavior: 2011

This paper is the thirty-fourth consecutive installment of the annual review of research concerning the endogenous opioid system. It summarizes papers published during 2011 that studied the behavioral effects of molecular, pharmacological and genetic manipulation of opioid peptides, opioid receptors, opioid agonists and opioid antagonists. The particular topics that continue to be covered include the molecular-biochemical effects and neurochemical localization studies of endogenous opioids and their receptors related to behavior (Section 2), and the roles of these opioid peptides and receptors in pain and analgesia (Section 3); stress and social status (Section 4); tolerance and dependence (Section 5); learning and memory (Section 6); eating and drinking (Section 7); alcohol and drugs of abuse (Section 8); sexual activity and hormones, pregnancy, development and endocrinology (Section 9); mental illness and mood (Section 10); seizures and neurologic disorders (Section 11); electrical-related activity and neurophysiology (Section 12); general activity and locomotion (Section 13); gastrointestinal, renal and hepatic functions (Section 14); cardiovascular responses (Section 15); respiration (Section 16); and immunological responses (Section 17).

Depot naltrexone decreases rewarding properties of sugar in patients with opioid dependence

BACKGROUND

Opioid neurotransmission mediates hedonic value of sweet tastants; their intake may be exaggerated by the consumption of exogenous opioids (e.g., opioid dependence). Sweet Taste Test (STT) is a validated quantitative instrument assessing taste perception and hedonic features of sugar (sucrose) using a randomized and double-blind administration at five different sucrose concentrations ranging from 0.05 to 0.83 M.

METHODS

The STT and cue-induced craving procedure were administered to opioid-dependent patients (n = 15) before and 1 week after the injection of a long-acting depot naltrexone (XRNT) preparation.

RESULTS

Analyses of covariance, employing sucrose concentration and its perceived taste as covariates, showed that XRNT therapy significantly reduced the self-reported hedonic and motivational characteristics of sucrose. Greater reductions in both these characteristics were associated with more diminution in the cue-induced opioid craving.

CONCLUSIONS

Opioid antagonism in opioid-dependent subjects leads to a smaller sweet taste reward, which, in turn, may be proportional to decreased opioid craving. These pilot results support the heuristic value of the STT as a potential marker of the XRNT treatment response and call for further inquiry into potential clinical applications of the test.