Acamprosate: recent findings and future research directions

Use of pharmacotherapies in the treatment of alcohol use disorders and opioid dependence in primary care

Substance-related and addictive disorders are chronic relapsing conditions that substantially impact public health. Effective treatments for these disorders require addressing substance use/dependence comprehensively as well as other associated comorbidities. Comprehensive addressing of substance use in a medical setting involves screening for substance use, addressing substance use directly with the patient, and formulating an appropriate intervention. For alcohol dependence and opioid dependence, pharmacotherapies are available that are safe and effective when utilized in a comprehensive treatment paradigm, such as medication assisted treatment. In primary care, substance use disorders involving alcohol, illicit opioids, and prescription opioid abuse are common among patients who seek primary care services. Primary care providers report low levels of preparedness and confidence in identifying substance-related and addictive disorders and providing appropriate care and treatment. However, new models of service delivery in primary care for individuals with substance-related and addictive disorders are being developed to promote screening, care and treatment, and relapse prevention. The education and training of primary care providers utilizing approved medications for the treatment of alcohol use disorders and opioid dependence in a primary care setting would have important public health impact and reduce the burden of alcohol abuse and opioid dependence.

Six-month outcome in bipolar spectrum alcoholics treated with acamprosate after detoxification: a retrospective study

Background: Glutamate system is modified by ethanol and contributes both to the euphoric and the dysphoric consequences of intoxication, but there is now growing evidence that the glutamatergic system also plays a central role in the neurobiology and treatment of mood disorders, including major depressive disorders and bipolar disorders. We speculate that, using acamprosate, patients with bipolar depression (BIP-A) can take advantage of the anti-glutamate effect of acamprosate to “survive” in treatment longer than peers suffering from non-bipolar depression (NBIP-A) after detoxification. Method: We retrospectively evaluated the efficacy of a long-term (six-month) acamprosate treatment, after alcohol detoxification, in 41 patients (19 males and 22 females), who could be classified as depressed alcoholics, while taking into account the presence/absence of bipolarity. Results: During the period of observation most NBIP-A patients relapsed, whereas a majority of BIP-A patients were still in treatment at the end of their period of observation. The cumulative proportion of ‘surviving’ patients was significantly higher in BIP-A patients, but this finding was not related to gender or to other demographic or clinically investigated characteristics. The treatment time effect was significant in both subgroups. The treatment time-group effect was significant (and significantly better) for bipolar patients on account of changes in the severity of their illness. Limitations: Retrospective methodology and the lack of DSM criteria in diagnosing bipolarity. Conclusions: Bipolarity seems to be correlated with the efficacy of acamprosate treatment in inducing patients to refrain from alcohol use after detoxification (while avoiding relapses) in depressed alcoholics. Placebo-controlled clinical trials are now warranted to check the validity of this hypothesis.

Impact of acamprosate on plasma amyloid-β precursor protein in youth: a pilot analysis in fragile X syndrome-associated and idiopathic autism spectrum disorder suggests a pharmacodynamic protein marker

BACKGROUND

Understanding of the pathophysiology of autism spectrum disorder (ASD) remains limited. Brain overgrowth has been hypothesized to be associated with the development of ASD. A derivative of amyloid-β precursor protein (APP), secreted APPα (sAPPα), has neuroproliferative effects and has been shown to be elevated in the plasma of persons with ASD compared to control subjects. Reduction in sAPPα holds promise as a novel molecular target of treatment in ASD. Research into the neurochemistry of ASD has repeatedly implicated excessive glutamatergic and deficient GABAergic neurotransmission in the disorder. With this in mind, acamprosate, a novel modulator of glutamate and GABA function, has been studied in ASD. No data is available on the impact of glutamate or GABA modulation on sAPPα function.

METHODS

Plasma APP derivative levels pre- and post-treatment with acamprosate were determined in two pilot studies involving youth with idiopathic and fragile X syndrome (FXS)-associated ASD. We additionally compared baseline APP derivative levels between youth with FXS-associated or idiopathic ASD.

RESULTS

Acamprosate use was associated with a significant reduction in plasma sAPP(total) and sAPPα levels but no change occurred in Aβ40 or Aβ42 levels in 15 youth with ASD (mean age: 11.1 years). Youth with FXS-associated ASD (n = 12) showed increased sAPPα processing compared to age-, gender- and IQ-match youth with idiopathic ASD (n = 11).

CONCLUSIONS

Plasma APP derivative analysis holds promise as a potential biomarker for use in ASD targeted treatment. Reduction in sAPP (total) and sAPPα may be a novel pharmacodynamic property of acamprosate. Future study is required to address limitations of the current study to determine if baseline APP derivative analysis may predict subgroups of persons with idiopathic or FXS-associated ASD who may respond best to acamprosate or to potentially other modulators of glutamate and/or GABA neurotransmission.

Brief report: Pilot single-blind placebo lead-in study of acamprosate in youth with autistic disorder

RATIONALE

An excitatory/inhibitory (E:I) imbalance marked by enhanced glutamate and deficient gamma-aminobutyric acid (GABA) neurotransmission may contribute to the pathophysiology of autism spectrum disorders (ASD).

OBJECTIVES

We report on the first single-blind placebo lead-in trial of acamprosate, a drug with putative mechanisms restoring E:I imbalance, in twelve youth with ASD.

MATERIALS AND METHODS

We conducted a 12-week single-blind, placebo lead-in study of acamprosate in youth age 5-17 years with autistic disorder.

RESULTS

Six of nine subjects who received active drug treatment were deemed treatment responders (defined by a score at final visit of "very much improved" or "much improved" on the Clinical Global Impressions Improvement scale) and ≥25% improvement on the Aberrant Behavior Checklist Social Withdrawal subscale.

CONCLUSION

Future larger-scale dose finding studies of acamprosate in ASD may be warranted given this preliminary indication of benefit.

The development of acamprosate as a treatment against alcohol relapse

INTRODUCTION

Globally, alcohol abuse and dependence are significant contributors to chronic disease and injury and are responsible for nearly 4% of all deaths annually. Acamprosate (Campral), one of only three pharmacological treatments approved for the treatment of alcohol dependence, has shown mixed efficacy in clinical trials in maintaining abstinence of detoxified alcoholics since studies began in the 1980s. Yielding inconsistent results, these studies have prompted skepticism.

AREAS COVERED

Herein, the authors review the preclinical studies which have assessed the efficacy of acamprosate in various animal models of alcohol dependence and discuss the disparate findings from the major clinical trials. Moreover, the authors discuss the major limitations of these preclinical and clinical studies and offer explanations for the often-contradictory findings. The article also looks at the importance of the calcium moiety that accompanies the salt form of acamprosate and its relevance to its activity.

EXPERT OPINION

The recent discovery that large doses of calcium largely duplicate the effects of acamprosate in animal models has introduced a serious challenge to the widely held functional association between this drug and the glutamate neurotransmission system. Future research on acamprosate or newer pharmacotherapeutics should consider assessing plasma and/or brain levels of calcium as a correlate or mediating factor in anti-relapse efficacy. Further, preclinical research on acamprosate has thus far lacked animal models of chemical dependence on alcohol, and the testing of rodents with histories of alcohol intoxication and withdrawal is suggested.

Alcohol use disorders and current pharmacological therapies: the role of GABA(A) receptors

Alcohol use disorders (AUD) are defined as alcohol abuse and alcohol dependence, which create large problems both for society and for the drinkers themselves. To date, no therapeutic can effectively solve these problems. Understanding the underlying mechanisms leading to AUD is critically important for developing effective and safe pharmacological therapies. Benzodiazepines (BZs) are used to reduce the symptoms of alcohol withdrawal syndrome. However, frequent use of BZs causes cross-tolerance, dependence, and cross-addiction to alcohol. The FDA-approved naltrexone and acamprosate have shown mixed results in clinical trials. Naltrexone is effective to treat alcohol dependence (decreased length and frequency of drinking bouts), but its severe side effects, including withdrawal symptoms, are difficult to overcome. Acamprosate showed efficacy for treating alcohol dependence in European trials, but two large US trials have failed to confirm the efficacy. Another FDA-approved medication, disulfiram, does not diminish craving, and it causes a peripheral neuropathy. Kudzu is the only natural medication mentioned by the National Institute on Alcohol Abuse and Alcoholism, but its mechanisms of action are not yet established. It has been recently shown that dihydromyricetin, a flavonoid purified from Hovenia, has unique effects on GABAA receptors and blocks ethanol intoxication and withdrawal in alcoholic animal models. In this article, we review the role of GABAA receptors in the treatment of AUD and currently available and potentially novel pharmacological agents.

Getting a grip on problem gambling: what can neuroscience tell us?

In problem gamblers, diminished cognitive control and increased impulsivity is present compared to healthy controls. Moreover, impulsivity has been found to be a vulnerability marker for the development of pathological gambling (PG) and problem gambling (PrG) and to be a predictor of relapse. In this review, the most recent findings on functioning of the brain circuitry relating to impulsivity and cognitive control in PG and PrG are discussed. Diminished functioning of several prefrontal areas and of the anterior cingulate cortex (ACC) indicate that cognitive-control related brain circuitry functions are diminished in PG and PrG compared to healthy controls. From the available cue reactivity studies on PG and PrG, increased responsiveness towards gambling stimuli in fronto-striatal reward circuitry and brain areas related to attentional processing is present compared to healthy controls. At this point it is unresolved whether PG is associated with hyper- or hypo-activity in the reward circuitry in response to monetary cues. More research is needed to elucidate the complex interactions for reward responsivity in different stages of gambling and across different types of reward. Conflicting findings from basic neuroscience studies are integrated in the context of recent neurobiological addiction models. Neuroscience studies on the interface between cognitive control and motivational processing are discussed in light of current addiction theories.

Clinical implications: We suggest that innovation in PG therapy should focus on improvement of dysfunctional cognitive control and/or motivational functions. The implementation of novel treatment methods like neuromodulation, cognitive training and pharmacological interventions as add-on therapies to standard treatment in PG and PrG, in combination with the study of their effects on brain-behavior mechanisms could prove an important clinical step forward towards personalizing and improving treatment results in PG.

New insights into the molecular pathophysiology of fragile X syndrome and therapeutic perspectives from the animal model

Fragile X syndrome is the most common monogenetic form of intellectual disability and is a leading cause of autism. This syndrome is produced by the reduced transcription of the fragile X mental retardation (FMR1) gene, and it is characterized by a range of symptoms heterogeneously expressed in patients such as cognitive impairment, seizure susceptibility, altered pain sensitivity and anxiety. The recent advances in the understanding of the pathophysiological mechanisms involved have opened novel potential therapeutic approaches identified in preclinical rodent models as a necessary preliminary step for the subsequent evaluation in patients. Among those possible therapeutic approaches, the modulation of the metabotropic glutamate receptor signaling or the GABA receptor signaling have focused most of the attention. New findings in the animal models open other possible therapeutic approaches such as the mammalian target of rapamycin signaling pathway or the endocannabinoid system. This review summarizes the emerging data recently obtained in preclinical models of fragile X syndrome supporting these new therapeutic perspectives.

Nociceptin/orphanin FQ decreases glutamate transmission and blocks ethanol-induced effects in the central amygdala of naive and ethanol-dependent rats

The central nucleus of the amygdala (CeA) mediates several addiction-related processes and nociceptin/orphanin FQ (nociceptin) regulates ethanol intake and anxiety-like behaviors. Glutamatergic synapses, in the CeA and throughout the brain, are very sensitive to ethanol and contribute to alcohol reinforcement, tolerance, and dependence. Previously, we reported that in the rat CeA, acute and chronic ethanol exposures significantly decrease glutamate transmission by both pre- and postsynaptic actions. In this study, using electrophysiological techniques in an in vitro CeA slice preparation, we investigated the effects of nociceptin on glutamatergic transmission and its interaction with acute ethanol in naive and ethanol-dependent rats. We found that nociceptin (100-1000 nM) diminished basal-evoked compound glutamatergic receptor-mediated excitatory postsynaptic potentials (EPSPs) and spontaneous and miniature EPSCs (s/mEPSCs) by mainly decreasing glutamate release in the CeA of naive rats. Notably, nociceptin blocked the inhibition induced by acute ethanol (44 mM) and ethanol blocked the nociceptin-induced inhibition of evoked EPSPs in CeA neurons of naive rats. In neurons from chronic ethanol-treated (ethanol-dependent) rats, the nociceptin-induced inhibition of evoked EPSP amplitude was not significantly different from that in naive rats. Application of [Nphe1]Nociceptin(1-13)NH2, a nociceptin receptor (NOP) antagonist, revealed tonic inhibitory activity of NOP on evoked CeA glutamatergic transmission only in ethanol-dependent rats. The antagonist also blocked nociceptin-induced decreases in glutamatergic responses, but did not affect ethanol-induced decreases in evoked EPSP amplitude. Taken together, these studies implicate a potential role for the nociceptin system in regulating glutamatergic transmission and a complex interaction with ethanol at CeA glutamatergic synapses.

Acamprosate produces its anti-relapse effects via calcium

Alcoholism is one of the most prevalent neuropsychiatric diseases, having an enormous health and socioeconomic impact. Along with a few other medications, acamprosate (Campral-calcium-bis (N-acetylhomotaurinate)) is clinically used in many countries for relapse prevention. Although there is accumulated evidence suggesting that acamprosate interferes with the glutamate system, the molecular mode of action still remains undefined. Here we show that acamprosate does not interact with proposed glutamate receptor mechanisms. In particular, acamprosate does not interact with NMDA receptors or metabotropic glutamate receptor group I. In three different preclinical animal models of either excessive alcohol drinking, alcohol-seeking, or relapse-like drinking behavior, we demonstrate that N-acetylhomotaurinate by itself is not an active psychotropic molecule. Hence, the sodium salt of N-acetylhomotaurinate (i) is ineffective in alcohol-preferring rats to reduce operant responding for ethanol, (ii) is ineffective in alcohol-seeking rats in a cue-induced reinstatement paradigm, (iii) and is ineffective in rats with an alcohol deprivation effect. Surprisingly, calcium salts produce acamprosate-like effects in all three animal models. We conclude that calcium is the active moiety of acamprosate. Indeed, when translating these findings to the human situation, we found that patients with high plasma calcium levels due to acamprosate treatment showed better primary efficacy parameters such as time to relapse and cumulative abstinence. We conclude that N-acetylhomotaurinate is a biologically inactive molecule and that the effects of acamprosate described in more than 450 published original investigations and clinical trials and 1.5 million treated patients can possibly be attributed to calcium.

MT-7716, a novel selective nonpeptidergic NOP receptor agonist, effectively blocks ethanol-induced increase in GABAergic transmission in the rat central amygdala

The GABAergic system in the central amygdala (CeA) plays a major role in ethanol dependence and the anxiogenic-like response to ethanol withdrawal. A large body of evidence shows that Nociceptin/Orphanin FQ (N/OFQ) regulates ethanol intake and anxiety-like behavior. In the rat, ethanol significantly augments CeA GABA release, whereas N/OFQ diminishes it. Using electrophysiological techniques in an in vitro slice preparation, in this study we investigated the effects of a nonpeptidergic NOP receptor agonist, MT-7716 [(R)-2-3-[1-(Acenaphthen-1-yl)piperidin-4-yl]-2-oxo-2,3-dihydro-1H-benzimidazol-1-yl-N-methylacetamide hydrochloride hydrate], and its interaction with ethanol on GABAergic transmission in CeA slices of naïve rats. We found that MT-7716 dose-dependently (100-1000 nM) diminished evoked GABAA receptor-mediated inhibitory postsynaptic potentials (IPSPs) and increased paired-pulse facilitation (PPF) ratio of these evoked IPSPs, suggesting a presynaptic site of action of the MT-7716 by decreasing GABA release at CeA synapses. The presynaptic action of MT-7716 was also supported by the significant decrease in the frequency of miniature inhibitory postsynaptic currents (mIPSCs) induced by the nociceptin receptor (NOP) agonist. Interestingly, MT-7716 prevented the ethanol-induced augmentation of evoked IPSPs. A putative selective NOP antagonist, [Nphe1]Nociceptin(1-13)NH2, totally prevented the MT-7716-induced inhibition of IPSP amplitudes indicating that MT-7716 exerts its effect through NOPs. These data provide support for an interaction between the nociceptin and GABAergic systems in the CeA and for the anti-alcohol properties of the NOP activation. The development of a synthetic nonpeptidergic NOP receptor agonist such as MT-7716 may represent a useful therapeutic target for alcoholism.

The role of ionotropic glutamate receptors in childhood neurodevelopmental disorders: autism spectrum disorders and fragile x syndrome

Autism spectrum disorder (ASD) and Fragile X syndrome (FXS) are relatively common childhood neurodevelopmental disorders with increasing incidence in recent years. They are currently accepted as disorders of the synapse with alterations in different forms of synaptic communication and neuronal network connectivity. The major excitatory neurotransmitter system in brain, the glutamatergic system, is implicated in learning and memory, synaptic plasticity, neuronal development. While much attention is attributed to the role of metabotropic glutamate receptors in ASD and FXS, studies indicate that the ionotropic glutamate receptors (iGluRs) and their regulatory proteins are also altered in several brain regions. Role of iGluRs in the neurobiology of ASD and FXS is supported by a weight of evidence that ranges from human genetics to in vitro cultured neurons. In this review we will discuss clinical, molecular, cellular and functional changes in NMDA, AMPA and kainate receptors and the synaptic proteins that regulate them in the context of ASD and FXS. We will also discuss the significance for the development of translational biomarkers and treatments for the core symptoms of ASD and FXS.

Impaired activity-dependent neural circuit assembly and refinement in autism spectrum disorder genetic models

Early-use activity during circuit-specific critical periods refines brain circuitry by the coupled processes of eliminating inappropriate synapses and strengthening maintained synapses. We theorize these activity-dependent (A-D) developmental processes are specifically impaired in autism spectrum disorders (ASDs). ASD genetic models in both mouse and Drosophila have pioneered our insights into normal A-D neural circuit assembly and consolidation, and how these developmental mechanisms go awry in specific genetic conditions. The monogenic fragile X syndrome (FXS), a common cause of heritable ASD and intellectual disability, has been particularly well linked to defects in A-D critical period processes. The fragile X mental retardation protein (FMRP) is positively activity-regulated in expression and function, in turn regulates excitability and activity in a negative feedback loop, and appears to be required for the A-D remodeling of synaptic connectivity during early-use critical periods. The Drosophila FXS model has been shown to functionally conserve the roles of human FMRP in synaptogenesis, and has been centrally important in generating our current mechanistic understanding of the FXS disease state. Recent advances in Drosophila optogenetics, transgenic calcium reporters, highly-targeted transgenic drivers for individually-identified neurons, and a vastly improved connectome of the brain are now being combined to provide unparalleled opportunities to both manipulate and monitor A-D processes during critical period brain development in defined neural circuits. The field is now poised to exploit this new Drosophila transgenic toolbox for the systematic dissection of A-D mechanisms in normal versus ASD brain development, particularly utilizing the well-established Drosophila FXS disease model.

Pharmacological strategies for detoxification

Detoxification refers to the safe discontinuation from a substance of dependence and is distinct from relapse prevention. Detoxification usually takes between a few days and a few weeks to complete, depending on the substance being misused, the severity of dependence and the support available to the user. Psychosocial therapies alongside pharmacological treatments are essential to improve outcome. The dependencies considered in this overview are detoxification from opioids (with methadone, buprenorphine, α2-adrenoceptor agonists and adjunct medications), alcohol (with benzodiazepines, anti-glutamatergics and γ-aminobutyric acid (GABA)-ergic drugs), stimulants and cannabis (with no clear recommended pharmacological treatments), benzodiazepines (with dose tapering) and nicotine (with nicotine replacement therapy, antidepressants and partial agonists). Evidence is limited by a lack of controlled trials robust enough for review bodies, and more research is required into optimal treatment doses and regimes, alone and in combination.

Current pharmacological treatment approaches for alcohol dependence

INTRODUCTION

At present, the substances acamprosate, naltrexone and disulfiram are available for pharmacotherapy in alcohol dependence, but clinical studies found only modest effect sizes of these treatment options.

AREAS COVERED

This article focuses on current pharmacological treatment approaches for alcohol dependence, which have been evaluated in randomized, placebo-controlled trials (RCTs).

EXPERT OPINION

Besides the opioid system modulator nalmefene, which has recently been approved as a medication for the reduction of alcohol consumption, several compounds have been investigated in patients with alcohol dependence using a randomized, placebo-controlled design. In these studies, the antiepileptic drugs topiramate and gabapentin were found to be effective in improving several drinking-related outcomes, whereas levetiracetam failed to show efficacy in the treatment of alcohol dependence. Clinical studies using (low-dose) baclofen, a selective GABA-B receptor agonist, produced conflicting results, so that results of further trials are needed. Varenicline has also shown mixed results in two RCTs, but might possibly be useful in patients with comorbid nicotine dependence. The α1 adrenergic antagonist prazosin is currently under investigation in alcohol dependence with and without comorbid posttraumatic stress disorder (PTSD). Finally, first clinical evidence suggests that the 5-HT3 antagonist ondansetron might possibly be used in future within a pharmacogenetic treatment approach in alcohol dependence.

The role of the opioid system in alcohol dependence

The role of the brain opioid system in alcohol dependence has been the subject of much research for over 25 years. This review explores the evidence: firstly describing the opioid receptors in terms of their individual subtypes, neuroanatomy, neurophysiology and ligands; secondly, summarising emerging data from specific neurochemical, behavioural and neuroimaging studies, explaining the characteristics of addiction with a focus on alcohol dependence and connecting the opioid system with alcohol dependence; and finally reviewing the known literature regarding opioid antagonists in clinical use for alcohol dependence. Further interrogation of how modulation of the opioid system, via use of MOP (mu), DOP (delta) and KOP (kappa) agents, restores the balance of a dysregulated system in alcohol dependence should increase our insight into this disease process and therefore guide better methods for understanding and treating alcohol dependence in the future.

Two grams of sarcosine in schizophrenia - is it too much? A potential role of glutamate-serotonin interaction

Glutamate is the main excitatory neurotransmitter in the central nervous system. Dysfunction of the glutamatergic system plays an important role in the pathogenesis of schizophrenia. Therefore, glutamatergic agents such as N-methyl-D-aspartate receptor co-agonists (ie, glycine, D-cycloserine) and glycine transporter type 1 inhibitors (eg, sarcosine) are studied for their efficacy in ameliorating negative and cognitive symptomatology in patients with schizophrenia. We report the case of a 23-year-old schizophrenic patient treated with quetiapine and citalopram, who was offered concomitant sarcosine treatment. After obtaining an informed consent, we started administration of 2 g of sarcosine per day to treat persistent negative and cognitive symptoms. The patient's activity and mood improved within 2 weeks, but in the following 2 weeks the patient reported increased drive, activity, libido, unpleasant inner tension, and irritability. We ruled out hypomania and decided to decrease the daily dose of sarcosine to 1 g, which resulted in reduction of drive and irritability. Activity and mood improved compared with his state before adding sarcosine. We suggest a sarcosine dose between 1 g and 2 g per day with an initial dose of 2 g, but if side effects occur, the dose should be decreased to 1 g per day. We would like to emphasize the clinically important glutamate-serotonin interaction during concomitant use of sarcosine, citalopram, and quetiapine in our patient, which may lead to serious discomfort.

Results of a double-blind, placebo-controlled pharmacotherapy trial in alcoholism conducted in Germany and comparison with the US COMBINE study

The results of placebo-controlled trials (RCTs) with acamprosate or naltrexone vary substantially. Those differences have been attributed to differing patient characteristics, recruitment strategies, treatment settings and remuneration systems. We tested these assumptions by comparing a new double-blind, placebo-controlled randomized trial conducted in Germany (called PREDICT Study) with data from the US COMBINE Study. PREDICT was designed according to the protocol of the COMBINE Study. A total of 426 alcohol-dependent patients were compared to 459 COMBINE Study patients corresponding to the treatment cells in PREDICT. All patients received acamprosate, naltrexone or placebo for 3 months (PREDICT) or 4 months (COMBINE). Biweekly manualized 'medical management' to enhance compliance was delivered in both studies. Time until the first occurrence of heavy drinking was the main outcome measure. PREDICT found neither acamprosate nor naltrexone to supply any additional benefit compared with placebo, which is at variance with a positive naltrexone effect being reported in the COMBINE Study. A secondary comparison between both studies showed better overall treatment outcomes in PREDICT, although these patients had been more severely affected than their COMBINE counterparts. The divergence in results may be attributable to basic differences in the treatment environments (such as in-patient pre-treatment versus primary outpatient care). We suggest that identically designed RCTs conducted in different parts of the world may help improve the external validity of RCTs. This approach could be called 'comparative efficacy research'.

Impact of acamprosate on behavior and brain-derived neurotrophic factor: an open-label study in youth with fragile X syndrome

RATIONALE

Fragile X syndrome (FXS) is an inherited form of developmental disability and a single gene cause of autism. As a disorder with increasingly understood pathophysiology, FXS is a model form of developmental disability for targeted drug development efforts. Preclinical animal model findings have focused targeted drug treatment development in FXS on an imbalance between excessive glutamate and deficient gamma-aminobutyric acid (GABA) neurotransmission.

METHODS

We conducted a prospective open-label 10-week trial of acamprosate in 12 youth aged 6-17 years (mean age: 11.9 years) with FXS.

RESULTS

Acamprosate use (mean dose: 1,054  ±  422 mg/day) was associated with treatment response (defined by a Clinical Global Impressions Improvement (CGI-I) scale score of "very much improved" or "much improved") in nine of 12 (75 %) subjects. Improvement was noted in social behavior and inattention/hyperactivity using multiple standard behavioral outcome measures. No significant adverse effects or changes in vital signs, including weight or laboratory measures, occurred during treatment with acamprosate. Additionally, pre- and post-treatment blood biomarker analyses looking at brain-derived neurotrophic factor (BDNF) levels found a significant increase in BDNF with treatment. In our pilot sample, treatment response did not correlate with change in BDNF with treatment.

CONCLUSIONS

Acamprosate was generally safe and well tolerated and was associated with a significant improvement in social behavior and a reduction in inattention/hyperactivity. The increase in BDNF that occurred with treatment may be a useful pharmacodynamic marker in future acamprosate studies. Given these findings, a double-blind, placebo-controlled study of acamprosate in youth with FXS is warranted.

Predictability of alcohol relapse by hippocampal volumetry and psychometric variables

We examined the relationship between relapse risk/duration of abstinence and hippocampal volume as well as the moderating role of various psychological factors in 34 patients who fulfilled the diagnostic criteria for alcohol dependence according to ICD-10 and DSM-IV and 16 healthy controls (9 females and 7 males). This study is part of a single-blind, placebo-controlled, parallel-group treatment trial with the anticraving substance acamprosate administered for 3 months. Patients underwent a psychometric evaluation and a measurement of the hippocampus with magnetic resonance imaging before beginning medication (T0). At 2, 4, 8, and 12 weeks after treatment, abstinence was evaluated by phone. Afterwards all patients switched to a long-term open label study with acamprosate. Hippocampal volume did not constitute a predictive factor for relapse probability in abstinent alcoholics. Furthermore, stress level, depressivity, gender, and treatment with the anticraving substance acamprosate did not show a significant correlation with relapse probability. The current investigation could not identify significant risk factors for relapses after successful alcohol withdrawal. Further studies are required to identify crucial factors which are responsible for successful or unsuccessful relapse prevention.

Alcohol drinking and deprivation alter basal extracellular glutamate concentrations and clearance in the mesolimbic system of alcohol-preferring (P) rats

The present study determined the effects of voluntary ethanol drinking and deprivation on basal extracellular glutamate concentrations and clearance in the mesolimbic system and tested the hypothesis that chronic ethanol drinking would persistently increase basal glutamate neurotransmission. Three groups of alcohol-preferring (P) rats were used: 'water group (WG),' 'ethanol maintenance group (MG; 24-hour free choice water versus 15% ethanol)' and 'ethanol deprivation group (DG; 2 weeks of deprivation).' Quantitative microdialysis and Western blots were conducted to measure basal extracellular glutamate concentrations, clearance and proteins associated with glutamate clearance. Chronic alcohol drinking produced a 70-100% increase of basal extracellular glutamate concentrations in the posterior ventral tegmental area (4.0 versus 7.0 μM) and nucleus accumbens shell (3.0 versus 6.0 μM). Glutamate clearances were reduced by 30-40% in both regions of MG rats compared with WG rats. In addition, Western blots revealed a 40-45% decrease of excitatory amino transporter 1 (EAAT1) protein, but no significant changes in the levels of EAAT2 or cystine-glutamate antiporter in these regions of MG versus WG rats. The enhanced glutamate concentrations returned to control levels, accompanied by a recovery of glutamate clearance following deprivation. These results indicated that chronic alcohol drinking enhanced extracellular glutamate concentrations in the mesolimbic system, as a result, in part, of reduced clearance, suggesting that enhanced glutamate neurotransmission may contribute to the maintenance of alcohol drinking. However, because the increased glutamate levels returned to normal after deprivation, elevated glutamate neurotransmission may not contribute to the initiation of relapse drinking.

NMDA Receptor Modulators in the Treatment of Drug Addiction

Glutamate plays a pivotal role in drug addiction, and the N-methyl-d-aspartate (NMDA) glutamate receptor subtype serves as a molecular target for several drugs of abuse. In this review, we will provide an overview of NMDA receptor structure and function, followed by a review of the mechanism of action, clinical efficacy, and side effect profile of NMDA receptor ligands that are currently in use or being explored for the treatment of drug addiction. These ligands include the NMDA receptor modulators memantine and acamprosate, as well as the partial NMDA agonist d-Cycloserine. Data collected to date suggest that direct NMDA receptor modulators have relatively limited efficacy in the treatment of drug addiction, and that partial agonism of NMDA receptors may have some efficacy with regards to extinction learning during cue exposure therapy. However, the lack of consistency in results to date clearly indicates that additional studies are needed, as are studies examining novel ligands with indirect mechanisms for altering NMDA receptor function.

Novelty-seeking behaviors and the escalation of alcohol drinking after abstinence in mice are controlled by metabotropic glutamate receptor 5 on neurons expressing dopamine d1 receptors

BACKGROUND

Novel experiences activate the brain's reward system in a manner similar to drugs of abuse, and high levels of novelty-seeking and sensation-seeking behavior have been associated with increased susceptibility to alcohol and drug abuse. Here, we show that metabotropic glutamate receptor 5 (mGluR5) signaling on dopaminoceptive neurons is necessary for both novelty-seeking behavior and the abstinence-induced escalation of alcohol drinking.

METHODS

Mice harboring a transgene expressing microRNA hairpins against mGluR5 messenger RNA under the control of the D1 dopamine receptor gene promoter (mGluR5(KD-D1)) were tested in a battery of behavioral tests measuring learning abilities, anxiety levels, reactions to novelty, operant sensation seeking, and alcohol sensitivity. In addition, we have developed a method to assess long-term patterns of alcohol drinking in mice housed in groups using the IntelliCage system.

RESULTS

mGluR5(KD-D1) mice showed no behavioral deficits and exhibited normal anxiety-like behaviors and learning abilities. However, mGluR5(KD-D1) animals showed reduced locomotor activity when placed in a novel environment, and exhibited decreased interaction with a novel object. Moreover, unlike control animals, mutant mice did not perform instrumental responses under the operant sensation-seeking paradigm, although they learned to respond for food normally. When mGluR5(KD-D1) mice were provided access to alcohol, they showed similar patterns of consumption as wild-type animals. However, mutant mice did not escalate their alcohol consumption after a period of forced abstinence, but control mice almost doubled their intake.

CONCLUSIONS

These data identify mGluR5 receptors on D1-expressing neurons as a common molecular substrate of novelty-seeking behaviors and behaviors associated with alcohol abuse.

Pharmacotherapies for Overeating and Obesity

Obesity has become pandemic, and the annual cost in related illnesses and loss of productivity is already over $100 billion and rising. Research has shown that obesity can and does cause changes in behavior and in the brain itself that are very similar to changes caused by drugs of abuse. While food addiction is not the causal agent of all obesity, it is clear that many people no longer eat to survive, but instead survive to eat. This review considers the importance of the brain's reward system in food intake. The review also examines research developments and current treatments for obesity, including diet and exercise, psychotherapy, surgical interventions, and pharmacotherapies. Finally we discuss alterations in American society that are necessary for change to occur, and the diffculties therein.

Genetically selected alcohol preferring rats to model human alcoholism

Animal models have been successfully developed to mimic and study alcoholism. These models have the unique feature of allowing the researcher to control for the genetic characteristics of the animal, alcohol exposure and environment. Moreover, these animal models allow pharmacological, neurochemical and behavioral manipulations otherwise impossible. Unquestionably, one of the major contributions to the understanding of the neurobiological basis of alcoholism comes from data that have been obtained from the study of genetically selected alcohol preferring rat lines and from the consequences that alcohol drinking and environmental manipulations, (i.e., protracted alcohol drinking, intoxication, exposure to stress, etc.) have on them. In fact, if on the one hand genetic factors may account for about 50-60% of the risk of developing alcohol dependence, on the other hand protracted alcohol exposure is a necessary precondition to actually develop the disease, while environmental vulnerability factors may be crucial for disease progression. The present article will offer an overview of the different genetically selected alcohol preferring rat lines developed and used to study alcoholism. The predictive, face and construct validity of these animal models and the translational significance of findings achieved through their use will be critically discussed.

Family history of alcohol dependence and antidepressant response to an N-methyl-D-aspartate antagonist in bipolar depression

OBJECTIVES

Both ketamine and ethanol are N-methyl-d-aspartate (NMDA) receptor antagonists. Ketamine has rapid antidepressant properties in major depressive disorder (MDD) as well as bipolar depression. In individuals with MDD, a positive family history of alcohol dependence (FHP) was associated with greater improvement in depressive symptoms after ketamine administration compared to individuals whose family history of alcohol dependence was negative (FHN). This study investigated whether FHP influences ketamine's antidepressant and perceptual effects in individuals with bipolar depression.

METHODS

A post hoc analysis was conducted on 33 subjects with DSM-IV bipolar disorder (BD) type I or II depression pooled from two previously published studies. All subjects had undergone a double-blind, randomized, crossover trial of a single intravenous infusion of ketamine (0.5 mg/kg) combined with lithium or valproate therapy. Subjects were rated at baseline; at 40, 80, 120, and 230 min; and at days 1, 2, 3, 7, 10, and 14 post-infusion. The primary outcome measure was Montgomery-Åsberg Depression Rating Scale (MADRS) scores. Patients were categorized as FHP when they reported at least one first-degree relative with alcohol dependence. Measures of psychosis, dissociation, and dysphoria were also collected.

RESULTS

After ketamine infusion, subjects with FHP showed significantly greater improvement on MADRS scores than FHN subjects. In addition, patients with FHP had attenuated psychotomimetic and dissociative scores compared to FHN patients.

CONCLUSIONS

FHP appears to predict a more sustained antidepressant response to ketamine in individuals with BD. Family history of alcoholism may be an important consideration in the development of glutamatergic-based therapies for depression.

The central amygdala and alcohol: role of γ-aminobutyric acid, glutamate, and neuropeptides

Alcohol dependence is a chronically relapsing disorder characterized by compulsive drug seeking and drug taking, loss of control in limiting intake, and the emergence of a withdrawal syndrome in the absence of the drug. Accumulating evidence suggests an important role for synaptic transmission in the central amygdala (CeA) in mediating alcohol-related behaviors and neuroadaptative mechanisms associated with alcohol dependence. Acute alcohol facilitates γ-aminobutyric acid-ergic (GABAergic) transmission in CeA via both pre- and postsynaptic mechanisms, and chronic alcohol increases baseline GABAergic transmission. Acute alcohol inhibits glutamatergic transmission via effects at N-methyl-d-aspartate (NMDA) and AMPA receptors in CeA, whereas chronic alcohol up-regulates N-methyl-d-aspartate receptor (NMDAR)-mediated transmission. Pro- (e.g., corticotropin-releasing factor [CRF]) and anti-stress (e.g., NPY, nociceptin) neuropeptides affect alcohol- and anxiety-related behaviors, and also alter the alcohol-induced effects on CeA neurotransmission. Alcohol dependence produces plasticity in these neuropeptide systems, reflecting a recruitment of those systems during the transition to alcohol dependence.

Efficacy of acamprosate for alcohol dependence in a family medicine setting in the United States: a randomized, double-blind, placebo-controlled study

BACKGROUND

Acamprosate has been found to enhance rates of complete abstinence and to increase percent days abstinent (PDA) from alcohol relative to placebo treatment. As most U.S. clinical trials of acamprosate have been conducted in alcohol and other drug specialty clinics, there is a need to examine the efficacy of acamprosate in generalist settings. This study tested the efficacy of acamprosate versus placebo on the primary study outcome of PDA in the treatment of alcohol-dependent patients in a family medicine setting. Secondary study outcomes included percent heavy drinking days (%HDD) and gamma glutamyltransferase level (normal or high).

METHODS

A randomized, double-blind, placebo-controlled, parallel group design of acamprosate was conducted in 2 family medicine settings (North Carolina and Wisconsin). One hundred volunteers were recruited primarily by advertisement, and participants were assigned to 666 mg (2 pills) oral acamprosate 3 times daily (1,998 mg/d) or matching placebo over a 12-week period. All participants concomitantly received 5 sessions of a brief behavioral intervention from a family/primary care physician.

RESULTS

No significant treatment effect of acamprosate was found on PDA or the secondary outcomes. Significant treatment goal by time interaction effects was found on PDA and %HDD. Participants who had an initial goal of abstinence versus a reduction in alcohol use improved on average over time in PDA and had less %HDD from baseline to the end of treatment.

CONCLUSIONS

This clinical trial did not find evidence of efficacy for acamprosate compared to placebo among alcohol-dependent individuals recruited primarily by advertisement as studied in a primary care setting. Drinking outcomes significantly improved regardless of medication condition. A goal of abstinence was significantly associated with improved drinking outcomes, suggesting that alcohol-dependent patients with such a goal may do particularly well with counseling in a family medicine setting.

Involvement of mGlu5 and NMDA receptors in the antidepressant-like effect of acamprosate in the tail suspension test

Accumulating evidence supports the hypothesis that modulation of glutamatergic system via NMDA receptors and mGlu5 receptors might be an effective antidepressant therapy. However, clinical application of NMDA and mGlu5 antagonists in the therapy of depression is still an open question. In the present study we investigated potential antidepressant-like effect of a functional NMDA and mGlu5 receptor antagonist, acamprosate, which has been used in the therapy of human alcoholics as an anti-craving drug for more than 20 years and is considered as a safe substance. We have found potential antidepressant-like effect of acamprosate at doses of 100-400 mg/kg in the TST in C57BL/6J mice. Furthermore we have shown that the antidepressant-like effect of acamprosate used at a dose of 200 mg/kg was dependent on NMDA and mGlu5 receptor blockade, since NMDA (25 mg/kg) and mGlu5 receptor positive allosteric modulator, CDPPB (3 mg/kg), antagonized its activity in the TST. These data suggest that acamprosate may induce antidepressant-like effect and that NMDA and mGlu5 receptors are crucial targets of acamprosate in this action.

Ethanol withdrawal-induced brain metabolites and the pharmacological effects of acamprosate in mice lacking ENT1

Acamprosate is clinically used to treat alcohol-dependent patients. While the molecular and pharmacological mechanisms of acamprosate remain unclear, it has been shown to regulate γ-aminobutyric acid (GABA) or glutamate levels in the cortex and striatum. To investigate the effect of acamprosate on brain metabolites in the medial prefrontal cortex (mPFC) and nucleus accumbens (NAc), we employed in vivo 16.4 T proton magnetic resonance spectroscopy. We utilized type 1 equilibrative nucleoside transporter (ENT1) null mice since acamprosate attenuates ethanol drinking in these mice. Our findings demonstrated that ethanol withdrawal reduced GABA levels and increased phosphorylated choline compounds in the mPFC of both wild-type and ENT1 null mice. Notably, acamprosate normalized these withdrawal-induced changes only in ENT1 null mice. In the NAc, ethanol withdrawal increased glutamate and glutamine (Glx) levels only in wild-type mice. Interestingly, acamprosate reduced Glx levels in the NAc compared to the withdrawal state in both genotypes. These results provide a molecular basis for the pharmacological effect of acamprosate in the cortical-striatal circuit.

Alteration of glutamate/GABA balance during acute alcohol withdrawal in emergency department: a prospective analysis

AIMS

Animal studies suggest that in alcohol withdrawal the balance of neurotransmitters gamma aminobutyric acid (GABA) and glutamate is altered. To test this in humans, we aimed to measure plasma levels of glutamate, GABA and glutamate/GABA ratio in alcoholic patients presenting with complicated AWS with the same values in non-alcohol abuser/dependent controls and to determine prognostic factors for severe withdrawal.

METHODS

88 patients admitted to the emergency room for acute alcohol intoxication (DSM-IV) were prospectively included. Measurements of GABA and glutamate were performed on admission (Time 1, T1) and after 12 ± 2 h (T2). The experimental group (EG) was composed of 23 patients who presented at T2 with a severe AWS. The control group (CG) consisted of healthy subjects paired with the EG (gender and age). Logistic regression was performed in order to compare associated clinical and biological variables that could predict severe withdrawal.

RESULTS

The concentration of GABA in the EG at T1 was significantly lower than that in the CG. The concentration of glutamate in the EG at T1 was significantly higher than that in the CG. The glutamate/GABA ratio in the EG at T1 was significantly higher than the ratio in the CG. With a multivariate logistic regression model, glutamate level at admission remained the only criterion identified as a predictor of AWS at 12 h.

CONCLUSION

Decreased synthesis of GABA and increased synthesis of glutamate might be related to withdrawal symptoms experienced on brutal cessation of chronic alcohol intake.

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.

Craving correlates with mesolimbic responses to heroin-related cues in short-term abstinence from heroin: an event-related fMRI study

Craving is an important factor in relapse to drug abuse, and cue-induced craving is an especially powerful form of this construct. Neuroimaging methods have been utilized to study drug cue-induced craving and neural correlates in the human brain. However, very few studies have focused on characterizing craving and the neural responses to heroin-related cues in short-term abstinent heroin-dependent patients. Twenty-four heroin-dependent subjects and 20 demographically matched drug-naïve subjects participated in this study. An event-related cue-reactivity paradigm was employed, while changes in blood oxygen level-dependent (BOLD) signals were acquired by functional magnetic resonance imaging (fMRI). The heroin-dependent group reported significantly increased craving following exposure to heroin-related cues. Direct comparison between the two groups showed that brain activation to heroin-related minus neutral cues was significantly greater for the heroin-dependent group in the bilateral nucleus accumbens (NAc), caudate, putamen, amygdala, hippocampus/parahippocampus, midcingulate cortex, dorsolateral prefrontal cortex (DLPFC), orbitofrontal cortex (OFC), medial frontal gyrus (MeFG), midbrain, thalamus, left anterior cingulate cortex (ACC), posterior cingulate cortex (PCC), and subcallosal gyrus. Changes in craving in the heroin-dependent group correlated positively with brain activation in the bilateral NAc, caudate, right putamen, and left ACC. The abstinence duration correlated positively with brain activation in the left caudate and right parahippocampal gyrus. In conclusion, the cue-reactivity paradigm significantly activated neural responses in the mesolimbic dopamine (DA) system and prefrontal cortex (PFC) and induced increased craving in short-term abstinent heroin-dependent patients. We suggest that these response patterns characterize the high vulnerability of relapse in short-term abstinent heroin-dependent subjects.

Baseline trajectories of heavy drinking and their effects on postrandomization drinking in the COMBINE Study: empirically derived predictors of drinking outcomes during treatment

The Combined Pharmacotherapies and Behavioral Interventions (COMBINE) Study sought to answer questions about the benefits of combining behavioral and pharmacological interventions (naltrexone and acamprosate) in alcohol-dependent patients. Our goals were to identify trajectories of heavy drinking before randomization in COMBINE, to characterize patients in these trajectories, and to assess whether prerandomization trajectories predict drinking outcomes. We analyzed daily indicators of heavy drinking 90 days before randomization using a trajectory-based approach. Each patient was assigned to the most likely prerandomization heavy-drinking trajectory, and the baseline characteristics of participants in the baseline trajectories were compared. The main and interactive effects of these trajectories and treatment factors (acamprosate, naltrexone, or combined behavioral intervention) on summary drinking measures during active treatment (16 weeks) were assessed. We identified five trajectories of heavy drinking prerandomization: "T1: frequent heavy drinkers"; "T2: very frequent heavy drinkers"; "T3: nearly daily heavy drinkers"; "T4: daily heavy drinkers"; and "T5: daily heavy drinkers stopping early" before randomization. Trajectory membership was significantly associated with all drinking outcomes. Patients in "T5: daily heavy drinkers stopping early" had comparable drinking outcomes to those in "T1: frequent heavy drinkers," whereas the remaining trajectories were associated with significantly worse outcomes. The baseline trajectory did not interact significantly with the treatment condition. These exploratory analyses confirmed the hypothesis that baseline trajectories predict postrandomization drinking outcomes. Interestingly, "T5: daily heavy drinkers stopping early" had outcomes that were comparable to the least severe baseline trajectory "T1: frequent heavy drinkers," and baseline trajectories of heavy drinking did not moderate the treatment effects.

Acamprosate for treatment of alcohol dependence: mechanisms, efficacy, and clinical utility

Acamprosate, or N-acetyl homotaurine, is an N-methyl-D-aspartate receptor modulator approved by the Food and Drug Administration (FDA) as a pharmacological treatment for alcohol dependence. The exact mechanism of action of acamprosate is still under investigation, but the drug appears to work by promoting a balance between the excitatory and inhibitory neurotransmitters, glutamate and gamma-aminobutyric acid, respectively, and it may help individuals with alcohol dependence by reducing withdrawal-associated distress. Acamprosate has low bioavailability, but also has an excellent tolerability and safety profile. In comparison with naltrexone and disulfiram, which are the other FDA-approved treatments for alcohol dependence, acamprosate is unique in that it is not metabolized by the liver and is also not impacted by alcohol use, so can be administered to patients with hepatitis or liver disease (a common comorbid condition among individuals with alcohol dependence) and to patients who continue drinking alcohol. Acamprosate has demonstrated its efficacy in more than 25 placebo-controlled, double-blind trials for individuals with alcohol dependence, and has generally been found to be more efficacious than placebo in significantly reducing the risk of returning to any drinking and increasing the cumulative duration of abstinence. However, acamprosate appears to be no more efficacious than placebo in reducing heavy drinking days. Numerous trials have found that acamprosate is not significantly more efficacious than naltrexone or disulfiram, and the efficacy of acamprosate does not appear to be improved by combining acamprosate with other active medications (eg, naltrexone) or with psychosocial treatment (eg, cognitive-behavioral therapy). In this review, we present the data on acamprosate, including its pharmacology, efficacy, safety, and tolerability in the treatment of alcohol dependence.

Neuropeptide modulation of central amygdala neuroplasticity is a key mediator of alcohol dependence

Alcohol use disorders are characterized by compulsive drug-seeking and drug-taking, loss of control in limiting intake, and withdrawal syndrome in the absence of drug. The central amygdala (CeA) and neighboring regions (extended amygdala) mediate alcohol-related behaviors and chronic alcohol-induced plasticity. Acute alcohol suppresses excitatory (glutamatergic) transmission whereas chronic alcohol enhances glutamatergic transmission in CeA. Acute alcohol facilitates inhibitory (GABAergic) transmission in CeA, and chronic alcohol increases GABAergic transmission. Electrophysiology techniques are used to explore the effects of neuropeptides/neuromodulators (CRF, NPY, nociceptin, dynorphin, endocannabinoids, galanin) on inhibitory transmission in CeA. In general, pro-anxiety peptides increase, and anti-anxiety peptides decrease CeA GABAergic transmission. These neuropeptides facilitate or block the action of acute alcohol in CeA, and chronic alcohol produces plasticity in neuropeptide systems, possibly reflecting recruitment of negative reinforcement mechanisms during the transition to alcohol dependence. A disinhibition model of CeA output is discussed in the context of alcohol dependence- and anxiety-related behaviors.

Advancing addiction treatment: what can we learn from animal studies?

Substance addiction is a maladaptive behavior characterized by compulsive and uncontrolled self-administration of a substance (drug). Years of research indicate that addictive behavior is the result of complex interactions between the drug, the user, and the environment in which the drug is used; therefore, addiction cannot simply be attributed to the neurobiological actions of a drug. However, despite the obvious complexity of addictive behavior, animal models have both advanced understanding of addiction and contributed importantly to the development of medications to treat this disease. We briefly review recent animal models used to study drug addiction and the contribution of data generated by these animal models for the clinical treatment of addictive disorders.

An open-label naturalistic pilot study of acamprosate in youth with autistic disorder

To date, placebo-controlled drug trials targeting the core social impairment of autistic disorder (autism) have had uniformly negative results. Given this, the search for new potentially novel agents targeting the core social impairment of autism continues. Acamprosate is U.S. Food and Drug Administration-approved drug to treat alcohol dependence. The drug likely impacts both gamma-aminobutyric acid and glutamate neurotransmission. This study describes our initial open-label experience with acamprosate targeting social impairment in youth with autism. In this naturalistic report, five of six youth (mean age, 9.5 years) were judged treatment responders to acamprosate (mean dose 1,110 mg/day) over 10 to 30 weeks (mean duration, 20 weeks) of treatment. Acamprosate was well tolerated with only mild gastrointestinal adverse effects noted in three (50%) subjects.

Critical thoughts on current rodent models for evaluating potential treatments of alcohol addiction and withdrawal

Despite years of neurobiological research that have helped to identify potential therapeutic targets, we do not have a reliable pharmacological treatment for alcoholism. There are a range of possible explanations for this failure, including arguments that alcoholism is a spectrum disorder and that different population subtypes may respond to different treatments. This view is supported by categorisations such as early- and late-onset alcoholism, whilst multifactorial genetic factors may also alter responsivity to pharmacological agents. Furthermore, experience of alcohol withdrawal may play a role in future drinking in a way that may distinguish alcoholism from other forms of addiction. Additionally, our neurobiological models, based largely upon results from rodent studies, may not mimic specific aspects of the human condition and may reflect different underlying phenomena and biological processes from the clinical pattern. As a result, potential treatments may be targeting inappropriate aspects of alcohol-related behaviours. Instead, we suggest a more profitable approach is (a) to identify well-defined intermediate behavioural phenotypes in human experimental models that reflect defined aspects of the human clinical disorder and (b) to develop animal models that are homologous with those phenotypes in terms of psychological processes and underlying neurobiological mechanisms. This review describes an array of animal models currently used in the addiction field and what they tell us about alcoholism. We will then examine how established pharmacological agents have been developed using only a limited number of these models, before describing some alternative novel approaches to achieving homology between animal and human experimental measures.

Acamprosate-responsive brain sites for suppression of ethanol intake and preference

Acamprosate suppresses alcohol intake and craving in recovering alcoholics; however, the central sites of its action are unclear. To approach this question, brain regions responsive to acamprosate were mapped using acamprosate microimplants targeted to brain reward and circadian areas implicated in alcohol dependence. mPer2 mutant mice with nonfunctional mPer2, a circadian clock gene that gates endogenous timekeeping, were included, owing to their high levels of ethanol intake and preference. Male wild-type (WT) and mPer2 mutant mice received free-choice (15%) ethanol/water for 3 wk. The ethanol was withdrawn for 3 wk and then reintroduced to facilitate relapse. Four days before ethanol reintroduction, mice received bilateral blank or acamprosate-containing microimplants releasing ∼50 ng/day into reward [ventral tegmental (VTA), peduculopontine tegmentum (PPT), and nucleus accumbens (NA)] and circadian [intergeniculate leaflet (IGL) and suprachiasmatic nucleus (SCN)] areas. The hippocampus was also targeted. Circadian locomotor activity was measured throughout. Ethanol intake and preference were greater in mPer2 mutants than in wild-type (WT) mice (27 g·kg(-1)·day(-1) vs. 13 g·kg(-1)·day(-1) and 70% vs. 50%, respectively; both, P < 0.05). In WTs, acamprosate in all areas, except hippocampus, suppressed ethanol intake and preference (by 40-60%) during ethanol reintroduction. In mPer2 mutants, acamprosate in the VTA, PPT, and SCN suppressed ethanol intake and preference by 20-30%. These data are evidence that acamprosate's suppression of ethanol intake and preference are manifest through actions within major reward and circadian sites.

Glutamatergic medications for the treatment of drug and behavioral addictions

Historically, most pharmacological approaches to the treatment of addictive disorders have utilized either substitution-based methods (i.e., nicotine replacement or opioid maintenance) or have targeted monoaminergic or endogenous opioidergic neurotransmitter systems. However, substantial evidence has accumulated indicating that ligands acting on glutamatergic transmission are also of potential utility in the treatment of drug addiction, as well as various behavioral addictions such as pathological gambling. The purpose of this review is to summarize the pharmacological mechanisms of action and general clinical efficacy of glutamatergic medications that are currently approved or are being investigated for approval for the treatment of addictive disorders. Medications with effects on glutamatergic transmission that will be discussed include acamprosate, N-acetylcysteine, d-cycloserine, gabapentin, lamotrigine, memantine, modafinil, and topiramate. We conclude that manipulation of glutamatergic neurotransmission is a relatively young but promising avenue for the development of improved therapeutic agents for the treatment of drug and behavioral addictions.

Translational research in addiction: toward a framework for the development of novel therapeutics

The development of novel substance use disorder (SUD) therapeutics is insufficient to meet the medical needs of a growing SUD patient population. The identification of translatable SUD models and tests is a crucial step in establishing a framework for SUD therapeutic development programs. The present review begins by identifying the clinical features of SUDs and highlights the narrow regulatory end-point required for approval of a novel SUD therapeutic. A conceptual overview of dependence is provided, followed by identification of potential intervention targets in the addiction cycle. The main components of the addiction cycle provide the framework for a discussion of preclinical models and their clinical analogs, all of which are focused on isolated behavioral end-points thought to be relevant to the persistence of compulsive drug use. Thus, the greatest obstacle to successful development is the gap between the multiplicity of preclinical and early clinical end-points and the regulatory end-point of sustained abstinence. This review proposes two pathways to bridging this gap: further development and validation of the preclinical extended access self-administration model; inclusion of secondary end-points comprising all of the measures highlighted in the present discussion in Phase 3 trials. Further, completion of the postdictive validation of analogous preclinical and clinical assays is of high priority. Ultimately, demonstration of the relevance and validity of a variety of end-points to the ultimate goal of abstinence will allow researchers to identify truly relevant therapeutic mechanisms and intervention targets, and establish a framework for SUD therapeutic development that allows optimal decision-making and resource allocation.

Acamprosate in the treatment of binge eating disorder: a placebo-controlled trial

OBJECTIVE

To assess preliminarily the effectiveness of acamprosate in binge eating disorder (BED).

METHOD

In this 10-week, randomized, placebo-controlled, flexible dose trial, 40 outpatients with BED received acamprosate (N = 20) or placebo (N = 20). The primary outcome measure was binge eating episode frequency.

RESULTS

While acamprosate was not associated with a significantly greater rate of reduction in binge eating episode frequency or any other measure in the primary longitudinal analysis, in the endpoint analysis it was associated with statistically significant improvements in binge day frequency and measures of obsessive-compulsiveness of binge eating, food craving, and quality of life. Among completers, weight and BMI decreased slightly in the acamprosate group but increased in the placebo group.

DISCUSSION

Although acamprosate did not separate from placebo on any outcome variable in the longitudinal analysis, results of the endpoint and completer analyses suggest the drug may have some utility in BED.

Alcohol research: past, present, and future

Created forty years ago, the National Institute on Alcohol Abuse and Alcoholism (NIAAA) has played a major role in the great strides made in the understanding, treatment, prevention, and public acceptance of alcohol-use disorders. Throughout most of U.S. history "habitual drunkenness" was viewed as a problem of moral degeneracy or character flaw inherent in the individual. However, the wealth of scientific evidence amassed throughout NIAAA's history has established alcoholism as a medical condition, that is, as a disease for which affected individuals should feel no shame or be treated with disdain. We look at the developments in alcohol epidemiology, typology, etiology, prevention, and treatment research over the past 40 years. We also discuss how NIAAA addresses alcohol disorders from a life-course framework, affecting all stages of the lifespan, from fetus through child, adolescent, and young adult, to midlife/senior adult, with each stage involving different risks, consequences, prevention efforts, and treatment strategies.

Acamprosate reduces ethanol drinking behaviors and alters the metabolite profile in mice lacking ENT1

Acamprosate is clinically used to treat alcoholism. However, the precise molecular functionality of acamprosate in the central nervous system remains unclear, although it is known to antagonize glutamate action in the brain. Since elevated glutamate signaling, especially in the nucleus accumbens (NAc), is implicated in several aspects of alcoholism, we utilized mice lacking type 1 equilibrative nucleoside transporter (ENT1), which exhibit increased glutamate levels in the NAc as well as increased ethanol drinking behaviors. We found that acamprosate significantly reduced ethanol drinking of mice lacking ENT1 (ENT1(-/-)) while having no such effect in wild-type littermates. We then analyzed the basal and acamprosate-treated accumbal metabolite profiles of ENT1(-/-) and wild-type mice using in vivo 16.4T proton magnetic resonance spectroscopy (MRS). Our data show that basal glutamate+glutamine (Glx), glutamate, glutamine and N-acetylaspartatic acid (NAA) levels are increased in the nucleus accumbens (NAc) of ENT1(-/-) compared to wild-type mice. We then found that acamprosate treatment significantly reduced Glx and glutamine levels while increasing taurine levels in the NAc of only ENT1(-/-) compared to their saline-treated group while normalizing other metabolite compared to wild-type mice. This study will be useful in the understanding of the molecular basis of acamprosate in the brain.

Baseline trajectories of drinking moderate acamprosate and naltrexone effects in the COMBINE study

BACKGROUND

The COMBINE study evaluated the effects of acamprosate, naltrexone, and the Combined Behavioral Intervention (CBI). In secondary analyses, our goals were to identify trajectories of any drinking prior to randomization, to characterize subjects in these trajectories, and to assess whether prerandomization trajectories predict drinking outcomes and moderate treatment response.

METHODS

We analyzed daily indicators of any drinking in 90 days prior to randomization using a trajectory-based approach. General linear models and generalized logistic regression assessed main and interactive effects of prerandomization drinking trajectories and treatment on summary drinking measures during active treatment.

RESULTS

We identified five trajectories of any drinking prior to randomization: "T1: frequent drinkers", "T2: very frequent drinkers", "T3: nearly daily drinkers", "T4: consistent daily drinkers", and "T5: daily drinkers stopping early". During treatment, "T3: nearly daily drinkers" and "T4: consistent daily drinkers" had significantly worse drinking outcomes than "T1: frequent drinkers", while "T5: daily drinkers stopping early" had comparable drinking outcomes to "T1: frequent drinkers". Acamprosate significantly increased the chance of abstinence from heavy drinking for the "T2: very frequent drinking" trajectory but decreased the chance of abstinence from heavy drinking for "T5: daily drinkers stopping early". Naltrexone differentially improved rates of continuous abstinence for very frequent drinkers.

CONCLUSIONS

Acamprosate benefited very frequent drinkers and contrary to expectations was associated with poorer response compared to placebo for consistent daily drinkers who had longer durations of pretreatment abstinence (e.g., ≥14 days). Baseline drinking trajectories also moderated naltrexone effects. These findings may help clinicians identify patients for whom acamprosate and naltrexone may be most beneficial.

Using glutamate homeostasis as a target for treating addictive disorders

Well-developed cellular mechanisms exist to preserve glutamate homeostasis and regulate extrasynaptic glutamate levels. Accumulating evidence indicates that disruptions in glutamate homeostasis are associated with addictive disorders. The disruptions in glutamate concentrations observed after prolonged exposure to drugs of abuse are associated with changes in the function and activity of several key components within the homeostatic control mechanism, including the cystine/glutamate exchanger xc(-) and the glial glutamate transporter, EAAT2/GLT-1. Changes in the balance between synaptic and extrasynaptic glutamate levels in turn influence signaling through presynaptic and postsynaptic glutamate receptors, and thus affect synaptic plasticity and circuit-level activity. In this review, we describe the evidence for impaired glutamate homeostasis as a critical mediator of long-term drug-seeking behaviors, how chronic neuroadaptations in xc(-) and the glutamate transporter, GLT-1, mediate a disruption in glutamate homeostasis, and how targeting these components restores glutamate levels and inhibits drug-seeking behaviors.

Individualised treatment in alcohol-dependent patients

Long-term relapse prevention is the biggest challenge in treating alcohol-dependent patients. It is equally based on psychotherapy and pharmacotherapy. Psychotherapy includes motivational interviewing, community reinforcement, cognitive behavioural therapy, motivational enhancement, twelve-step facilitation, social network behaviour therapy, cue exposure, etc. For pharmacological treatment, we dispose of disulfiram, acamprosate and naltrexone. Reviews and meta-analyses reveal only modest effect sizes of these approaches probably because they are usually tested in large and heterogeneous samples where "one size does not fit all". However, attempts to form more homogeneous subgroups for which specific psychotherapies should be more effective ("matching") also failed. We suppose that this failure may have to do with the fact that these studies used only psychopathology and behavioural analyses as a basis for subtyping. Things look more promising once biologically defined endophenotypes are used as well in order to form more homogeneous subgroups. For example, naltrexone treatment seems more effective in carriers of a specific variant of the mu-opioid receptor gene. The same could be true for acamprosate if a newly found polymorphism was used to preselect potential responders. Very recently biological differences between patient groups are also being detected using functional imaging. Naltrexone is suggested to work better in a subgroup of patients with higher cue reactivity when shown appetitive alcohol pictures. MR spectroscopy of brain glutamate levels may detect potential acamprosate responders. On such a basis, an individualised approach in the treatment of alcoholism ("personalised medicine") seems to hold promise.