Cannabinoid receptor 1 blocker rimonabant (SR 141716) for treatment of alcohol dependence: results from a placebo-controlled, double-blind trial

Reduced cannabinoid CB1 receptor binding in alcohol dependence measured with positron emission tomography

Brain cannabinoid CB1 receptors contribute to alcohol-related behaviors in experimental animals, but their potential role in humans with alcohol dependence is poorly understood. We measured CB1 receptors in alcohol dependent patients in early and protracted abstinence, and in comparison with control subjects without alcohol use disorders, using positron emission tomography and [(18)F]FMPEP-d2, a radioligand for CB1 receptors. We scanned 18 male in-patients with alcohol dependence twice, within 3-7 days of admission from ongoing drinking, and after 2-4 weeks of supervised abstinence. Imaging data were compared with those from 19 age-matched healthy male control subjects. Data were also analyzed for potential influence of a common functional variation (rs2023239) in the CB1 receptor gene (CNR1) that may moderate CB1 receptor density. On the first scan, CB1 receptor binding was 20-30% lower in patients with alcohol dependence than in control subjects in all brain regions and was negatively correlated with years of alcohol abuse. After 2-4 weeks of abstinence, CB1 receptor binding remained similarly reduced in these patients. Irrespective of the diagnostic status, C allele carriers at rs2023239 had higher CB1 receptor binding compared with non-carriers. Alcohol dependence is associated with a widespread reduction of cannabinoid CB1 receptor binding in the human brain and this reduction persists at least 2-4 weeks into abstinence. The correlation of reduced binding with years of alcohol abuse suggests an involvement of CB1 receptors in alcohol dependence in humans.

A spontaneous deletion of α-synuclein is associated with an increase in CB1 mRNA transcript and receptor expression in the hippocampus and amygdala: effects on alcohol consumption

α-Synuclein (α-syn) protein and endocannabinoid CB1 receptors are primarily located in presynaptic terminals. An association between α-syn and CB1 receptors has recently been established in Parkinson's disease, but it is completely unknown whether there is an association between these two proteins in alcohol addiction. Therefore, we aimed to examine the α-syn mRNA transcript and protein expression levels in the prefrontal cortex, striatum, amygdala and hippocampus. These brain regions are the most frequently implicated in alcohol and other drug addiction. In these studies, we used C57BL/6 mice carrying a spontaneous deletion of the α-syn gene (C57BL/6(Snca-/-) ) and their respective controls (C57BL/6(Snca) (+/) (+) ). These animals were monitored for spontaneous alcohol consumption (3-10%) and their response to a hypnotic-sedative dose of alcohol (3 g kg(-1) ) was also assessed. Compared with the C57BL/6(Snca+/+) mice, we found that the C57BL/6(Snca-/-) mice exhibited a higher expression level of the CB1 mRNA transcript and CB1 receptor in the hippocampus and amygdala. Furthermore, C57BL/6(Snca-/-) mice showed an increase in alcohol consumption when offered a 10% alcohol solution. There was no significant difference in sleep time after the injection of 3 g/kg alcohol. These results are the first to reveal an association between α-syn and the CB1 receptor in the brain regions that are most frequently implicated in alcohol and other drug addictions.

Lipids and addiction: how sex steroids, prostaglandins, and cannabinoids interact with drugs of abuse

Lipidomics aims to identify and characterize all endogenous species of lipids and understand their roles in cellular signaling and, ultimately, the functioning of the organism. We are on the cusp of fully understanding the functions of many of the lipid signaling systems that have been identified for decades (e.g., steroids, prostaglandins), whereas our understanding of newer lipid signaling systems (e.g., endocannabinoids, N-acyl amides) still lags considerably behind. With an emphasis on their roles in the neurophysiology of addiction, we will examine three classes of lipids--sex steroids, prostaglandins, and cannabinoids--and how they work synergistically in the neurocircuitry of motivation. We will first give a brief overview of the biosynthesis for each class of lipid and its receptors, and then summarize what is known about the collective roles of the lipids in cocaine and alcohol abuse. This approach provides a novel view of lipid signaling as a class of molecules and their synergistic roles in addiction.

Endocannabinoid system: A newer molecular target for the treatment of alcohol-related behaviors

The cannabinoid (CB) receptors, endocannabinoids (eCB) and their synthesizing and catabolizing enzymes and the proteins involved in their transport, constitute what is now recognized as the eCB system. The eCBs are a class of lipids that have been identified as retrograde messengers and produce their effects via presynaptic CB receptors. The major function of the eCBs has been suggested to be that of modulating the release of several neurotransmitters implicated in a number of biological functions that include reward and reinforcement. There is now significant evidence to suggest that the eCB system plays an important role in the development of alcohol tolerance, dependence and relapse. Recent studies suggest that the pharmacological manipulation of the eCB system has the potential not only to block the direct reinforcing properties of alcohol but also alleviate behavioral abnormalities associated with relapse. There is also accumulating evidence that points to the possible utility of the eCB system targeted drugs in the treatment of alcoholism-related behavioral disorders. The agents that block CB1 receptor function or inhibit the synthesis of eCBs are attractive candidate drugs that need to be explored. Further understanding of the role of the eCB system in molecular mechanism/s that underlies alcoholism-related behaviors should lead to a better treatment of this devastating disorder.

A review of the interactions between alcohol and the endocannabinoid system: implications for alcohol dependence and future directions for research

Over the past fifty years a significant body of evidence has been compiled suggesting an interaction between the endocannabinoid (EC) system and alcohol dependence. However, much of this work has been conducted only in the past two decades following the elucidation of the molecular constituents of the EC system that began with the serendipitous discovery of the cannabinoid 1 receptor (CB1). Since then, novel pharmacological and genetic tools have enabled researchers to manipulate select components of the EC system, to determine their contribution to the motivation to consume ethanol. From these preclinical studies, it is evident that CB1 contributes the motivational and reinforcing properties of ethanol, and chronic consumption of ethanol alters EC transmitter levels and CB1 expression in brain nuclei associated with addiction pathways. These results are augmented by in vitro and ex vivo studies showing that acute and chronic treatment with ethanol produces physiologically relevant alterations in the function of the EC system. This report provides a current and comprehensive review of the literature regarding the interactions between ethanol and the EC system. We begin be reviewing the studies published prior to the discovery of the EC system that compared the behavioral and physiological effects of cannabinoids with ethanol in addition to cross-tolerance between these drugs. Next, a brief overview of the molecular constituents of the EC system is provided as context for the subsequent review of more recent studies examining the interaction of ethanol with the EC system. These results are compiled into a summary providing a scheme for the known changes to the components of the EC system in different stages of alcohol dependence. Finally, future directions for research are discussed.

Pyrazole carbohydrazide derivatives of pharmaceutical interest

The main purpose of this paper is to provide an insight into the biological activities of pyrazole derivatives which contain the carbohydrazide moiety.

Reduced alcohol intake and reward associated with impaired endocannabinoid signaling in mice with a deletion of the glutamate transporter GLAST

A hyperglutamatergic state has been hypothesized to drive escalation of alcohol intake. This hypothesis predicts that an impairment of glutamate clearance through inactivation of the astrocytic glutamate transporter, GLAST (EAAT1), will result in escalation of alcohol consumption. Here, we used mice with a deletion of GLAST to test this prediction. WT and GLAST KO mice were tested for alcohol consumption using two-bottle free-choice drinking. Alcohol reward was evaluated using conditioned place preference (CPP). Sensitivity to depressant alcohol effects was tested using the accelerating rotarod, alcohol-induced hypothermia, and loss of righting reflex. Extracellular glutamate was measured using microdialysis, and striatal slice electrophysiology was carried out to examine plasticity of the cortico-striatal pathway as a model system in which adaptations to the constitutive GLAST deletion can be studied. Contrary to our hypothesis, GLAST KO mice showed markedly decreased alcohol consumption, and lacked CPP for alcohol, despite a higher locomotor response to this drug. Alcohol-induced ataxia, hypothermia, and sedation were unaffected. In striatal slices from GLAST KO mice, long-term depression (LTD) induced by high frequency stimulation, or by post-synaptic depolarization combined with the l-type calcium channel activator FPL 64176 was absent. In contrast, normal synaptic depression was observed after application of the cannabinoid 1 (CB1) receptor agonist WIN55,212-2. Constitutive deletion of GLAST unexpectedly results in markedly reduced alcohol consumption and preference, associated with markedly reduced alcohol reward. Endocannabinoid signaling appears to be down-regulated upstream of the CB1 receptor as a result of the GLAST deletion, and is a candidate mechanism behind the reduction of alcohol reward observed.

Innate difference in the endocannabinoid signaling and its modulation by alcohol consumption in alcohol-preferring sP rats

The present study was undertaken to examine whether genetically predetermined differences in components of the endocannabinoid system were present in the brain of Sardinian alcohol-preferring (sP) and Sardinian alcohol-non-preferring (sNP) rats, a pair of rat lines selectively bred for opposite alcohol preference. The effects of acquisition and maintenance of alcohol drinking, alcohol withdrawal, and alcohol re-exposure on the endocannabinoid system was also assessed in the striatum of sP rats. The findings revealed significantly higher density of the CB1 receptors and levels of CB1 receptor mRNA, CB1 receptor-mediated G-protein coupling, and endocannabinoids in the cerebral cortex, hippocampus and striatum of alcohol-naive sP rats than sNP rats. A significantly lower expression of mFAAH enzyme was evident in the hippocampus of alcohol-naive sP rats. Alcohol drinking (during both acquisition and maintenance phases) in sP rats resulted in a significant reduction in striatal CB1 receptor-mediated G-protein coupling whereas alcohol withdrawal attenuated this effect. Alcohol consumption was also associated with markedly increased levels of endocannabinoids in the striatum. Co-administration of the CB1 receptor antagonist, rimonabant (SR141716A) reduced alcohol intake, and reversed alcohol-induced changes in CB1 receptor-mediated G-protein activation. These findings provided a new insight into a potential genetic basis of excessive alcohol consumption, suggesting innate differences in the endocannabinoid system might be associated with higher alcohol preference in sP rats. The data also indicate a modulation of CB1 receptor-mediated signaling following alcohol consumption, and further strengthen the potential of the endocannabinoid system as a target for the treatment of alcohol related behaviors.

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.

Antagonist-elicited cannabis withdrawal in humans

Cannabinoid CB1 receptor antagonists have potential therapeutic benefits, but antagonist-elicited cannabis withdrawal has not been reported in humans. Ten male daily cannabis smokers received 8 days of increasingly frequent 20-mg oral Δ⁹-tetrahydrocannabinol (THC) dosages (40-120 mg/d) around-the-clock to standardize cannabis dependence while residing on a closed research unit. On the ninth day, double-blind placebo or 20- (suggested therapeutic dose) or 40-mg oral rimonabant, a CB1-cannabinoid receptor antagonist, was administered. Cannabis withdrawal signs and symptoms were assessed before and for 23.5 hours after rimonabant. Rimonabant, THC, and 11-hydroxy-THC plasma concentrations were quantified by mass spectrometry. The first 6 subjects received 20-mg rimonabant (1 placebo); the remaining 4 subjects received 40-mg rimonabant (1 placebo). Fourteen subjects enrolled; 10 completed before premature termination because of withdrawal of rimonabant from clinical development. Three of 5 subjects in the 20-mg group, 1 of 3 in the 40-mg group, and none of 2 in the placebo group met the prespecified withdrawal criterion of 150% increase or higher in at least 3 visual analog scales for cannabis withdrawal symptoms within 3 hours of rimonabant dosing. There were no significant associations between visual analog scale, heart rate, or blood pressure changes and peak rimonabant plasma concentration, area-under-the-rimonabant-concentration-by-time curve (0-8 hours), or peak rimonabant/THC or rimonabant/(THC + 11-hydroxy-THC) plasma concentration ratios. In summary, prespecified criteria for antagonist-elicited cannabis withdrawal were not observed at the 20- or 40-mg rimonabant doses. These data do not preclude antagonist-elicited withdrawal at higher rimonabant doses.

Involvement of the endocannabinoid system in alcohol dependence: the biochemical, behavioral and genetic evidence

BACKGROUND

Recent advances in the understanding of alcohol dependence suggest that the endocannabinoid system (ECS) plays a key role in the neurobiological mechanisms underlying this pathology.

METHODS

The aim of the present review is to show the currently available biochemical, behavioral and genetic evidence on the involvement of the ECS in alcohol dependence.

DISCUSSION

Firstly, biochemical studies have shown that both chronic and acute administration of ethanol produce alterations in different elements of this neurotransmission system. Secondly, the pharmacological and genetic manipulation of the ECS in rodents result in altered ethanol-related behavior. Furthermore, rodent strains with different preference for ethanol differ in their ECS state. Also, genetic studies have described that particular polymorphisms in the genes coding for some elements of this system are associated with some phenotypes of alcohol dependence. Finally, the possible efficacy of cannabinoid receptor blockers in the prevention of relapse to alcohol has been tested in clinical trials.

CONCLUSION

Altogether, these multiple lines of evidence suggest that the ECS is implicated in the development of alcohol abuse and dependence.

Pharmacological activation/inhibition of the cannabinoid system affects alcohol withdrawal-induced neuronal hypersensitivity to excitotoxic insults

Cessation of chronic ethanol consumption can increase the sensitivity of the brain to excitotoxic damages. Cannabinoids have been proposed as neuroprotectants in different models of neuronal injury, but their effect have never been investigated in a context of excitotoxicity after alcohol cessation. Here we examined the effects of the pharmacological activation/inhibition of the endocannabinoid system in an in vitro model of chronic ethanol exposure and withdrawal followed by an excitotoxic challenge. Ethanol withdrawal increased N-methyl-D-aspartate (NMDA)-evoked neuronal death, probably by altering the ratio between GluN2A and GluN2B NMDA receptor subunits. The stimulation of the endocannabinoid system with the cannabinoid agonist HU-210 decreased NMDA-induced neuronal death exclusively in ethanol-withdrawn neurons. This neuroprotection could be explained by a decrease in NMDA-stimulated calcium influx after the administration of HU-210, found exclusively in ethanol-withdrawn neurons. By contrast, the inhibition of the cannabinoid system with the CB1 receptor antagonist rimonabant (SR141716) during ethanol withdrawal increased death of ethanol-withdrawn neurons without any modification of NMDA-stimulated calcium influx. Moreover, chronic administration of rimonabant increased NMDA-stimulated toxicity not only in withdrawn neurons, but also in control neurons. In summary, we show for the first time that the stimulation of the endocannabinoid system is protective against the hyperexcitability developed during alcohol withdrawal. By contrast, the blockade of the endocannabinoid system is highly counterproductive during alcohol withdrawal.

Cannabinoid receptor type I modulates alcohol-induced liver fibrosis

The cannabinoid system (CS) is implicated in the regulation of hepatic fibrosis, steatosis and inflammation, with cannabinoid receptors 1 and 2 (CB1 and CB2) being involved in regulation of pro- and antifibrogenic effects. Daily cannabis smoking is an independent risk factor for the progression of fibrosis in chronic hepatitis C and a mediator of experimental alcoholic steatosis. However, the role and function of CS in alcoholic liver fibrosis (ALF) is unknown so far. Thus, human liver samples from patients with alcoholic liver disease (ALD) were collected for analysis of CB1 expression. In vitro, hepatic stellate cells (HSC) underwent treatment with acetaldehyde, Δ9-tetrahydrocannabinol H₂O₂, endo- and exocannabinoids (2-arachidonoylglycerol (2-AG) and [THC]), and CB1 antagonist SR141716 (rimonabant). In vivo, CB1 knockout (KO) mice received thioacetamide (TAA)/ethanol (EtOH) to induce fibrosis. As a result, in human ALD, CB1 expression was restricted to areas with advanced fibrosis only. In vitro, acetaldehyde, H₂O₂, as well as 2-AG and THC, alone or in combination with acetaldehyde, induced CB1 mRNA expression, whereas CB1 blockage with SR141716 dose-dependently inhibited HSC proliferation and downregulated mRNA expression of fibrosis-mediated genes PCα1(I), TIMP-1 and MMP-13. This was paralleled by marked cytotoxicity of SR141716 at high doses (5-10 μmol/L). In vivo, CB1 knockout mice showed marked resistance to alcoholic liver fibrosis. In conclusion, CB1 expression is upregulated in human ALF, which is at least in part triggered by acetaldehyde (AA) and oxidative stress. Inhibition of CB1 by SR141716, or via genetic knock-out protects against alcoholic-induced fibrosis in vitro and in vivo.

Addiction research centres and the nurturing of creativity department of addictive behaviour and addiction medicine, central institute of Mental Health, Mannheim, University of Heidelberg

Addictive behaviour is as prevalent in Germany as in other western countries, but in contrast to some European countries and the United States, very little money was given to this research field. Change came in the early 1990s, when the German government started to launch specific grants for addiction research. The first chair in addiction research was created in 1999 (Karl Mann) at the Central Institute of Mental Health Mannheim (CIMH; University of Heidelberg). The recruitment of a pre-clinical alcohol researcher as head of the department of psychopharmacology followed (Rainer Spanagel). This 'addiction research cluster' collaborates with several research groups at the CIMH (such as genetics). We inaugurated a clinical trial network which now comprises up to 20 treatment centres throughout Germany. Like most authors, we found effect sizes of different treatment modalities more in the low to moderate range, perhaps because of the heterogeneity of large patient samples. Therefore, we concentrated upon the biological basis of addiction in order to define more homogeneous 'subtypes' of patients for a better match with existing treatments. Results concerning genetics and neuroimaging (both animal and human) are promising, and could move our field towards a more personalized treatment approach. Our funding has been extended over the years, including involvement in several large European grants. We are studying substance-related problems as well as so-called 'behavioural addictions'. As a natural consequence of this development, we are deeply involved both in informing the general public on addiction issues as well as in counselling policy makers in Germany.

Emerging drugs to treat alcoholism

IMPORTANCE OF THE FIELD

Alcoholism is a widespread disorder with substantial mortality and negative treatment outcomes. To date, few medications have been found to reduce relapse rates or drinking in alcohol-dependent patients.

AREAS COVERED IN THIS REVIEW

This review focuses on drugs that have been clinically tested for the treatment of alcohol dependence in clinical trials, pilot trials or which are considered to have a clinical perspective. For this purpose, a detailed Medline search was conducted on this issue. Although the neurochemical basis of alcoholism and the neuronal circuitry mediating its psychotropic effects have been explored in great detail in recent years, few drugs have emerged for the treatment of alcohol dependence, also because pharmaceutical companies have only a limited interest in this area of research. Acamprosate and the opioid antagonist naltrexone have been found to be effective, although data are mixed. A depot formula of naltrexone and the alternate opioid antagonist nalmefene have been studied in clinical trials and will presumably be introduced in the markets soon. Other emerging drugs are topiramate, novel acetaldehyde dehydrogenase (ALDH) inhibitors, baclofen, a combination therapy of gababentin and flumazenil and drugs targeting the cortitropin-releasing factor/neuropeptide Y mediated stress axis.

WHAT THE READER WILL GAIN

Insights on the neurochemical basis of alcohol dependence and possible targets of medications.

TAKE HOME MESSAGE

Acamprosate, naltrexone and the ALDH inhibitor disulfiram are proven medications for the treatment of alcohol dependence with modest efficacy. Novel alternate medications, a depot formulation of the opioid antagonist naltrexone and another oral opioid antagonist, nalmefene, are available now with good evidence for clinical efficacy. Novel ALDH inhibitors, antiepileptic drugs such as topiramate and drugs targeting the stress axis are currently among the most promising emerging drugs.

Cannabinoid-dopamine interaction in the pathophysiology and treatment of CNS disorders

Endocannabinoids and their receptors, mainly the CB(1) receptor type, function as a retrograde signaling system in many synapses within the CNS, particularly in GABAergic and glutamatergic synapses. They also play a modulatory function on dopamine (DA) transmission, although CB(1) receptors do not appear to be located in dopaminergic terminals, at least in the major brain regions receiving dopaminergic innervation, e.g., the caudate-putamen and the nucleus accumbens/prefrontal cortex. Therefore, the effects of cannabinoids on DA transmission and DA-related behaviors are generally indirect and exerted through the modulation of GABA and glutamate inputs received by dopaminergic neurons. Recent evidence suggest, however, that certain eicosanoid-derived cannabinoids may directly activate TRPV(1) receptors, which have been found in some dopaminergic pathways, thus allowing a direct regulation of DA function. Through this direct mechanism or through indirect mechanisms involving GABA or glutamate neurons, cannabinoids may interact with DA transmission in the CNS and this has an important influence in various DA-related neurobiological processes (e.g., control of movement, motivation/reward) and, particularly, on different pathologies affecting these processes like basal ganglia disorders, schizophrenia, and drug addiction. The present review will address the current literature supporting these cannabinoid-DA interactions, with emphasis in aspects dealing with the neurochemical, physiological, and pharmacological/therapeutic bases of these interactions.

Endogenous cannabinoids in post-mortem brains of Cloninger type 1 and 2 alcoholics

The endogenous cannabinoid (EC) system has been recently implicated in several neuropsychiatric disorders. This study analyzed post-mortem brain regions of Cloninger type 1 (n=9) and 2 (n=8) alcoholics and non-alcoholic controls (n=10) for ECs by quantitative liquid chromatography with triple quadrupole mass spectrometric detection. A significant difference was found in anandamide (AEA) levels in nucleus accumbens (NAcc) between the three groups (p=0.047). AEA levels were significantly lower when compared to controls in both perigenual anterior cingulate (p=0.017) and frontal cortices (p=0.018) of type 1 alcoholics. Similar trends were observed for dihomo-gamma-linolenoyl ethanolamide and docosahexaenoyl ethanolamide, but not for 2-arachidonoylglycerol, palmitoyl ethanolamide, or oleoyl ethanolamide. Although preliminary, and from diagnostic groups with a relatively small number of subjects and substantially different mean ages for each group, these results suggest that the EC system may be hyperactive in type 2 alcoholics and hypoactive in type 1 alcoholics.

Converging action of alcohol consumption and cannabinoid receptor activation on adult hippocampal neurogenesis

Alcoholism is characterized by successive periods of abstinence and relapse, resulting from long-lasting changes in various circuits of the central nervous system. Accumulating evidence points to the endocannabinoid system as one of the most relevant biochemical systems mediating alcohol addiction. The endocannabinoid system regulates adult neurogenesis, a form of long-lasting adult plasticity that occurs in a few areas of the brain, including the dentate gyrus. Because exposure to psychotropic drugs regulates adult neurogenesis, it is possible that neurogenesis might be implicated in the pathophysiology, and hence treatment, of neurobiological illnesses related to drugs of abuse. Here, we investigated the sensitivity of adult hippocampal neurogenesis to alcohol and the cannabinoid receptor agonist WIN 55,212-2 (WIN). Specifically, we analysed the potential link between alcohol relapse, cannabinoid receptor activation, and adult neurogenesis. Adult rats were exposed to subchronic alcohol binge intoxication and received the cannabinoid receptor agonist WIN. Another group of rats were subjected to an alcohol operant self-administration task. Half of these latter animals had continuous access to alcohol, while the other half were subjected to alcohol deprivation, with or without WIN administration. WIN treatment, when administered during alcohol deprivation, resulted in the greatest increase in alcohol consumption during relapse. Together, forced alcohol binge intoxication and WIN administration dramatically reduced hippocampal neurogenesis. Furthermore, adult neurogenesis inversely correlated with voluntary consumption of alcohol. These findings suggest that adult hippocampal neurogenesis is a key factor involved in drug abuse and that it may provide a new strategy for the treatment of alcohol addiction and dependence.

Rimonabant (SR141716) has no effect on alcohol self-administration or endocrine measures in nontreatment-seeking heavy alcohol drinkers

RATIONALE

There is an extensive literature showing that the CB(1) cannabinoid receptor antagonist rimonabant (SR141716) decreases alcohol consumption in animals, but little is known about its effects in human alcohol drinkers.

METHODS

In this study, 49 nontreatment-seeking heavy alcohol drinkers participated in a 3-week study. After a 1-week baseline, participants received either 20 mg/day of rimonabant or placebo for 2 weeks under double-blind conditions. During these 3 weeks, participants reported their daily alcohol consumption by telephone. Subsequently, they participated in an alcohol self-administration paradigm in which they received a priming dose of alcohol followed by the option of consuming either eight alcohol drinks or receiving $3.00 for each nonconsumed drink. Endocrine measures and self-rating scales were also obtained.

RESULTS

Rimonabant did not change alcohol consumption during the 2 weeks of daily call-ins. Similarly, the drug did not change either alcohol self-administration or endocrine measures during the laboratory session.

CONCLUSION

We conclude that the daily administration of 20 mg of rimonabant for 2 weeks has no effect on alcohol consumption in nontreatment-seeking heavy alcohol drinkers.

Management of alcohol use disorders

Welcome to the third module in our Continuing Professional Development Section (CPD). CPD is now a key element in the clinical activity of all health professionals and a cornerstone of good clinical governance throughout mental health services. This section of the Irish Journal of Psychological Medicine will provide CPD modules dedicated to key topics in mental health care. In order to assist learning and self-assessment, multiple choice questions will be provided at the end of each module.

This module and its multiple choice questions are available online on the website of the Irish Journal of Psychological Medicine (www.ijpm.org). The CPD policy of the College of Psychiatry of Ireland indicates that psychiatrists who participate in suitable online learning which fits the criteria for CPD may claim CPD points under the Personal CPD category (up to a maximum of 5 points per year).

We are confident that this CPD Section of the Irish Journal of Psychological Medicine will prove to be a valuable resource for consultant psychiatrists, psychiatric trainees and all journal readers. We welcome feedback from readers and, especially, any suggestions for topics to be covered in future CPD modules. Suggestions should be emailed to: psychological@medmedia.ie

CB1 receptor blockade decreases ethanol intake and associated neurochemical changes in fawn-hooded rats

BACKGROUND

This study was undertaken to identify the neurochemical changes underlying the attenuation of voluntary ethanol intake induced by the cannabinoid CB1 receptor antagonist AM251 in fawn-hooded rats.

METHODS

Rats were exposed to the 2-bottle-choice paradigm (ethanol 10% v/v or water) for 15 days. After this period, rats received AM251 (3 to 6 mg/kg, i.p.) or vehicle.

RESULTS

Voluntary ethanol intake decreased (30%) with the administration of incremental dosages of AM251 (3 mg/kg, 5 days and 6 mg/kg, 5 days) in rats with acquired high preferring ethanol consumption (>3.5 g of ethanol/kg/d). Ethanol intake significantly decreased proopiomelanocortin expression in the arcuate nucleus (38.31%) and micro-opioid-DAMGO-stimulated [(35)S]-GTPgamma binding in the caudate-putamen (40%), nucleus accumbens core (AccC) (32.87%), and shell (AccS) (34.21%). Moreover, ethanol intake increased tyrosine hydroxylase (TH) gene expression in the substantia nigra (24%) and ventral tegmental area (23%) and corticotrophin-releasing gene expression in the paraventricular hypothalamic nucleus (41.6%). The reduction of ethanol intake induced by AM251 was associated with blockade or significant reduction of the changes produced by ethanol in the expression of these genes in key regions related to drug dependence. Interestingly, treatment with AM251 reduced (20%) TH gene expression in rats drinking only water. In this respect, the action of AM251 in reducing TH gene expression may not be specific.

CONCLUSION

Taken together, these results revealed that blockade of cannabinoid CB1 receptors (CB1r) decreased voluntary ethanol intake in ethanol-habituated rats by normalizing the neurochemical alterations induced by ethanol.

Systematic review and meta-analysis on the adverse events of rimonabant treatment: considerations for its potential use in hepatology

Background

The cannabinoid-1 receptor blockers have been proposed in the management of obesity and obesity-related liver diseases (fatty liver as NAFLD or NASH). Due to increasing number of patients to be potentially treated and the need to assess the advantage of this treatment in terms of risk/benefit, we analyze the side events reported during the treatment with rimonabant by a systematic review and meta-analysis of all randomized controlled studies.

Methods

All published randomized controlled trials using rimonabant versus placebo in adult subjects were retrieved. Relative risks (RR) with 95% confidence interval for relevant adverse events and number needed to harm was calculated.

Results

Nine trials (n = 9635) were considered. Rimonabant 20 mg was associated with an increased risk of adverse event (RR 1.35; 95%CI 1.17-1.56), increased discontinuation rate (RR 1.79; 95%CI 1.35-2.38), psychiatric (RR 2.35; 95%CI 1.66-3.34), and nervous system adverse events (RR 2.35; 95%CI 1.49-3.70). The number needed to harm for psychiatric adverse events is 30.

Conclusion

Rimonabant is associated with an increased risk of adverse events. Despite of an increasing interest for its use on fatty liver, the security profile and efficacy it is needs to be carefully assessed before its recommendation. At present the use of rimonabant on fatty liver cannot be recommended.

The future of endocannabinoid-oriented clinical research after CB1 antagonists

INTRODUCTION

Great interest has been shown by the medical community and the public in the cannabinoid CB(1) receptor antagonists, such as rimonabant, for treatment of obesity, metabolic syndrome, and possibly drug addiction.

DISCUSSION

This novel class of drug has therapeutic potential for other disorders, as the endocannabinoid system is involved in various health conditions. However, rimonabant, the first clinically available member of this class of drugs, has been linked to increased risk of anxiety, depression, and suicidality. Due to those risks, the European Medicines Agency called for its withdrawal from the market in October, 2008. Shortly after this decision, several pharmaceutical companies (Sanofi-aventis, Merck, Pfizer, Solvay) announced that they would stop further clinical research on this class of drug. Here, we provide an overview of those events and make several suggestions for continuing such clinical research, while safeguarding the safety of patients and clinical trial subjects.

Cannabinoid receptor antagonists: pharmacological opportunities, clinical experience, and translational prognosis

The endogenous cannabinoid (CB) (endocannabinoid) signaling system is involved in a variety of (patho)physiological processes, primarily by virtue of natural, arachidonic acid-derived lipids (endocannabinoids) that activate G protein-coupled CB1 and CB2 receptors. A hyperactive endocannabinoid system appears to contribute to the etiology of several disease states that constitute significant global threats to human health. Consequently, mounting interest surrounds the design and profiling of receptor-targeted CB antagonists as pharmacotherapeutics that attenuate endocannabinoid transmission for salutary gain. Experimental and clinical evidence supports the therapeutic potential of CB1 receptor antagonists to treat overweight/obesity, obesity-related cardiometabolic disorders, and substance abuse. Laboratory data suggest that CB2 receptor antagonists might be effective immunomodulatory and, perhaps, anti-inflammatory drugs. One CB1 receptor antagonist/inverse agonist, rimonabant, has emerged as the first-in-class drug approved outside the United States for weight control. Select follow-on agents (taranabant, otenabant, surinabant, rosonabant, SLV-319, AVE1625, V24343) have also been studied in the clinic. However, rimonabant's market withdrawal in the European Union and suspension of rimonabant's, taranabant's, and otenabant's ongoing development programs have highlighted some adverse clinical side effects (especially nausea and psychiatric disturbances) of CB1 receptor antagonists/inverse agonists. Novel CB1 receptor ligands that are peripherally directed and/or exhibit neutral antagonism (the latter not affecting constitutive CB1 receptor signaling) may optimize the benefits of CB1 receptor antagonists while minimizing any risk. Indeed, CB1 receptor-neutral antagonists appear from preclinical data to offer efficacy comparable to or better than that of prototype CB1 receptor antagonists/inverse agonists, with less propensity to induce nausea. Continued pharmacological profiling, as the prelude to first-in-man testing of CB1 receptor antagonists with unique modes of targeting/pharmacological action, represents an exciting translational frontier in the critical path to CB receptor blockers as medicines.

Cannabinoid CB1 receptor antagonists as potential pharmacotherapies for drug abuse disorders

Since the discovery of the cannabinoid CB1 receptor (CB1R) in 1988, and subsequently of the CB2 receptor (CB2R) in 1993, there has been an exponential growth of research investigating the functions of the endocannabinoid system. The roles of CB1Rs have been of particular interest to psychiatry because of their selective presence within the CNS and because of their association with brain-reward circuits involving mesocorticolimbic dopamine systems. One potential role that has become of considerable focus is the ability of CB1Rs to modulate the effects of the drugs of abuse. Many drugs of abuse elevate dopamine levels, and the ability of CB1R antagonists or inverse agonists to modulate these elevations has suggested their potential application as pharmacotherapies for treating drug abuse disorders. With the identification of the selective CB1R antagonist, rimonabant, in 1994, and subsequently of other CB1R antagonists, there has been a rapid expansion of research investigating their ability to modulate the effects of the drugs of abuse. This review highlights some of the preclinical and clinical studies that have examined the effects of CB1R antagonists under conditions potentially predictive of their therapeutic efficacy as treatments for drug abuse disorders.