Ability of baclofen in reducing alcohol intake and withdrawal severity: I--Preclinical evidence

Off-label and investigational drugs in the treatment of alcohol use disorder: A critical review

Compounds known to be successful in the treatment of alcohol use disorder include the aversive agent, Disulfiram, the glutamatergic NMDA receptor antagonist, Acamprosate, and the opioid receptor antagonists, Naltrexone and Nalmefene. Although all four are effective in maintaining abstinence or reduction of alcohol consumption, only a small percentage of patients receive pharmacological treatment. In addition, many other medications have been investigated for their therapeutic potential in the treatment of alcohol use disorder. In this review we summarize and compare Baclofen, Gabapentin, Topiramate, Ondansetron, Varenicline, Aripiprazole, Quetiapine, Clozapine, Antidepressants, Lithium, Neuropeptide Y, Neuropeptide S, Corticotropin-releasing factor antagonists, Oxytocin, PF-05190457, Memantine, Ifenprodil, Samidorphan, Ondelopran, ABT-436, SSR149415, Mifepristone, Ibudilast, Citicoline, Rimonabant, Surinabant, AM4113 and Gamma-hydroxybutyrate While some have shown promising results in the treatment of alcohol use disorder, others have disappointed and should be excluded from further investigation. Here we discuss the most promising results and highlight medications that deserve further preclinical or clinical study. Effective, patient-tailored treatment will require greater understanding provided by many more preclinical and clinical studies.

Ethnopharmacological Applications Targeting Alcohol Abuse: Overview and Outlook

Excessive alcohol consumption is the cause of several diseases and thus is of a major concern for society. Worldwide alcohol consumption has increased by many folds over the past decades. This urgently calls for intervention and relapse counteract measures. Modern pharmacological solutions induce complete alcohol self-restraint and prevent relapse, but they have many side effects. Natural products are most promising as they cause fewer adverse effects. Here we discuss in detail the medicinal plants used in various traditional/folklore medicine systems for targeting alcohol abuse. We also comprehensively describe preclinical and clinical studies done on some of these plants along with the possible mechanisms of action.

Baclofen and the Alcohol Withdrawal Syndrome-A Short Review

The Alcohol Withdrawal Syndrome (AWS), which may occur with or without delirium, is a frequent consequence of sudden alcohol cessation in patients with moderate to severe Alcohol Dependence Syndrome (ADS). Withdrawal as a result of habituation to alcohol is part of the definition of the Alcohol Dependence Syndrome (ICD10). Since the recognition of Delirium Tremens, in the early nineteenth century, the management of the syndrome, an acute medical emergency, has proven controversial. The barbiturates, chlormethiazole, and recently the safer benzodiazepines transformed the management of these conditions. The benzodiazepines, particularly diazepam and chlordiazepoxide, are now the most used first line agents in the treatment of AWS. In addition, a number of other agents, including baclofen, a GABA-B receptor agonist, have the potential to suppress the alcohol withdrawal syndrome. In this review we review the potential use of baclofen in its role to treat AWS. We summarize initial case reports as well as more recent randomized trials of AWS treatment with baclofen. We conclude that currently there is not enough evidence to support the use of baclofen as a first line treatment for AWS. More research will be needed to determine where baclofen might have a role in second-line management of the Alcohol Withdrawal Syndrome on its own or in combination with benzodiazepines or other agents.

Suppressing Effect of Baclofen on Multiple Alcohol-Related Behaviors in Laboratory Animals

This paper summarizes the several lines of experimental evidence demonstrating the ability of the prototypic GABA_B receptor agonist, baclofen, to suppress multiple alcohol-related behaviors in laboratory rodents and non-human primates exposed to validated experimental models of alcohol use disorder (AUD). Specifically, treatment with baclofen has repeatedly been reported to suppress alcohol-induced locomotor stimulation, alcohol drinking (including binge- and relapse-like drinking), operant oral alcohol self-administration, alcohol seeking, and reinstatement of alcohol seeking in rats and mice. Treatment with baclofen also reduced operant oral alcohol self-administration in baboons. Several of these effects appear to be mediated by GABA_B receptors located in the ventral tegmental area. The often observed co-occurrence of "desired" pharmacological effects and "unwanted" sedative effects represents the major drawback of the preclinical, anti-alcohol profile of baclofen. Collectively, these data underline the role of the GABA_B receptor in the mediation of several alcohol-related behaviors. These data possess remarkable translational value, as most of the above effects of baclofen have ultimately been reproduced in AUD patients.

A Review of the Potential Mechanisms of Action of Baclofen in Alcohol Use Disorder

Baclofen, a GABA-B receptor agonist, is a promising treatment for alcohol use disorder (AUD). Its mechanism of action in this condition is unknown. GABA-B receptors interact with many biological systems potentially involved in AUD, including transduction pathways and neurotransmitter systems. Preclinical studies have shown that GABA-B receptors are involved in memory storage and retrieval, reward, motivation, mood and anxiety; neuroimaging studies in humans show that baclofen produces region-specific alterations in cerebral activity; GABA-B receptor activation may have neuroprotective effects; baclofen also has anti-inflammatory properties that may be of interest in the context of addiction. However, none of these biological effects fully explain the mechanism of action of baclofen in AUD. Data from clinical studies have provided a certain number of elements which may be useful for the comprehension of its mechanism of action: baclofen typically induces a state of indifference toward alcohol; the effective dose of baclofen in AUD is extremely variable from one patient to another; higher treatment doses correlate with the severity of the addiction; many of the side effects of baclofen resemble those of alcohol, raising the possibility that baclofen acts as a substitution drug; usually, however, there is no tolerance to the effects of baclofen during long-term AUD treatment. In the present article, the biological effects of baclofen are reviewed in the light of its clinical effects in AUD, assuming that, in many instances, clinical effects can be reliable indicators of underlying biological processes. In conclusion, it is proposed that baclofen may suppress the Pavlovian association between cues and rewards through an action in a critical part of the dopaminergic network (the amygdala), thereby normalizing the functional connectivity in the reward network. It is also proposed that this action of baclofen is made possible by the fact that baclofen and alcohol act on similar brain systems in certain regions of the brain.

R(+)-Baclofen, but Not S(-)-Baclofen, Alters Alcohol Self-Administration in Alcohol-Preferring Rats

Racemic baclofen [(±)-baclofen] has repeatedly been reported to suppress several -alcohol-motivated behaviors, including alcohol drinking and alcohol -self-administration, in rats and mice. Recent data suggested that baclofen may have bidirectional, stereospecific effects, with the more active enantiomer, R(+)-baclofen, suppressing alcohol intake and the less active enantiomer, S(-)-baclofen, stimulating alcohol intake in mice. The present study was designed to investigate whether this enantioselectivity of baclofen effects may also extend to the reinforcing properties of alcohol in rats. To this end, selectively bred Sardinian alcohol-preferring (sP) rats were initially trained to lever respond on a fixed ratio 4 (FR4) schedule of reinforcement for alcohol (15%, v/v) in daily 30-min sessions. Once responding had stabilized, rats were tested with vehicle, (±)-baclofen (3 mg/kg), R(+)-baclofen (0.75, 1.5, and 3 mg/kg), and S(-)-baclofen (6, 12, and 24 mg/kg) under the FR4 schedule of reinforcement. Treatment with 3 mg/kg (±)-baclofen reduced the number of lever responses for alcohol and estimated amount of self-administered alcohol by approximately 60% in comparison to vehicle treatment. R(+)-baclofen was approximately twice as active as (±)-baclofen: treatment with 1.5 mg/kg R(+)-baclofen decreased both variables to an extent similar to that of the decreasing effect of 3 mg/kg (±)-baclofen. Conversely, treatment with all doses of S(-)-baclofen failed to affect alcohol self administration. These results (a) confirm that non-sedative doses of (±)-baclofen effectively suppressed the reinforcing properties of alcohol in sP rats and (b) apparently do not extend to operant alcohol self-administration in sP rats the capability of S(-)-baclofen to stimulate alcohol drinking in mice.

Pharmacotherapy of acute alcoholic hepatitis in clinical practice

Severe alcoholic hepatitis (AH) is an acute form of alcohol induced liver disease with a poor prognosis that is seen in the patients who consume large quantities of alcohol. The diagnosis of AH is based on the appropriate alcohol intake history and is supported with clinical and histological features, and several scoring systems. Glucocorticoids are the mainstay for treating severe AH with pentoxifylline used as an alternative to steroids in addition to total alcohol abstinence. Liver transplantation is a possible therapeutic option for severe AH. Among the anti-craving medications able to improve abstinence rate, baclofen seems to be effective and safe in the alcoholic patients affected by severe liver damage.

Death of an alcohol-dependent patient following intentional drug intoxication: implication of baclofen?

Used in the treatment of spasticity at low doses, baclofen is also prescribed off-label at high doses for the treatment of alcohol dependence. Several cases of baclofen intoxication have been reported, but only 1 case deals with the treatment of alcohol dependence. Thus, we report the first death in the context of baclofen off-label use of an alcohol-dependent patient with a high blood baclofen concentration after intentional drug intoxication. The safety profile of baclofen in the treatment of alcohol dependence is reviewed and discussed, underlining the obligatory caution that may support any prescription of high doses of baclofen in this off-label indication and especially in patients with concomitant psychiatric disorders.

Baclofen blocks expression and sensitization of anxiety-like behavior in an animal model of repeated stress and ethanol withdrawal

BACKGROUND

Repeated exposures to forced ethanol diets (EDs) or restraint stress sensitize anxiety-like behavior during a future ethanol withdrawal. The present investigation assessed whether pretreatment of rats with agents targeting receptor systems thought to be important in treating relapse in alcoholic patients would prevent sensitization of anxiety-like behavior.

METHODS

Groups of rats were exposed to either (1) three 5-day cycles of ED with 2 days of withdrawal between cycles, (2) continuous ED, or (3) 5 days of ED in a single cycle preceded by 2 episodes of restraint stress 6 days apart. Drugs [baclofen, acamprosate, naloxone, lamotrigine, ifenprodil, dizocilpine (MK-801), CGS19755, diazepam, flumazenil, or 6-methyl-2-(phenylethynyl)pyridine] were given prophylactically during the first and second withdrawal periods only or, in separate baclofen experiments, acutely during the third withdrawal or during withdrawal from continuous ED. Baclofen administration preceded each stress session in the stress-withdrawal protocols. Anxiety-like behavior was assessed in the social interaction (SI) test 5 hours after the ethanol was removed or after 3 days of abstinence.

RESULTS

Baclofen (1.25, 2.5, and 5 mg/kg), flumazenil (5 mg/kg), and diazepam (1 mg/kg) blocked the reduction in SI induced by ethanol withdrawal. Among the drugs that alter glutamate function, only acamprosate (300 mg/kg) was effective. In the stress protocols, baclofen (5 mg/kg) given before each of the 2 restraint stress sessions before ethanol exposure or before stress during abstinence also attenuated SI deficits.

CONCLUSIONS

These findings suggest that GABAB and GABAA, but not glutamate or opioid mechanisms, are involved in adaptive changes associated with anxiety-like behavior induced by these repeated ethanol-withdrawal and stress-withdrawal paradigms. The lack of action of agents attenuating different aspects of glutamate function suggests that acamprosate's action is related to some other, as yet undetermined, mechanism.

Evaluation for the withdrawal syndrome from gamma-hydroxybutyric acid (GHB), gamma-butyrolactone (GBL), and 1,4-butanediol (1,4-BD) in different rat lines

A severe and life-threatening gamma-hydroxybutyric acid (GHB) withdrawal syndrome, clinically similar to the alcohol withdrawal syndrome, is increasingly being reported in GHB addicts. We investigated for the occurrence of withdrawal in Wistar and Sprague-Dawley rats, and in the selectively bred lines of GHB-sensitive (GHB-S) and Sardinian alcohol-preferring (sP) rats, following chronic administration of GHB, gamma-butyrolactone (GBL), and/or 1,4-butanediol (1,4-BD). Using validated rodent alcohol withdrawal scoring scales, little to no spontaneous or pharmacologically precipitated withdrawal effects were observed in Wistar, Sprague-Dawley, or GHB-S rats. Conversely, sP rats displayed both spontaneous and precipitated audiogenic seizures following abrupt cessation of chronic GHB or 1,4-BD administration and following pharmacological challenge with the GABA(B) receptor-selective antagonist, SCH 50911, respectively.

Long-term administration of Delta9-tetrahydrocannabinol desensitizes CB1-, adenosine A1-, and GABAB-mediated inhibition of adenylyl cyclase in mouse cerebellum

Cannabinoid CB(1) receptors in the cerebellum mediate the inhibitory effects of Delta(9)-tetrahydrocannabinol (THC) on motor coordination. Intracellular effects of CB(1) receptors include inhibition of adenylyl cyclase via activation of G(i/o) proteins. There is evidence for the convergence of other neuronal receptors, such as adenosine A(1) and GABA(B), with the cannabinoid system on this signaling pathway to influence motor function. Previous studies have shown that brain CB(1) receptors are desensitized and down-regulated by long-term THC treatment, but few studies have examined the effects of long-term THC treatment on downstream effector activity in brain. Therefore, these studies examined the relationship between CB(1), adenosine A(1), and GABA(B) receptors in cerebella of mice undergoing prolonged treatment with vehicle or THC at the level of G protein activation and adenylyl cyclase inhibition. In control cerebella, CB(1) receptors produced less than additive inhibition of adenylyl cyclase with GABA(B) and A(1) receptors, indicating that these receptors are localized on overlapping populations of cells. Long-term THC treatment produced CB(1) receptor down-regulation and desensitization of both cannabinoid agonist-stimulated G protein activation and inhibition of forskolin-stimulated adenylyl cyclase. However, G protein activation by GABA(B) or A(1) receptors was unaffected. It is noteworthy that heterologous attenuation of GABA(B) and A(1) receptor-mediated inhibition of adenylyl cyclase was observed, even though absolute levels of basal and forskolin- or G(s)-stimulated activity were unchanged. These results indicate that long-term THC administration produces a disruption of inhibitory receptor control of cerebellar adenylyl cyclase and suggest a potential mechanism of cross-tolerance to the motor incoordinating effects of cannabinoid, GABA(B), and A(1) agonists.