The use of very high-doses of baclofen for the treatment of alcohol-dependence: a case series

Phenibut: Review and Pharmacologic Approaches to Treating Withdrawal

β-Phenyl-γ-aminobutyric acid (phenibut) is an analog of the inhibitory neurotransmitter γ-aminobutyric acid (GABA) that was first synthesized in Russia in the early 1960s. It is marketed as a nootropic (smart drug) to improve cognitive performance, and to treat generalized and social anxiety, insomnia, and alcohol withdrawal. The use of phenibut is legal in the USA and it is widely available online without a prescription. Increased public awareness of phenibut has led to a growing number of reports of acute intoxication and withdrawal. In this review, we describe the pharmacology of phenibut, the presentation and management of acute intoxication, and regulatory issues, placing particular emphasis on the treatment of acute withdrawal, for which there are no comparative studies. Among 29 cases of phenibut withdrawal, patients were successfully treated with baclofen, benzodiazepines, and phenobarbital, as individual agents or in various combinations. Ancillary medications included antipsychotics, dexmedetomidine, gabapentin, and pregabalin. After stabilization, a number of patients did well on baclofen tapers, whereas others were weaned off benzodiazepines or phenobarbital. Phenobarbital may be preferred over baclofen, or used as an added agent, in patients at risk for seizures. As long as phenibut remains legal, cases of phenibut intoxication and withdrawal are likely to increase. As urine or plasma drug screening for phenibut is not widely available, it is vital that clinicians obtain a detailed medication history in patients presenting to the emergency department with nonspecific symptoms that may represent phenibut intoxication or withdrawal. Further, clinicians may wish to consult an addiction specialist or toxicologist in these situations.

Non-medical use of baclofen: A case series and review of the literature

BACKGROUND

Baclofen is widely used for spastic disorders and, most recently, for addictive disorders. The first signals of baclofen abuse occurred in the last decade. This study aims to assess the motives, diversion sources, and routes of administration associated with the non-medical use of baclofen and examine health problems related to the non-medical use of baclofen.

METHODS

Spontaneous reports of baclofen abuse reported to the addictovigilance centre of East France were analysed. A literature search was conducted using PubMed®, Web of Sciences®, and Google Scholar® databases. Both investigations were performed in February 2021 without a time limit.

RESULTS

Forty-six cases were analysed (33 from the literature review and 13 from the addictovigilance base). Baclofen's non-medical use mainly affected male subjects with addictive history, but issues of primary abuse in subjects without any substance abuse history were also observed. Euphoria search was the most common reason for misuse. The route of administration included oral, snorting, and sublingual use. Some cases involving illegal sources were also observed. Most patients misusing baclofen presented severe complications, mainly represented by neurological and respiratory disturbances. Physical and psychological dependence on baclofen was observed in three persons.

CONCLUSIONS

Although baclofen abuse remains relatively infrequent or (most likely) underestimated, this study helped confirm baclofen's intrinsic abuse potential and make visible the baclofen-abuse-related health visible harms. Careful consideration and benefit-risk analysis should be employed when prescribing baclofen, and emergency departments should be aware of baclofen dangers in abuse situations.

Preventive Effects of Baclofen but Not Diazepam on Hippocampal Memory and Glucocorticoid Alterations After Prolonged Alcohol Withdrawal in Mice

Our study aims at comparing in C57/Bl male mice, the impact of repeated injections of baclofen (an agonist of GABAB receptor) or diazepam (a benzodiazepine acting through a positive allosteric modulation of GABAA receptor) administered during the alcohol-withdrawal period on hippocampus-dependent memory impairments and brain regional glucocorticoid dysfunction after a short (1-week) or a long (4-week) abstinence. Hence, mice were submitted to a 6-month alcohol consumption (12%v/v) and were progressively withdrawn to water. Then, after a 1- or 4-weeks abstinence, they were submitted to a contextual memory task followed by measurements of corticosterone concentrations in the dorsal hippocampus (dHPC), the ventral hippocampus (vHPC) and the prefrontal cortex (PFC). Results showed that 1- and 4-week withdrawn mice exhibited a severe memory deficit and a significant abnormal rise of the test-induced increase of corticosterone (TICC) in the dHPC, as compared to water-controls or to mice still under alcohol consumption. Repeated daily systemic administrations of decreasing doses of diazepam (ranged from 0.5 to 0.12 mg/kg) or baclofen (ranged from 1.5 to 0.37 mg/kg) during the last 15 days of the withdrawal period, normalized both memory and TICC scores in the dHPC in 1-week withdrawn animals; in contrast, only baclofen-withdrawn mice showed both normal memory performance and TICC scores in the dHPC after a 4-week withdrawal period. In conclusion, the memory improvement observed in 4-week withdrawn mice administered with baclofen stem from the protracted normalization of glucocorticoid activity in the dHPC, a phenomenon encountered only transitorily in diazepam-treated withdrawn mice.

Recent Advances in the Potential of Positive Allosteric Modulators of the GABAB Receptor to Treat Alcohol Use Disorder

Aims

The effects of alcohol on gamma-aminobutyric acid (GABA) transmission are key for the development and maintenance of alcohol use disorder (AUD). Previous research consistently indicates that GABA_B receptor agonists such as baclofen can attenuate addiction-related behaviors in preclinical models of AUD. More importantly, baclofen has also shown promise in clinical studies, particularly in severely alcohol-dependent patients. However, despite this promise, other clinical studies have not confirmed its efficacy and chiefly, larger clinical trials have not been conducted. Therefore, with the exception of France, baclofen is not approved for the treatment of AUD in any other country. Furthermore, it is also important to keep in mind that some patients treated with baclofen may experience important side-effects, including sedation, drowsiness and sleepiness.

Methods

This short review will first discuss the history of baclofen for AUD treatment. We will then summarize preclinical behavioral results that have investigated the efficacy of GABA_B PAMs for addiction treatment, with a special focus on our recent work that investigated the effects of ADX71441, a novel GABA_B PAM, on several alcohol-related behaviors in rats that model important aspects of human AUD. Finally, in light of the recent criticism about the translational value of animal models of addiction, the specific translational potential of our work and of other preclinical studies that have unanimously reported the efficacy of GABA_B PAMs to attenuate multiple alcohol-related behaviors will be discussed.

Results

Positive allosteric modulators (PAMs) of the GABA_B receptor offer an attractive alternative approach to baclofen and have the potential to achieve mechanistic and therapeutic effects similar to GABA_B agonists, while avoiding the tolerance and toxicity issues associated with baclofen. To date, all preclinical behavioral results have invariably shown the efficacy of GABA_B PAMs for addiction treatment.

Conclusions

Preclinical studies indicate that GABA_B PAMs have a higher therapeutic index than orthosteric agonists, at least in terms of mitigating the sedative effects of GABA_B agonism. This predicts that GABA_B PAMs have a high translational potential in humans and merit being tested clinically, in particular in patients with severe AUD.

Toxicological considerations in the prescription of baclofen for the treatment of substance use disorders

Introduction: For many years, applications for baclofen have widened in the treatment of substance abuse disorder (SUD), mainly alcohol use disorder, with a growing rate of off-label prescriptions in Europe. Clinical effects seem to be both a decrease of craving and anxiety, leading to a decrease of drug or alcohol consumption. We described baclofen poisoning circumstances, therapeutic options and outcomes when used in substance use disorders.Areas covered: This review summarizes the toxicological considerations where baclofen was prescribed in humans for substance use or abuse disorder in randomized clinical trials, case series, case reports and observational studies between 1990 and 2020 according to the Preferred Reporting Items for Systemic reviews and Meta-Analysis.Expert opinion: The most frequent cause of severe intoxication is self-poisoning. A dose above 180 mg are expected to cause severe toxicity and death. The treatment is only symptomatic as no antidote is available. Off-label prescription remains unsafe because the optimal dose is not known and varies greatly between patients. As SUD are frequently associated with psychiatric disorders and such patients may have suicidal thoughts, the risk of self-poisoning is high. Potential co-ingestants should also be considered, especially CNS depressants, and they need to be closely monitored.

Developing neuroscience-based treatments for alcohol addiction: A matter of choice?

Excessive alcohol use is the cause of an ongoing public health crisis, and accounts for ~5% of global disease burden. A minority of people with recreational alcohol use develop alcohol addiction (hereafter equated with "alcohol dependence" or simply "alcoholism"), a condition characterized by a systematically biased choice preference for alcohol at the expense of healthy rewards, and continued use despite adverse consequences ("compulsivity"). Alcoholism is arguably the most pressing area of unmet medical needs in psychiatry, with only a small fraction of patients receiving effective, evidence-based treatments. Medications currently approved for the treatment of alcoholism have small effect sizes, and their clinical uptake is negligible. No mechanistically new medications have been approved since 2004, and promising preclinical results have failed to translate into novel treatments. This has contributed to a reemerging debate whether and to what extent alcohol addiction represents a medical condition, or reflects maladaptive choices without an underlying brain pathology. Here, we review this landscape, and discuss the challenges, lessons learned, and opportunities to retool drug development in this important therapeutic area.

Targeting the Glucocorticoid Receptors During Alcohol Withdrawal to Reduce Protracted Neurocognitive Disorders

Persistent regional glucocorticoid (GC) dysregulation in alcohol-withdrawn subjects emerges as a key factor responsible for protracted molecular and neural alterations associated with long-term cognitive dysfunction. Regional brain concentrations of corticosterone vary independently from plasma concentrations in alcohol-withdrawn subjects, which may account for the treatment of alcohol withdrawal-induced persistent pathology. Thus, from a pharmacological point of view, a main issue remains to determine the relative efficacy of compounds targeting the GC receptors to attenuate or suppress the long-lasting persistence of brain regional GC dysfunctions in abstinent alcoholics, as well as persistent changes of neural plasticity. Data from animal research show that acting directly on GC receptors during the withdrawal period, via selective antagonists, can significantly counteract the development and persistence of cognitive and neural plasticity disorders during protracted abstinence. A critical remaining issue is to better assess the relative long-term efficacy of GC antagonists and other compounds targeting the corticotropic axis activity such as gamma-aminobutyric acid A (GABA_A) and GABA_B agonists. Indeed, benzodiazepines (acting indirectly on GABA_A receptors) and baclofen (agonist of the GABA_B receptor) are the compounds most widely used to reduce alcohol dependence. Clinical and preclinical data suggest that baclofen exerts an effective and more powerful counteracting action on such persistent cognitive and endocrine dysfunctions as compared to diazepam, even though its potential negative effects on memory processes, particularly at high doses, should be better taken into account.

Baclofen in the Treatment of Patients With Alcohol Use Disorder and Other Mental Health Disorders

A limited number of medications are approved to treat Alcohol Use Disorder (AUD). Furthermore, the magnitude of their therapeutic effect is relatively modest, suggesting the potential for subtypes of patients who respond to a specific medication. The use of these medications is also limited in clinical practice by a series of contraindications such as medical comorbidities and/or concurrent use of other medications. In recent years, animal and human studies have been conducted to evaluate the efficacy of baclofen, a GABAB receptor agonist approved for clinical use as a muscle relaxant, in the treatment of AUD. However, these studies have yielded contrasting results. Despite this discrepancy, baclofen is often used off-label to treat AUD, especially in some European countries and Australia. Recently, several factors have been considered to try to shed light on the potential reasons and mechanisms underlying the inconsistent results obtained until now. The presence of a psychiatric comorbidity may be amongst the abovementioned factors playing a role in explaining different responses to baclofen treatment in terms of alcohol drinking outcomes. Therefore, the aim here was to conduct a narrative review of the scientific literature related to the use of baclofen in AUD, both in patients with and without concomitant psychiatric disorders. All clinical studies (randomized and controlled, open-label, retrospective, human laboratory studies, and case reports) were analyzed and discussed, bearing in mind other potential factors that may have influenced baclofen response, including dose administered, severity of AUD, use of other psychosocial therapies, and the presence of physical disorders. This review indicates that the most frequent psychiatric comorbidities in patients affected by AUD undergoing baclofen treatment are anxiety and mood disorders. Unfortunately, no definitive conclusions can be drawn due to the lack of specific analyses on whether baclofen efficacy is different in AUD patients with comorbid psychiatric disorders vs. those without. Therefore, it will be critical that psychiatric comorbidities are considered in the planning of future studies and in the analysis of the data, with the ultimate goal of understanding whether subtypes of AUD patients may respond best to baclofen.

The Use of Baclofen as a Treatment for Alcohol Use Disorder: A Clinical Practice Perspective

Alcohol use disorder (AUD) is a brain disorder associated with high rates of mortality and morbidity worldwide. Baclofen, a selective gamma-aminobutyric acid-B (GABA-B) receptor agonist, has emerged as a promising drug for AUD. The use of this drug remains controversial, in part due to uncertainty regarding dosing and efficacy, alongside concerns about safety. To date there have been 15 randomized controlled trials (RCTs) investigating the use of baclofen in AUD; three using doses over 100 mg/day. Two additional RCTs have been completed but have not yet been published. Most trials used fixed dosing of 30-80 mg/day. The other approach involved titration until the desired clinical effect was achieved, or unwanted effects emerged. The maintenance dose varies widely from 30 to more than 300 mg/day. Baclofen may be particularly advantageous in those with liver disease, due to its limited hepatic metabolism and safe profile in this population. Patients should be informed that the use of baclofen for AUD is as an "off-label" prescription, that no optimal fixed dose has been established, and that existing clinical evidence on efficacy is inconsistent. Baclofen therapy requires careful medical monitoring due to safety considerations, particularly at higher doses and in those with comorbid physical and/or psychiatric conditions. Baclofen is mostly used in some European countries and Australia, and in particular, for patients who have not benefitted from the currently used and approved medications for AUD.

Safety Challenges of Using High Dose Baclofen for Alcohol Use Disorder: A Focused Review

Since the early 2000s, the gamma-aminobutyric acid type B (GABA-B) receptor agonist baclofen has been extensively used for treating alcohol use disorder (AUD). In some countries, like France, Australia, or Germany, baclofen has been used at patient-tailored dose regimens, which can reach 300 mgpd or even more in some patients. The GABA-B-related pharmacology of baclofen expose patients to a specific profile of neuropsychiatric adverse drug reactions (ADRs), primarily some frequent sedative symptoms whose risk of occurrence and severity are both related to the absolute baclofen dosing and the kinetics of dose variations. Other frequent neuropsychiatric ADRs can occur, i.e., tinnitus, insomnia, or dizziness. More rarely, other serious ADRs have been reported, like seizures, manic symptoms, or sleep apnea. However, real-life AUD patients are also exposed to other sedative drugs, like alcohol of course, but also benzodiazepines, other drugs of abuse, or other sedative medications. Consequently, the occurrence of neuropsychiatric safety issues in these patients is essentially the result of a complex multifactorial exposure, in which baclofen causality is rarely obvious by itself. As a result, the decision of initiating baclofen, as well as the daily dose management should be patient-tailored, according the medical history but also the immediate clinical situation of the patient. The overall safety profile of baclofen, as well as the clinical context in which baclofen is used, have many similarities with the use of opiate substitution medications for opiate use disorder. This empirical statement has many implications on how baclofen should be managed and dosing should be adjusted. Moreover, this constant patient-tailored adjustment can be difficult to adapt in the design of clinical trials, which may explain inconsistent findings in baclofen-related literature on AUD.

Systematic review: Baclofen dosing protocols for alcohol use disorders used in observational studies

The popularity of baclofen as an anti-craving agent in the treatment of alcohol use disorders (AUDs) has increased, especially in patients with established liver disease. However, evidence-based guidelines to inform practice are lacking. The aim of this systematic review is explore the prescribing practices of baclofen in AUD treatment. Electronic databases were searched for relevant articles from 2002. Assessment of eligibility criteria for inclusion was performed independently by two investigators. The main outcomes of interest were maximum dose, starting dose, titration regimen, effectiveness, and tolerability. Twenty-five studies reporting outcomes in 613 patients treated with baclofen for an AUD were identified. Starting doses ranged between 5 and 50mg/d. Titration was study-dependent, and doses were increased until either therapeutic target (abstinence or study-defined low risk drinking) was achieved or adverse events resulted in a dose reduction or discontinuation. The maximum dose for individual patients ranged between 20 and 630mg/d. Seven studies reported at least one patient using >300mg/d. In studies with 10 or more patients, we found a negative correlation between dose and proportion of patients achieving the therapeutic goal. However, this was skewed by one study. A range of serious adverse events were reported. Most were reported at doses over 100mg/d, but others presented at lower doses. Baclofen is a promising therapeutic in this area. Evidence is required, however, to support practitioners in prescribing doses that optimise outcomes and reduce adverse events.

Microinjection of baclofen and CGP7930 into the ventral tegmental area suppresses alcohol self-administration in alcohol-preferring rats

Systemic administration of the orthosteric agonist, baclofen, and several positive allosteric modulators (PAMs) of the GABA_B receptor has repeatedly been reported to decrease operant oral alcohol self-administration in rats. The aim of the present study was to evaluate the contribution of the mesolimbic dopamine system to the reducing effect of baclofen and GABA_B PAMs on the reinforcing properties of alcohol. To this end, baclofen or the GABA_B PAM CGP7930 were microinjected into the ventral tegmental area (VTA) of selectively bred, Sardinian alcohol-preferring (sP) rats trained to self-administer alcohol. Baclofen (0, 0.03, 0.1, and 0.3 μg) or CGP7930 (0, 5, 10, and 20 μg) were microinjected via indwelling unilateral guide cannula aiming at the left hemisphere of the VTA. Treatment with baclofen resulted in a dose-related suppression of the number of lever-responses for alcohol and the amount of self-administered alcohol. No dose of baclofen altered rat motor-performance, evaluated by the inverted screen test immediately before the self-administration session. Treatment with CGP7930 halved the number of lever-responses for alcohol and amount of self-administered alcohol, with no effect on rat motor-performance. Site-specificity was investigated testing the effect of microinjection of baclofen and CGP7930 into the left hemisphere of deep mesencephalic nucleus: compared to vehicle, neither 0.3 μg baclofen nor 20 μg CGP7930 altered lever-responding for alcohol and amount of self-administered alcohol. Collectively, the results of the present study suggest the involvement of GABA_B receptors located in the VTA in the mediation of alcohol reinforcing properties in sP rats. This article is part of the "Special Issue Dedicated to Norman G. Bowery".

Class I HDAC Inhibitors: Potential New Epigenetic Therapeutics for Alcohol Use Disorder (AUD)

Alcohol use disorder (AUD) represents a serious public health issue, and discovery of new therapies is a pressing necessity. Alcohol exposure has been widely demonstrated to modulate epigenetic mechanisms, such as histone acetylation/deacetylation balance, in part via histone deacetylase (HDAC) inhibition. Epigenetic factors have been suggested to play a key role in AUD. To date, 18 different mammalian HDAC isoforms have been identified, and these have been divided into four classes. Since recent studies have suggested that both epigenetic mechanisms underlying AUD and the efficacy of HDAC inhibitors (HDACIs) in different animal models of AUD may involve class I HDACs, we herein report the development of class I HDACIs, including information regarding their structure, potency, and selectivity. More effort is required to improve the selectivity, pharmacokinetics, and toxicity profiles of HDACIs to achieve a better understanding of their efficacy in reducing addictive behavior.

Efficacy and safety of high-dose baclofen for the treatment of alcohol dependence: A multicentre, randomised, double-blind controlled trial

Previous randomised placebo-controlled trials with low-to-medium doses of baclofen (30-60mg) showed inconsistent results, but case studies suggested a dose-response effect and positive outcomes in patients on high doses of baclofen (up to 270mg). Its prescription was temporary permitted for the treatment of alcohol dependence (AD) in France, and baclofen is now widely prescribed. Recently, a small RCT found a strong effect of a mean dose of 180mg baclofen. In the present study the efficacy and safety of high doses of baclofen was examined in a multicentre, double-blind, placebo-controlled trial. 151 patients were randomly assigned to either six weeks titration and ten weeks high-dose baclofen (N=58; up to 150mg), low-dose baclofen (N=31; 30mg), or placebo (N=62). The primary outcome measure was time to first relapse. Nine of the 58 patients (15.5%) in the high-dose group reached 150mg and the mean baclofen dose in this group was 93.6mg (SD=40.3). No differences between the survival distributions for the three groups were found in the time to first relapse during the ten-weeks high-dose phase (χ²=0.41; p=0.813) or the 16-weeks complete medication period (χ²=0.04; p=0.982). There were frequent dose-related adverse events in terms of fatigue, sleepiness, and dry mouth. One medication related serious adverse event occurred in the high-dose baclofen group. Neither low nor high doses of baclofen were effective in the treatment of AD. Adverse events were frequent, although generally mild and transient. Therefore, large-scale prescription of baclofen for the treatment of AD seems premature and should be reconsidered.

An Unusual Case of Baclofen Abuse

Baclofen was initially used for the treatment of spastic conditions. Last decade has seen its emergence as a treatment of profound interest in alcohol dependence, opiates and cocaine abuse, and tobacco addiction. However, the published literature on baclofen abuse is sparse. Here, we report a patient with baclofen abuse.

How can we Improve on Modeling Nicotine Addiction to Develop Better Smoking Cessation Treatments?

Clinically effective smoking cessation treatments are few in number, mainly varenicline, bupropion, and nicotine replacement therapy being prescribed by health organizations. Of the many compounds tested for smoking cessation, a good proportion fail in human trials despite positive findings in rodents. This chapter aims to cover the uses and some pit falls of current methodologies employed to discover clinical treatments in the laboratory. Complicating factors include the complex nature of genetics in tobacco smoking and the comorbidity associated with other psychiatric disorders, which has not been addressed fully in the rodent laboratory. This chapter reviews the evidence from intravenous nicotine self-administration studies and proposes modifications on how we can improve the validity of the animal models by incorporating clinically relevant factors considered to be critical in tobacco smoking. For example, choice procedures that incorporate alternative reinforcers, use of reinstatement models, and second-order schedules of reinforcement are proposed to have better scientific validity that may lead to better clinical outcomes. Furthermore, improved experimental methods will also improve our chances of discovering effective treatments that ultimately may mitigate the effects of tobacco smoking with regard to health worldwide.

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.