Safety reports on the off-label use of baclofen for alcohol-dependence: recommendations to improve causality assessment

Full-Profile Pharmacokinetic Study of High Dose Baclofen in Subjects With Alcohol Use Disorder

Baclofen a gamma amino-butyric acid type B (GABA-B) receptor agonist, which has raised some interest for the treatment of alcohol use disorder (AUD), occasionally at dose up to 300 mg/d. We conducted the first full-profile pharmacokinetic study on baclofen in AUD subjects, up to the oral daily dose of 300 mg. Sixty subjects treated for AUD with marketed baclofen were enrolled in a prospective phase-1 study. Participants were divided into four dose groups (1: <60 mg/d; 2: 60-120 mg/d; 3: >120 mg/d-180 mg/d; and 4: >180 mg/d), and they underwent a full-profile pharmacokinetic analysis of baclofen, using a nonlinear mixed effects modeling. The influence of different clinical and biological covariates was assessed in an upward modeling. Fifty-seven participants completed the study (522 observed concentrations collected). Racemic baclofen showed a linear pharmacokinetic profile, corresponding to a one-compartment model, with no influencing clinical or biological factor. The pharmacokinetic parameters of baclofen were (bootstrap 95% confidence intervals): absorption constant (Ka) 1.64 1/h (1.34-2), clearance (Cl/F) 11.6 L/h (10.8-12.3) and volume of distribution (Vd/F) 72.8 L (66.5-80.4) leading to a half-life of 4.4 h. The interindividual variability (IIV) was 44% (19-65), 21% (16-27), and 22% (11-36) for Ka, Cl/F, and Vd/F, respectively. The residual variability was 24% (21-26). No serious adverse event was reported. Registration: EudraCT #2013-003412-46.

Pharmacologically controlled drinking in the treatment of alcohol dependence or alcohol use disorders: a systematic review with direct and network meta-analyses on nalmefene, naltrexone, acamprosate, baclofen and topiramate

BACKGROUND AND AIMS

Pharmacologically controlled drinking in the treatment of alcohol dependence or alcohol use disorders (AUDs) is an emerging concept. Our objective was to explore the comparative effectiveness of drugs used in this indication.

DESIGN

Systematic review with direct and network meta-analysis of double-blind randomized controlled trials (RCTs) assessing the efficacy of nalmefene, naltrexone, acamprosate, baclofen or topiramate in non-abstinent adults diagnosed with alcohol dependence or AUDs. Two independent reviewers selected published and unpublished studies on Medline, the Cochrane Library, Embase, ClinicalTrials.gov, contacted pharmaceutical companies, the European Medicines Agency and the Food and Drug Administration, and extracted data.

SETTING

Thirty-two RCTs.

PARTICIPANTS

A total of 6036 patients.

MEASUREMENTS

The primary outcome was total alcohol consumption (TAC). Other consumption outcomes and health outcomes were considered as secondary outcomes.

FINDINGS

No study provided direct comparisons between drugs. A risk of incomplete outcome data was identified in 26 studies (81%) and risk of selective outcome reporting in 17 (53%). Nalmefene [standardized mean difference (SMD) = -0.19, 95% confidence interval (CI) = -0.29, -0.10; I²  = 0%], baclofen (SMD = -1.00, 95% CI = -1.80, -0.19; one study) and topiramate (SMD = -0.77, 95% CI = -1.12, -0.42; I²  = 0%) showed superiority over placebo on TAC. No efficacy was observed for naltrexone or acamprosate. Similar results were observed for other consumption outcomes, except for baclofen (the favourable outcome on TAC was not reproduced). The number of withdrawals for safety reasons increased under nalmefene and naltrexone. No treatment demonstrated any harm reduction (no study was powered to explore health outcomes). Indirect comparisons suggested that topiramate was superior to nalmefene, naltrexone and acamprosate on consumption outcomes, but its safety profile is known to be poor.

CONCLUSIONS

There is currently no high-grade evidence for pharmacological treatment to control drinking using nalmefene, naltrexone, acamprosate, baclofen or topiramate in patients with alcohol dependence or alcohol use disorder. Some treatments show low to medium efficacy in reducing drinking across a range of studies with a high risk of bias. None demonstrates any benefit on health outcomes.

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.

Alcohol addiction - the safety of available approved treatment options

INTRODUCTION

Alcohol Use Disorders (AUD) is a leading cause of mortality and morbidity worldwide. At present disulfiram, naltrexone and acamprosate are approved for the treatment of AUD in U.S. and Europe. Nalmefene is approved in Europe and sodium oxybate is approved in Italy and Austria only. Baclofen received a 'temporary recommendation for use' in France.

AREAS COVERED

The safety of the above mentioned medications on liver, digestive system, kidney function, nervous system, pregnancy and lactation and their possible side effects are described and discussed.

EXPERT OPINION

Mechanism of action and metabolism of these drugs as well as patients' clinical characteristics can affect the safety of treatment. All approved medications are valid tools for the treatment of AUD in patients without advanced liver disease. For some drugs, attention should be paid to patients with renal failure and medications may be used with caution, adjusting the dosage according to kidney function. In patients with AUD and advanced liver disease, at present only baclofen has been formally tested in randomized controlled trials showing its safety in this population.

Binge Drinking: Current Diagnostic and Therapeutic Issues

The concept of binge drinking (BD) refers to patterns of heavy episodic alcohol consumption, with BD primarily occurring among adolescents and young adults. Several official definitions of BD have been proposed, in particular by the World Health Organization, the National Institute on Alcoholism and Alcohol Abuse, and the Substance Abuse and Mental Health Services Administration. Nevertheless, none of these definitions address the psychosocial and medical consequences of the type of alcohol use seen in BD. In practice, BD can thus correspond to either hazardous or harmful use of alcohol (HUA), while the episodic nature of heavy drinking in BD means that it does not meet the criteria for 'alcohol dependence'. This diagnostic differentiation is important because it determines which type of intervention is recommended. Psychosocial, rather than pharmacological, interventions are recommended as first-line treatment for adults with HUA, while pharmacological treatment is recommended for alcohol dependence; however, HUA appears to be associated with much poorer outcomes in adolescents, which could thus warrant early use of pharmacotherapy in this patient group. For HUA, and especially in adolescents, there is currently a severe lack of data regarding the efficacy and safety of the different drugs that have been approved for adults with alcohol dependence. Various guidelines propose the use of drugs for some types of BD but that use remains off-label and empirical, which raises important safety and ethical concerns. Future research on BD should systematically assess the criteria for HUA to better differentiate its subtypes with actual consequences and better address the heterogeneity of BD in terms of both clinical profiles and outcomes. Regarding pharmacotherapy, some national guidelines have recommended nalmefene for 'mild' dependence or second-line treatment for HUA, but such recommendations are not supported by evidence. Only naltrexone has been investigated in HUA but not in adolescents. More clinical trials should be conducted among adolescents with BD and HUA criteria to determine the most appropriate use of drugs in this particularly vulnerable population of subjects.

Phone-based safety monitoring of the first year of baclofen treatment for alcohol use disorder: the BACLOPHONE cohort study protocol

BACKGROUND

In France, baclofen is frequently used off-label for alcohol use disorder (AUD). Baclofen has been associated with diverse adverse events (AEs), but the causality of these AEs has never been properly assessed.

METHODS/DESIGN

BACLOPHONE is a prospective multicenter cohort study conducted in the Hauts-de-France and Normandie French regions. BACLOPHONE consists of the phone-based monitoring of 792 patients during their first year of baclofen treatment for AUD. Two initial phone interviews assess the medical history, current medications, and substance use as well as complete the alcohol use identification test (AUDIT) and severity of alcohol dependence questionnaire (SADQ). Daily alcohol use and baclofen doses are noted throughout the follow-up. For every reported AE, additional phone interviews determine the seriousness of the AE, the causality of baclofen using validated causality algorithms, and the final outcome. The main objective of the study is to determine the rate of patients who stop baclofen due to an AE during the first year of treatment.

DISCUSSION

BACLOPHONE will provide important safety data on baclofen as a complement to the forthcoming efficacy data of randomized clinical trials.