[A system of prescriptions without drug approval: example of baclofen]

A capture-recapture method for estimating the incidence of off-label prescriptions: the example of baclofen for alcohol use disorder in France

The local/regional incidence of off-label prescriptions can be difficult to estimate. Capture-recapture models can be used to indirectly estimate population sizes. Here, we used a capture-recapture model to estimate the number of patients treated off-label with baclofen for alcohol use disorder in northern France in 2013. Three capture sources were used: (i) the active case file at the region's largest Addiction Unit, (ii) the regional pharmacovigilance centre, and (iii) a sample of community pharmacies. After between-source overlaps had been identified, we used a log-linear model to produced eight estimates. Two models displayed the best goodness-of-fit, with estimates [95% confidence interval] of 1123 [714-2162] and 2180 [1598-2870] subjects, respectively. These two values are in line with a previous estimate of 1624 patients, based on an analysis of the French national health insurance database in 2013. Capture-recapture methods can be usefully applied to estimate the prevalence of OLPs in a specific geographical area, when direct counting is not feasible or the estimate through claim database is not possible.

The dose-effect relationship of baclofen in alcohol dependence: A 1-year cohort study

OBJECTIVE

Our aim is to study the relationship between dose of baclofen and effectiveness in alcohol dependence.

METHODS

Two hundred two patients with alcohol dependence, who received baclofen treatment for drinking reduction, were followed up for 1 year. For each patient-month of treatment, the maximum daily dose of baclofen (DDB) and average weekly alcohol consumption (AWAC) were calculated. We defined a favorable drinking outcome as an AWAC under 200 g/w for at least 2 consecutive months. We divided the DDB of each patient-month into 3 categories (low dose: <90 mg/d, medium dose: 90-150 mg/d, and high dose: >150 mg/d) and investigated the relationship between reaching a favorable outcome and the concurrent DDB category in a time-varying Cox regression analysis. Hazard ratios (HRs) were adjusted based on age, sex, and initial AWAC.

RESULTS

One hundred forty subjects were followed during at least 1 month. Of these patients, 58 (41%) had a favorable drinking outcome. In comparison to low dose, medium dose was associated with a decreased rate of favorable drinking outcome (HR = 0.42; 95% CI [0.20, 0.88]), whereas no difference was found with high dose (HR = 1.31; 95% CI [0.65, 2.64]).

CONCLUSION

The relationship between dose of baclofen and favorable drinking outcome was U-shaped, that is, was increased at low and high doses compared to medium doses.

Characteristics of Patients with Alcohol Dependence Seeking Baclofen Treatment in France: A Two-Centre Comparative Cohort Study

AIM

To characterize the profile of patients seeking baclofen treatment for alcohol dependence in France.

METHOD

We compared retrospectively baclofen seekers and baclofen non-seekers within a cohort of consecutive outpatients with alcohol dependence who attended a first appointment for alcohol treatment at two French addiction centres between September 2012 and March 2014. We documented socio-demographic characteristics; comorbid psychiatric, addiction, alcohol dependence features; patients' initial drinking goal, and referral status; and treatment retention at 6 and 12 months.

RESULTS

Of the 289 patients identified, 107 were baclofen seekers and 182 were baclofen non-seekers. The only parameters significantly associated with baclofen seekers in multivariate analyses were a greater baseline alcohol consumption (β = 15.4, 95% CI: 0.18-30.65, P = 0.05), a controlled-drinking initial goal (OR = 14.9, 95% CI: 7.7-29, P < 0.0001) and self-referral (OR = 6.6, 95% CI: 3.7-12, P < 0.0001), baclofen seekers being eight times more likely to be self-referred and treatment-naïve (OR = 8.8, 95% CI: 4.1-18.9, P < 0.0001). Baclofen seekers were more likely to be retained in treatment at 6 months (OR = 3.5, 95% CI: 1.8-6.7, P < 0.0001) and 12 months (OR = 1.9, 95% CI: 1.1-3.2, P = 0.019).

CONCLUSION

In France, the perspective of controlled drinking offered by baclofen treatment may have attracted more self-referred patients, including those without previous alcohol treatment, to attend treatment, than the usual treatment options. These findings raise the question as to whether future public health strategies on alcohol should more prominently promote some aspects of alcohol treatment, such as patient's preference and treatment options, in order to reduce the treatment gap in alcohol dependence.

Baclofen for alcohol dependence: Relationships between baclofen and alcohol dosing and the occurrence of major sedation

High-dose baclofen, i.e., 300 mg/d or more, has recently emerged as a strategy for treating alcohol dependence. The impact that the co-exposure of large amounts of alcohol and baclofen has on sedation is unclear. In a prospective cohort of 253 subjects with alcohol dependence, we collected daily alcohol and baclofen doses across the first year of baclofen treatment and the monthly maximum subjective sedation experienced by each patient (0-10 visual analog scale). For each patient-month, we determined the average weekly alcohol consumption (AWAC; standard-drinks/week) and the maximum daily dose of baclofen (DDB; mg/d). The occurrence of an episode of major sedation (EMS) during a patient-month was defined as a sedation score ≥7. The relationship between the EMS occurrence and the concurrent AWAC and DDB was investigated using a generalized estimating equation model. In total, 1528 patient-months were compiled (70 with an EMS). Univariate analyses demonstrated that the rate of patient-month to EMS increased gradually with AWAC (p<0.001), from 0.9% for AWAC=0 to 9.4% for AWAC >35. There was also a significant gradual risk for EMS associated with DDB (<0.001). Multivariate analysis demonstrated a significant interaction between DDB and AWAC on EMS risk (p=0.047). Each 20mg/d increase in DDB was associated with an OR of EMS in AWAC >35 of 1.22 (95%CI, 1.08-1.38) versus 1.11 (95%CI, 0.96-1.29) in AWAC=1-35, and 0.95 (95%CI, 0.76-1.19) in AWAC=0. The level of sedation observed in patients using baclofen for alcohol dependence appears to directly depend on the immediate doses of both the baclofen and the alcohol.

[Baclofen and liver cirrhosis: literature review and safety precautions implemented within the system CAMTEA]

The off-label prescribing of high dose baclofen (HDB) has been recently spreading in France. The impact of HDB on subjects with liver cirrhosis remains poorly known. The main pharmacodynamic and pharmacokinetic data on baclofen result from studies on healthy subjects or using low doses of treatment. The specific biodisponibility and elimination of HDB have not been studied yet in cirrhosis. National pharmacovigilance reports suggest that a careful use of baclofen or even HDB could be possible in compensated cirrhosis. However, theoretical risks of baclofen overdose exist in cases of hepatorenal syndrome or portosystemic shunt. Baclofen could also induce a specific pharmacological potentiation of hepatic encephalopathy and gastropathy. Within CAMTEA, a regional team-based multidisciplinary system for delivering and monitoring off-label medications in alcohol use disorders, a set of predefined precautions for using baclofen in cirrhosis have been implemented, until further information becomes available. These precautions notably consist of a protocolized process for declaring adverse events, and a hepatologic follow-up associated with the usual multidisciplinary care system set up within CAMTEA.

Off-label baclofen prescribing practices among French alcohol specialists: results of a national online survey

OBJECTIVE

To evaluate, among alcohol specialists belonging to the Société Française d'Alcoologie (SFA), i.e., the French Alcohol Society, the proportion of physicians who prescribed off-label baclofen for alcohol use disorders (AUDs). The secondary objective was to depict the features of individual prescribing and monitoring practices.

METHODS

On-line survey among 484 French alcohol specialists. Physicians were asked whether they prescribed baclofen for AUDs. If they did not, the reasons for this choice were investigated. If they did, the features of the physician's prescribing practice were explored, including the number of patients treated, the mean and maximum doses, the monitoring precautions and the pharmacovigilance reporting. Participants were also asked about their empirical findings on HDB's efficacy and safety.

RESULTS

In total, 302 physicians (response rate of 62.4%) participated in the survey. Data from 296 participants were analysed, representing 59.4% of all active prescribing physicians belonging to the SFA. HDB use was declared by 74.6% of participants (mean dose 109.5 ± 43.6 mg/d; maximum dose 188 ± 93.3 mg/d). However, 79.2% of prescribers had treated less than 30 patients, and 67.8% used HDB as a second-line medication. Although HDB was perceived as more efficacious than approved drugs by 54.3% of prescribers, it was also declared less safe by 62.8%. Nonetheless, 79.7% of prescribers had never filed any pharmacovigilance report. Non-prescribers (25.6%) were primarily deterred by the current lack of scientific data and official regulation.

CONCLUSION

A majority of French alcohol specialists reported using HDB, although often on a limited number of their patients. HDB was considered efficacious but also potentially hazardous. Despite this, physicians reported minimal safety data to the health security system. While French health authorities are planning to draft a specific regulatory measure for framing off-label HDB prescribing practices, the sustained education of prescribers on spontaneous pharmacovigilance reporting should be enhanced.

Severe tinnitus induced by off-label baclofen

OBJECTIVE

The γ-aminobutyric acid type B (GABA-B) receptor agonist baclofen is approved for spasticity up to the dose of 80 mg/d. Recently, off-label use of high-dose baclofen (HDB), up to 400 mg/d, has been increasing for treating alcohol use disorders (AUDs), although the efficacy and safety profiles of HDB are relatively unknown. We report 2 cases of tinnitus in patients treated with HDB for AUD.

CASE SUMMARIES

The first case concerns a 60-year-old man who reported tinnitus when he reached a 180 mg/d dose of baclofen after 3 months of treatment. Tinnitus persisted until the dose was reduced to 90 mg/d. The second case concerns a 45-year-old woman who presented with tinnitus when she reached a 210 mg/d dose of baclofen after 4 months of treatment. Tinnitus persisted until the dose was reduced to 60 mg/d.

DISCUSSION

Using the Naranjo scale, imputability to baclofen was considered probable in both cases. GABA-B receptors have been reported to be implicated in both the etiology and the treatment of tinnitus. There may be an individual susceptibility to develop tinnitus under baclofen therapy because of some GABA-B genetic polymorphisms that remain to be determined.

CONCLUSION

HDB may be responsible for the occurrence of severe tinnitus, possibly in a dose-dependent manner. This appears to be coherent with the previously known involvement of GABA-B receptors in the pathophysiology of tinnitus.

Baclofen for alcohol dependence in France: incidence of treated patients and prescription patterns--a cohort study

Recently, baclofen has been widely promoted for treatment of alcohol dependence in France. Our aim was firstly to describe the incidence of patients newly treated with baclofen for alcohol dependence in France from 2007 to 2011, and secondly to describe baclofen prescription patterns and prescribers. A retrospective cohort study of patients newly treated with baclofen was conducted using the "Echantillon Généraliste des Bénéficiaires" database (EGB). Patients with a first dispensation of baclofen between 01/01/2007 and 31/12/2011, followed by a second in the next 120 days, were included. Patients were considered treated with baclofen for neurological conditions if at least one of the following conditions was found to be true: (1) presence of a neurological condition for which baclofen could be prescribed, (2) dispensation of dantrolene, another anti-spastic drug, or (3) hospitalization for a neurological condition for which baclofen could be prescribed. We assumed that all the remaining patients were treated for alcohol dependence. During the 5-year period, 676 patients were incident users. While the annual incidence rate of patients newly treated with baclofen for neurological conditions remained stable, the annual incidence rate of patients newly treated with baclofen for alcohol dependence increased by a factor of 2.9 between 2007 (0.09/1000 person-years) and 2011 (0.26/1000 person-years). In the alcohol dependence group, median duration of baclofen treatment was 143.5 [74.0; 377.0] days; median daily dose was 24.4 [14.8; 39.5] mg. This study demonstrated the rapidly increasing use of baclofen in France for treatment of alcohol dependence.

Assessing alcohol versus baclofen withdrawal syndrome in patients treated with baclofen for alcohol use disorder

Baclofen is a γ-aminobutyric acid B (GABA-B) receptor agonist that is approved for spasticity. Recently, the off-label use of baclofen for alcohol use disorder (AUD) has increased. However, baclofen is known to induce a neuroadaptation process, which may be identified by the occurrence of a specific baclofen withdrawal syndrome (BWS), that is, confusion, agitation, seizures, and delirium. The same set of symptoms characterizes alcohol withdrawal syndrome (AWS), which could lead to mistaking BWS for AWS in some situations. We report the cases of 3 patients under a chronic baclofen treatment for AUD. The patients emergently presented with a clinical state of confusion that was initially diagnosed and treated as AWS, with limited effect of benzodiazepines. Retrospectively, using a validated algorithm for assessing drug-induced withdrawal, we determined that all of these clinical cases were consistent with BWS. Both AWS and BWS should be considered in the case of acute confusion or delirium occurring in patients treated with baclofen for AUD. Moreover, further research should investigate to what extent GABA-A and GABA-B induce shared or distinct neuroadaptation processes and withdrawal syndromes.

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.