Clobazam: a newly approved but well-established drug for the treatment of intractable epilepsy syndromes

Upregulation of ACSL, ND75, Vha26 and sesB genes by antiepileptic drugs resulted in genotoxicity in drosophila

Clobazam (CLB) and Vigabatrin (VGB) are commonly used antiepileptic drugs (AEDs) in the treatment of epilepsy. Here, we have examined the genotoxic effect of these AEDs in Drosophila melanogaster. The Drosophila larvae were exposed to different concentrations of CLB and VGB containing food media. The assessment encompassed oxidative stress, DNA damage, protein levels, and gene expression profiles. In the CLB-treated group, a reduction in reactive oxygen species (ROS) and lipid peroxidation (LPO) levels was observed, alongside increased levels of superoxide dismutase (SOD), catalase (CAT), and nitric oxide (NO). Conversely, the VGB-treated group displayed contrasting results, with increased ROS and LPO and decreased SOD, CAT, and NO levels. However, both CLB and VGB induced DNA damage in Drosophila. Proteomic analysis (SDS-PAGE and OHRLCMS) in the CLB and VGB groups identified numerous proteins, including Acyl-CoA synthetase long-chain, NADH-ubiquinone oxidoreductase 75 kDa subunit, V-type proton ATPase subunit E, ADP/ATP carrier protein, malic enzyme, and DNA-binding protein modulo. These proteins were found to be associated with pathways like growth promotion, notch signaling, Wnt signaling, neuromuscular junction (NMJ) signaling, bone morphogenetic protein (BMP) signaling, and other GABAergic mechanisms. Furthermore, mRNA levels of ACSL, ND75, Vha26, sesB, and Men genes were upregulated in both CLB and VGB-treated groups. These findings suggest that CLB and VGB could have the potential to induce genotoxicity and post-transcriptional modifications in humans, highlighting the importance of monitoring their effects when used as AEDs.

Evaluation of one-year effectiveness of clobazam as an add-on therapy to anticonvulsant monotherapy in participants with epilepsy having uncontrolled seizure episodes: An Indian experience

OBJECTIVES

To prospectively study the effectiveness and safety of clobazam as an add-on therapy in patients with epilepsy whose seizures are not adequately controlled with antiseizure medicine (ASM) monotherapy.

METHODS

We conducted a prospective, observational study at 28 neurology outpatient clinics in India from June 2017 to October 2019. Consecutive patients with epilepsy (older than 3 years) with inadequate seizure control with ASM monotherapy were initiated on clobazam. Patients were followed up at 1, 3, 6, 9, and 12 months. Seizure control and adverse events were assessed through personal interviews and seizure diaries.

RESULTS

Out of 475 eligible patients, data of 429 patients (men: 65.5%) were evaluated (46 excluded due to protocol deviations). The median age was 25 (range, 3-80 years) years and the median duration of epilepsy was 3 (0.1-30) years. The majority of patients had focal epilepsy (55.0%) and genetic generalized epilepsy (40.1%). The one-year follow-up was completed by 380 (88.5%) patients. At one-year follow-up, 317 (83.4%; N = 380) patients in the study remained seizure free. These 317 patients who were seizure free at 12 months comprised 73.9% of the evaluable population (N = 429). In 98.8% of patients, the primary reason for adding clobazam was inadequate control of seizures with treatment. During one-year follow-up, a total of 113 (22.6%) patients experienced at least one adverse event which included 103 (20.6%) patients who experienced 386 episodes of seizures.

CONCLUSION

The study provides preliminary evidence that clobazam is effective and well-tolerated as add-on therapy for a period of one year among patients with epilepsy inadequately stabilized with monotherapy.

TRIAL REGISTRATION NUMBER

CTRI/2017/12/010906.

Neurocognitive Effects of Antiseizure Medications in Children and Adolescents with Epilepsy

Impairments in cognition are common in epilepsy and may be caused or exacerbated by antiseizure medications (ASMs). Positive effects on cognition may also be seen with some ASMs. Cognitive outcomes are of particular concern in children who may be at an increased risk of cognitive adverse effects of treatment. A comprehensive literature search was conducted in PubMed in order to evaluate the evidence for cognitive changes associated with treatment with ASMs in paediatric epilepsy patients. The ASMs considered were those in the current edition of the British National Formulary (BNF). For most ASMs, remarkably few studies providing robust data on cognitive effects in paediatric patients were identified. The available evidence suggests cognitive impairments may be associated with treatment with phenobarbital. Topiramate and phenytoin are also associated with negative effects on cognition, in particular word-finding difficulties and other language deficits with topiramate, but there are few data available specifically on children. Lamotrigine, levetiracetam and fenfluramine are associated with improvements in some cognitive domains, although it is unclear whether these effects are directly attributable to the medications or are a result of improvements in seizures. Neutral effects on cognition (no substantial evidence of worsening) were suggested for carbamazepine, everolimus, lacosamide, oxcarbazepine, perampanel and valproate. There is limited data for cannabidiol, clobazam, eslicarbazepine acetate, ethosuximide, rufinamide, vigabatrin and zonisamide, although the available evidence suggests these drugs are not associated with severe cognitive impairment. There was too little information to reach conclusions about the effects of brivaracetam, felbamate, gabapentin, pregabalin, retigabine, stiripentol or tiagabine.

Dravet Syndrome: A Review of Current Management

Dravet syndrome is a debilitating epileptic encephalopathy of childhood with few treatment options available in the United States before 2018. In the modern era, new genetic testing options will allow diagnosis closer to disease onset. Three new medicines-stiripentol, cannabidiol, and fenfluramine-have documented efficacy and safety as adjunctive therapies for treating pharmacoresistant Dravet syndrome. Early diagnosis resulting in earlier treatment with these and other medications may improve prognosis of long-term outcomes, including less severity of cognitive, motor, and behavioral impairments. New rescue medication formulations can now manage acute seizures and help prevent status epilepticus via intranasal, buccal, and intramuscular routes as opposed to rectal administration. Preventing status epilepticus and generalized tonic-clonic seizures could potentially lower the risk of sudden unexpected death in epilepsy. With this changing landscape in diagnostic and treatment options comes questions and controversies for the practicing clinician, especially as diagnostic techniques outpace clinical treatment strategies. Critical decision points include when to start treatment, what pharmacotherapy combinations to try first, which rescue medication to recommend, and how to advise parents on controversial topics (e.g., immunizations). Given that most patients require polypharmacy, clinicians must be cognizant of drug-drug interactions between new medicines, existing anti-epileptic drugs, and other medications to manage comorbidities and must have an understanding of available therapeutic drug monitoring strategies and pharmacokinetic parameters. This review places new diagnostic, treatment and acute care options into the modern era and provides an overview of the challenges and opportunities facing the pediatric epileptologist in this rapidly changing landscape.

Persistent Hypersomnolence Following Clobazam in a Child With Epilepsy and Undiagnosed CYP2C19 Polymorphism

We describe an 11-year-old female who presented with severe hypersomnolence after receiving 1 week of modest doses of clobazam (CLB). In reviewing the above case, we considered that the hypersomnolence could be related to a pharmacodynamic, pharmacokinetic, or pharmacogenomic issue associated with CLB or to a combination of these factors. Although serum concentrations of CLB and its active metabolite are sensitive to factors that affect cytochrome-dependent metabolism, drug-drug interactions were omitted as a cause of the hypersomnolence. Subsequent DNA analysis of the cytochrome P450 2C19 gene revealed the patient as *2/*2 genotype with poor metabolizer enzyme activity. Because genetic testing of all patients treated with CLB is currently not practical, CLB dose/concentration ratios and pharmacokinetic drug-drug interaction impact models may be indicated. Genetic testing should be considered when an adverse effect suggests the possibility of a polymorphism important to drug metabolism.

Rashes and other hypersensitivity reactions associated with antiepileptic drugs: A review of current literature

This article provides an overview of the pathogenesis and risk factors associated with antiepileptic drug (AED) hypersensitivity reactions, provides prescribing guidelines that may minimize the risk of antiepileptic induced rashes, and discusses treatment options for rashes. Articles indexed in PubMed, Science Citation, and Google Scholar (January 1946-March 2019) were systematic searched using the following key terms: hypersensitivity, rash, antiepileptic, epilepsy, cross-sensitivity, desensitization, patch testing and supplemented with our clinical experiences. Additional references were identified from a review of literature citations. AEDs are associated with cutaneous adverse reactions. Aromatic AEDs and higher titration rates are associated with increased risk of hypersensitivity reaction. Patient characteristics, underlying health conditions, and genetic variations may increase the likelihood of a hypersensitivity reaction. Once a hypersensitivity reaction occurs, the likelihood of cross sensitivity to another AED increases, especially among other aromatic AEDs. Withdrawal of the causal agent and initiation of a lower risk agent usually leads to resolution of symptoms. Desensitization protocols may be an option for patients whose seizures only respond to the AED causing the rash.

Clobazam as an adjunctive treatment for infantile spasms

Infantile spasms constitute a catastrophic epileptic condition. Seizures in approximately half of children with infantile spasms fail to improve with initial treatment attempts; at present, data regarding alternative treatments are limited. We assessed the efficacy of clobazam as an adjunctive therapy in patients whose seizures failed to respond to initial regimens of standard treatment for infantile spasms. All patients from Severance Children's Hospital who received clobazam as adjunctive therapy for infantile spasms were selected for the study. The efficacy of clobazam was evaluated by assessing the daily spasm frequency. Patients were categorized as complete responders if the spasms disappeared within 2 weeks of introducing clobazam, and the patients became spasm-free during weeks 3 and 4. Tolerability was gauged by analyzing adverse events and discontinuation rates. In all, 171 patients qualified for the analysis. Clobazam was introduced after the administration of 2.6 (median; interquartile range [IQR], 1.0-4.0) failed antiepileptic drugs (AEDs), at the age of 8.2 months (IQR, 6.0-10.0 months). After clobazam therapy was initiated, 38 (22.2%) patients became spasm-free for ≥2 weeks. Thirteen out of the 38 complete responders remained spasm-free until the last follow-up and did not require the administration of other AEDs. In 10 patients, the electroencephalogram (EEG) tracings were also within normal limits. These patients were successfully weaned off of all AEDs. Patients with conditions of unknown etiology, who had fewer prior exposures to AEDs, and had not received prior adrenocorticotropic hormone (ACTH)/steroids were more likely to have complete spasm control than the others. Adverse effects were minor, and only 6 of 101 (6%) patients who experienced adverse events had their treatments discontinued during the 3-month follow-up period. The most common adverse events observed were hypersalivation, sedation, and sleep disturbance. Thus, clobazam might be an effective and safe alternative therapeutic option in patients whose seizures failed to respond to initial regimens of standard treatment for infantile spasms. Further prospective studies on clobazam for infantile spasms, focusing on specific good response groups, dosing protocols, and long-term outcome are needed.

Hypothermia in an Adolescent Due to Probable Drug-Drug Interaction Involving Clobazam

We report on a 16-year-old female who developed hypothermia as a result of a drug-drug interaction that produced supratherapeutic serum concentrations of clobazam. Although clobazam and its active metabolite (N-desmethylclobazam) are metabolized by cytochrome 2C19 (CYP2C19), literature suggests that clobazam-associated drug interactions involving this isoenzyme are not clinically relevant because of its wide therapeutic index. This report describes clobazam-associated hypothermia due to supratherapeutic serum concentrations of clobazam that resulted from the combination of 2 CYP2C19 inhibitors.

Intractable Generalized Epilepsy: Therapeutic Approaches

PURPOSE OF REVIEW

To summarize recent developments in therapeutic options, both medical and surgical, for patients with drug-resistant generalized epilepsy syndromes, which continue to be a multifaceted challenge for patients and physicians.

RECENT FINDINGS

Newer generation pharmaceutical options are now available, such as brivaracetam, rufinamide, lacosamide, perampanel, and cannabidiol. Less restrictive dietary options appear to be nearly as effective as classic ketogenic diet for amelioration of seizures. The latest implantable devices include responsive neurostimulation and deep brain stimulation. Corpus callosotomy is an effective treatment for some seizure types, and newer and less invasive approaches are being explored. Resective surgical options have demonstrated success in carefully selected patients despite generalized electrographic findings on electroencephalogram. The current literature reflects a widening range of clinical experience with newer anticonvulsant medications including cannabinoids, dietary therapies, surgical approaches, and neurostimulation devices for patients with intractable generalized epilepsy.

Impact of Drug Interactions on Clobazam and N-Desmethylclobazam Concentrations in Pediatric Patients With Epilepsy

BACKGROUND

Clobazam (CLB) is approved as adjunctive treatment for seizures associated with Lennox-Gastaut syndrome in patients aged 2 years and older. It is converted to an active metabolite N-desmethylclobazam (NCLB) by CYP3A4, which is then broken down to an inactive metabolite by CYP2C19. This study characterizes the impact of CYP3A4 and CYP2C19 drug interactions on CLB and NCLB serum concentrations (Cp) and concentration/dose (Cp/D) ratios in pediatric patients with epilepsy.

METHODS

This was a retrospective chart review including patients older than 1 month, who received CLB between April 2012 and March 2017. Extracted data included patient demographics, CLB daily dose, CLB and NCLB Cp, calculated CLB and NCLB Cp/Cp and Cp/D ratios, and all concomitant drugs.

RESULTS

The study included 995 CLB concentration sets from 302 patients (median age 7.6 years and range 0.2-40.1 years). Pharmacokinetic variability was extensive, as seen by widespread ranges of CLB and NCLB Cp, NCLB/CLB Cp ratio, and 3 Cp/D ratios (CLB, NCLB, and CLB + NCLB). Comedications, described as CYP3A4 inducers and/or CYP2C19 inhibitors (carbamazepine, eslicarbazepine, felbamate, (fos)phenytoin, oxcarbazepine, pentobarbital, phenobarbital, rufinamide, and topiramate), generally increased NCLB/CLB Cp ratio (267%-400%), NCLB Cp/D ratio (167%-202%), and CLB + NCLB Cp/D ratio (142%-185%) and decreased CLB Cp/D ratio (47%-76%) compared with a group of concentration sets in patients receiving only neutral comedications (P < 0.025 for all comparisons). Older age was associated with higher Cp/D ratios (mg/kg), indicative of decreased clearance.

CONCLUSIONS

Pharmacokinetic variability of CLB in pediatric patients is extensive, and it is influenced by drug-drug interactions and age. Therapeutic drug monitoring of CLB and active metabolite NCLB with calculation of various Cp/Cp and Cp/D ratios can provide useful insight into CLB pharmacokinetics and help differentiate between causes of variability.

Pharmacokinetics of clobazam oral soluble film

OBJECTIVE

Clobazam oral soluble film (COSF) is a novel dosage form under development for the adjunctive treatment of seizures associated with Lennox-Gastaut syndrome. The present study was undertaken to assess the pharmacokinetics of clobazam administered as single doses of COSF 20 and 10 mg compared with clobazam tablets (CTAB) 20 and 10 mg in healthy adults. A secondary objective was to assess the safety and tolerability of single doses of COSF 20 and 10 mg.

METHODS

A total of 51 adult volunteers were enrolled in a single-dose, open-label, randomized four-sequence, four-period, crossover study with treatments (A) COSF 20 mg, (B) CTAB 20 mg, (C) COSF 10 mg, and (D) CTAB 10 mg. Pharmacokinetic sampling for clobazam and N-desmethylclobazam was carried out until 21 days postdose with a 28-day washout. Subjects were monitored for adverse events (AEs) throughout the study. Visual inspections of the administration site were performed before and after COSF administration to monitor for mucosal irritation.

RESULTS

COSF at single doses of 10 and 20 mg was bioequivalent to CTAB at equivalent doses for both clobazam and its active metabolite N-desmethylclobazam. The pharmacokinetics of both formulations was dose-proportional at doses of 10 and 20 mg. The number of AEs and the number of subjects experiencing AEs were dose-related across the treatment groups, with somnolence the most common event. None of these events was severe or serious, and most were mild. There was no evidence for local irritation at the administration site following COSF.

SIGNIFICANCE

COSF is a novel clobazam dosage form that is bioequivalent to CTAB. Because of its ease of administration, COSF may be expected to improve adherence, reduce likelihood of dosing error, and provide more accurate dosing than formulations of clobazam that are currently available.

A Comprehensive Overview of the Clinical Pharmacokinetics of Clobazam

Clobazam (CLB) is a 1,5‐benzodiazepine that has been widely used as an anxiolytic and antiseizure drug (ASD) since it was first synthesized over 50 years ago. CLB was approved in the United States in 2011 as adjunctive therapy for seizures in patients ≥2 years old with Lennox‐Gastaut syndrome. CLB pharmacokinetics (PK) have been studied in single‐ and multiple‐dose administrations in healthy subjects. Salient features include high bioavailability, linear PK, and negligible effects from coadministration of other ASDs. CLB is highly and extensively absorbed, with little effect from food; time to maximum plasma concentration is 0.5 to 4 hours following the dose. After CLB doses of 20 to 40 mg/day, the volume of distribution is 99 to 120 L, with oral clearance ranging from 1.9 to 2.3 L/h. CLB is lipophilic and distributes throughout the body after oral administration. It is metabolized in the liver by cytochrome P450 (CYP) isoenzymes CYP3A, CYP2C19, and CYP2B6, and its main active metabolite is N‐desmethylclobazam. The half‐life of CLB after a single oral dose ranges from 36 to 42 hours; the half‐life of N‐desmethylclobazam ranges from 59 to 74 hours. The metabolites of CLB are primarily excreted renally. Population PK modeling using data from healthy subjects and patients with Lennox‐Gastaut syndrome indicates that race, sex, age, weight, and renal function do not influence CLB PK. As CLB has been extensively studied since the 1970s, this review is meant to provide a consolidated and comprehensive resource on CLB PK for both prescribers and scientists alike.

How do we diagnose and treat epilepsy with myoclonic-atonic seizures (Doose syndrome)? Results of the Pediatric Epilepsy Research Consortium survey

OBJECTIVE

To obtain and assess opinions on EMAS diagnostic criteria, recommended investigations, and therapeutic options, from a large group of physicians who care for children with EMAS.

METHODS

The EMAS focus group of PERC created a survey to assess the opinions of pediatric neurologists who care for children with EMAS regarding diagnosis and treatment of this condition, which was sent to members of PERC, AES, and CNS. A Likert scale was used to assess the respondents' opinions on the importance of diagnostic and exclusion criteria (five point scale), investigations (four point scale), and treatment (six point scale) of EMAS. Inclusion/exclusion criteria were then classified as critical, strong, or modest. Investigations were classified as essential, recommended, or possible. Therapies were classified as first line, beneficial, indeterminate benefit, or contraindicated.

RESULTS

Survey results from the 76 participants determined the following: EMAS inclusion criteria: history suggestive of MAS (critical), recorded or home video suggestive of MAS, generalized discharges on inter-ictal EEG, normal neuroimaging, normal development prior to seizure onset (strong). EMAS exclusionary criteria: epileptic spasms, abnormal neuroimaging, focal abnormal exam, seizure onset <six months or >six years (strong).

RECOMMENDED INVESTIGATIONS

EEG and MRI (essential), amino acids, organic acids, fatty acid/acylcarnitine profile, microarray, genetic panel, lactate/pyruvate, CSF and serum glucose/lactate (strong).

RECOMMENDED TREATMENTS

Valproic acid (first line), topiramate, zonisamide, levetiracetam, benzodiazepines, and dietary therapies (beneficial).

SIGNIFICANCE

To date, no similar surveys have been published, even though early syndrome identification and initiation of effective treatment have been associated with improved outcome in EMAS. Medications that exacerbate seizures in EMAS have also been identified. This survey identified critical and preferred diagnostic electro clinical features, investigations, and treatments for EMAS. It will guide future research and is a crucial first step in defining specific diagnostic criteria, recommended evaluation, and most effective therapies for EMAS.

New antiepileptic drugs: focus on ezogabine, clobazam, and perampanel

Ezogabine, clobazam, and perampanel are among the newest antiseizure drugs approved by the Food and Drug Administration between 2011 and 2012. Ezogabine and perampanel are approved for adjunctive treatment of partial epilepsy. Perampanel is also approved for adjunctive treatment of primary generalized tonic–clonic seizures. Ezogabine and perampanel have novel mechanisms of action. Ezogabine binds to voltage-gated potassium channels and increases the M-current thereby causing membrane hyperpolarization. Perampanel is a selective, non-competitive 2-amino-3-(3-hydroxy-5-methyl-isoxazol-4-yl)propanoic acid receptor antagonist, which reduces neuronal excitation. Clobazam has been used worldwide since the 1970s and is approved for adjunctive treatment of seizures associated with Lennox-Gastaut syndrome. Clobazam is the only 1,5-benzodiazepine currently in clinical use, which is less sedating than the commonly used 1,4-benzodiazepines. Phase III multicenter, randomized, double-blind, placebo-controlled trials demonstrated efficacy and good tolerability of these 3 new antiepileptic drugs. These drugs represent a welcome addition to the armamentarium of practitioners, but it remains to be seen how they will affect the landscape of pharmacoresistant epilepsy.

Emerging Antiepileptic Drugs for Severe Pediatric Epilepsies

The medical management of the epilepsy syndromes of early childhood (eg, infantile spasms, Dravet syndrome, and Lennox-Gastaut syndrome) is challenging; and requires careful evaluation, classification, and treatment. Pharmacologic therapy continues to be the mainstay of management for these children, and as such it is important for the clinician to be familiar with the role of new antiepileptic drugs. This article reports the clinical trial data and personal experience in treating the severe epilepsies of childhood with the recently Food and Drug Administration-approved new antiepileptic drugs (vigabatrin, rufinamide, perampanel, and clobazam) and those in clinical trials (cannabidiol, stiripentol, and fenfluramine). Genetic research has also identified an increasing number of pediatric developmental and seizure disorders that are possibly treatable with targeted drug therapies, focused on correcting underlying neural dysfunction. We highlight recent genetic advances, and how they affect our treatment of some of the genetic epilepsies, and speculate on the use of targeted genetic treatment (precision medicine) in the future.

Clobazam and clonazepam use in epilepsy: Results from a UK database incident user cohort study

OBJECTIVE

To compare patient characteristics and treatment patterns among clobazam (CLB) and clonazepam (CZP)-treated patients with epilepsy in a longitudinal primary care database.

METHODS

In this pharmacoepidemiological study, real-life usage data from the Clinical Practice Research Database (CPRD) were evaluated. The CPRD collects data from approximately 690 primary care practices throughout the UK. Data included were from patients with ≥1 incident CLB or CZP prescription from 1995 to 2011 and were present in the database for ≥182 days prior to the index date (date patient was first prescribed CLB or CZP within the study period).

RESULTS

Of 21,099 patients who met inclusion criteria, 18.4% were receiving CLB and 81.6% were receiving CZP. More patients used CLB for epilepsy than CZP (76.1% vs 8.7%). CLB-treated adults (≤18years) were younger than those treated with CZP (41.0 vs 48.2 years; p<0.001), while CLB-treated children (≤18 years) were older than those treated with CZP (8.8 vs 7.3 years, p<0.001). The median CLB dosage did not change from baseline to last follow-up, while median CZP dosage increased 25% in adults and 50% in children. Median treatment duration, as well as retention rate up to 10 years, was similar between CLB and CZP in each age group.

CONCLUSIONS

Among adult and pediatric patients in the UK, CLB is more often prescribed for epilepsy than CZP. The median CLB dosage used by both adults and children remained stable over the 16-year study period, while the median CZP dosage increased in both adults and children.

Comprehensive overview: efficacy, tolerability, and cost-effectiveness of clobazam in Lennox-Gastaut syndrome

Clobazam is the newest medication approved by the US Food and Drug Administration (FDA) for the treatment of Lennox–Gastaut syndrome (LGS) in patients at least 2 years of age, although the medication has been available in countries around the world to treat epilepsy and anxiety disorders for many years. Though classified as a benzodiazepine, the drug differs structurally from other drugs in the class as it possesses nitrogen atoms at the 1 and 5 positions within the heterocyclic ring rather than at the 1 and 4 positions. This difference and the classification of clobazam as a partial agonist are believed to be responsible for the decreased incidence of sedative effects compared to other benzodiazepines. Adverse events associated with clobazam use in clinical trials have generally been mild to moderate in nature. Data from an open-label extension trial have confirmed that clobazam is efficacious for the treatment of seizures associated with LGS, particularly atonic seizures (drop seizures), over the long term. Tolerance to the drug’s antiepileptic effects does not seem to be a common occurrence. The drug has proven to be a cost-effective option for therapy, particularly due to its ability to decrease the number of seizures that require medical treatment. Clobazam represents a welcome addition to the treatment options for LGS.

Clobazam: A Safe, Efficacious, and Newly Rediscovered Therapeutic for Epilepsy

Clobazam is an oral 1,5-benzodiazepine used worldwide for the treatment of many types of epilepsies, although it is currently only approved for Lennox-Gastaut syndrome in the USA. This anticonvulsant and anxiolytic therapeutic has repeatedly demonstrated great efficacy and a high safety profile in refractory epilepsy as well as in a few monotherapy trials in both children and adults. Clobazam allosterically activates the GABAA receptor, and it binds less to subunits that mediate sedative effects than other benzodiazepines. It acts quickly, maintaining a therapeutic effect for a long duration due to its active metabolite, N-desmethylclobazam. Dosage is between 5 mg and 40 mg a day, depending on patient weight, efficacy, and tolerability. Efficacy tolerance has not been a problem in the best studies. Clobazam has provided many benefits to epileptic patients. It should be used by clinicians early as an adjuvant therapy in the treatment of refractory epilepsy and even considered as monotherapy in a broad spectrum of epilepsy syndromes.

Withdrawal-related adverse events from clinical trials of clobazam in Lennox-Gastaut syndrome

To assess withdrawal-related adverse event (AE) rates following abrupt clobazam discontinuation in Phase I trials and gradual clobazam tapering (2-3 weeks) following discontinuation from III trials met the criteria for potential/III trials, we evaluated AE data from four multiple-dosage Phase I trials (duration: 8-34 days). Therapeutic (20 and 40 mg/day) and supratherapeutic clobazam dosages (120 and 160 mg/day) were administered. Adverse events (AEs) were also assessed for patients with Lennox-Gastaut syndrome enrolled in Phase II (OV-1002) and Phase III (OV-1012) studies (duration ≤15 weeks) and in the open-label extension (OLE) trial OV-1004 (≤5 years). Potential withdrawal-related AEs were identified by preferred terms, provided that the AEs occurred ≥1 day following and ≤30 days after the last clobazam doses, or were deemed withdrawal symptoms by investigators. Clinical Institute Withdrawal Assessment for Benzodiazepines (CIWA-B) scale was used to evaluate withdrawal intensity in three of the four Phase I trials. A total of 207 participants in Phase I trials received steady-state clobazam dosages of 20-160 mg/day, 182 received clobazam dosages of ≥40 mg/day, and 94 received clobazam dosages of ≥120 mg/day. Abrupt clobazam discontinuation led to 193 withdrawal-related AEs for 68 Phase I participants. Nearly 50% of AEs occurred after discontinuation of clobazam dosages of ≥120 mg/day. Adverse events were mild or moderate and included headache (14% of Phase I participants), insomnia (12.6%), tremor (10.1%), and anxiety (8.7%). The CIWA-B scores varied (range: 0-59). Most scores were <30, indicating possible mild benzodiazepine withdrawal. III trials met the criteria for potential/III patients received clobazam dosages of ≤40 mg/day, and those in the OLE trial received clobazam dosages of ≤80 mg/day. Eighty-seven patients discontinued clobazam and were gradually tapered. No withdrawal-related AEs or incidences of status epilepticus were reported. Withdrawal-related AEs observed in Phase I studies following abrupt clobazam discontinuation at therapeutic and supratherapeutic dosages were generally mild. No withdrawal-related AEs occurred when dosages were tapered over 3 weeks, after short- or long-term clobazam use (≤5 years).

Clobazam: effect on frequency of seizures and safety profile in different subgroups of children with epilepsy

BACKGROUND

Clobazam has been used in clinical practice as an adjunctive treatment for diverse seizure types and epilepsy syndromes. We evaluated the efficacy and safety of clobazam in a large sample of patients with refractory epilepsy at a tertiary pediatric center.

METHODS

We retrospectively reviewed patients treated with clobazam between January 2001 and July 2013 who had a follow-up visit at least one month after starting clobazam. Response was defined as ≥50% reduction in seizure frequency compared with baseline seizure frequency during the 3 months before the introduction of clobazam. We examined the relationship between dose range and response rate.

RESULTS

Four-hundred twenty-five patients were prescribed clobazam, of whom 300 (median age 9.1 years, interquartile range 4.7-13.3 years) had follow-up data greater than 1 month. Median follow-up was 5 months (interquartile range 3-11 months). Response to treatment with clobazam was observed in 203 of 300 (67.7%) patients, of whom 84 (28%) became seizure-free. The median starting dose was 0.2 (interquartile range 0.13-0.33) mg/kg/day with a target dose of 0.48 (0.26-0.80) mg/kg/day. Twenty-seven (9%) patients discontinued clobazam, 16 (59.3%) because adverse effects, 10 (37%) because of a lack of efficacy, and one (3.7%) because of a combination of adverse effects and lack of efficacy. The most common adverse effects were tiredness in 44 of 300 (14.6%) and mood or behavioral changes in 23 (7.7%).

CONCLUSIONS

Clobazam is a well-tolerated antiepileptic drug with good response rates in pediatric patients with refractory epilepsy.

Advances in anti-epileptic drug testing

In the past twenty-one years, 17 new antiepileptic drugs have been approved for use in the United States and/or Europe. These drugs are clobazam, ezogabine (retigabine), eslicarbazepine acetate, felbamate, gabapentin, lacosamide, lamotrigine, levetiracetam, oxcarbazepine, perampanel, pregabalin, rufinamide, stiripentol, tiagabine, topiramate, vigabatrin and zonisamide. Therapeutic drug monitoring is often used in the clinical dosing of the newer anti-epileptic drugs. The drugs with the best justifications for drug monitoring are lamotrigine, levetiracetam, oxcarbazepine, stiripentol, and zonisamide. Perampanel, stiripentol and tiagabine are strongly bound to serum proteins and are candidates for monitoring of the free drug fractions. Alternative specimens for therapeutic drug monitoring are saliva and dried blood spots. Therapeutic drug monitoring of the new antiepileptic drugs is discussed here for managing patients with epilepsy.

Experience in the use of clobazam in the treatment of Lennox-Gastaut syndrome

Clobazam is a 1,5-benzodiazepine used successfully worldwide since the 1970s as an anxiolytic and antiepileptic drug. Since its recent Food and Drug Administration (FDA) approval in the United States in 2011 as adjunctive treatment for Lennox-Gastaut syndrome, it has continued to show sustained efficacy and a better safety and tolerability profile compared with other benzodiazepines. The two randomized, controlled studies that led to the US FDA approval, as well as the follow-up multicenter, open-label study of clobazam, showed ≥50% seizure reduction for more than 50% of Lennox-Gastaut syndrome patients, while none of the other FDA-approved treatments for LGS have demonstrated efficacy rates better than 50%. Clobazam appears to have a safe profile and sustained effectiveness over the first 3 years of use in LGS and other epilepsy syndromes with intractable seizures, which makes it a viable long-term treatment option.