A Comprehensive Overview of the Clinical Pharmacokinetics of Clobazam

Evaluating the patient needs and tolerability of Clobazam liquid formulation (Likozam® 1 mg/mL): A French patient and care-givers' centered survey

BACKGROUND

Clobazam (CLB) is a 1,5-benzodiazepine, currently used as add-on anti-seizure medication in complex and drug-resistant epilepsies. In France, CLB is available in three galenic forms and in a masterful one. The aim of this survey is to assess the experience of patients and families on CLB galenic forms focusing on CLB liquid formulation, Likozam® 1 mg/ml exclusively available in hospitals' pharmacies.

METHODS

We performed a survey on the use of benzodiazepines with the Dravet syndrome Alliance (ASD) France. The survey was distributed on their site (http://www.dravet.fr/) and addressed to caregivers of patients who received CLB in any galenic form. The survey was co-developed by ASD and the Reference Centre for Rare Epilepsies, Necker. It included both open and closed questions. We used a 5-point Likert scale to assess the caregiver opinion on every formulation received, addressing medication palatability, dose adaptability, ability to take the drug without help, easiness of swallowing and access to treatment. Finally, we had some additional questions for the CLB liquid form.

RESULTS

Eighty-seven patients aged 2 to 41 years (mean age 13, standard deviation ± 6.6) participated in this study. They presented Dravet syndrome (DS) (71/87, 82 %), Lennox-Gastaut syndrome (LGS) (4/87, 4 %), infantile epileptic spasms syndrome (IESS) (1/87, 1 %), and epilepsy with myoclonic atonic seizures (EMAtS) (1/87, 1 %). The epilepsy syndrome was unknown for 10/87 (12 %). The mean age at the first CLB prescription was 9 years (standard deviation ± 5.9, range age 1-35 years). Most patients (69/87, 79.3 %) had polytherapy. CLB most frequent formulations were the liquid (Likozam® 1 mg/mL) (44/87, 50.5 %) and the pill formulation (Urbanyl® 5 mg) (43/87, 49.4 %). The liquid formulation was selected as the most appropriate by 49,4% of caregivers, due to the greater easiness of administration and the dose adaptability. The easiness of access to treatment was the major issue against this formulation as it is currently available only in hospitals' pharmacies.

CONCLUSION

Our study revealed an unmet need of CLB liquid form mainly in infants and young children, where easy to swallow and adaptable small doses are required during CLB introduction or discontinuation. However, some impactful issues such as access to treatment, palatability or liquid quantity administered should be optimized to improve patient and families' acceptability of liquid CLB.

Relative Bioavailability of Cenobamate Administered as a Crushed Tablet, Either Orally or via Nasogastric Tube, versus an Intact Whole Tablet

Cenobamate is approved for the treatment of focal seizures in adults and is currently available as an oral tablet. Alternative methods of drug administration are needed for patients who are unable to swallow whole intact tablets. This phase 1, open-label, randomized, single-dose, three-way crossover (3-period, 3-treatment, 6-sequence) study (NCT05572255), conducted in healthy volunteers, assessed the relative bioavailability of a crushed 200-mg cenobamate tablet administered orally or via nasogastric (NG) tube compared with an intact 200-mg tablet. Each treatment was separated by a 13-day washout period. Plasma samples for cenobamate concentration analysis were collected pre-dose and at multiple time points up to 264 h post-dose. Standard bioequivalence study criteria were applied to the relative bioavailability assessments. All 90% confidence intervals of test-to-reference geometric mean ratios for cenobamate pharmacokinetic parameters (Cmax, AUClast, and AUCinf) were within 85-110% (predefined limit, 80-125%), suggesting no difference in cenobamate exposures following administration of an intact tablet orally or a crushed tablet orally or via NG tube. All treatment-emergent adverse events (TEAEs) were classified as mild and resolved. There were no deaths or other serious AEs (SAEs), and no TEAEs led to discontinuation. Our results indicate that the administration of cenobamate as a crushed tablet taken orally or via an NG tube can provide additional flexibility when patients cannot swallow intact tablets. Based on the results of this study, cenobamate is now approved by FDA to be taken whole or the tablets can be crushed. The crushed tablet can be mixed with water and either administered by mouth as an oral suspension or administered via a nasogastric tube.

Multiple ASM Administration via Percutaneous Feeding Tube as a Cause of Pseudo-Refractoriness Leading to Recurrent Seizure Clusters

It is important to identify true refractoriness of seizures, before escalation of anti-seizure medications, to avoid side effects of medications. Bioavailability of medications changes with the formulations used and changes significantly with the route of administration. Both of these were significantly impacted in a lady who was being fed via percutaneous endoscopic gastrostomy (PEG) feeds and deemed refractory to medications. After altering the formulations and the method, she became seizure-free.

Human Data on Pharmacokinetic Interactions of Cannabinoids: A Narrative Review

Concomitant use of cannabinoids with other drugs may result in pharmacokinetic drug-drug interactions, mainly due to the mechanism involving Phase I and Phase II enzymes and/or efflux transporters. Cannabinoids are not only substrates but also inhibitors or inducers of some of these enzymes and/or transporters. This narrative review aims to provide the available information reported in the literature regarding human data on the pharmacokinetic interactions of cannabinoids with other medications. A search on Pubmed/Medline, Google Scholar, and Cochrane Library was performed. Some studies were identified with Google search. Additional articles of interest were obtained through cross-referencing of published literature. All original research papers discussing interactions between cannabinoids, used for medical or recreational/adult-use purposes, and other medications in humans were included. Thirty-two studies with medicinal or recreational/adult-use cannabis were identified (seventeen case reports/series, thirteen clinical trials, and two retrospective analyses). In three of these studies, a bidirectional pharmacokinetic drug-drug interaction was reported. In the rest of the studies, cannabinoids were the perpetrators, as in most of them, concentrations of cannabinoids were not measured. In light of the widespread use of prescribed and non-prescribed cannabinoids with other medications, pharmacokinetic interactions are likely to occur. Physicians should be aware of these potential interactions and closely monitor drug levels and/or responses. The existing literature regarding pharmacokinetic interactions is limited, and for some drugs, studies have relatively small cohorts or are only case reports. Therefore, there is a need for high-quality pharmacological studies on cannabinoid-drug interactions.

Concomitant cannabidiol does not impact safety and effectiveness of diazepam nasal spray for seizure clusters: Post hoc analysis of a phase 3 safety study

People with epilepsy may experience episodes of frequent seizure activity (seizure clusters, acute repetitive seizures), and benzodiazepines are the cornerstone of rescue treatment. Cannabidiol (CBD) can be used as an adjunctive treatment for epilepsy, and it may interact with other antiseizure drugs, such as benzodiazepines. Here, we examined the safety and effectiveness of intermittent use of diazepam nasal spray in patients with seizure clusters who also received CBD treatment. This analysis included data from patients aged 6 to 65 years enrolled in a phase 3, long-term safety study of diazepam nasal spray. Age- and weight-based dosing of diazepam nasal spray were administered during a 12-month treatment period. Concomitant CBD use was recorded, and treatment-emergent adverse events (TEAEs) were collected. Of 163 treated patients, 119 (73.0%) did not receive CBD, 23 (14.1%) received the US Food and Drug Administration-approved highly purified CBD and 21 (12.9%) received another form of CBD. On average, patients receiving highly purified CBD were younger and more likely to have epileptic encephalopathies, including Dravet syndrome or Lennox-Gastaut syndrome, than patients who received another CBD preparation or no CBD. Rates of TEAEs and serious TEAEs were greater in patients who received any form of CBD (90.9% and 45.5%, respectively) compared with no CBD (79.0% and 26.1%, respectively). However, the lowest rates of TEAEs attributed to diazepam nasal spray were reported in patients who received highly purified CBD (13.0%), and this result was maintained in those who received concomitant clobazam. Use of second doses of diazepam nasal spray, a proxy for effectiveness, was lowest in the highly purified-CBD group (8.2%) compared with the no-CBD (11.6%) and other-CBD groups (20.3%). These results suggest that CBD does not alter the safety and effectiveness of diazepam nasal spray and supports concomitant use in appropriate patients.

Addition of clobazam successfully treating drug resistant seizures in Heidenhain variant Creutzfeldt Jakob disease: A case report

Creutzfeldt Jakob Disease (CJD) is a rapidly progressive and fatal neurodegenerative disease that is uncommonly accompanied with seizures. In this case report, we describe a 63-year-old male patient who presented with a 3-week history of visual disturbances and clonic movement of his left arm. Additionally, the patient was reported to have developed erratic behaviors along with insomnia during this period. An EEG showed 4 electrographic seizures of bilateral temporo-occipital onset characterized by 1.5 Hz periodic discharges, lasting 2-13 min. Levetiracetam was started and titrated to the maximal dose however seizures continued so lacosamide and clonazepam were initiated. Despite these aggressive treatments, seizures continued, and oral clobazam 5 mg BID replaced clonazepam. Continued electrographic seizures warranted an increase in clobazam to 10 mg BID after which the seizures stopped; of note, lateralized periodic discharges (LPDs) remained. The patient's symptoms were consistent with the Heidenhain variant, along with probable CJD due to positive RT-QuIC assay, positive 14-3-3 protein, MRI FLAIR hyperintensities, and EEG findings. Although the patient passed away 3 weeks following admission as a result of CJD, we propose that there may be clinical benefit in the use of clobazam in suspected CJD patients presenting with seizures, and its use merits further investigation.

Evaluating the efficacy of prototype antiseizure drugs using a preclinical pharmacokinetic approach

OBJECTIVE

Pharmacokinetics (PK) of a drug drive its exposure, efficacy, and tolerability. A thorough preclinical PK assessment of antiseizure medications (ASMs) is therefore essential to evaluate the clinical potential. We tested protection against evoked seizures of prototype ASMs in conjunction with analysis of plasma and brain PK as a proof-of-principle study to enhance our understanding of drug efficacy and duration of action using rodent seizure models.

METHODS

In vivo seizure protection assays were performed in adult male CF-1 mice and Sprague Dawley rats. Clobazam (CLB), N-desmethyl CLB (NCLB), carbamazepine (CBZ), CBZ-10,11-epoxide (CBZE), sodium valproate (VPA), and levetiracetam (LEV) concentrations were quantified in plasma and brain using liquid chromatography-tandem mass spectrometry. Mean concentrations of each analyte were calculated and used to determine PK parameters via noncompartmental analysis in Phoenix WinNonLin.

RESULTS

NCLB concentrations were approximately 10-fold greater than CLB in mice. The antiseizure profile of CLB was partially sustained by NCLB in mice. CLB concentrations were lower in rats than in mice. CBZE plasma exposures were approximately 70% of CBZ in both mice and rats, likely contributing to the antiseizure effect of CBZ. VPA showed a relatively short half-life in both mice and rats, which correlated with a sharp decline in efficacy. LEV had a prolonged brain and plasma half-life, associated with a prolonged duration of action in mice.

SIGNIFICANCE

The study demonstrates the utility of PK analyses for understanding the seizure protection time course in mice and rats. The data indicate that distinct PK profiles of ASMs between mice and rats likely drive differences in drug efficacy between rodent models.

Retrospective analysis of metabolite patterns of clobazam and N-desmethylclobazam in human plasma by LC-MS/MS

Introduction

Clobazam is a benzodiazepine drug, used to treat Lennox-Gastaut syndrome in patients aged 2 years and older.

Objective

To support patient care, our laboratory developed a liquid chromatography tandem mass spectrometry (LC-MS/MS) method for the quantification of clobazam (CLB) and its major active metabolite N-desmethylclobazam (N-CLB) in human plasma or serum samples.

Methods

The chromatographic separation was achieved with an Agilent Zorbax Eclipse Plus C-18 RRHD column with mobile phase consisting of 0.05% formic acid in 5 mM ammonium formate, pH 3.0 and 0.1% formic acid in acetonitrile at a flow rate of 600 µL/minute and an injection volume of 5 µL. The detection was performed on a triple quadrupole mass spectrometer in multiple reaction monitoring mode to monitor precursor-to-product ion transitions in positive electrospray ionization mode.

Results

The method was validated over a concentration range of 20-2000 ng/mL for CLB and 200-10,000 ng/mL for N-CLB. The lower limit of quantification was 20 ng/mL for CLB and 200 ng/mL for N-CLB with good accuracy and precision. The method performance was successfully evaluated by comparison with two different external laboratories. Retrospective data analysis was performed to evaluate the positivity rate and metabolic patterns for clobazam from our patient population, as a reference laboratory. Among the positive samples, both parent and metabolite were detected in 96.4% of the samples.

Conclusion

The method was developed to support therapeutic drug monitoring and the data generated from retrospective analysis could be useful for result interpretation in conjunction with clinical patient information.

Lacosamide effectiveness and tolerability in patients with drug-resistant epilepsy and severe disability under polytherapy: Therapy optimization as emerging from an observational study

OBJECTIVE

We explored the efficacy and safety of lacosamide combined with inhibitors of fast-inactivated sodium channels or with other antiepileptic drugs, in patients with drug refractory focal epilepsy associated with intellectual or psychiatric disability.

METHODS

Observational study of lacosamide including the monitoring of lacosamide trough plasma levels and of electroencephalograms.

RESULTS

We followed up 44 patients from the start of lacosamide therapy for up to 3 years, with a clinical, electroencephalogram (EEG), and pharmacological follow-up. Median patients' age was 32.7 years, median age at epilepsy onset was 3.5 years. Intellectual disability was severe in 55.4% of the cohort and drug refractoriness was diagnosed in 88.6% of patients, who had predominantly focal seizures (80%). The severity of their epilepsy was suggested by the use of combined therapies with non-sodium blockers and sodium blockers in 75% of patients. Lacosamide was added to previous therapies and up-titrated to a median of 300 mg/d. Lacosamide add-on led to simplification of the previous drug regimen with a dose reduction in 87.9% of users of sodium blockers and in 66.7% of users of non-sodium blockers, and to withdrawal of previously administered sodium blockers in 48.5% users and non-sodium blockers in 47.6% users. Lacosamide was prescribed at lower doses in the presence of oxcarbazepine (p = 0.029), lamotrigine (p = 0.015), and topiramate (p < 0.001). Mean lacosamide plasma levels were 6.0 ± 2.4 mg/L; they were in linear correlation with the administered dose (R² = 0.38, p < 0.001) and were influenced by the association with lamotrigine (p = 0.008), zonisamide (p = 0.012), and clobazam (p = 0.028). Lacosamide combination regimens led to an average reduction of 42% in baseline seizure frequency, with 50% patients reporting ≥50% seizure frequency reduction. Efficacy was directly correlated with lacosamide dose (R² = 0.47, p < 0.001, B = 0.53) and trough plasma levels (R² = 0.31, p < 0.001, B = 0.16). Electroencephalogram profiles were improved in 40.9% of patients and EEG improvement was not significantly correlated with seizure frequency reduction. Lacosamide safety was good, with 37 adverse reactions in 30 patients, of which 50% were attributed to lacosamide and led to lacosamide withdrawal in 18% of cases. The retention rate of lacosamide was of 88.6% at 1 year, 86.4% at 2 years, and 72.7% after three years. The severity of intellectual disability was directly correlated with increased possibility of lacosamide retention (OR = 0.46 per severity tier, p = 0.016).

CONCLUSION

Lacosamide add-on allowed dose reduction of previous therapies and reduced the frequency of seizures, showing good tolerability even at high doses, without exceeding reference plasma levels.

Pharmacokinetic Drug-Drug Interactions among Antiepileptic Drugs, Including CBD, Drugs Used to Treat COVID-19 and Nutrients

Anti-epileptic drugs (AEDs) are an important group of drugs of several generations, ranging from the oldest phenobarbital (1912) to the most recent cenobamate (2019). Cannabidiol (CBD) is increasingly used to treat epilepsy. The outbreak of the SARS-CoV-2 pandemic in 2019 created new challenges in the effective treatment of epilepsy in COVID-19 patients. The purpose of this review is to present data from the last few years on drug–drug interactions among of AEDs, as well as AEDs with other drugs, nutrients and food. Literature data was collected mainly in PubMed, as well as google base. The most important pharmacokinetic parameters of the chosen 29 AEDs, mechanism of action and clinical application, as well as their biotransformation, are presented. We pay a special attention to the new potential interactions of the applied first-generation AEDs (carbamazepine, oxcarbazepine, phenytoin, phenobarbital and primidone), on decreased concentration of some medications (atazanavir and remdesivir), or their compositions (darunavir/cobicistat and lopinavir/ritonavir) used in the treatment of COVID-19 patients. CBD interactions with AEDs are clearly defined. In addition, nutrients, as well as diet, cause changes in pharmacokinetics of some AEDs. The understanding of the pharmacokinetic interactions of the AEDs seems to be important in effective management of epilepsy.

Precision Medicine into Clinical Practice: A Web-Based Tool Enables Real-Time Pharmacogenetic Assessment of Tailored Treatments in Psychiatric Disorders

The management of neuropsychiatric disorders involves different pharmacological treatments. In order to perform efficacious drug treatments, the metabolism of CYP genes can help to foresee potential drug–drug interactions. The NeuroPGx software is an open-source web-based tool for genotype/diplotype/phenotype interpretation for neuropharmacogenomic purposes. The software provides information about: (i) the genotypes of evaluated SNPs (single nucleotide polymorphisms); (ii) the main diplotypes in CYP genes and corresponding metabolization phenotypes; (iii) the list of neuropsychiatric drugs with recommended dosage adjustment (according to CPIC and DPWG guidelines); (iv) the list of possible (rare) diplotypes and corresponding metabolization phenotypes. The combined application of NeuroPGx software to the OpenArray technology results in an easy, quick, and highly automated device ready to be used in routine clinical practice.

Determination of Clobazam and Its Major Metabolite N-desmethylclobazam in Human Plasma with High-Performance Liquid Chromatography

Clobazam (CLB) is a benzodiazepine that is used in many types of epilepsy. Although therapeutic drug monitoring (TDM) of CLB is not routine, there is evidence that TDM may be of value in conditions where pharmacokinetic alterations are suspected. Therefore, determination of both CLB and its active metabolite concentrations is essential for TDM. Herein, we present a simple and practical method for determination of CLB and N-desmethylclobazam (NDMCLB) in human plasma by high-performance liquid chromatography (HPLC). The drugs were extracted by hexane:dichloromethane (1:1, v/v) from 0.3 mL plasma. The separation was carried out with a C18 reverse phase column using a mobile phase of water:acetonitrile (57:43, v/v) pumped at 0.8 mL/min. The analytes were detected at 228 nm. The method was linear over the concentration range 20–500 ng/mL for CLB and 200–3000 ng/mL for NDMCLB. The intra-day coefficient of variation (CV) was <10% for CLB and <6% for NDMCLB, while the inter-day CV for CLB was <16%. The metabolite inter-day CV was <6%. The accuracy of intra- and inter-day assessments determined for CLB and NDMCLB was within ±10%. This paper describes a rapid, reliable, and simple method for measuring CLB and its metabolite NDMCLB in human plasma. This UV-HPLC procedure offers acceptable precision and accuracy to quantify CLB and its metabolite in human plasma.

Drug-induced liver injury associated with antiseizure medications from the FDA Adverse Event Reporting System (FAERS)

PURPOSE

Treatment with antiseizure medications (ASMs) confers a risk of drug-induced liver injury (DILI), especially for older ASMs. We sought to quantify recent reports of DILI attributed to both older and newer generation ASMs and survey newly marketed ASMs for hepatotoxicity in a large post-marketing database.

METHODS

We queried over 2.6 million adverse event reports made to the FDA Adverse Event Reporting System (FAERS) database between July 1, 2018 and March 31, 2020 for DILI due to ASMs commonly used in clinical practice. Patient characteristics and outcomes were assessed. We calculated the reporting odds ratio (ROR) of DILI for each individual ASM versus all non-ASM reports.

RESULTS

A total of 2175 DILI cases were attributed to an ASM during the study period. 97.2% of these were designated as serious reactions, which include death, hospitalization, disability, and other life-threatening outcomes. A number of older and newer generation ASMs were associated with DILI, specifically: carbamazepine (ROR 2.92), phenobarbital (ROR 2.91), oxcarbazepine (ROR 2.58), phenytoin (ROR 2.40), valproate (ROR 2.22), lamotrigine (ROR 2.06), clobazam (ROR 1.67), levetiracetam (ROR 1.56), and diazepam (ROR 1.53). However, increased odds of DILI were not seen with zonisamide, perampanel, stiripentol, lacosamide, clonazepam, pregabalin, felbamate, eslicarbazepine, cannabidiol, topiramate, gabapentin, ethosuximide, brivaracetam, or primidone. Vigabatrin, tiagabine, and rufinamide all had zero reports of DILI.

CONCLUSIONS

The majority of newer generation ASMs were not significantly associated with DILI. Future studies utilizing FAERS in conjunction with other data sources will be critical for the ongoing surveillance of DILI, particularly as newly marketed ASMs continue to enter into widespread clinical use.

New Methods Used in Pharmacokinetics and Therapeutic Monitoring of the First and Newer Generations of Antiepileptic Drugs (AEDs)

The review presents data from the last few years on bioanalytical methods used in therapeutic drug monitoring (TDM) of the 1st-3rd generation and the newest antiepileptic drug (AEDs) cenobamate in patients with various forms of seizures. Chemical classification, structure, mechanism of action, pharmacokinetic data and therapeutic ranges for total and free fractions and interactions were collected. The primary data on bioanalytical methods for AEDs determination included biological matrices, sample preparation, dried blood spot (DBS) analysis, column resolution, detection method, validation parameters, and clinical utility. In conclusion, the most frequently described method used in AED analysis is the LC-based technique (HPLC, UHPLC, USLC) combined with highly sensitive mass detection or fluorescence detection. However, less sensitive UV is also used. Capillary electrophoresis and gas chromatography have been rarely applied. Besides the precipitation of proteins or LLE, an automatic SPE is often a sample preparation method. Derivatization was also indicated to improve sensitivity and automate the analysis. The usefulness of the methods for TDM was also highlighted.

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.

An evaluation of clobazam tablets and film (AQST-120) for the treatment of Lennox-Gastaut syndrome

Introduction: Lennox-Gastaut syndrome (LGS) is a chronic, epileptic encephalopathy, characterized by multiple seizure types, distinctive slow spike-wave patterns in the electroencephalogram (EEG), and severe cognitive and behavioral comorbidities. Seizures are typically refractory and long-term prognosis is poor. No antiseizure drug (ASD) is fully effective as a monotherapy. Clobazam (CLB) was licensed in the United States in 2011 as an adjunctive therapy for seizures in LGS. In 2018, a new formulation, CLB oral soluble film (COSF) (AQST-120), was approved by the Federal Drug Administration (FDA) for the same indication. Areas covered: The authors summarize current pharmacological options and guidelines for the management of seizures in LGS and efficacy and safety findings from phase II and III randomized controlled trials of adjunctive CLB in patients with LGS. An open-label extension trial is also considered. A pharmacokinetic comparison of COSF and CLB tablets is also undertaken. Expert opinion: CLB is partly effective as an add-on therapy in treating seizures in LGS. Adverse effects, pharmacokinetic interactions and the potential for tolerance with long-term treatment should be weighed against the clinical benefit when considering the introduction of CLB in this population. COSF has a similar pharmacokinetic profile to CLB tablets and may help to improve adherence to treatment.