A case of a potential drug interaction between clobazam and etravirine-based antiretroviral therapy

Safety profile of clobazam in the real world: an analysis of FAERS database and systematic review of case reports

BACKGROUND

Most of the safety data of clobazam came from well-designed clinical trials, while the real-world information is insufficient.

RESEARCH DESIGN AND METHODS

We performed a disproportionality analysis of the FDA Adverse Event Reporting System (FAERS) database through OpenVigil 2 and conducted a systematic review of case reports regarding adverse drug reactions (ADR) linked to clobazam.

RESULTS

The analysis of FAERS identified 595 ADR signals. Nervous system disorders cantains the most positive signals among all system organ classes (SOCs). Except for seizure (n = 1696) and somnolence (n = 813), drug interactions (n = 492) were the most frequently reported positive signals. A total of 502 unique citations were initially retrieved and 31 individual cases from 28 publications were included. Skin reactions were the most reactions (n = 9), containing three types of severe reactions not alerted in the instruction. Five cases were caused by interactions between clobazam and other antiepileptic drugs, etravirine-based antiretroviral therapy, omeprazole, or meropenem. One patient died of aspiration pneumonia.

CONCLUSIONS

Clinicians must pay attention to severe skin reactions and monitor the signs of suspicious respiratory infections/inflammations and central sedation. Patients with skin reactions will benefit from the withdrawal of clobazam and the treatment with glucocorticoids. The drug reactions between clobazam with severe or moderate cytochrome P450 (CYP) 3A4 or CYP2C19 inhibitors or other antiepileptic drugs should also be alerted.

A retrospective non-interventional study evaluating the pharmacokinetic interactions between cenobamate and clobazam

Cenobamate is an antiseizure medication (ASM) approved for the treatment of partial-onset seizures in adults. As both an inductor and an inhibitor of hepatic enzymes, cenobamate affects the metabolism of other ASMs, among which is clobazam. To our knowledge, the extent of interaction between cenobamate and clobazam and its clinical significance have not been studied yet. In this retrospective study we assessed serum concentrations of clobazam and N-desmethylclobazam (NCLB)in five patients before and after co-medication with cenobamate and calculated the percentage increase in concentration-to-dose ratio (CDR) of both. We were able to demonstrate that the addition of cenobamate resulted in an increase in serum concentration and consequently in CDR of NCLB in all patients. However this occurred in variable degrees: NCLB concentration showed an increase of 1208 μg/L (CDR145%) in one patient and between 1691 μ/L (CDR 819%) and 3995 μ/L (CDR 1852%) in the other four. This resulted in fatigue, which improved after dose reduction of CLB. Therefore, it is to be concluded that concomitant administration of cenobamate and clobazam can lead to a substantial increase in serum concentrations of NCLB. This can have a positive therapeutic effect on one hand; however, on the other hand, this can lead to unwanted fatigue.

Cannabidiol Interactions with Medications, Illicit Substances, and Alcohol: a Comprehensive Review

Cannabidiol, a non-intoxicating phytocannabinoid, has potential therapeutic effects over a broad range of disorders. Recently, there has been increased interest in CBD, as several studies showed promising anticonvulsant efficacy with few side effects. In 2018, a CBD-based oral solution, Epidiolex®, was approved by the FDA to treat two severe forms of pediatric epilepsy, Dravet syndrome, and Lennox-Gastaut syndrome. Although only these two syndromes are recognized indications for CBD, it has been consumed in an unregulated fashion for a variety of indications including chronic pain, muscle stiffness, inflammation, anxiety, smoking cessation, and even cancer. While CBD legislation in the USA is confusing due to the differences in state and federal laws, CBD has proliferated in the US market in several forms such as CBD oil or capsules, hemp oil/extract, and also as an ingredient in several dietary supplements, syrups, teas, and creams. With the ever-increasing use of CBD and its widespread availability to the general public, it is important to examine and report on possible drug-drug interactions between CBD and other therapeutic agents as well as addictive substances such as alcohol and tobacco. A detailed literature search for CBD's possible interactions was conducted using online databases. As expected, CBD has been reported to interact with anti-epileptic drugs, antidepressants, opioid analgesics, and THC, but surprisingly, it interacts with several other common medications, e.g. acetaminophen, and substances including alcohol. This review provides a comprehensive list of interacting drugs. The possible mechanisms for these drug-drug interactions are presented in table format. Given the growing popularity of CBD as a medication and the dearth of available information on CBD drug-drug interactions, it is critical to be aware of current drug-drug interactions and it will be important to investigate the impact of CBD upon concomitant medication use in future randomized, controlled trials.

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.

Clinical Impact of Co-medication of Levetiracetam and Clobazam with Proton Pump Inhibitors: A Drug Interaction Study

BACKGROUND

Clobazam (CLBZ) metabolized primarily by Cytochrome P-450 isoenzyme CYP3A4 than with CYP2C19, Whereas Levetiracetam (LEV) is metabolized by hydrolysis of the acetamide group. Few CYP enzymes are inhibited by Proton Pump Inhibitors (PPIs) Pantoprazole, Esomeprazole, and Rabeprazole in different extents that could affect drug concentrations in blood. The aim of the present study was to evaluate the effect of these PPIs on the plasma concentrations of LEV and CLBZ.

METHODS

Blood samples from 542 patients were included out of which 343 were male and 199 were female patients and were categorized as control and test. Plasma samples analyzed using an HPLC-UV method. Plasma concentrations were measured and compared to those treated and those not treated with PPIs. One way ANOVA and games Howell post hoc test used by SPSS 20 software.

RESULTS

CLBZ concentrations were significantly 10 folds higher in patients treated with Pantoprazole (P=0.000) and 07 folds higher in patients treated with Esmoprazole and Rabeprazole (P=0.00). Whereas plasma concentration of LEV control group has no statistical and significant difference when compared to pantoprazole (P=0.546) and with rabeprazole and esomeprazole was P=0.999.

CONCLUSION

The effect of comedication with PPIs on the plasma concentration of clobazam is more pronounced for pantoprazole to a greater extent when compared to esomeprazole and rabeprazole. When pantoprazole is used in combination with clobazam, dose reduction of clobazam should be considered, or significance of PPIs is seen to avoid adverse effects.

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.

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.

The Pharmacology and Toxicology of Third-Generation Anticonvulsant Drugs

Epilepsy is a neurologic disorder affecting approximately 50 million people worldwide, or about 0.7% of the population [1]. Thus, the use of anticonvulsant drugs in the treatment of epilepsy is common and widespread. There are three generations of anticonvulsant drugs, categorized by the year in which they were developed and released. The aim of this review is to discuss the pharmacokinetics, drug-drug interactions, and adverse events of the third generation of anticonvulsant drugs. Where available, overdose data will be included. The pharmacokinetic properties of third-generation anticonvulsant drugs include relatively fewer drug-drug interactions, as well as several unique and life-threatening adverse events. Overdose data are limited, so thorough review of adverse events and knowledge of drug mechanism will guide expectant management of future overdose cases. Reporting of these cases as they occur will be necessary to further clarify toxicity of these drugs.

Effects of CYP2C19 and P450 oxidoreductase polymorphisms on the population pharmacokinetics of clobazam and N-desmethylclobazam in japanese patients with epilepsy

BACKGROUND

Clobazam (CLB) is a 1,5-benzodiazepine with antiepileptic properties. More than 70% of administered CLB is dealkylated to yield N-desmethylclobazam (N-CLB), a pharmacologically active metabolite, by cytochrome P450 (CYP) 3A4 and CYP2C19. The subsequent inactivation of N-CLB is primarily catalyzed by CYP2C19. Meanwhile, P450 oxidoreductase (POR) is the obligatory electron donor to all microsomal CYP enzymes. The aim of this study was to evaluate the impact of the CYP2C19 and POR genotypes on the pharmacokinetic parameters of CLB and N-CLB.

METHODS

This retrospective study included 85 Japanese patients with epilepsy who were treated with CLB. CYP2C19*2, *3, and P450 oxidoreductase (POR) *28 (rs1057868C>T) polymorphisms were evaluated. A total of 128 steady-state concentrations for both CLB and N-CLB were collected from the patients. A nonlinear mixed-effects model identified the pharmacokinetics of CLB and N-CLB; the covariates included CYP2C19 and POR genotypes, weight, gender, daily CLB dose, and coadministered antiepileptic drugs.

RESULTS

Among the 85 patients, the allele frequencies of CYP2C19*2, CYP2C19*3, and POR*28 were 27.6%, 12.9%, and 41.2%, respectively. A one-compartment model with first-order absorption and/or elimination showed that the clearance of CLB and N-CLB was significantly lower by 18.1% and 84.9%, respectively, in the CYP2C19 poor metabolizers compared with the homozygous extensive metabolizers. The CLB clearance was 44% higher in subjects homozygous for the POR*28 T allele than in those homozygous for the POR*28 C allele, although the genotypes did not affect the N-CLB clearance. The concomitant use of phenobarbital, phenytoin, and zonisamide significantly affected the CLB clearance, whereas that of carbamazepine, phenytoin, and valproic acid affected the N-CLB clearance. The weight also significantly influenced the CLB clearance and volume of distribution of both CLB and N-CLB.

CONCLUSIONS

Our results showed that the CYP2C19 and/or POR genotypes have an impact on the CLB and/or N-CLB clearance. These results suggest that determining the CYP2C19 and/or POR genotypes is helpful for obtaining appropriate serum CLB and N-CLB concentrations and preventing an overdose when starting CLB therapy.

Clobazam therapeutic drug monitoring: a comprehensive review of the literature with proposals to improve future studies

BACKGROUND

Clobazam was recently approved for Lennox-Gastaut syndrome in the United States. There is no published review article focused on clobazam therapeutic drug monitoring (TDM) in English.

METHODS

More than 200 clobazam articles identified by a PubMed search were carefully reviewed for information on clobazam pharmacokinetics. Clobazam is mainly metabolized by a cytochrome P450 (CYP) isoenzyme, CYP3A4, to its active metabolite, N-desmethylclobazam. Then, N-desmethylclobazam is mainly metabolized by CYP2C19 unless the individual has no CYP2C19 activity [poor metabolizer (PM)].

RESULTS

Using a mechanistic approach to reinterpret the published findings of steady-state TDM and single-dosing pharmacokinetic studies, 4 different serum clobazam concentration ratios were studied. The available limited steady-state TDM data suggest that the serum N-desmethylclobazam/clobazam ratio can be useful for clinicians, including identifying CYP2C19 PMs (ratio >25 in the absence of inhibitors). There are 3 possible concentration/dose (C/D) ratios. The clobazam C/D ratio has the potential to measure the contribution of CYP3A4 activity to the clearance of clobazam from the body. The N-desmethylclobazam C/D ratio does not seem to be a good measure of clobazam clearance and should be substituted with the total (clobazam + N-desmethylclobazam) C/D ratio.

CONCLUSIONS

Future clobazam TDM studies need to use trough concentrations after steady state has been reached (>3 weeks in normal individuals and several months in CYP2C19 PMs). These future studies need to explore the potential of clobazam and total C/D ratios. Better studies on the relative potency of N-desmethylclobazam compared with the parent compound are needed to provide weighted total serum concentrations that correct for the possible lower N-desmethylclobazam pharmacodynamic activity. Standardization and more studies of C/D ratios from clobazam and other drugs can be helpful to move TDM forward.

Safe Treatment of Seizures in the Setting of HIV/AIDS

OPINION STATEMENT

HIV(+) patients are at increased risk for developing seizures due to the vulnerability of the central nervous system to HIV-associated diseases, immune dysfunction, and metabolic disturbances. In patients with acute seizures, standard protocols still apply with urgent seizure cessation being the priority. Management of the person with established epilepsy who contracts HIV is challenging, but the decision to initiate chronic antiepileptic drug (AED) therapy in an HIV(+) patient is also difficult. Chronic treatment guidelines emphasize the interactions between AEDs and antiretroviral (ARV) medications, but provide no explicit advice regarding when to initiate an AED, what medication to select, and/or the duration of treatment. Epidemiologic data regarding seizure recurrence risk in HIV(+) individuals is not available. The risk of further seizures likely depends upon the underlying etiology for the seizure(s) and patients' immune status and may be increased by the use of efavirenz (an ARV). The issues for consideration include AED-ARV interactions, organ dysfunction, seizure type, and drug side effects, which may worsen or be confused with symptoms of HIV and/or epilepsy. Co-administration of enzyme inducing (EI)-AEDs and ARVs can result in virological failure, breakthrough seizure activity, AED toxicity, and/or ARV toxicity. Where available, the AED of choice in HIV(+) patients is levetiracetam due to its broad spectrum activity, ease of use, minimal drug interactions, and favorable side effect profile. Lacosamide, gabapentin, and pregabalin are also favored choices in patients with partial onset seizures and/or those failing levetiracetam. Where newer AEDs are not available, valproic acid may be the treatment of choice in terms of an AED, which will not cause enzyme induction-associated ARV failure, but its side effect profile causes other obvious problems. In resource-limited settings (RLS) where only EI-AEDs are available, there are no good treatment options and further pressure needs to be placed upon policymakers to address this care gap and public health threat.