A Phase 2, Double-Blind, Placebo-Controlled Trial to Investigate Potential Drug-Drug Interactions Between Cannabidiol and Clobazam.

We investigated the effects of cannabidiol (CBD; 21-day maintenance dose) on the pharmacokinetics (PK) of clobazam (CLB) and monitored the safety of CBD (or placebo) plus CLB in 20 patients with uncontrolled epilepsy on stable doses of CLB. Blood samples collected until 24 hours postdose were evaluated by liquid chromatography tandem mass spectrometry. PK parameters of CLB and major metabolite N-desmethylclobazam (N-CLB), valproic acid, stiripentol, levetiracetam, topiramate, plant-derived highly purified CBD (Epidiolex in the United States; 100 mg/mL oral solution) and its major metabolites were derived using noncompartmental analysis. There was no evidence of a drug-drug interaction (DDI) between CBD and CLB: geometric mean ratio (GMR) of day 33:day 1 CLB was 1.0 (90%CI, 0.8-1.2) for Cmax and 1.1 (90%CI, 0.9-1.2) for AUCtau . There was a significant DDI between CBD and N-CLB: the GMR of day 33:day 1 N-CLB was 2.2 (90%CI, 1.4-3.5) for Cmax and 2.6 (90%CI, 2.0-3.6) for AUCtau . Placebo had no effect on CLB or N-CLB; CBD had no effect on levetiracetam. Data were insufficient regarding DDIs with other antiepileptic drugs. The safety profile of CBD (20 mg/kg/day) with CLB was acceptable; all but 1 adverse events (AEs) were mild or moderate. One serious AE (seizure cluster) led to CBD discontinuation. One patient withdrew after intolerable AEs. Although there was no evidence of a CBD and CLB DDI, there was a significant DDI between CBD and N-CLB. The safety profile of GW Pharmaceuticals' CBD formulation with CLB was consistent with other GW-sponsored trials.

Pharmacokinetic Variability During Long-Term Therapeutic Drug Monitoring of Valproate, Clobazam, and Levetiracetam in Patients With Dravet Syndrome.

BACKGROUND: The use of therapeutic drug monitoring (TDM) for antiseizure medications (ASMs) may contribute to treatment optimization in individual patients. This study included patients with Dravet syndrome as they often require close monitoring because of polypharmacy with various ASMs. The aim was to use long-term TDM to investigate pharmacokinetic variability of ASMs in these patients. METHODS: Retrospective data from patients with Dravet syndrome were collected from the TDM database at the Section for Clinical Pharmacology, National Center for Epilepsy in Norway (2008-2018). Concentration/(dose/kg)ratios (C/D ratios) were calculated for the ASMs and the concentration (C/C ratio) for N-desmethylclobazam. In patients with at least 3 measurements, the CV for C/D ratios for intrapatient and interpatient variability was calculated. RESULTS: Fifty-three patients (30 male patients/23 female patients) between 2 and 50 years of age (mean, 16 years) were included. Pharmacokinetic variability of the total number of measurements of valproate (n = 417), clobazam and N-desmethylclobazam (n = 328), and levetiracetam (n = 238) was determined. Interpatient variability was more pronounced than intrapatient variability (coefficient of variations: valproate, 65% vs. 24%; levetiracetam, 71% vs. 27%; and clobazam/N-desmethylclobazam, 47%/77% vs. 35%/55%) (P < 0.01). Comedication with stiripentol (n = 16) increased the C/D ratio of valproate by 63% and of clobazam by 133% and the C/C ratio of N-desmethylclobazam/clobazam by 104% (P < 0.05). Younger age also contributed to pharmacokinetic variability. CONCLUSIONS: Long-term TDM revealed extensive variability in serum concentrations over time; the variability was lowest for levetiracetam, moderate for valproate, and highest for clobazam. Pharmacokinetic variability and interactions can thus be identified and adjusted to facilitate decision making to achieve the optimal treatment outcome.

Cannabidiol efficacy and clobazam status: A systematic review and meta-analysis.

OBJECTIVE: To evaluate the potential impact of concomitant clobazam (CLB) use on the efficacy of cannabidiol (CBD) treatment in patients with Dravet syndrome and Lennox-Gastaut syndrome using meta-analytical techniques. METHODS: We searched for randomized, placebo-controlled, single- or double-blinded trials. The proportion of patients who achieved ≥50% reduction from baseline in seizure frequency during the treatment period was assessed according to CLB status. Risk ratios (RRs) with 95% confidence intervals (CIs) were estimated. RESULTS: Four trials were included and enrolled 714 participants, 429 for the add-on CBD group and 285 for the add-on placebo group. Among CBD-treated patients, 240 (55.9%) were taking concomitant CLB (CLB-On) and 189 (44.1%) were not taking concomitant CLB (CLB-Off); in placebo-treated patients, 158 (55.4%) were CLB-On and 127 (44.6%) CLB-Off. The percentages of patients who had at least 50% reduction in seizure frequency during the treatment period were 29.1% in the CBD arm and 15.7% in the placebo group among CLB-Off patients (RR = 1.80, 95% CI = 1.12-2.90, P = .015). Among CBL-On patients, the ≥50% reduction in seizure frequency was found in 52.9% and 27.8% in the CBD and placebo groups, respectively (RR = 1.85, 95% CI = 1.40-2.44, P < .001). SIGNIFICANCE: CBD was associated with a higher rate of seizure response in comparison to placebo when added to the existing antiepileptic regimen both in patients taking and in those not taking concomitant CLB. The lack of randomization for CLB status and the limited sample size need to be considered in the interpretation of the findings.

Does cannabidiol have antiseizure activity independent of its interactions with clobazam? An appraisal of the evidence from randomized controlled trials.

Four pivotal randomized placebo-controlled trials have demonstrated that adjunctive therapy with cannabidiol (CBD) improves seizure control in patients with Dravet syndrome (DS) and Lennox-Gastaut syndrome (LGS). Between 47% and 68% of patients allocated to CBD treatment in these trials were receiving clobazam (CLB), which shows complex interactions with CBD resulting, in particular, in a 3.4- to 5-fold increase in plasma concentration of the active metabolite norclobazam. This raises concern as to the role played by these interactions in determining the reduction in seizure frequency in CBD-treated patients, and the question of whether CBD per se has clinically evident antiseizure effects. We appraised available evidence on the clinical consequences of the CBD-CLB interaction, focusing on subgroup analyses of seizure outcomes in patients on and off CLB comedication in the pivotal CBD trials, as provided by the European Medicines Agency Public Assessment Report. Evaluation of the results of individual trials clearly showed that improvement in seizure control over placebo was greater when CBD was added on to CLB than when it was added on to other medications. However, seizure control was also improved in patients off CLB, and despite the small sample size the difference vs placebo was statistically significant for the 10 mg/kg/d dose in one of the two LGS trials. Stronger evidence for an antiseizure effect of CBD independent of an interaction with CLB emerges from meta-analyses of seizure outcomes in the pooled population of LGS and DS patients not receiving CLB comedication. Although these results need to be interpreted taking into account methodological limitations, they provide the best clinical evidence to date that CBD exerts therapeutic effects in patients with epilepsy that are independent of its interaction with CLB. Greater antiseizure effects, and a greater burden of adverse effects, are observed when CBD is combined with CLB.

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.

Protein precipitation method for determination of clobazam and N-desmethylclobazam in human plasma by LC-MS/MS.

A protein precipitation method for the determination of clobazam (CLB) and its major active metabolite N-desmethylclobazam (N-CLB) in human plasma by liquid chromatography tandem mass spectrometry (LC-MS/MS) was established. CLB and N-CLB were extracted from human plasma samples by protein precipitation with methanol. Analyte separation was done using a Phenomenex Kinetex™ Biphenyl (50 × 2.1 mm, 1.7 µm) column using isocratic elution with a mobile phase of 5 mm ammonium formate with 0.01% ammonium hydroxide (40%) and methanol (60%) at a flow rate of 0.4 mL/min and an injection volume of 10 µL. The detection was performed on a triple quadrupole mass spectrometer in multiple reaction monitoring mode to monitor the precursor-to-product ion transitions of m/z 301.1 → 259.0, 306.0 → 263.9 for CLB and CLB-D5 and 287.0 → 245.0, 292.0 → 250.0 for N-CLB and N-CLB-D5 in positive electrospray ionization mode, respectively. The method was validated over a concentration range of 2.0-750 ng/mL for CLB and 0.7-200 ng/mL for N-CLB on SCIEX Triple Quad 4500 MS System. Total run time was 5 min. This method has been designed for bioequivalence study for formulations containing 20 mg of CLB.

Drug-drug interactions and pharmacodynamics of concomitant clobazam and cannabidiol or stiripentol in refractory seizures.

OBJECTIVE: The goal of this study was to characterize the drug-drug interactions between clobazam and 2 antiseizure drugs, cannabidiol and stiripentol, for treatment of refractory seizures through the use of pharmacokinetic modeling. METHODS: A population pharmacokinetic/pharmacodynamic model was developed to characterize the combined effect of clobazam and its active metabolite, N-desmethylclobazam (i.e., N-clobazam), on seizure protection in patients with Lennox-Gastaut syndrome using data from the phase 3 CONTAIN trial. Drug-drug interactions between clobazam and cannabidiol were examined by comparing model-generated data to data from a study of 13 patients taking concomitant clobazam and cannabidiol. Modeling data were also descriptively compared with studies of patients administered both clobazam and stiripentol. Sedation-related adverse events from CONTAIN were analyzed to determine the exposure-somnolence relationship of clobazam. RESULTS: Exposure-efficacy analysis from the pharmacokinetic/pharmacodynamic model using CONTAIN data indicated that clobazam (half-maximal effective concentration [EC50], 303 ng/mL) was 3 times more potent than N-clobazam (EC50, 899 ng/mL). After administration of clobazam, when both clobazam and N-clobazam concentrations were each 1 to 2 times the EC50 value (clobazam dose, 20 mg), 70.0%-74.9% seizure protection was predicted; when concentrations were >2 times the EC50 value (clobazam dose, 40 mg), 74.0%-96.9% seizure protection was predicted. Generalized additive model analyses demonstrated decreased seizure probability with higher plasma concentration of clobazam. Coadministration of stiripentol and clobazam resulted in increased respective median plasma concentrations of clobazam and N-clobazam (1.1-1.2 times and 5.2-8.2 times) compared with administration of placebo and clobazam. Probability of somnolence significantly increased with age and higher N-clobazam plasma concentration. SIGNIFICANCE: Awareness of drug-drug interactions between clobazam and cannabidiol is needed when adding cannabidiol or stiripentol to a regimen of clobazam or vice versa. Based upon our population pharmacokinetic/pharmacodynamic model, we predict that an increase in N-clobazam levels, which patient data show may enhance efficacy and/or make adverse events such as somnolence more likely.

A Phase 1, Open-Label, Pharmacokinetic Trial to Investigate Possible Drug-Drug Interactions Between Clobazam, Stiripentol, or Valproate and Cannabidiol in Healthy Subjects.

GW Pharmaceuticals' formulation of highly purified cannabidiol oral solution is approved in the United States for seizures associated with Lennox-Gastaut and Dravet syndromes in patients aged ≥2 years, for which clobazam, stiripentol, and valproate are commonly used antiepileptic drugs. This open-label, fixed-sequence, drug-drug interaction, healthy volunteer trial investigated the impact of cannabidiol on steady-state pharmacokinetics of clobazam (and N-desmethylclobazam), stiripentol, and valproate; the reciprocal effect of clobazam, stiripentol, and valproate on cannabidiol and its major metabolites (7-hydroxy-cannabidiol [7-OH-CBD] and 7-carboxy-cannabidiol [7-COOH-CBD]); and cannabidiol safety and tolerability when coadministered with each antiepileptic drug. Concomitant cannabidiol had little effect on clobazam exposure (maximum concentration [Cmax ] and area under the concentration-time curve [AUC], 1.2-fold), N-desmethylclobazam exposure increased (Cmax and AUC, 3.4-fold), stiripentol exposure increased slightly (Cmax , 1.3-fold; AUC, 1.6-fold), while no clinically relevant effect on valproate exposure was observed. Concomitant clobazam with cannabidiol increased 7-OH-CBD exposure (Cmax , 1.7-fold; AUC, 1.5-fold), without notable 7-COOH-CBD or cannabidiol increases. Stiripentol decreased 7-OH-CBD exposure by 29% and 7-COOH-CBD exposure by 13%. There was no effect of valproate on cannabidiol or its metabolites. Cannabidiol was moderately well tolerated, with similar incidences of adverse events reported when coadministered with clobazam, stiripentol, or valproate. There were no deaths, serious adverse events, pregnancies, or other clinically significant safety findings.

Clinical consequences related to a defective elimination of clobazam caused by homozygous mutated CYP2C19 allele.

Introduction: Voluntary drug intoxication with benzodiazepines is common and in most cases without consequences. We report an interesting case of voluntary drug intoxication with clobazam (CLB) in a patient with a homozygous mutated CYP2C19 genotype. Case report: A 63-year-old Caucasian man was admitted to an intensive care unit for voluntary drug intoxication with CLB (1200 mg) complicated by prolonged hospitalization (46 days). The levels of CLB and N-desmethylclobazam (NCLB) in plasma were initially 8.3 and 14.8 mg/L. The persistence of a high concentration of NCLB (14.3 mg/L on day 30) suggested a lack of elimination. A homozygous mutated allele of CYP2C19*2 without enzyme activity was discovered. To overcome this phenotype, NCLB metabolism was induced by administering 100 mg of phenobarbital for 10 days, allowing patient improvement. Discussion: NCLB is the major active metabolite of CLB with a longer half-life and much higher steady-state plasma concentrations compared to the parent drug. The half-life elimination of CLB is 18 h that of NCLB is between 40 and 50 h. However, there is considerable inter-individual variation in the metabolism of CLB and of the report NCLB/CLB under the dependence of genotype of CYP2C19. These polymorphisms are not generally well-known by physicians and may lead to severe poisoning.

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.