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.

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.

Drug-metabolism mechanism: Knowledge-based population pharmacokinetic approach for characterizing clobazam drug-drug interactions.

A metabolic mechanism-based characterization of antiepileptic drug-drug interactions (DDIs) with clobazam in patients with Lennox-Gastaut syndrome (LGS) was performed using a population pharmacokinetic (PPK) approach. To characterize potential DDIs with clobazam, pharmacokinetic (PK) data from 153 patients with LGS in study OV-1012 (NCT00518713) and 18 healthy participants in bioavailability study OV-1017 were pooled. Antiepileptic drugs (AEDs) were grouped based on their effects on the cytochrome P450 (CYP) isozymes responsible for the metabolism of clobazam and its metabolite, N-desmethylclobazam (N-CLB): CYP3A inducers (phenobarbital, phenytoin, and carbamazepine), CYP2C19 inducers (valproic acid, phenobarbital, phenytoin, and carbamazepine), or CYP2C19 inhibitors (felbamate, oxcarbazepine). CYP3A4 inducers-which did not affect the oral clearance of clobazam-significantly increased the formation of N-CLB by 9.4%, while CYP2C19 inducers significantly increased the apparent elimination rate of N-CLB by 10.5%, resulting in a negligible net change in the PK of the active metabolite. CYP2C19 inhibitors did not affect N-CLB elimination. Because concomitant use of AEDs that are either CYP450 inhibitors or inducers with clobazam in the treatment of LGS patients had negligible to no effect on clobazam PK in this study, dosage adjustments may not be required for clobazam in the presence of the AEDs investigated here.

Role of P-glycoprotein in refractoriness of seizures to antiepileptic drugs in Lennox-Gastaut syndrome.

Mechanism of seizure refractoriness to antiepileptic drugs in children with Lennox-Gastaut syndrome is not known. Efflux of antiepileptic drugs due to increased expression/function of P-glycoprotein, a multidrug efflux transporter protein on the cell surface is a proposed mechanism. The authors studied the expression/function of P-glycoprotein on peripheral blood mononuclear cells of 29 children with Lennox-Gastaut syndrome, 23 children with other epilepsies, and 19 healthy children. The authors found a higher P-glycoprotein expression/function in Lennox-Gastaut syndrome, a higher percent positive cells as compared to children with other epilepsy (P < 0.001) and to healthy controls (P = 0.012), higher P-glycoprotein expression as compared to healthy controls (P = 0.003), a higher total P-glycoprotein expression (relative florescence intensity × percent positive cells) as compared to children with other epilepsies (P < 0.001) and healthy controls (P < 0.001), and a higher P-glycoprotein function as compared to children with other epilepsies (P = 0.001) and healthy controls (P = 0.002). These findings may explain seizure refractoriness to anti-epileptic drugs in Lennox-Gastaut syndome.