Add-On Cannabidiol Reduces Seizure Frequency in Treatment-Refractory Epilepsy

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Countable seizure types were recorded in parents' and caregivers' clinical diaries during a 4-week baseline period.

The addition of cannabidiol (CBD) to a routine antiepileptic drug regimen is a favorable and effective treatment option for patients with treatment‐resistant epilepsies, according to results of an interim analysis of an expanded-access program (EAP) published in Epilepsia.

A total of 25 EAP centers that enrolled patients being treated with antiepileptic drugs who had treatment‐resistant epilepsies were included in the interim analysis. In the safety assessment, 607 patients were enrolled. Countable seizure types were recorded in parents’ and caregivers’ clinical diaries during a 4-week baseline period. Investigators administered a 2 to 10 mg/kg/day dose of oral CBD titrated to a 25 to 50 mg/kg/day maximum dose.

Patients visited the study center every 2 to 4 weeks through 16 weeks, followed by every 2 to 12 weeks after the first 16-week study period. In addition to safety, the investigators assessed the efficacy of add-on CBD. Efficacy was defined as the percentage change from baseline in the median monthly convulsive and total seizure frequency as well as the percentage of patients with seizure reductions of ≥50%, ≥75%, and 100% compared with baseline.

In the cohort, the median dose of CBD received was 25 mg/kg/day, and the median duration of study treatment was 48 weeks. The study investigators observed a 51% reduction in median monthly convulsive seizures and a 48% reduction in total seizures at 12 weeks in patients receiving add-on CBD. At 12 weeks, the proportion of patients with convulsive seizure reductions of ≥50%, ≥75%, and 100% were 52%, 31%, and 11%, respectively. The most frequent adverse events in the cohort included diarrhea (29%) and somnolence (22%); however, the treatment was generally well tolerated.

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The lack of a placebo group as well as the lack of data on the reasoning behind treatment dose reductions represent primary limitations of the analysis.

Findings from the study of EAPs offer greater insight into “the long‐term treatment effect of CBD that support the recent evidence from rigorous, double‐blind, placebo‐controlled trials showing meaningful reductions in seizure frequency for patients who received add‐on CBD vs placebo.”


Szaflarski JP, Bebin EM, Comi AM, et al. Long‐term safety and treatment effects of cannabidiol in children and adults with treatment‐resistant epilepsies: expanded access program results. Epilepsia. 2018;59:1540-1548.