Literature Review

Long-Term Data Suggest Benefits of Adjunctive CBD in Treatment-Resistant Epilepsies

The drug promotes sustained reductions in seizure frequency and contributes to seizure freedom for some patients.


Pooled data from an expanded-access program provide further evidence that adjunctive cannabidiol (CBD) provides meaningful reductions in seizure frequency in patients with treatment-resistant epilepsies. The data were published in the August issue of Epilepsia.

Studies have recently indicated that adjunctive CBD effectively reduces seizures associated with Lennox-Gastaut syndrome and Dravet syndrome. An expanded-access program was created in January 2014 to offer CBD to patients with treatment-resistant epilepsies. Data on safety, tolerability, and efficacy during the first year of the study have been reported. Jerzy P. Szaflarski, MD, PhD, Professor of Neurology at the University of Alabama at Birmingham, and colleagues examined results for safety outcomes at 144 weeks and efficacy outcomes at 96 weeks.

Jerzy P. Szaflarski, MD, PhD

An Expanded-Access Program

All participants in the program had treatment-resistant epilepsy and were receiving stable doses of antiepileptic drugs (AEDs) for at least four weeks before enrollment. During a four-week baseline period, parents and caregivers kept diaries of all countable seizure types. Participants subsequently received a plant-based oral pharmaceutical formulation of CBD (100 mg/mL). Treatment was initiated at a dose of 2–10 mg/kg/day and was titrated to a maximum dose of 25–50 mg/kg/day.

Patients were examined every two to four weeks until the 16th week, and every two to 12 weeks after that point. The efficacy outcomes included the percentage change from baseline in median monthly convulsive seizure frequency and total seizure frequency, and the percentages of patients with at least 50%, at least 75%, and 100% reductions in seizures, compared with baseline. Investigators documented adverse events at each visit.

CBD Was Well Tolerated

The safety analysis included 607 patients, and the efficacy analysis included 580 patients. Among patients included in the safety analysis, 24% withdrew from the study. The most common reasons for withdrawal were lack of efficacy (15%) and adverse events (5%). Participants’ mean age was 13, and 52% of patients were male. The median number of concomitant AEDs was three, the median dose of CBD was 25 mg/kg/day, and the median treatment duration was 48 weeks.

At 12 weeks, adjunctive CBD was associated with a 51% reduction in median monthly convulsive seizures and a 48% reduction in total seizures. Reductions in these seizure types were similar through 96 weeks. At 12 weeks, 52% of patients had a reduction in convulsive seizures of at least 50%, 31% had a reduction of at least 75%, and 11% had a 100% reduction. These response rates were similar through 96 weeks of treatment.

CBD was generally well tolerated. The most common adverse events were diarrhea (29%) and somnolence (22%). About 10% of patients had abnormal liver adverse events, and 75% of them were taking valproate. Among patients taking concomitant clobazam, 38% had somnolence, compared with 14% of patients not taking concomitant clobazam.

The expanded-access program is not placebo-controlled, and neither patients nor investigators are blinded. Furthermore, reporting methods varied between study sites. Despite these limitations, the data indicate that adjunctive CBD significantly reduces seizure frequency, according to the authors.

The data support the results of double-blind, placebo-controlled trials that found that add-on CBD reduces seizure frequency, compared with placebo. The FDA in June approved Epidiolex, the formulation of CBD used in the expanded-access program, for the treatment of seizures associated with Dravet syndrome and Lennox-Gastaut syndrome.

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