CBD Reduced Seizures by 45-87% Over Nearly Three Years in Treatment-Resistant Focal Epilepsy

What the researchers found

CBD treatment was associated with median reductions of 51-87% in focal seizures and 44-87% in total seizures in the TSC group, and 46-75% and 45-71% in the non-TSC group, sustained through 144 weeks. Responder rates were similar between groups. Adverse events occurred in 91% of TSC and 96% of non-TSC patients. Median CBD dose was about 23-25 mg/kg/day.

Why it matters

While CBD (Epidiolex) is FDA-approved for certain epilepsy syndromes including TSC, its effectiveness in non-TSC focal epilepsies has been less documented. This study shows sustained long-term benefit across multiple types of focal epilepsy, potentially expanding the clinical applications of CBD.

The numbers in context

N=140 patients. 33 TSC (median age 11.9, range 2-31), 107 non-TSC (median age 17.8, range 2-73). Non-TSC subtypes: cortical dysplasia 14%, frontal lobe 10%, cortical malformation 9%. CBD dose: TSC 25 mg/kg/day, non-TSC 23 mg/kg/day. Seizure reduction sustained through 144 weeks. AEs: 91% TSC, 96% non-TSC.

How the study worked

Open-label expanded access program following 140 patients with treatment-resistant focal epilepsies (33 with TSC, 107 with other focal epilepsies) receiving plant-derived CBD (Epidiolex) at doses up to 25-50 mg/kg/day for up to 144 weeks.

What this study cannot tell us

Open-label study without placebo control, so the magnitude of benefit may be overestimated. Expanded access population may have different characteristics than typical patients. High adverse event rates, though many AEs may be related to concomitant medications. Dropout over 144 weeks may create survivorship bias.

How to read the evidence

Moderate evidence from a long-term open-label expanded access program with a reasonable sample size, though limited by the lack of placebo control.

When this study was published

2025 analysis of long-term data from the CBD Expanded Access Program.

The bigger picture

This long-term data strengthens the case for CBD as a treatment option beyond its currently approved epilepsy indications. The similar effectiveness across different focal epilepsy types suggests the anticonvulsant mechanism may be broadly applicable rather than specific to certain epilepsy syndromes.

Questions still open

• Would randomized controlled trials confirm these results in non-TSC focal epilepsies? What is the optimal long-term dose? How does CBD compare to or complement other anti-seizure medications for focal epilepsies? What drives the high adverse event rate?

Common questions

Read the original research

Long-term efficacy and safety of cannabidiol in patients with treatment-resistant focal epilepsies treated in the Expanded Access Program.

Epilepsia, 66(10), 3730-3740

Citation

Patel, Anup D; Szaflarski, Jerzy P; Lyons, Paul D; Boffa, Michael; Greco, Teresa; Saurer, Timothy B; Rajasekaran, Karthik; Simontacchi, Kelly C; Thiele, Elizabeth A. (2025). Long-term efficacy and safety of cannabidiol in patients with treatment-resistant focal epilepsies treated in the Expanded Access Program.. Epilepsia, 66(10), 3730-3740. https://doi.org/10.1111/epi.18496

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