CBD does have independent anti-seizure effects, though clobazam interaction boosts them | Research

The takeaway

Meta-analysis of pivotal CBD trials found that seizure improvement was greater when CBD was added to clobazam, but CBD also significantly reduced seizures in patients not taking clobazam, supporting independent anti-seizure effects.

Neurologists prescribing Epidiolex, epilepsy researchers, and regulatory scientists.

CBD reduces seizures even without clobazam

What the researchers found

47-68% of CBD trial patients were taking clobazam, which shows complex interactions with CBD (3.4-5 fold norclobazam increase). Seizure improvement was greater when CBD was added to clobazam vs other medications. However, seizure control was also improved in patients not on clobazam, and was statistically significant for the 10 mg/kg/d dose in one LGS trial. Meta-analyses of pooled LGS and DS patients not on clobazam provided stronger evidence of independent CBD anti-seizure effects.

Why it matters

This addresses the critical question of whether CBD is truly anti-epileptic or merely boosting clobazam levels, concluding that both mechanisms contribute.

The numbers in context

4 pivotal RCTs. 47-68% on clobazam. Norclobazam increase: 3.4-5 fold. Independent effect significant at 10 mg/kg/d in one LGS trial. Meta-analysis of non-clobazam patients showed significant benefit.

How the study worked

Appraisal of four pivotal randomized placebo-controlled CBD trials (Dravet and Lennox-Gastaut syndromes), using subgroup analyses from the European Medicines Agency Public Assessment Report.

What this study cannot tell us

Subgroup analyses were not pre-specified. Small numbers in non-clobazam subgroups. Meta-analysis of subgroups has inherent limitations.

How to read the evidence

Meta-analysis of pivotal RCTs with subgroup analyses, the strongest available evidence despite methodological caveats.

When this study was published

2020 analysis of pivotal trial data.

The bigger picture

This analysis provides the most nuanced assessment to date: CBD has independent anti-seizure effects, but its interaction with clobazam amplifies both the benefits and the side effects.

Questions still open

Should CBD dosing be different for patients on vs off clobazam? Would CBD be FDA-approved if the clobazam interaction were fully accounted for?

Common questions

Does CBD work for seizures on its own?

This meta-analysis found CBD does reduce seizures independently of its interaction with clobazam, though the effect is greater when both drugs are used together.

How does CBD interact with clobazam for epilepsy?

CBD increases levels of clobazam's active metabolite 3.4-5 fold, amplifying both seizure reduction and side effects. This interaction contributes to but does not fully explain CBD's anti-seizure effects.

Read the original research

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

Epilepsia, 61(6), 1082-1089

View on PubMed ↗Publisher’s paper ↗

Citation

Bialer, Meir; Perucca, Emilio. (2020). Does cannabidiol have antiseizure activity independent of its interactions with clobazam? An appraisal of the evidence from randomized controlled trials.. Epilepsia, 61(6), 1082-1089. https://doi.org/10.1111/epi.16542