Meta-analysis of 4 RCTs confirms CBD reduces seizures with and without clobazam co-treatment | Research

The takeaway

A stratified meta-analysis of four large RCTs confirmed CBD (Epidiolex) significantly reduced seizures regardless of clobazam co-use, though the effect was larger with clobazam and certain side effects increased with the combination.

Neurologists prescribing CBD, epilepsy patients, pharmacologists studying drug interactions

CBD reduced seizures vs. placebo both with clobazam (p < .0001) and without (p = .023)

What the researchers found

CBD vs. placebo seizure reduction: treatment ratio 0.59 (p < .0001) with clobazam, 0.85 (p = .0226) without clobazam. 50% responder rate odds ratio: 2.51 (p < .0001) with clobazam, 2.40 (p = .0020) without. Somnolence, rash, pneumonia, and aggression were more common with concomitant clobazam.

Why it matters

A persistent question has been whether CBD's seizure benefit depends on its interaction with clobazam rather than direct anticonvulsant effects. This meta-analysis demonstrates independent efficacy.

The numbers in context

With clobazam: treatment ratio 0.59 (p < .0001), 50% responder OR 2.51. Without clobazam: treatment ratio 0.85 (p = .0226), 50% responder OR 2.40. AEs higher with clobazam for somnolence, rash, pneumonia, aggression.

How the study worked

Stratified meta-analysis of 4 large RCTs (2 Lennox-Gastaut, 2 Dravet syndrome) evaluating CBD 10 and 20 mg/kg/day. Results stratified by clobazam use. Negative binomial regression and logistic regression used. Pharmacokinetic exposure-response analysis included.

What this study cannot tell us

Post-hoc stratified analysis of existing trials, not prospective; the difference in treatment ratios with/without clobazam could reflect a synergistic effect; cannot fully exclude confounding by clobazam indication.

How to read the evidence

Meta-analysis of 4 large, well-designed RCTs with stratified analysis and pharmacokinetic data.

When this study was published

Published in 2020.

The bigger picture

This resolves a critical clinical question: CBD has genuine anticonvulsant effects independent of clobazam, though the combination may provide additional benefit. Clinicians can now confidently prescribe CBD to patients not taking clobazam.

Questions still open

Is there a true synergistic effect between CBD and clobazam? Would patients do better adding clobazam to CBD vs. CBD alone?

Common questions

Does CBD only work because of its interaction with clobazam?

No. This meta-analysis shows CBD significantly reduced seizures even in patients not taking clobazam. The 50% responder rate was similar with or without clobazam (OR 2.51 vs. 2.40), confirming CBD has independent anticonvulsant effects.

Should CBD be combined with clobazam for best results?

The seizure frequency reduction was somewhat larger with clobazam co-treatment, suggesting possible added benefit. However, the combination also increased side effects like somnolence and rash. The decision should weigh individual patient factors.

Read the original research

Cannabidiol efficacy independent of clobazam: Meta-analysis of four randomized controlled trials.

Acta neurologica Scandinavica, 142(6), 531-540

View on PubMed ↗Publisher’s paper ↗

Citation

Devinsky, Orrin; Thiele, Elizabeth A; Wright, Stephen; Checketts, Daniel; Morrison, Gilmour; Dunayevich, Eduardo; Knappertz, Volker. (2020). Cannabidiol efficacy independent of clobazam: Meta-analysis of four randomized controlled trials.. Acta neurologica Scandinavica, 142(6), 531-540. https://doi.org/10.1111/ane.13305