CBD and clobazam work better together through both drug interaction and direct brain effects | Research

The takeaway

CBD enhanced clobazam's anti-seizure effects in a Dravet syndrome mouse model through two distinct mechanisms: increasing clobazam blood levels (pharmacokinetic) and directly enhancing GABA receptor activity together (pharmacodynamic).

Pediatric neurologists prescribing CBD, epilepsy researchers, and pharmacologists studying drug interactions.

Two mechanisms, not just one

What the researchers found

CBD potently inhibited liver enzymes (CYP3A4, CYP2C19) that metabolize clobazam and its metabolite, increasing plasma clobazam levels. However, a sub-anticonvulsant dose of CBD did not improve seizure outcomes despite raising clobazam levels, while an anticonvulsant dose did. This proves the interaction is not purely pharmacokinetic. CBD and clobazam together also enhanced inhibitory GABA receptor activation, revealing a novel pharmacodynamic mechanism.

Why it matters

Critics have suggested CBD's anti-seizure effect in clinical trials was just a side effect of boosting clobazam levels. This study refutes that claim by showing CBD has genuine anticonvulsant activity and a direct pharmacodynamic interaction with clobazam at GABA receptors.

The numbers in context

CBD potently inhibited CYP3A4-mediated clobazam metabolism and CYP2C19-mediated N-desmethylclobazam metabolism. Sub-anticonvulsant CBD dose did NOT improve outcomes despite raising clobazam levels. Anticonvulsant CBD dose improved efficacy against both thermally-induced and spontaneous seizures.

How the study worked

Multi-method preclinical study: in vitro enzyme inhibition assays, mouse pharmacokinetic studies, the Scn1a+/- Dravet syndrome mouse model for seizure testing (thermally induced and spontaneous seizures), and Xenopus oocyte GABA receptor electrophysiology.

What this study cannot tell us

Mouse model of Dravet syndrome, while well-established, may not fully represent human disease. In vitro enzyme and receptor studies may not perfectly predict in vivo interactions. Specific dose translation to humans requires clinical confirmation.

How to read the evidence

Rated moderate because this uses multiple rigorous preclinical methods including a validated genetic model of Dravet syndrome, though human confirmation is still needed.

When this study was published

Published in 2019, after FDA approval of Epidiolex. Understanding the CBD-clobazam interaction remains clinically relevant.

The bigger picture

This study changes how we interpret CBD-clobazam clinical trial data. Rather than CBD being a passive drug interaction, the two compounds appear to have genuine therapeutic synergy through complementary mechanisms at GABA receptors.

Questions still open

Should clobazam doses be specifically adjusted when combined with CBD to optimize the pharmacodynamic synergy? Does this dual mechanism explain why CBD appears more effective in patients already on clobazam? Are there other anti-epileptic drugs that might show similar synergy with CBD?

Common questions

Does CBD really work for seizures or does it just boost other drugs?

Both. This study showed CBD genuinely enhances seizure control through its own anticonvulsant activity AND by boosting clobazam levels. A sub-therapeutic CBD dose raised clobazam levels but did not improve outcomes, proving the effect is not just about drug levels.

How do CBD and clobazam interact in the brain?

They both enhance GABA receptor activity, which is the brain's main inhibitory system. Together, they activate these receptors more than either drug alone, providing a synergistic anti-seizure effect.

Should medication doses be adjusted when using both?

The study confirms CBD increases clobazam blood levels by inhibiting its metabolism. Clinicians typically monitor clobazam levels and adjust doses when adding CBD, but the pharmacodynamic synergy suggests the combination itself has therapeutic value.

Read the original research

Coadministered cannabidiol and clobazam: Preclinical evidence for both pharmacodynamic and pharmacokinetic interactions.

Epilepsia, 60(11), 2224-2234

View on PubMed ↗Publisher’s paper ↗

Citation

Anderson, Lyndsey L; Absalom, Nathan L; Abelev, Sarah V; Low, Ivan K; Doohan, Peter T; Martin, Lewis J; Chebib, Mary; McGregor, Iain S; Arnold, Jonathon C. (2019). Coadministered cannabidiol and clobazam: Preclinical evidence for both pharmacodynamic and pharmacokinetic interactions.. Epilepsia, 60(11), 2224-2234. https://doi.org/10.1111/epi.16355