CBD is approved for three epilepsy syndromes, but drug interactions complicate interpreting trial results | Research

The takeaway

CBD has been approved for Dravet syndrome, Lennox-Gastaut syndrome, and tuberous sclerosis complex based on multiple RCTs, but its interaction with clobazam (raising levels of the active metabolite N-desmethylclobazam) complicates interpreting how much of the benefit comes from CBD itself.

Neurologists, epileptologists, pharmacists managing CBD therapy, clinical trial designers

CBD prominently raises N-desmethylclobazam levels, complicating efficacy interpretation

What the researchers found

Pharmaceutical-grade CBD has been approved for seizures in Dravet syndrome, Lennox-Gastaut syndrome, and tuberous sclerosis complex based on multiple randomized placebo-controlled trials. However, CBD prominently increases plasma levels of N-desmethylclobazam (the active metabolite of clobazam), a commonly co-prescribed medication, making it difficult to separate CBD's independent antiseizure effects from those mediated through this drug interaction.

Why it matters

CBD is one of the few cannabis-derived medicines with regulatory approval for specific conditions. Understanding the clobazam interaction is critical for clinicians to properly attribute treatment effects and manage combination therapy.

The numbers in context

Approved for 3 epilepsy syndromes (Dravet, Lennox-Gastaut, tuberous sclerosis complex); multiple mechanisms including GPR antagonism, TRPV1 desensitization, adenosine signaling, GABA enhancement; prominent increase in N-desmethylclobazam levels in co-treated patients

How the study worked

Comprehensive narrative review of CBD's mechanisms of action, pharmacokinetics, clinical trial evidence, drug interactions, and remaining knowledge gaps in epilepsy treatment.

What this study cannot tell us

Narrative rather than systematic review. Cannot quantify the independent contribution of CBD versus the clobazam interaction effect. Oral bioavailability is low and variable. Limited pharmacokinetic data in infants and young children.

How to read the evidence

Comprehensive review of strong clinical trial evidence, though the clobazam interaction creates an unresolved confound in the evidence base.

When this study was published

Published in 2021.

The bigger picture

The clobazam interaction raises a fundamental question in cannabis pharmacology: when a compound interacts with co-prescribed drugs, how do you separate its direct effects from those amplified through drug interactions? This has implications for dosing, attribution of benefit, and future trial design.

Questions still open

How large is CBD's antiseizure effect independent of the clobazam interaction? Would CBD monotherapy trials resolve this question? What are the optimal plasma concentrations for seizure control?

Common questions

Is CBD effective for epilepsy?

CBD has regulatory approval for seizures in Dravet syndrome, Lennox-Gastaut syndrome, and tuberous sclerosis complex based on randomized controlled trials. However, part of the observed benefit may be mediated through CBD boosting levels of co-prescribed clobazam rather than direct antiseizure action.

What is the clobazam interaction?

CBD inhibits the enzyme that breaks down N-desmethylclobazam (the active metabolite of clobazam, a commonly co-prescribed anti-epileptic). This raises levels of the metabolite, potentially amplifying clobazam's effects. This makes it hard to know how much seizure reduction comes from CBD directly versus enhanced clobazam exposure.

Read the original research

Cannabidiol in the treatment of epilepsy: Current evidence and perspectives for further research.

Neuropharmacology, 185, 108442

View on PubMed ↗Publisher’s paper ↗

Citation

Franco, Valentina; Bialer, Meir; Perucca, Emilio. (2021). Cannabidiol in the treatment of epilepsy: Current evidence and perspectives for further research.. Neuropharmacology, 185, 108442. https://doi.org/10.1016/j.neuropharm.2020.108442