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Randomised controlled trials show that purified pharmaceutical CBD (Epidiolex) reduces seizures in Dravet and Lennox-Gastaut syndromes, approved by the FDA in 2018; retail CBD oils are not equivalent. This is the strongest single evidence base in cannabis medicine, and it is specific.
What the research says
Randomised controlled trials showed that a purified, pharmaceutical CBD (Epidiolex) significantly reduces seizures in Dravet syndrome and Lennox-Gastaut syndrome, two severe childhood epilepsies. The FDA approved it in 2018, and added tuberous sclerosis complex in 2020.
This is not the same as shop CBD
The approved medicine is a high, precisely dosed, pharmaceutical-grade CBD given under medical supervision. Over-the-counter CBD oils are not equivalent, are not dosed for epilepsy, and should never replace prescribed anti-seizure treatment.
This distinction matters more here than almost anywhere else in cannabis.
At a glance
What to be careful about
Prescription CBD interacts with other anti-seizure drugs (notably clobazam) and can affect liver enzymes, so it is monitored by specialists. Never adjust epilepsy treatment based on general information.
Continue exploring
Phase 3 Clinical Trial Dosing (10-25 mg/kg/day), GPR55 Antagonism, and CYP2C19 Clobazam Interactions
In pivotal Phase 3 randomized controlled trials, pharmaceutical oral cannabidiol solution (Epidiolex/Epidyolex, 100 mg/mL in sesame oil) titrated to 10-20 mg/kg/day reduced median monthly convulsive seizure frequency by 38.9% in Dravet syndrome (Devinsky et al., 2017, PubMed PMID 28538134) and reduced drop seizures by 43.9% in Lennox-Gastaut syndrome (Thiele et al., 2018, PubMed PMID 29395273), with efficacy up to 25 mg/kg/day in tuberous sclerosis complex (Thiele et al., 2021, PubMed PMID 33346789). Unlike THC, CBD exerts anticonvulsant activity via non-CB1 pathways including GPR55 antagonism, TRPV1 desensitization, and equilibrative nucleoside transporter 1 (ENT1) adenosine reuptake inhibition. Clinically, CBD strongly inhibits hepatic cytochrome P450 2C19 (CYP2C19), increasing plasma concentrations of the active clobazam metabolite N-desmethylclobazam by up to 3-fold and requiring serum transaminase (ALT/AST) monitoring, especially in patients co-prescribed valproate (Geffrey et al., 2015, PubMed PMID 26114620).
Frequently asked questions
Which epilepsy syndromes is prescription cannabidiol (Epidiolex/Epidyolex) approved to treat?
Purified pharmaceutical cannabidiol is approved by the FDA and EMA as an adjunctive treatment for seizures associated with Dravet syndrome, Lennox-Gastaut syndrome, and tuberous sclerosis complex (TSC).
How does prescription CBD interact with clobazam and valproate?
CBD inhibits the hepatic enzyme CYP2C19, which can triple blood levels of the active clobazam metabolite N-desmethylclobazam (causing sedation), and co-administration with valproate increases the risk of elevated liver transaminases (ALT/AST).
Can over-the-counter retail CBD oil replace prescribed anti-seizure medication?
No. Retail CBD oils lack standardized pharmaceutical dosing (10-25 mg/kg/day), purity verification, and clinical hepatic monitoring, and must never replace prescribed anti-seizure medications.
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