Cannabis and Epilepsy: CBD, Epidiolex, and the State of Research
Epilepsy was one of the first breakthroughs for medical cannabis in modern medicine — and the area where the scientific evidence is strongest. With Epidiolex (pure CBD), the first cannabis-based medication was approved by the FDA and EMA for the treatment of certain forms of epilepsy. What this milestone means, how CBD affects seizures, and who it applies to.
Epidiolex: The first approved cannabis medication worldwide
The story begins with desperate parents and the case of Charlotte Figi:
- Charlotte Figi (2006–2020): Patient with Dravet syndrome with over 300 seizures per week. Completely treatment-resistant to conventional antiepileptic drugs. Parents started CBD oil treatment in 2012 — seizure frequency dropped to under 5 per month. This story became known worldwide and drove research forward
- Epidiolex (GW Pharmaceuticals): Pharmaceutical-grade pure CBD (99%+ purity, in sesame oil). FDA approval: 2018 (USA). EMA approval as Epidyolex: 2019 (EU)
- Approved indications:
- Dravet syndrome (severe myoclonic epilepsy of childhood) — from 2 years of age
- Lennox-Gastaut syndrome (severe pediatric epilepsy syndrome) — from 2 years of age
- Tuberous Sclerosis Complex (TSC) — FDA addition 2020
- In Germany: Epidyolex is prescription-only in Germany. Statutory health insurance (GKV) reimbursement is usually available for approved indications — consultation with the health insurance provider is necessary
Mechanism of action: How CBD reduces seizures
The exact mechanism is not yet fully understood, but several pathways are established:
- GPR55 antagonism: GPR55 is an “orphan receptor” that can be overactive in epilepsy. CBD blocks GPR55 and thereby reduces neuronal excitability
- TRPV1 modulation: CBD activates TRPV1 channels (capsaicin receptor) — which paradoxically has an inhibitory effect on excessive neuronal activity
- GABA Enhancement: CBD indirectly modulates GABAergic transmission — GABA is the most important inhibitory neurotransmitter. More GABA activity = less seizure readiness
- Anandamide Increase: CBD inhibits FAAH (the enzyme that breaks down anandamide) — higher endogenous endocannabinoid levels have antiepileptic effects
- Sodium Channel Blockade: At high concentrations, CBD inhibits sodium channels — similar to classical antiepileptics (phenytoin, carbamazepine)
- Not via CB1: The antiepileptic effect of CBD does not primarily act through CB1 — therefore, no psychoactive high and no tolerance issues as with THC
Clinical Study Results
The studies on Epidiolex are the strongest evidence in medical cannabis:
- Dravet Syndrome (Devinsky 2017, NEJM): Randomized, placebo-controlled study. CBD reduced convulsive seizure frequency by 39% vs. 13% placebo. 5% of patients became seizure-free (placebo: 0%). Statistically significant, p<0.001
- Lennox-Gastaut (Thiele 2018, Lancet): Drop seizure reduction with CBD 43% vs. 21% placebo. Both study groups significant. CBD tested at 10 mg/kg/day and 20 mg/kg/day
- Adverse effects in studies: Elevated liver values (ALT/AST) in 10% — particularly when taken with valproate. Drowsiness, reduced appetite, diarrhea. Reversible after dose adjustment
- Drug interactions: Epidiolex inhibits CYP2C19 and CYP3A4 — interactions with clobazam (often co-medicated), valproate, stiripentol should be considered
THC in epilepsy: caution advised
In contrast to CBD, THC has a more complex profile in epilepsy:
- THC can have antiepileptic effects in low doses (via CB1 in GABAergic interneurons)
- In higher doses or with chronic use, THC can provoke or exacerbate seizures — especially in predisposed individuals
- No THC-containing preparation has epilepsy approval
- For epilepsy patients: only CBD-based therapy under specialist neurological supervision
What applies to patients
- Epidiolex is the only evidence-based CBD therapy for epilepsy — not comparable to OTC CBD oils from the supermarket or drugstore
- Self-medication with CBD oil for epilepsy is dangerous — dosage, purity and interactions require neurological specialist supervision
- For inquiries with the health insurance: Epidyolex is approved, reimbursement by statutory health insurance is usually possible for Dravet and LGS diagnosis
- Off-label: Some neurologists also use CBD for other treatment-resistant forms of epilepsy — no standardized guideline recommendation
How CBD works in the body — detailed mechanisms of action:
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