Purified cannabidiol (CBD) is the only cannabis compound with proven benefit for treatment-resistant epilepsy. The FDA has approved Epidiolex, a prescription CBD oral solution, for seizures linked to Lennox-Gastaut syndrome, Dravet syndrome, and tuberous sclerosis complex. Smoked marijuana, THC-rich products, and unregulated CBD oils do not have the same evidence and can cause harm.
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What treatment-resistant epilepsy means
Treatment-resistant (also called refractory or intractable) epilepsy means seizures continue after two anti-seizure medications have failed to control them. Up to 30% of people with epilepsy fall into this category. At that point, doctors consider other options: surgery, neurostimulation, dietary therapy, and in some cases, prescription CBD.
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What the evidence supports
Evidence supports pharmaceutical-grade CBD, not artisanal or recreational cannabis. The FDA approval rests on randomized controlled trials in three severe childhood-onset epilepsy syndromes. In those trials, CBD reduced seizure frequency by a meaningful amount in some patients, though it is not a cure and not every patient responds.
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Conditions with good evidence
- Dravet syndrome: a rare genetic epilepsy starting in infancy.
- Lennox-Gastaut syndrome: a severe childhood epilepsy with multiple seizure types.
- Tuberous sclerosis complex: a genetic disorder causing tumors in organs, including the brain.
For other epilepsy types, evidence is weak or absent. Some small studies suggest CBD might help, but they are not enough to support routine use.
What does not work
There is no reliable evidence that smoked marijuana, high-THC strains, or over-the-counter CBD products control seizures. THC can trigger seizures in some people and cause cognitive problems. Unregulated CBD products often contain inconsistent amounts of CBD, THC, or contaminants.
Before starting CBD for epilepsy
Work with a neurologist experienced in epilepsy and cannabis-based medicines. Self-treatment is risky.
- Confirm the epilepsy type with a neurologist. Some seizures mimic others, and treatment differs.
- List all current medications, including anti-seizure drugs, over-the-counter products, and supplements.
- Review liver function with blood tests. CBD can raise liver enzymes, with valproate in particular.
- Ask about insurance coverage or patient assistance for Epidiolex. The medication is expensive.
- Set a realistic goal: fewer seizures, not zero seizures. Track baseline seizure frequency for at least a month.
How prescription CBD is dosed
Dosing is individualized and starts low. Your neurologist will adjust based on response and side effects.
- Start with the dose your doctor prescribes, often 2.5 mg per kg twice daily.
- Make increases no sooner than every week, under medical guidance.
- Measure doses with the syringe provided. Kitchen spoons are inaccurate.
- Keep a seizure diary noting date, time, type, duration, and any side effects.
- Attend follow-up visits for blood tests and dose adjustments.
Safety and side effects
CBD is not risk-free. Common side effects include sleepiness, fatigue, diarrhea, decreased appetite, and weight loss. More serious risks:
- Liver injury: signs include yellow eyes, dark urine, stomach pain, or nausea. Get urgent care.
- Drug interactions: CBD raises levels of clobazam and can interact with valproate, warfarin, and other drugs.
- Seizure worsening: some people have more seizures on CBD. Report any increase right away.
Do not stop anti-seizure medication all at once. Stopping any epilepsy drug can trigger severe withdrawal seizures.
When to reconsider
If seizures do not improve after 3 to 6 months at a tolerated dose, talk with your neurologist about other options. Non-cannabis treatments may work better for your specific epilepsy. In some cases, surgery or dietary therapy offers a better chance of seizure freedom.
Keep expectations grounded. CBD helps some people with treatment-resistant epilepsy, but it is not a cure-all. The right choice depends on epilepsy type, overall health, and careful medical supervision.