Cannabidiol and Epilepsy: Specific Indications and Evidence

Prescription medicine only

This page is about one prescription medicine made of purified cannabidiol (CBD), used for a few rare, severe epilepsies. It is not about CBD oils, gummies, cannabis flower or any product bought without a prescription. Results for the medicine do not carry over to those products. Seizure treatment is managed by a specialist team; never stop or change a seizure medicine on your own, and a seizure emergency is a call to local emergency services (911 in the US). Laws and approvals change; this is not legal advice or medical advice.

Evidence labels used: approved medicine, established, promising but limited, insufficient evidence and evidence of harm.

The approved indications

Label: approved medicine for these syndromes. The FDA says it has concluded this product is safe and effective for its intended use. [5] It is the only FDA-approved drug containing CBD. [5]

What the trials showed

The US label reports median changes in monthly seizures from baseline. In two Lennox-Gastaut studies, drop seizures fell 17% to 22% with placebo and 37% to 44% across the studied amounts of the medicine. [1] In a Dravet syndrome study, convulsive seizures fell 13% with placebo versus 39% with the medicine. [1] In a TSC study, seizures fell 20% versus 43%. [1] These are group medians, not a promise for one person.

The EMA summary reports reductions in drop seizures of up to 64% versus up to 31% on placebo, both taken with clobazam, and in convulsive seizures of up to 61% versus up to 38%. [2] Label: established for these syndromes when added to other medicines.

What systematic reviews say

• A 2025 meta-analysis of seven randomized trials found CBD probably increased the number of people with at least a 50% fall in monthly seizures, and probably increased serious adverse events at the higher studied amount. For most other comparisons it called the effects uncertain. [6]
• A 2023 BMJ umbrella review of 101 meta-analyses found CBD improved 50% seizure reduction with high certainty, but increased pneumonia, gastrointestinal events and sleepiness. [7]
• A 2022 review found a significant CBD effect for epilepsy, graded high. [8]
• An older 2014 Cochrane review, written before approval, said no reliable conclusions could be drawn. [9]

Other epilepsy types

NCCIH says not enough research exists on cannabinoids for other, more common forms of epilepsy to reach conclusions. [10] Label: insufficient evidence. NICE has recommended research on cannabis-based products for severe treatment-resistant epilepsy. [4]

Risks and who needs extra care

The US label warns of dose-related liver enzyme rises: ALT above three times the upper limit of normal in 12% to 13% of treated patients in controlled studies versus 1% on placebo. [1] Risk is higher with valproate, and clobazam also increases it. [1] The label asks for liver blood tests before and during treatment. [1]

Other label warnings:

• Sleepiness. Somnolence and sedation affected 32% of treated patients in Lennox-Gastaut and Dravet studies versus 11% on placebo, and more often with clobazam. [1]
• Mood. Antiepileptic drugs as a class raise the risk of suicidal thoughts or behavior. [1]
• Common effects. Decreased appetite, diarrhea, fatigue, rash, sleep problems and infections were also reported. [1]
• Interactions. CBD raises levels of an active clobazam by-product, which may increase clobazam side effects. [1]

The EMA found a higher risk of liver problems that can be managed with restrictions and regular liver monitoring. [2] In England, NICE recommends continuing only if seizure frequency has fallen by at least 30% on checks every six months. [4]

Unapproved CBD products have not been evaluated by the FDA for effectiveness, dosage, interactions or safety. [5] See approved cannabinoid medicines, CBD, CBD medication interactions, liver considerations for cannabinoids and how prescription cannabinoids are regulated.