Purified CBD reduced seizures in Dravet and Lennox-Gastaut syndromes and received FDA approval

What the researchers found

This review compiled all available evidence on cannabis-derived treatments for epilepsy, from artisanal products through FDA-approved purified CBD.

While artisanal CBD products showed high rates of reported seizure improvement in surveys and retrospective studies, these lacked controlled dosing and rigorous design.

The stronger evidence came from open-label expanded access programs (EAPs) and randomized controlled trials of highly purified CBD (Epidiolex). The EAPs showed significant seizure frequency improvement across various treatment-resistant epilepsy types. The RCTs demonstrated significant seizure reduction compared to placebo specifically in Dravet syndrome and Lennox-Gastaut syndrome.

Important safety findings: the most common side effects were diarrhea and sedation, with sedation much more common in patients also taking clobazam. Liver enzyme elevations occurred, particularly in patients also taking valproate. CBD significantly increases levels of N-desmethylclobazam (clobazam's active metabolite) through CYP2C19 inhibition. Other possible interactions were identified with rufinamide, zonisamide, topiramate, and eslicarbazepine.

Why it matters

This review documents the journey from anecdotal reports to FDA approval for CBD in epilepsy, one of the most significant developments in cannabinoid medicine. The detailed drug interaction data is critical for clinicians managing patients on multiple anti-epileptic drugs.

The numbers in context

RCTs showed significant seizure reduction vs. placebo in Dravet and Lennox-Gastaut syndromes. Most common side effects: diarrhea and sedation. CBD inhibits CYP2C19, increasing N-desmethylclobazam levels. Possible interactions with rufinamide, zonisamide, topiramate, eslicarbazepine.

How the study worked

Comprehensive review of published evidence on CBD for epilepsy, including artisanal product surveys, open-label expanded access programs, randomized placebo-controlled trials, and pharmacokinetic interaction studies.

What this study cannot tell us

Much of the artisanal product evidence comes from surveys and uncontrolled studies. The RCTs focused on two specific epilepsy syndromes and may not generalize to all epilepsy types. Long-term safety data was still accumulating at the time of publication. The review does not cover THC-containing preparations in detail.

How to read the evidence

This review covers randomized controlled trials that led to FDA approval, representing strong evidence for CBD in these specific epilepsy syndromes.

When this study was published

Published in 2018, shortly after FDA approval of Epidiolex. Post-marketing data and additional indications have since emerged.

The bigger picture

The CBD-for-epilepsy story represents the most successful translation of cannabinoid research into approved medicine. It demonstrates that rigorous clinical trials can validate cannabinoid therapeutics, and it highlights the importance of understanding drug interactions in patients taking multiple medications.

Questions still open

• Will CBD prove effective for epilepsy types beyond Dravet and Lennox-Gastaut syndromes? Could specific ratios of CBD to THC provide additional therapeutic benefit for seizure control? How should clinicians manage the CBD-clobazam interaction in practice?

Common questions

Read the original research

Cannabis for the Treatment of Epilepsy: an Update.

Current neurology and neuroscience reports, 18(11), 73

Citation

Gaston, Tyler E; Szaflarski, Jerzy P. (2018). Cannabis for the Treatment of Epilepsy: an Update.. Current neurology and neuroscience reports, 18(11), 73. https://doi.org/10.1007/s11910-018-0882-y

Explore the wider topic

• CBD Oil Quality Guide: How to Avoid Snake Oil
• Anxiety After Quitting Weed: When to Consider Medication
• Cannabis for Chemotherapy Nausea: What the Evidence Actually Shows
• Cannabis for Chronic Pain: What the Research Actually Supports
• Cannabis and Epilepsy: The Epidiolex Story and What It Means
• Does CBD Actually Work for Anxiety? What the Evidence Shows
• Does CBD Help with Weed Withdrawal? What Studies Show
• CBD vs THC: The Differences That Actually Matter
• The Proven Medical Benefits of Cannabis: What Research Supports
• Quitting Weed Before Surgery
• Weed and Medications: What Changes When You Quit
• Quitting Weed During Pregnancy: What You Need to Know
• Quitting Weed While Pregnant: What You Need to Know
• Cannabis and Older Adults: Risks Seniors Should Know
• Cannabis and Breastfeeding: THC in Breast Milk