Long-term CBD for Dravet Syndrome: Sustained Benefit Over 48 Weeks
What Researchers Found About Epilepsy and Cannabis
The Study at a Glance
Published
Epilepsia, 2019
Researchers
Multiple institutions (International)
Study Type
Observational StudyParticipants
264 patients · Median 274 days (up to 512 days)
Key Finding
Long-term CBD treatment had an acceptable safety profile and led to sustained, clinically meaningful reductions in seizure frequency in patients with treatment-resistant Dravet syndrome.
Key Finding: Long-term CBD treatment had an acceptable safety profile and led to sustained, clinically meaningful reductions in seizure frequency in patients with treatment-resistant Dravet syndrome.
What Researchers Studied About Epilepsy and Cannabis
Dravet syndrome is a severe childhood epilepsy that does not respond well to standard treatments. Previous randomized trials showed CBD reduced seizures, but long-term effects were unknown.
This was an open-label extension trial for patients who completed the original randomized controlled trials (GWPCARE1 and GWPCARE2).
By November 2016, 278 patients had completed the original trials, and 264 (95%) enrolled in this extension study.
How This Observational Study Was Conducted
Patients received pharmaceutical CBD oral solution (100 mg/mL), titrated from 2.5 to 20 mg/kg/day over 2 weeks, with their existing medications.
Based on response and tolerance, CBD could be reduced or increased up to 30 mg/kg/day.
Median treatment duration was 274 days (range 1-512 days). Mean modal dose was 21 mg/kg/day. Patients received a median of 3 concomitant antiepileptic medications.
Epilepsy Treatment Results
The Main Results:
- 1264 patients enrolled (95% of those completing original trials)
- 2Median treatment duration: 274 days (up to 512 days)
- 3Adverse events in 93.2% of patients, mostly mild (36.7%) or moderate (39.0%)
- 4Common AEs: diarrhea (34.5%), fever (27.3%), decreased appetite (25.4%), somnolence (24.6%)
- 56.4% (17 patients) discontinued due to adverse events
- 617.2% (22/128) on valproic acid had liver transaminase elevations 3x upper limit of normal
- 7Convulsive seizures: 38-44% median reduction from baseline over 48 weeks
- 8Total seizures: 39-51% median reduction from baseline over 48 weeks
- 985% of patients/caregivers reported improvement at week 48
By the Numbers
| Statistic | What It Means |
|---|---|
| 264 patients | Dravet syndrome patients enrolled in long-term extension (95% of eligible) |
| 38-44% | Median reduction in convulsive seizures sustained over 48 weeks |
| 85% | Patients/caregivers reporting improvement on Global Impression of Change scale |
| 17.2% | Patients on valproic acid with elevated liver enzymes (3x normal) |
Dravet syndrome patients enrolled in long-term extension (95% of eligible)
Median reduction in convulsive seizures sustained over 48 weeks
Patients/caregivers reporting improvement on Global Impression of Change scale
Patients on valproic acid with elevated liver enzymes (3x normal)
What This Means for Epilepsy Patients
This study provides important long-term safety and effectiveness data for CBD in Dravet syndrome.
Over a median of 274 days (some up to 512 days), CBD maintained its seizure-reducing effect. Convulsive seizures were reduced by 38-44% and total seizures by 39-51%.
At 48 weeks, 85% of patients or caregivers reported improvement.
While adverse events were common (93.2% had at least one), most were mild or moderate. The most concerning finding was that 17.2% of patients also taking valproic acid had significantly elevated liver enzymes, requiring monitoring.
For families dealing with treatment-resistant Dravet syndrome, this provides reassurance that CBD benefits can be sustained over the long term with acceptable safety.
Quick Answers: Epilepsy and Cannabis
Direct answers based on the findings of this study:
Research Summary: Answers are based on published peer-reviewed studies and represent research findings, not medical recommendations. Individual results may vary. Always consult a healthcare provider before making treatment decisions.
How long can you take CBD for epilepsy?
Yes, CBD can be taken safely long-term. 264 Dravet patients took CBD for a median of 274 days (some up to 512 days) with sustained seizure reduction (38-44% for convulsive seizures) and acceptable safety.
Source: Devinsky et al., Epilepsia, 2019 (PMID: 30582156)
Does CBD keep working for seizures over time?
Yes. In a 264-patient extension study, CBD maintained its effect over 48 weeks: convulsive seizures reduced 38-44%, total seizures reduced 39-51%. 85% of patients/caregivers reported continued improvement at week 48.
Source: Devinsky et al., Epilepsia, 2019 (PMID: 30582156)
What should I monitor with long-term CBD use?
Liver function requires monitoring, especially if taking valproic acid (17.2% had elevated enzymes). Common long-term side effects include diarrhea (34.5%), fever (27.3%), decreased appetite (25.4%), and sleepiness (24.6%). 6.4% discontinued due to adverse events.
Source: Devinsky et al., Epilepsia, 2019 (PMID: 30582156)
This is educational content, not medical advice
The research summarized here is for informational purposes only. Individual results may vary, and what works in studies may not work the same way for everyone. Always consult with a qualified healthcare provider before making changes to your treatment plan or starting medical cannabis therapy.
Important Limitations
This study has some caveats to keep in mind when interpreting the results:
- Open-label design (no placebo comparison in extension)
- Adverse events common (93.2% had at least one)
- Liver enzyme elevations in 17.2% of patients on valproic acid
- Cannot separate CBD effect from natural disease fluctuation
- 6.4% discontinued due to adverse events
The Bottom Line on Cannabis for Epilepsy
This open-label extension of 264 Dravet syndrome patients shows CBD benefits are sustained long-term. Over 48 weeks, convulsive seizures decreased 38-44% and total seizures 39-51%. 85% reported improvement. Adverse events were common but mostly mild/moderate. Those on valproic acid need liver monitoring (17.2% had enzyme elevations). This confirms CBD is a viable long-term treatment for this severe epilepsy.
Do You Qualify for Medical Marijuana?
If you're living with Epilepsy, you may qualify for a medical marijuana card. Our licensed physicians can evaluate you from home via telehealth.
Related Research & Resources
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Source
Devinsky O, Nabbout R, Miller I, et al. "Long-term cannabidiol treatment in patients with Dravet syndrome: An open-label extension trial" Epilepsia. 2019. DOI: 10.1111/epi.14628
Important Information
Study Age: This study was published 7 years ago. Newer research may have updated or refined these findings.
Not Medical Advice: This research summary is for educational purposes only. It should not be used to diagnose, treat, cure, or prevent any disease or medical condition. Always consult a qualified healthcare provider before starting or changing any treatment.
Individual Variation: Research findings represent group averages. Your individual response to cannabis may differ based on genetics, other medications, underlying conditions, and many other factors.
Last reviewed: January 25, 2026
Important Notices
Research Summary Disclaimer
This content represents our interpretation of published scientific research for educational purposes. It should not be used to make treatment decisions without consulting a qualified healthcare provider. Individual results may vary from study findings.
FDA Notice
These statements have not been evaluated by the FDA. Cannabis is not intended to diagnose, treat, cure, or prevent any disease. The FDA has not approved cannabis for any medical condition except specific prescription medications.
Copyright & Fair Use
Research summaries are provided under fair use (17 U.S.C. § 107) for educational purposes. We provide brief summaries with attribution, not full reproductions. All studies remain the intellectual property of their respective authors and publishers.
Data Sources
Study information sourced from PubMed®, U.S. National Library of Medicine. Inclusion does not imply endorsement by NLM, NIH, or the federal government.
For complete information, see our Terms of Use and Research Content Policy.
FAQs: Cannabis for Epilepsy
Does CBD work long-term for Dravet syndrome?
Yes. In this extension study of 264 patients, CBD maintained its seizure-reducing effect over a median of 274 days (some up to 512 days). Convulsive seizures were reduced 38-44% and total seizures 39-51% at week 48. 85% reported improvement.
What are the long-term side effects of CBD for epilepsy?
Adverse events occurred in 93.2% of patients but were mostly mild (36.7%) or moderate (39.0%). Common side effects were diarrhea (34.5%), fever (27.3%), decreased appetite (25.4%), and sleepiness (24.6%). 6.4% discontinued due to adverse events.
Is CBD safe with valproic acid?
Caution is needed. In this study, 17.2% of patients taking both CBD and valproic acid had liver enzyme elevations at least 3 times the upper limit of normal. Regular liver monitoring is recommended for patients on both medications.