15-03-2016 | CBD and cannabis in the treatment of epilepsy

15 March 2016
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Despite recent advances in the understanding and treatment of epilepsy, up to 30% of people living with the condition do not respond to existing anti-epileptic drugs (AEDs) and continue to experience regular, debilitating and potentially life-threatening seizures.

Much needed research to find new and better treatments is continuing around the world. In the past few years, there has been a lot of discussion about the potential benefits of cannabis and its derivatives in treating epilepsy, particularly rare, devastating paediatric conditions such as Dravet syndrome.

In the US, many states have approved cannabis for medical use, and a small number of states have fully legalised it. Additionally, other states have introduced legislation to permit clinical trials of a pharmaceutical CBD drug called Epidolex under tight regulation.

There have been an increasing number of reports of families in the US for whom cannabis-based products have had success in reducing seizures. This is thought to be because of the non-psychoactive component of cannabis called cannabidiol (CBD). In addition to the anecdotal reports, a limited number of studies of CBD in animal models have shown anti-convulsant effects but the mechanism of action is not yet understood.


Trials on Epidolex, a CBD-only pharmaceutical drug are currently underway in the US, UK and other countries. Epidiolex has not yet been approved for use by any national regulatory authority but has received FDA Orphan Drug Designation and Fast Track Designation in the US for both Dravet syndrome and Lennox-Gastaut syndrome.

In March 2016, results of the first pivotal Phase 3 study of Epidolex for Dravet syndrome were announced. The study involved 120 patients (average age 10 years) who were randomised to either Epidolex or placebo. After 14 weeks, patients taking Epidiolex achieved a median reduction in monthly convulsive seizures of 39% compared with a reduction on placebo of 13%. These are positive findings and additional, larger Phase 3 trials are now being conducted in Dravet syndrome, with other trials underway or planned in Lennox-Gastaut Syndrome and Tuberous Sclerosis Complex.

As an organisation that funds epilepsy research, Epilepsy Ireland welcomes all research that seeks to develop safe and effective treatments for epilepsy including these trials which could potentially lead to a new approved treatment for people with a range of devastating epilepsy syndromes.

The manufacturer of Epidolex, GW Pharmaceuticals is now seeking regulatory approval for the drug in Europe and the US for Dravet syndrome. Should Epidolex or any other epilepsy treatment containing CBD be approved for use in Ireland, Epilepsy Ireland will advocate for access to the drug for those who could benefit from its prescribing.

Non Pharmaceutical products

A clear distinction needs to be drawn between products such as Epidolex that are undergoing rigorous efficacy and safety testing to achieve regulatory approval and non-pharmaceutical products that are not licenced for medicinal use. There are serious concerns about the safety and risks associated with unregulated, unstandardised non-pharmaceutical products containing cannabis extracts, in particular those that contain tetrahydrocannabinol (THC), the main psycho-active element in cannabis.

While there have been positive anecdotal accounts of these products, particularly in the US, there have also been reports of cannabis/ CBD products making seizures worse in children, as well as other negative side effects. Some animal studies have also highlighted the potential for CBD to be pro-convulsant (increasing the risk of a seizure) in some cases.

Currently, no robust evidence from high quality scientific studies exists to support the use of non-pharmaceutical cannabis-based products for the treatment of epilepsy. In relation to these products, individual successful cases do not provide strong enough evidence to expose large amounts of people to the unknown and unquantifiable risks associated with unregulated, unstandardised products. In the absence of robust evidence, these products cannot be considered as safe or effective treatments for epilepsy.

Given the devastating impact of conditions like Dravet Syndrome and the limited success of existing drugs in treating these rare conditions, it is understandable that many affected families will want to reach out to investigate potential new treatment avenues. However, further research, in the form of well-regulated clinical trials represent the only safe and objective way to assess the potential that any CBD or cannabis product may hold in the mainstream treatment of epilepsy. Further research in this area is badly needed and Epilepsy Ireland remains open to receiving and assessing funding applications under our Research Funding Scheme from researchers who want to pursue this area of research.

Legal position

In Ireland, cannabis is currently a Schedule 1 drug controlled under the Misuse of Drugs legislation which makes it an offence to be in possession of cannabis or many of its extracts (including THC). CBD itself is not a controlled substance under Irish law. However, a product that contains CBD is also likely to contain additional substances that are controlled under legislation. If a CBD-based product contains other substances e.g THC in quantities which would bring that product within the Misuse of Drugs Acts, it is a controlled substance and it is illegal to import, possess or supply it.

Additionally, even if the product is true CBD-only, it may meet the definition of a medicinal product, which would require it to have the appropriate authorisation or registration in Ireland.

Further Information

June 2014 issue of leading epilepsy medical journal Epilepsia

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