Individual research recommendation details

Recommendation ID

NG144/4

Question

Does the addition of THC to CBD have an effect on seizure frequency, brain structure and neuropsychological performance when compared with both CBD alone and placebo in epileptic disorders in children, young people and adults?

Any explanatory notes
(if applicable)

Why the committee made the research recommendations
The only cannabis-based medicinal product available for the treatment of epilepsy is epidyolex, which is licensed specifically for Dravet and Lennox-Gastaut syndromes. All other cannabis-based medicinal products are unlicensed for epilepsy. The committee were aware from cases highlighted by stakeholders that individual patients have reported having fewer seizures with these medicines when other treatments have not fully controlled the seizures. But current research is limited and of low quality, making it difficult to assess just how effective these medicines are for people with epilepsy. Published randomised controlled trials have focused on the use of pure CBD in people with Dravet and Lennox-Gastaut syndromes. People with these epilepsy syndromes also report a very high rate of adverse events. Open-label studies (clinical trials in which the treatment and placebo groups are not disguised) of cannabis-based medicinal products in other types of epilepsy have also shown a very high level of adverse events (in up to 98% of people), but it was not possible to determine how many of these were due to the cannabis-based products.
The committee discussed the limited evidence and agreed that it did not warrant a practice recommendation. However, they also agreed that they should not make a recommendation against the use of cannabis-based medicinal products as this would restrict further research in this area and would prevent people who are currently apparently benefiting from continuing with their treatment. Specialists, people with epilepsy and their carers should continue to make treatment decisions in the best interests of each person with epilepsy, in line with the GMC's guidance for doctors. However, people seeking treatment for severe epilepsy should be made aware that currently there is no clear evidence of the safety and effectiveness of cannabis-based medicinal products.
The committee agreed that more evidence is needed on the effectiveness of cannabis-based medicinal products in severe treatment-resistant epilepsy and made a research recommendation to inform future practice. They discussed that some individual funding requests are denied because of lack of evidence of effectiveness. More research across different types of epilepsy may address this evidence gap.
The committee discussed the constituents of cannabis-based medicinal products. They were aware that it is difficult to extract pure CBD without other cannabinoids being present in trace amounts and this varies depending on extraction methods. Some medicines contain either purified 'pure' CBD alone (with trace amounts of other cannabinoids) or CBD combined with higher than trace amounts of THC. Most studies of cannabis-based medicinal products for severe epilepsy have evaluated 'pure' CBD, but the committee agreed it is important to know whether adding medicinal amounts of THC to CBD offers benefits or affects the type of adverse events observed. They decided to make a research recommendation on how the constituents of a cannabis-based medicinal product influence its effectiveness.

Source guidance details

Comes from guidance

Cannabis-based medicinal products

Number

NG144

Date issued

November 2019

Other details