Safety and Efficacy of CBD in Treatment-Resistant Epilepsy

7th December 2020

The use of Cannabis Sativa plants for medicinal purposes has been recorded for thousands of years in an abundance of societies. Epilepsy is one of the conditions for which there is historic evidence of cannabis treatment. These findings are now being mirrored in modern medicine as an increasing number of countries, including the UK, begin to incorporate the use of cannabis-based medications in treatment-resistant epilepsy.

In 2018, the UK re-scheduled cannabis, placing it in schedule 2 of the Misuse of Drugs Act 1971. This move meant that specialist clinicians would be able to prescribe cannabis-based medicines in certain cases. The rescheduling was largely influenced by the experiences of children living with severe forms of rare treatment-resistant epilepsy who had found success with cannabis medications.

CBD and Epilepsy

A number of clinical trials and studies have examined the potential of cannabinoids in the treatment of some forms of epilepsy. Past studies have assessed various forms of cannabis including full extract and CBD isolate formulations, such as Epidyolex.

Epidyolex is a CBD-based medication which is licensed in the UK for patients with Lennox-Gastaut and Dravet syndromes where their epilepsy is refractory to conventional anti-epileptic medications. This medication has been found to be effective in reducing seizures in children with these syndromes.

Safety and Efficacy of CBD as an Epilepsy Treatment

One study assessed the experiences of 47 children with treatment-resistant epilepsy who received Epidyolex as an adjunct therapy. The study was conducted at three major paediatric referral centres in Georgia, USA, where seizure frequency was recorded at baseline and months 3, 6, 12, 18, 24, and 36. Patients were also placed in either a high dose or a low dose and their response analysed separately.

Researchers identified a statistically significant reduction in seizures for patients in both sub-groups during the first three months of CBD treatment. Seizure frequency at 6,12,18,24, and 36 months of treatment was also significantly altered in comparison to baseline.

By Month 3, 59% of patients had experienced at least a 50% reduction in seizure frequency. The remaining patients (41%) also experienced a reduction in seizure frequency; however, this did not reach the 50% threshold. At month 36, 81% of patients continued to report reductions in seizure frequency of at least 50% across both the low and high dose-groups. Four patients from each sub-group achieved 100% seizure-free days by month 36.

Two patients experienced an increase in seizure frequency from baseline. While this was believed to partly due to the low number of seizures experienced at baselines as well as adjustments made for the number of missing recorded days. Despite an increase in frequency, the patients continued with treatment as they experienced improvements in quality of life and cognition, as well as seizure severity.

Treatment-Emergent Adverse Events (TEAE)

All 47 patients included in the study experienced more than one TEAE. While some TEAEs required hospitalisation, this was believed to be the cause of one or more underlying TEAE and none were considered to be related to the CBD treatment. All TEAE were resolved.

Overall, researchers reported a consistent safety profile for CBD treatment throughout the study. The most common TEAEs experienced by participants during the study period were upper respiratory infection, gastrointestinal disorders, pyrexia, and somnolence, which are consistent with other studies involving children and adults treated with the same formulation of CBD. Children who were titrated to the high-dose were found to experience an increase in TEAEs after the transition, suggesting that increasing the dose of CBD may correlate to increases in TEAEs.


The authors of this study note that the results recorded support and expand on the findings of previous studies. They conclude that CBD, as a treatment option for treatment-resistant epilepsies, is well-tolerated as a long-term option for children in doses up to 50mg/kg/day. In this study, CBD treatment was seen to support a reduction in major seizure frequency and an increase in seizure-free days for many participants.

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