Epilepsy and Medical Cannabis: Beyond Epidyolex

Epidyolex and Its Limitations

• Epidyolex (pharmaceutical-grade CBD) is licensed in the UK for Dravet syndrome, Lennox-Gastaut syndrome, and tuberous sclerosis complex
• Many patients with other treatment-resistant epilepsy syndromes do not qualify for Epidyolex under its current marketing authorisation
• Epidyolex contains CBD isolate only; patients with broader seizure types may benefit from full-spectrum or THC-containing products
• Access barriers including NHS formulary restrictions mean that some eligible patients still struggle to obtain Epidyolex via the NHS

While Epidyolex represents a landmark in cannabis-based medicine, it addresses only a fraction of the epilepsy patients who may benefit from cannabinoid therapy.

THC-Containing Products in Epilepsy

• THC has demonstrated anticonvulsant properties in both animal models and a growing body of clinical case series
• Some patients with treatment-resistant epilepsy respond better to whole-plant extracts than to CBD isolate alone, suggesting an entourage effect
• THCA (the non-psychoactive acid precursor of THC) shows anticonvulsant activity in preclinical studies and is present in many medical cannabis products
• UK specialist epileptologists are increasingly willing to prescribe Schedule 2 cannabis products for patients who fail standard and licensed treatments

The evidence for THC and full-spectrum cannabis in epilepsy is building steadily, with several specialist centres in the UK now managing patients on such regimens.

The Access Journey for Epilepsy Patients

• A consultant neurologist with expertise in epilepsy must initiate the prescription for cannabis-based medicines under UK regulations
• Patients should document at least two or three failed antiepileptic drug trials before approaching a prescriber for cannabis
• The cost of private cannabis prescribing for epilepsy can be substantial; some NHS trusts have funding routes via individual funding requests
• Patient advocacy groups including the End Our Pain campaign have been instrumental in improving access for childhood epilepsy patients

Persistent advocacy and improved NHS commissioning guidance have steadily expanded access for epilepsy patients, though significant inequalities in provision remain across the UK.

Monitoring and Safety in Epilepsy

• Seizure diaries are essential for quantifying the treatment response to cannabis in epilepsy
• Drug interactions are a significant concern; CBD in particular inhibits CYP2C19, potentially raising levels of clobazam and other co-administered antiepileptics
• Liver function monitoring is recommended for patients on high-dose CBD, as transaminase elevations were observed in Epidyolex trials
• Dose changes should be made slowly and under specialist supervision to avoid precipitating withdrawal seizures

Safe and effective use of cannabis in epilepsy requires close collaboration between the patient, family, and a specialist multidisciplinary team with experience in both epilepsy and cannabis-based medicines.