Cannabidiol

How it works

Its precise antiseizure mechanism is not fully defined but is independent of cannabinoid CB1/CB2 receptors, with effects thought to involve modulation of intracellular calcium and other neuronal signalling pathways.

Prescribing in practice

• Monitor liver function because cannabidiol can cause dose-related hepatocellular transaminase elevations, especially when combined with valproate or clobazam.
• It interacts significantly with clobazam, increasing exposure to the active clobazam metabolite and the risk of sedation.
• Withdraw gradually if discontinuing, as with other antiseizure medicines.

Monitoring

Check liver transaminases and bilirubin before starting and periodically during treatment, with closer monitoring in those on valproate or with pre-existing hepatic impairment.

Counselling the patient

• Attend for blood tests to monitor the liver as advised.
• Report drowsiness, loss of appetite, jaundice or abdominal pain.
• Do not stop the medicine abruptly without specialist advice.

Evidence & guidelines

Efficacy in Dravet and Lennox-Gastaut syndromes was demonstrated in randomised placebo-controlled trials, and it is recommended in specific NICE technology appraisals.