This page is an educational summary and does not constitute clinical guidance or a recommendation for use. Prescribing, dosing and treatment decisions should be made on the basis of individual patient assessment, current clinical guidelines and the treating healthcare professional's judgement.
What is CBD?
Cannabidiol (CBD) is a non-psychoactive cannabinoid found in Cannabis sativa. It is the active ingredient in Epidiolex — the first plant-derived cannabinoid to receive EMA marketing authorisation. Unlike THC, CBD does not produce intoxication and has low abuse potential.
Pharmacology
CBD has complex multi-target pharmacology: CB1 negative allosteric modulation (reduces THC psychoactivity in combination products); 5-HT1A agonism (anxiolytic effects); TRPV1 agonism (analgesic/anti-inflammatory); GPR55 antagonism (anticonvulsant contribution).
Pharmacokinetics
Oral bioavailability 6–19% (increased substantially by high-fat meal). Metabolised primarily by CYP3A4 and CYP2C19. Half-life 18–32 hours at steady state.
Key drug interactions: Inhibits CYP2C19 (clobazam — increased sedation; dose adjustment often required); CYP3A4 inhibition (tacrolimus, ciclosporin — TDM essential); UGT inhibition with valproate (hepatotoxicity risk — monitor LFTs).
Evidence Base
Dravet syndrome: Phase 3 RCT (Devinsky, NEJM 2017) — 39% reduction in convulsive seizure frequency vs placebo. Basis for Epidiolex EMA approval.
Lennox-Gastaut: Two Phase 3 RCTs — significant drop seizure reduction.
Anxiety: Multiple smaller RCTs show anxiolytic signal; lacks large RCT support for formal indications.
Pain: Limited as single agent; stronger evidence in THC:CBD combination (Sativex).
Adverse Effects
Diarrhoea and nausea (most common, dose-related); fatigue; elevated transaminases at higher doses; hepatotoxicity (rare, increased risk with valproate). No psychoactive effects. Does not impair driving at therapeutic doses as a single agent.
GMP Manufacturing Considerations
Decarboxylation of CBDA→CBD must be validated. THC removal to specification limits requires validated purification. CBD stability better than THC but degrades oxidatively — nitrogen blanketing and light-protective packaging recommended. CBN accumulation indicates degradation and should be a specification parameter.
See the Cannabis Glossary for definitions of related cultivation, extraction and quality terms.
References
- Devinsky O et al. Trial of Cannabidiol for Drug-Resistant Seizures in Dravet Syndrome. NEJM. 2017.
- Iffland K, Grotenhermen F. Update on Safety and Side Effects of Cannabidiol. Cannabis Cannabinoid Res. 2017.
- EMA. Epidiolex Summary of Product Characteristics.