Research Library
Drug interactions
Cytochrome P450 effects, the grapefruit rule, and medications that deserve extra caution.
Overview
Cannabidiol inhibits several liver enzymes that metabolize common prescription drugs, which can raise blood levels of those drugs.
This is the single most practical safety topic for anyone taking daily medication.
What the evidence supports
- CBD inhibits CYP3A4 and CYP2C19 — the same broad pathway as the grapefruit warning.
- Clinically documented interactions include clobazam, valproate, warfarin, and some immunosuppressants.
- Separating doses does not reliably eliminate the interaction; monitoring does.
Where the evidence is thin
- Most interaction data comes from high pharmaceutical doses, not typical wellness doses.
- Topical and inhaled routes are less studied than oral.
Selected studies
Systematic review · 2021
Cannabinoid-drug interactions: a review of the evidence
Balachandran P, et al. · Journal of Clinical Pharmacology
Summarizes CYP-mediated interactions and flags medications needing monitoring.
Find this study on PubMed (opens in a new tab)Observational · 2017
Interactions between cannabidiol and commonly used antiepileptic drugs
Gaston TE, et al. · Epilepsia
Clobazam levels rose substantially when CBD was added.
Find this study on PubMed (opens in a new tab)Guideline · 2020
Grapefruit-drug interaction guidance applied to cannabidiol
Various · Clinical guidance summary
If a medication carries a grapefruit warning, treat CBD with the same caution.
Find this study on PubMed (opens in a new tab)