Drug interaction reference
Most cannabis sites avoid this topic because it's clinical. We don't — but with one rule: we only list interactions with real pharmacological evidence, name the mechanism, and link the source. Then we tell you to talk to your clinician.
The information below is educational. Cannabis can interact with prescription medications in ways your specific health, age, and dose make different from this generic reference. Always discuss cannabis use with the clinician who prescribes your medications — especially if you take blood thinners, anti-seizure meds, immunosuppressants, or controlled substances.
How cannabis interacts with medications
Two mechanisms account for most of the interactions on this page:
- CYP enzyme inhibition.Your liver uses a family of enzymes (CYP450) to break down most medications. CBD is a strong inhibitor of CYP3A4, CYP2C9, and CYP2C19 — three of the most important. When CBD slows these enzymes down, drugs metabolized by them can build up in your blood. This is why CBD + warfarin can cause bleeding, and CBD + clobazam triggers excess sedation.
- Additive central-nervous-system effects. THC depresses the CNS — slows reaction time, causes sedation. Combine with other CNS depressants (benzodiazepines, opioids, alcohol) and effects stack.
Useful resources beyond this page: NCCIH overview · Mayo Clinic CBD · Drugs.com interactions.