CBD and THC Can Interfere With How Your Body Processes Other Medications

CBD was consistently identified as a potent inhibitor of CYP3A4, CYP2C9, and CYP2C19 — enzymes that metabolize approximately 80% of therapeutic drugs. CYP2C19 could also be induced under certain conditions. CYP2D6 showed minimal or no modulation. THC also showed inhibitory effects but was less consistently studied.

Systematic review per PRISMA guidelines searching PubMed, SciELO, ScienceDirect, and Scopus for studies published January 2019 to March 2025. Included in vitro, in vivo, and ex vivo studies evaluating phytocannabinoid effects on hepatic CYP450 isoforms. Four studies met eligibility criteria.

With millions of people using CBD products alongside prescription medications, understanding drug interactions is critical for safety. The strong inhibition of CYP3A4 alone is clinically significant — this enzyme metabolizes drugs like blood thinners, statins, and anti-seizure medications.

As CBD becomes widely available over the counter, many users don't realize it can significantly alter how their body processes other medications. This review provides the scientific basis for why patients should inform healthcare providers about CBD use, especially if taking medications metabolized by CYP3A4.

Only 4 studies met criteria, reflecting limited but growing research. Mostly in vitro data — clinical significance at typical CBD doses uncertain. THC less studied than CBD. Individual variation in CYP enzyme activity not captured.