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Medication Interactions with CBD & THC

Cannabinoids will interact with many prescriptions. This can happen either by interacting with the same receptor, or through the Cytochrome P450 enzyme.

Cytochrome P450 has over 50 enzymes (isozymes), and 6 of them will metabolize about 90% of medications. 1 out of 15 people have exaggerated responses to medications, and this is due to an altered response with the p450 enzyme. These enzymes are concentrated in the liver, and are also found in the small intestine, kidney, lungs, placenta, and blood.

An example of how medication interactions can happen. Clobazam is a prescription for treating epilepsy in children. CBD can increase blood levels of Clobazam, and if the blood levels go to high, side effects can occur. Such as:

Cytochrome P450 isozyme CYP1A2


THC is a CYP1A2 inducer. THC may decrease serum concentrations of:



Inducers of isozyme CYP1a2 may decrease levels of THC.


Some prescriptions can inhibit the isozyme CYP1a2, and can increase THC levels:



Alcohol may increase THC levels.

Cytochrome P450 isozyme CYP3A4 and CYP2D6


CYP3A4 inhibitors slightly increase THC levels.


CYP3A4 inducers slightly decrease THC and CBD levels.


CBD is a potent inhibitor of CYP3A4 and CYP2D6.CBD may increase serum concentrations of:


Inhibitors of isozyme CYP2D6 may increase CBD levels:


Cannabinoids will interact with the same receptors as many medications. This information is on the following page:

Beyond CB1 & CB2: 21 receptors in the endocannabinoid system



TOM LYNCH, PharmD, AMY PRICE, MD. The Effect of Cytochrome P450 Metabolism on Drug Response, Interactions, and Adverse Effects. Eastern Virginia Medical School, Norfolk, Virginia

Am Fam Physician. 2007 Aug 1;76(3):391-396.


Sevrioukova, Irina F., Poulos, Thomas L. Structure and mechanism of the complex between cytochrome P4503A4 and ritonavir. PNAS October 26, 2010 107 (43) 18422-18427


Ogu CC, Maxa JL. Drug interactions due to cytochrome P450. Proceedings (Baylor University Medical Center). 2000;13(4):421-423.


Enzyme Inducer Plus Enzyme Inhibitor: What Will Happen?

OCTOBER 05, 2012

John R. Horn, PharmD, FCCP, and Philip D. Hansten, PharmD

Pharmacy times