Cytochrome P450 2C19 (CYP2C19)

Cytochrome P450 2C19 is a liver enzyme that metabolizes a range of medications, including some antidepressants, proton pump inhibitors, and the active metabolite of clobazam.

The enzyme is one member of the large cytochrome P450 family that breaks down foreign compounds so they can be excreted. Its activity varies widely between people because of inherited genetic differences; some individuals are poor metabolizers and others are ultra-rapid, which changes how they respond to drugs that depend on this pathway. Clinical pharmacology references list which medications are substrates, inhibitors, or inducers of CYP2C19.

Cannabidiol is a documented inhibitor of CYP2C19 in laboratory and clinical studies. The most studied consequence is the rise in N-desmethylclobazam levels when prescription CBD is taken with clobazam, which increases sedation. Similar effects are possible with other CYP2C19 substrates, though most have not been studied directly. Readers meet this enzyme in drug interaction warnings and pharmacogenetic reports, and it is a common reason pharmacists ask about cannabinoid use when reviewing a medication list.