Cytochrome P450 3A4 (CYP3A4)

Cytochrome P450 3A4 is the most abundant drug-metabolizing enzyme in the human liver and intestine, involved in breaking down a large share of prescription medications.

The enzyme handles a very wide variety of compounds, including many statins, calcium channel blockers, immunosuppressants, benzodiazepines, and hormonal contraceptives. Because so many drugs share this pathway, CYP3A4 is at the center of a large number of known drug interactions. Grapefruit juice is the familiar example of a dietary CYP3A4 inhibitor that raises blood levels of affected drugs. Activity varies with genetics, age, liver health, and other substances present.

CYP3A4 is one of the main enzymes that metabolize cannabidiol, and laboratory studies show that cannabidiol can inhibit it in turn. This two-way relationship means other CYP3A4 drugs can change CBD levels, and CBD may change theirs. Clinical data on most specific combinations are sparse, so prescribing information for prescription CBD advises caution with strong inhibitors and inducers. Readers encounter this enzyme in interaction checkers and pharmacist consultations.