CBD potently inhibits CYP3A4 and CYP2C19

Richard Rose reports

Heads up:

"CBD potently inhibits CYP3A4 and CYP2C19 (a liver enzyme that acts on 5-10% of drugs in current clinical use, including the anti-platelet clopidogrel (Plavix), anti-ulcer drugs such as omeprazole, anti-seizure drugs such as mephenytoin, the anti-malarial proguanil, and the anxiolytic diazepam). These liver enzymes are needed to metabolize many drugs.

CBD is well tolerated and has a large therapeutic index but this can't be said for other pharmaceuticals and any alteration of liver enzyme metabolism can put a patient at risk of toxicity from the other co-administered drug.

In 1998, various researchers showed that grapefruit juice, and grapefruit in general, is a potent inhibitor of CYP3A4, which can affect the metabolism of a variety of drugs, increasing their bioavailability. In some cases, this can lead to a fatal interaction with drugs like astemizole or terfenadine.

The effect of grapefruit juice with regard to drug absorption was originally discovered in 1989. The first published report on grapefruit drug interactions was in 1991 in the Lancet entitled "Interactions of Citrus Juices with Felodipine and Nifedipine" and was the first reported food-drug interaction clinically.

The effects of grapefruit last from 3–7 days, with the greatest effects when taken simultaneously with the drug. In addition to grapefruit, other fruits have similar effects. Noni (M. citrifolia), for example, is a dietary supplement typically consumed as a juice and also inhibits CYP3A4; pomegranate juice has this effect as well."

The best advise might be to re-consider using CBD if the prescription drug has a grapefruit warning on the label.