CYP3A4 is a member of the liver enzymes known as the cytochrome P450 mixed-function oxidase system. It’s one of the most important enzymes involved in the metabolism of drugs.

Researchers at the Norwegian University of Science and Technology in Trondheim evaluated several herbal remedies for their ability to inhibit CYP3A4.

First, the details.

  • Herbal remedies frequently used by cancer patients were studied in the lab.
    • Natto K2
    • Agaricus
    • Mistletoe
    • Noni juice
    • Green tea
    • Garlic

And, the results.

  • Garlic and Natto K2 were classified as non-inhibitors.
  • Agaricus, noni juice, mistletoe, and green tea inhibited CYP3A4 metabolism.
    • But the authors concluded that a clinically relevant interaction with CYP3A4 was unlikely.
  • The data support green tea as a probable inhibitor of intestinal CYP3A4.

The bottom line?
These results are based on experiments conducted in the laboratory and not in patients being treated with these herbals.

The researchers provide insight into possible drug-herbal interaction issues. However, more information is needed on dosing and conditions in which an interaction might be important in patients.

Information on drug interactions with green tea are listed here.

1/29/09 20:46 JR

Hi, I’m JR

John Russo, Jr., PharmD, is president of The MedCom Resource, Inc. Previously, he was senior vice president of medical communications at, a complementary and alternative medicine website.