CAM PoliticsLicorice

Potential for licorice-drug interactions

Glycyrrhizin is a major ingredient of licorice, which is sometimes used in the treatment of various diseases such as chronic hepatitis.

In animals, licorice or glycyrrhizin alters the activity of the CYP3A drug-metabolizing enzyme. Researchers at Central South University, in Hunan, People’s Republic of China looked for an effect in people.

First, the details.

  • 16 healthy adult men were assigned to take each treatment in different order.
    • Placebo or glycyrrhizin for 14 days.
  • On the 15th day, the benzodiazepine-type drug midazolam (Versed) was administered and blood samples were obtained to determine midazolam concentrations.

And, the results.

  • The area under the concentration-time curve (AUC; a measure of total drug uptake into the body) was about 5% greater after placebo than midazolam.

The bottom line?

The authors concluded, “Administration of glycyrrhizin resulted in a modest induction of CYP3A.”

In other words, there is the potential that taking licorice decreases the response to midazolam.

In another study, the same researchers reported that glycyrrhizin stimulates the CYP3A4 enzyme to metabolize the anti-ulcer drug omeprazole (Prilosec) faster, which resulted in lower omeprazole blood levels.

Another study in animals suggests there may be a similar effect when glycyrrhizin is taken with methotrexate (Rheumatrex).

It’s important to consider that cytochrome P450 3A (CYP3A) is involved in the biotransformation of more than half of all drugs currently available. Even based on the limited data reported in the 3 studies above, it would be prudent to check carefully for the use of licorice in patients who experience a sudden change in their response to drug treatment.

De-glycyrrhizinated licorice extracts would not be expected to cause these effects because they contain no glycyrrhizin.

4/20/10 13:27 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.