Licorice May Block Absorption of Organ Transplant Drug

Mar. 25 -- TUESDAY, March 24 (HealthDay News) -- People taking the immunosuppressant cyclosporine should avoid consuming licorice because it may weaken the drug's effectiveness and possibly lead to deadly consequences, new research suggests.

Chemists in Taiwan report that lab rats taking cyclosporine -- commonly used to help prevent organ rejection in transplant patients -- who were feed licorice or its main active ingredient, glycyrrhizin, did not absorb the medication well. For a transplant patient on cyclosporine, lowered levels of the medication could lead to rejection of the new organ, followed by illness and even death, said the researchers, who were to present their findings Tuesday at the American Chemical Society's annual meeting in Salt Lake City.

"I would suggest that transplant patients avoid taking licorice," researcher Pei-Dawn Lee Chao, a chemist at China Medical University in Taichung, Taiwan, said in an American Chemical Society news release.

The researchers, who are trying to determine why licorice interfered with the drug's absorption, said they didn't know how much licorice might cause a toxic reaction in humans.

Cyclosporine is also used to treat rheumatoid arthritis, juvenile myositis and various skin conditions, and it is known to interact poorly with some medicines, foods and herbs. St. John's wort, onions and ginger, for example, can also lower cyclosporine levels in the blood, while grapefruit juice can sending cyclosporine levels soaring.

Licorice has been reported to possibly interfere with high blood pressure medications, aspirin, anti-inflammatory drugs, insulin and oral contraceptives. The herb has been popular in folk medicine for centuries and is used by some combat stomach ulcers, bronchitis and sore throat. Because of its sweetness, glycyrrhizin is sometimes used in candy, teas and other foods.

More information

The U.S. National Center for Complementary and Alternative Medicine has more about licorice.

SOURCE: American Chemical Society, news release, March 24, 2009