Licorice May Block Effectiveness Of Drug Widely Used By Transplant Patients

Licorice May Block Effectiveness Of Drug Widely Used By Transplant Patients
ScienceDaily (Mar. 31, 2009) —

Chemists in Taiwan are reporting that an ingredient in licorice — widely used in various foods and herbal medicines — appears to block the absorption of cyclosporine, a drug used by transplant patients to prevent organ rejection. This drug interaction could potentially result in transplant rejection, causing illness and even death among patients worldwide who take cyclosporine and licorice together, the researchers caution.

The study is the first report of this potential drug interaction, the scientists say. Their findings will be presented at the American Chemical Society's 237th National Meeting.

"I would suggest that transplant patients avoid taking licorice," warns Pei-Dawn Lee Chao, Ph.D., a chemist at China Medical University in Taichung, Taiwan.

The researchers say they do not know exactly how much licorice it takes to have a toxic effect in humans. Since licorice-based products vary widely in their content of its main active ingredient, a substance called glycyrrhizin, Chao suggests that patients taking cyclosporine avoid licorice altogether. Thousands of patients also take cyclosporine for rheumatoid arthritis, certain skin conditions, and other diseases.

Researchers have known for years that certain medications, foods, and herbs can reduce levels of cyclosporine in the body and should be avoided when taking that immunosuppressant drug. These include St. John's wort, quercetin (an ingredient found in onions and other plants that's also a dietary supplement), onions, ginger, and ginkgo. Other studies show that some substances, such as grapefruit juice, can actually boost cyclosporine levels. Now, it appears that licorice will join the growing list of substances that reduce the absorption of cyclosporine, the researchers say.

In the new study, Chao and colleagues fed cyclosporine to laboratory rats with and without various doses of pure glycyrrhizin and natural licorice extract. Much to the scientists' surprise, levels of cyclosporine dropped in the animals fed licorice or glycyrrhizin.

The researchers are trying to find out why licorice interferes with cyclosporine. Chao says there are no known scientific reports linking consumption of licorice to ill effects in transplant patients. Doctors, however, have not been looking for such a link, she added. The government of Taiwan funded the research through the Committee of Chinese Medicine and Pharmacy, Ministry of Health, R.O.C.

Licorice is a popular herb that has been used in food and medicines for thousands of years. Its active ingredient, glycyrrhizin, is 50 times sweeter than sugar, leading to herb's popular use in candy, herbal teas, and other foods. Some alternative health care providers use licorice root to treat a wide range of illnesses, including the common cold, stomach ulcers, and liver disease.
The new study adds to a growing number of reports indicating that licorice can trigger potentially dangerous drug interactions. Other studies have shown that licorice can interfere with the effectiveness of high blood pressure medications, aspirin, anti-inflammatory drugs, insulin and oral contraceptives. Chao and colleagues say patients should check with their doctor before consuming licorice with any critical drugs that might trigger unhealthy interactions.

Trip to the Candy Store Might Help Ward Off Rare, but Deadly Infections

Licorice Root: Trip to the Candy Store Might Help Ward Off Rare, but Deadly Infections
ScienceDaily (Jan. 4, 2010) —

As it turns out, children were not the only ones with visions of sugar plums dancing in their heads over this past holiday season. In a new research report published in the January 2010 issue of the Journal of Leukocyte Biology, a team of scientists from the University of Texas Medical Branch and Shriners Hospitals for Children shows how a compound from licorice root (glycyrrhizin from Glycyrrhiza glabra) might be an effective tool in battling life-threatening, antibiotic-resistant infections resulting from severe burns.

Specifically, they found that in burned mice, glycyrrhizin improved the ability of damaged skin to create small proteins that serve as the first line of defense against infection. These proteins, called antimicrobial peptides, work by puncturing the cell membranes of bacteria similar to how pins pop balloons.

"It is our hope that the medicinal uses of glycyrrhizin will lead to lower death rates associated with infection in burn patients," said Fujio Suzuki, Ph.D., one of the researchers involved in the work. Suzuki also said that more research is necessary to determine if this finding would have any implications for people with cystic fibrosis, who can develop Pseudomonas aeruginosa infections in their lungs.

To make this discovery, Suzuki and colleagues used three groups of mice. The first group was normal, the second group was burned and untreated, and the third group was burned and treated with glycyrrhizin. The skin of the untreated burned mice did not have any detectable antimicrobial peptides that prevent bacteria from growing and spreading, but the normal mice did. The skin of the untreated burned mice also had immature myeloid cells, which indicate an inability of the skin to produce antimicrobial peptides needed to prevent infection. The mice treated with glycyrrhizin, however, were more like the normal mice as they had the antimicrobial peptides and no immature myeloid cells.

"Burns are the most painful of all injuries," said John Wherry, Ph.D., Deputy Editor of the Journal of Leukocyte Biology, "and the deadly Pseudomonas infections that can result from severe burns do more than add insult to those injuries. This research should serve as an important stepping stone toward helping develop new drugs that help prevent or treat Pseudomonas."