Licorice May Block Effectiveness of Drug

Photo: Plenty of colourful sweets with licorice

Licorice does not go well with
some medications; © SXC

In the study, Pei-Dawn Lee Chao Chao, a chemist at China Medical University in Taiwan, 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.

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 researchers do not know exactly how much licorice it takes to have a toxic effect in humans or why licorice interferes with cyclosporine. 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.

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 onions, ginger, or ginkgo. Other studies show that some substances, such as grapefruit juice, can actually boost cyclosporine levels.

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.; Source: American Chemical Society (ACS)