Problematic duo: medication plus liquorice

Larissa Melville completed her traineeship in the editorial team of . After studying biology at Ludwig Maximilians University and the Technical University of Munich, she first got to know digital media online at Focus and then decided to learn medical journalism from scratch.

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Whether stomach pain or cough: licorice extract can help. But be careful: Even small amounts could affect the effectiveness of drugs.

Licorice is a popular candy. The licorice extract it contains has also been used as a medicinal product for centuries. It helps with stomach ulcers, gastritis and airway inflammation as well as against menopausal symptoms.

Too much is unhealthy

But liquorice also has a downside: Too much of it is harmful to health. With prolonged use and in higher doses, it can cause an imbalance in the mineral balance. Water and sodium are retained in the body while a lot of potassium is lost. Water retention in the tissue (edema), high blood pressure and muscle weakness can result.

"But we wondered if even small amounts of liquorice could cause problems by disrupting drug metabolism or transport," says Professor of Medicinal Chemistry and Pharmacology Richard van Breemen of the University of Illinois at Chicago. In a laboratory experiment, he and his colleagues therefore investigated how licorice influences the effects of various drugs.

There are different types of licorice, which differ, for example, in the amount of the active ingredient glycyrrhizine. The research team took a closer look at three species: Glycyrrhiza uralensis, Glycyrrhiza inflata and Glycyrrhiza glabra.

Enzyme activity changed

The result: All three types of licorice changed the activity of enzymes in the liver that are involved in drug metabolism. "If these enzymes are stimulated or inhibited, the drugs are either processed too quickly or too slowly," says van Breemen. These changes could be a significant safety risk for people who take liquorice and medication on a daily basis, he says. This is especially true when licorice extract is given in higher doses in the form of dietary supplements.

"The Asian Glycyrrhiza inflata, for example, can inhibit the enzyme cytochrome CYP3A4, which is necessary for the metabolism of two thirds of all drugs - such as the anxiety-relieving alprazolam," reports van Breemen in an interview with Glycyrrhiza inflata also inhibits other liver enzymes that metabolize the anticoagulant warfarin and the diabetes drug tolbutamide, among other things.

Licorice is not the same as licorice. In the case of the European Glycyrrhiza glabra, the researchers were able to determine only a slight effect on the liver enzymes. “But this species is not free from side effects either,” warns the researcher.

The team is currently planning a clinical study to check the results obtained in laboratory tests.

50 to 100 grams of licorice - nothing more

The German Nutrition Society (DGE) recommends healthy people who regularly eat liquorice not to consume more than 50 to a maximum of 100 grams per day. This corresponds to a maximum of 100 milligrams of glycyrrhizin. DGE recommends that risk groups such as high blood pressure patients, diabetics and pregnant women do not consume large quantities of liquorice (over 50 grams per day) at all. The occasional consumption of small amounts, on the other hand, is also safe for these patients.

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