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Licorice

By

Laura Shane-McWhorter

, PharmD, University of Utah College of Pharmacy

Last full review/revision Jul 2020| Content last modified Jul 2020
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Natural licorice, which has a very sweet taste, is extracted from the root of a shrub (Glycyrrhiza glabra) and used medicinally as a capsule, tablet, or liquid extract. Most licorice candy made in the US is flavored artificially and does not contain natural licorice. Glycyrrhizin is the active ingredient in natural licorice. For people who are particularly sensitive to the effects of glycyrrhizin, specially treated licorice products that contain a much lower amount of glycyrrhizin (about one tenth) are available. These products are called deglycyrrhizinated licorice.

Claims

People most often take licorice to suppress coughs, to soothe a sore throat, and to relieve stomach upset. Applied externally, it is said to soothe skin irritation (eg, eczema). Licorice has also been claimed to help treat stomach ulcers and complications caused by hepatitis C or other liver diseases (1).

Evidence

Evidence indicates that licorice in combination with other herbs provides relief from the symptoms of functional dyspepsia and irritable bowel syndrome (2). However, clinical trials of both licorice alone and in combination are limited, and further evaluation is required. There are not enough data to determine whether licorice is effective for stomach ulcers or complications caused by hepatitis C. A review and meta-analysis of 5 randomized controlled trials (609 subjects) reported that topical licorice prior to endotracheal intubation prevented postoperative sore throats by 56% and cough by 39% (3).

Adverse effects

At lower dosages or normal consumption levels, few adverse reactions are evident. However, high doses of real licorice (> 1 oz/day) and glycyrrhizin cause renal sodium and water retention, possibly leading to high blood pressure, and potassium excretion, possibly causing low potassium levels (pseudoaldosteronism). Increased potassium excretion can be a particular problem for people who have heart disease and for those who take digoxin or diuretics that also increase potassium excretion. Such people and those who have high blood pressure should avoid taking licorice.

Licorice may increase the risk of premature delivery; thus, pregnant women should avoid licorice.

Drug interactions

Licorice may interact with warfarin and decrease its effectiveness, increasing the risk of blood clotting. As mentioned above, licorice may interact with digoxin by affecting potassium levels.

Licorice reference

  • Li X, Sun R, Liu R: Natural products in licorice for the therapy of liver diseases: progress and future opportunities. Pharmacol Res 144:210-226, 2019. doi: 10.1016/j.phrs.2019.04.025.

  • Ottillinger B, Storr M, Malfertheiner P, et al: STW 5 (Iberogast®)—a safe and effective standard in the treatment of functional gastrointestinal disorders. Wien Med Wochenschr 163(3-4): 65-72, 2013. doi: 10.1007/s10354-012-0169-x.

  • Kuriyama A, Maeda H: Topical application of licorice for prevention of postoperative sore throats in adults: a systematic review and meta-analysis. J Clin Anesth 54:25-32, 2019. doi: 10.1016/j.jclinane.2018.10.025.

More Information

The following is an English-language resource that may be useful. Please note that THE MANUAL is not responsible for the content of this resource.

Drugs Mentioned In This Article

Drug Name Select Trade
COUMADIN
LANOXIN
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NOTE: This is the Professional Version. CONSUMERS: Click here for the Consumer Version
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