Licorice is obtained from Glycyrrhiza glabra, varieties of which are indigenous to Europe and Asia. The medicinal parts include the unpeeled, dried roots and runners, the peeled dried roots, and the rhizome with the roots.

Licorice contains 7% to 10% glycyrrhizin (glycyrrhizic acid), natural sugars, glucose, mannose, sucrose, flavonoids, isoflavonoids, and sterols (betasitosterol and stigmasterol). Glycyrrhizin is a glycoside 50 times sweeter than sugar. Licorice has been found to stimulate the release of secretin, a potential mediator of antiulcer activity. Carbenoxolene, a semisynthetic ester of glycyrrhetic acid, is an active ingredient for treating stomach ulcers.

Licorice has shown anti-inflammatory and antiarthritic effects by inhibiting prostaglandin activity, which may make it useful in treating pain and inflammation from arthritis. The active ingredient, glycyrrhetinic acid, inhibits II-betahydroxydehydrogenase, an enzyme that prevents cortisol from acting as a mineralocorticoid. Inhibiting this enzyme allows increased mineralocorticoid activity, or aldosterone-like activity, leading to sodium and water retention and potassium excretion. Many reports have been made about severe toxicity caused by these effects. Licorice is available in products such as Herbal Nerve (Canada), Licorice Power, Lightning Cough Remedy, Phyto Power, and Wild Countryside Licorice Root.

Reported uses

Licorice is used to treat stomach ulcers and as an expectorant. It's also used in sweets, soft drinks, medicines, and chewing tobacco as a flavoring agent.

Administration

Capsules: 5 to 15 g a day of licorice root (200 to 600 mg glycyrrhizin) by mouth a day; daily intake greater than 50 g of the herb is considered toxic

Tea (steep 1 teaspoon oflicorice extract in 8 oz boiling water for 5 minutes): 1 cup of tea after each meal

Drops: 25 drops taken four times a day.

Hazards

Licorice can cause a variety of adverse reactions, including numbness, tingling paralysis, hypokalemia, and hypernatremia. There have been reports of hypertension, heart failure, and arrhythmias, most likely due to the effects of hypokalemia and hypernatremia. Licorice may cause edema, myopathy, and muscle cramps. Vision loss has also been reported. Use of licorice with antiarrhythmics such as procainamide and quinidine may cause hypokalemia and torsades de pointes. Use with antihypertensives may render the antihypertensive medication less effective. Use of licorice with corticosteroids may have an additive effect. Patients using licorice with digoxin are at risk for hypokalemia and digoxin toxicity. Use of diuretics with licorice may worsen hypokalemia. Smoking may reduce the metabolism of licorice and lead to potential licorice toxicity.

Patients who are pregnant, breast-feeding, or hypersensitive to licorice, or those with hypokalemia, arrhythmias, diabetes, glaucoma, or history of cerebrovascular accident or renal, hepatic, or cardiac disease should avoid the use of licorice.

Clinical considerations

Monitor patient for signs of hypokalemia or hypernatremia.

Assess other medications patient is taking for possible interactions.

Monitor patient's blood pressure closely.

Warn patient to notify his health care provider if he develops swelling, muscle cramps, tiredness, or weakness.

Warn patient not to take herb for symptoms prior to speaking with his health care provider, as this may delay medical diagnosis.

Tell patient to remind prescriber and pharmacist of any herbal or dietary supplement that he's taking when obtaining a new prescription.

Advise patient to consult his health care provider before using an herbal aration because a treatment with proven efficacy may be available.

Safety Risk Warn patient not to take large doses of licorice or use it for longer than 4 weeks at a time, because of the risk of toxicity.

Research summary

The concepts behind the use of licorice and the claims made regarding its effects haven't yet been validated scientifically.