Licorice Poisoning 

Updated: Apr 23, 2019
Author: Seth Schonwald, MD, FACEP; Chief Editor: Sage W Wiener, MD 

Overview

Practice Essentials

 Natural licorice is an extract from the root of Glycyrrhiza glabra, a 4- to 5-foot woody shrub that contains glycyrrhizic acid (GZA) and grows in subtropical climates in Europe, the Middle East, and Western Asia. Licorice extracts and its principal component, glycyrrhizin, have extensive use in foods, tobacco products, and snuff, and in traditional and herbal medicine.

As a result of these extensive applications, estimated consumption of licorice and glycyrrhizin in the United States is high: 0.027-3.6 mg glycyrrhizin per kilograms per day.[1] However, many candies marketed as licorice (eg, red licorice) have artificial licorice flavoring and do not contain glycyrrhizin.[2]   Licorice root that is sold as a dietary supplement can be found with the glycyrrhizin removed, resulting in a product known as deglycyrrhizinated licorice, or DGL.[3]

Licorice poisoning is rare. However, regular licorice ingestion can result in hypokalemia, hypernatremia, and water retention (see Presentation and Workup). Emergency treatment of licorice poisoning is largely supportive and consists primarily of monitoring for electrolyte abnormalities (especially of potassium) and other complications, with correction if necessary (see Treatment).

Background

Licorice (or liquorice) is a plant of ancient origin and steeped in history. Licorice has been used as a medicinal agent in a number of cultures,[4] dating back to ancient Egypt and China. Medicinal uses have included the following:

  • Cough suppression [5]
  • Gastric ulcer treatment [6]
  • Treatment of early Addison disease [7, 8]
  • Treatment of liver disease [9, 10]
  • As a laxative
  • Dementia symptom treatment [11]

Licorice flavor is found in a wide variety of licorice candies. Licorice is also found in some soft drinks (eg, root beer) and is in some herbal teas where it provides a sweet aftertaste.[12]

 Licorice extract (block, powder, or liquid) may be applied to cigarette tobacco at levels of about 1-4% to enhance and harmonize the flavor characteristics of smoke, improve moisture-holding characteristics of tobacco, and act as a surface-active agent for ingredient application.[13]

 

Pathophysiology

Natural licorice possesses both mineralocorticoid properties and glucocorticoid properties. Most licorice-flavored foods available in the United States do not contain GZA, and they do not produce the hypermineralocorticoid syndromes observed with the long-term consumption of moderate-to-significant amounts of natural licorice.

Consumption of large doses of GZA in licorice extract can lead to hypokalemia and serious hypertension, a syndrome known as hypermineralocorticoidism.[14, 15] Biochemical studies indicate that glycyrrhizinates inhibit 11-beta-hydroxysteroid dehydrogenase (type 2), the enzyme responsible for inactivating cortisol through conversion to cortisone. As a result, a continuous, high-level exposure to glycyrrhizin compounds can produce hypermineralocorticoid-like effects in both animals and humans. These effects are reversible upon withdrawal of licorice or glycyrrhizin.[1]

In the kidney, cortisol activation of mineralocorticoid receptors alters renal tubular exchange of sodium (retained), potassium (excreted), and hydrogen ions (excreted); producing an increased extracellular volume (hypertension,[16] edema), hypokalemia (weakness, muscle spasm),[17] and metabolic alkalosis.[18]

Pseudoprimary aldosteronism from chronic licorice ingestion is characterized by low serum and urinary aldosterone levels and decreased serum renin activity. This differs from true primary hyperaldosteronism caused by aldosterone-producing adenomas or primary adrenal hyperplasia, which is characterized by elevated urine and serum aldosterone levels.

Licorice can reduce the serum testosterone level, probably by blocking 17-hydroxysteroid dehydrogenase and 17,20 lyase.[19] Licorice has therefore been considered an adjuvant therapy of hirsutism and polycystic ovary syndrome.[20]

The exact amount of ingested GZA that produces mineralocorticoid toxicity is unclear. A meta-analysis to assess the effect of chronic ingestion of licorice found the mean daily dose of glycyrrhizic acid across 18 studies was 377.9 mg, which is approximately 189 g of black licorice a day, assuming 2.0 mg g−1 (0.2% w/w) glycyrrhizic acid in black licorice. However, the concentration of glycyrrhizic acid changes significantly dependent on the product. Licorice findings range between 0.26 and 7.9 mg g−1, while in health products the range was 0.30 to 7.9 mg g−1. A typical pack of Liquorice Allsorts was found to contain 91.0 mg, a serving of licorice tea contained 20.0 mg and a single licorice pipe contained 4.6 mg. With only limited and sporadic consumption of licorice, it would be difficult to ingest more than 500 mg of glycyrrhizic acid per day. Assuming an average concentration of 2.0 mg g−1 for black licorice confectionery, it would require consumption of 250 g per day to reach 500 mg of glycyrrhizic acid daily. While this quantity is relatively high, but as evidenced by numerous case reports, a small portion of the population does consume licorice at these levels.[21]

Prognosis

Patients generally fully recover with discontinuation of exposure. After licorice exposure is discontinued, spontaneous correction of hypertension and hypokalemia generally occur within several weeks; however, months may pass before the renin-aldosterone system becomes active again.[22] Muscle weakness/paralysis may resolve within days of potassium replacement.

Severe, and sometimes fatal, complications following ingestion of licorice can occur. In these cases, significant quantities of licorice have typically been consumed in the short- to medium-term. Reported complications include rhabdomyolysis, hypertensive encephalopathy and cardiac arrest and death.[21]

 

Presentation

History

Most patients with licorice poisoning report chronic toxicity from daily excessive ingestion of natural licorice products (not artificial licorice flavoring). Cases of poisoning are mostly chronic in nature, not acute; however, binging on licorice has also resulted in toxicity.[2] Symptoms of licorice toxicity may include the following:

  • Fatigue and muscle cramping
  • Dark urine (myoglobinuria)
  • Weakness (hypokalemia, myopathies)
  • Polyuria/nocturia (increased extracellular volume)
  • Edema (increased extracellular volume)
  • Dyspnea (pulmonary edema)
  • Headache (hypertension)
  • Paresthesias/dysesthesias (eg, burning sensations of extremities)
  • Impotence and diminished libido
  • Amenorrhea

Physical Examination

Findings on physical examination may include the following:

  • Edema (peripheral, pulmonary), secondary to increased extracellular fluid from water retention

  • High blood pressure,[23, 24] including dangerously high blood pressure with symptoms such as headache, nausea, vomiting, and hypertensive encephalopathy with strokelike effects (eg, hemiplegia)

  • Spasms/tetany

  • Hyporeflexia, muscle wasting, weakness, flaccid paralysis[25, 26]

  • Myoglobinuria/rhabdomyolysis[27]

  • Trousseau and Chvostek signs (from hypokalemia with alkalosis)

  • Cardiac arrest, dysrhythmias (rare) from hypokalemia

 

DDx

Diagnostic Considerations

Other causes of hypokalemia to be considered include the following:

  • Aminoglycosides
  • Barium poisoning
  • Beta-adrenergic agonists
  • Diarrhea
  • Diuretics
  • Enemas or laxative use
  • Hyperaldosteronism
  • Ileal loop
  • Insulin
  • Leukemia
  • Magnesium depletion
  • Periodic hypokalemic paralysis
  • Steroids
  • Theophylline

Other causes of hyperaldosteronism to be considered include the following:

Differential Diagnoses

 

Workup

Approach Considerations

Diagnosis is generally confirmed by combination of hypokalemia, increased urinary free cortisol, elevated cortisol-cortisone metabolite ratio, and low or absent urinary aldosterone. A low serum potassium level is the most helpful screening result for establishing mineralocorticoid excess in patients with hypertension. An elevated urinary potassium level may be present. Dilutional anemia may be present, and the hematocrit may be depressed. Hypokalemia, hypernatremia, and water retention are primary problems associated with chronic licorice ingestion.[2]

Licorice poisoning can cause hypokalemic rhabdomyolysis with resultant myoglobinuria and elevated serum creatine kinase level.[28, 29] Myoglobinuria can cause acute tubular necrosis. Emergency physicians should inquire about the consumption of products that may contain natural licorice extract when patients present with unexplained hypertension, hypokalemia, edema, rhabdomyolysis, or myoglobinuria.[30]

If clinically indicated, chest radiography may be performed to assess for pulmonary edema. If urine aldosterone levels are high in a patient with evidence of hypermineralocorticoidism (eg, hypertension, hypokalemia, suppression of the renin-angiotensin system), tumors rather than chronic licorice toxicity are more likely to be the cause, and abdominal computed tomography or magnetic resonance imaging scans may be warranted.

Electrocardiography should be performed to evaluate for hypokalemic changes and QT prolongation or dysrhythmia, including torsades des pointes. Pulse oximetry and arterial blood gas (ABG) measurement can be used to evaluate for pulmonary edema and respiratory muscle weakness.

Many tests are expensive and time-consuming. Consultation with an endocrinologist and toxicologist may be helpful for determining initial workup. Measure serum glycyrrhetinic acid (GRA) and glycyrrhizic acid (GZA) levels with enzyme-linked immunoabsorbent assay (ELISA) and high-performance liquid chromatography (HPLC). Measure the urinary GRA level with gas chromatography–mass spectrometry (GC-MS).

Ascertaining plasma renin activity and urine aldosterone level (24-h collections) is helpful; both are typically low. Determining urine cortisol levels (often elevated) and cortisol-cortisone metabolite ratios (often elevated) may be helpful.

 

Treatment

Approach Considerations

Prehospital care consists of supportive treatment, including airway, breathing, and circulatory support (ABCs), as clinically indicated. Cardiac monitoring should be performed if clinically indicated.

Emergency department care is as follows:

  • Toxicity typically develops after chronic excessive ingestion; most patients with a single acute ingestion will not develop toxicity
  • In cases of suspected chronic toxicity, monitor electrolytes, especially potassium
  • Supplement potassium, as indicated
  • Consider potassium-sparing diuretics, as needed
  • Treat rhabdomyolysis, if present, with hydration
  • Monitor for and treat electrolyte-induced dysrhythmias.
  • Monitor for and treat pulmonary edema and respiratory muscle weakness

Consider admitting patients with any of the following:

  • Severe electrolyte abnormalities
  • Symptomatic hypokalemia, especially if electrocardiographic changes are present (eg, prolonged QT)
  • Severe or symptomatic hypertension
  • Progressive weakness or paralysis
  • Rhabdomyolysis
  • Pulmonary edema

Consultations with an endocrinologist and a toxicologist may be helpful. Frequent assessment of hypertension and hypokalemia, as well as the need for further potassium supplements and diuretics, may be included in outpatient care.

Prevention

Avoiding ingestion of natural licorice in the following settings is reasonable:

  • Hypertension
  • Diuretic use
  • Sexual dysfunction
  • Pregnancy 
 

Medication

Medication Summary

The goals of pharmacotherapy are to reduce morbidity and to prevent complications. Administration of potassium-sparing diuretics that are aldosterone antagonists can counteract the cortisol activation of mineralocorticoid receptors caused by chronic licorice ingestion.

Diuretics, Potassium-Sparing

Class Summary

These agents may be used to correct potassium deficiency or fluid/electrolyte imbalance.

Spironolactone (Aldactone)

Spironolactone competes with aldosterone for receptor sites in distal renal tubules by increasing water and sodium chloride excretion while retaining potassium and hydrogen ions.

Triamterene (Dyrenium)

Triamterene is a potassium-sparing diuretic with relatively weak natriuretic properties. It exerts a diuretic effect on the distal renal tubule, inhibiting reabsorption of sodium in exchange for potassium and hydrogen. It increases sodium excretion and reduces the excessive loss of potassium and hydrogen associated with hydrochlorothiazide. This agent is not a competitive antagonist of mineralocorticoids; a potassium-conserving effect is observed in patients with Addison disease (ie, without aldosterone).