Contraindications and Precautions
Licorice should be used with caution in people with hypertension (or a genetic predisposition to hypertension) or fluid retention, and is contraindicated in hypotonia, severe renal insufficiency, hypokalaemia, liver cirrhosis and cholestatic liver disease. The effects are likely to be dose-dependent and more likely in people with essential hypertension with a particular tendency to 11HSD inhibition by licorice. It is also contraindicated in people with a deficiency in 11HSD.
Long-term use (>2 weeks) at therapeutic doses should be monitored closely due to the potential side-effects. Additionally, a high-potassium low-sodium diet should be consumed during treatment.
As licorice may questionably reduce testosterone levels in men, it should be used with caution in men with a history of impotence, infertility or decreased libido.
Licorice is contraindicated in pregnancy. A Finnish trial found that high consumption of licorice during pregnancy increased the likelihood of early delivery but did not significantly affect birth weight or maternal blood pressure.
Practice Points / Patient Counselling
• Licorice has been used as a food, flavouring agent and medicine since ancient times.
• It exhibits mineralocorticoid, anti-inflammatory, antioxidant, mucoprotective and ulcer-healing activity in humans. Antiviral, antibacterial, antitumour, expectorant and hepatoprotective effects have also been demonstrated in animal or test tube studies. Significant effects on oestrogen and testosterone levels remain to be established in controlled trials as evidence is inconsistent.
• Licorice is a popular treatment for respiratory tract infections, gastrointestinal ulcers and dyspepsia. It is also used to treat chronic stress and numerous other conditions, largely based on evidence of pharmacological activity.
• Glycyrrhetinic acid has been used topically as an anti-inflammatory agent and also together with cortisone preparations to increase effects.
• High-dose licorice (> 100 mg glycyrrhizin) used for more than 2 weeks can induce hypokalaemia and pseudoaldosteronism in susceptible individuals. As such, it should be used with caution and under professional supervision. Additionally, it interacts with numerous medicines. The deglycyrrhizinated licorice (DGL) form is considered safer.
Answers to Patients’ Frequently Asked Questions
What will this herb do for me?
Licorice has many effects in the body, the most well-established ones being reducing inflammation; enhancing healing of peptic ulcers; and treating infections such as bronchitis and cough.
When will it start to work?
Beneficial effects in peptic ulcer occur within 6-12 weeks, although deglycyrrhizinated licorice is usually used to avoid side-effects. Symptoms of dyspepsia should respond within the first few doses. Effects in bronchitis will vary between individuals.
Are there any safety issues?
Used in high doses for more than 2 weeks, licorice can induce several side-effects such as raised blood pressure and fluid retention and may interact with a number of drugs. The DGL (deglycyrrhizinated licorice) form is considered safer.