Many of the adverse effects attributed to licorice are due to glycyrrhetinic acid (GA) at doses above 100-400 mg/day. For this reason, the deglycyrrhizinated licorice (DGL) may be safer and more appropriate in cases where glycyrrhizin (GL) or GA are not required for efficacy.
Side-effects may be more pronounced in people with essential hypertension who appear to be more sensitive to the inhibition of 11HSD by licorice than normotensive subjects.
• Hypercortisolism and pseudohyperaldosteronism — associated with sodium retention, potassium loss and suppression of the renin-angiotensin-aldosterone system and presenting as hypertension, fluid retention, breathlessness, hypernatraemia and hypokalaemia.
• Hypokalaemia — may present as hypotonia and flaccid paralysis, peripheral oedema, polyuria, proximal myopathy, lethargy, paraesthesiae, muscle cramps, headaches, tetany, breathlessness and hypertension. In practice, licorice is often mixed with the potassium-rich herb dandelion leaf, which also has mild diuretic effects.
• Hypokalaemic paralysis — although rare, some cases have been reported as a result of chronic licorice use.
• Rhabdomyolysis — a number of cases are reported in the scientific literature as a result of severe hypokalaemia.
• Dropped head syndrome — a case report exists of DHS (isolated weakness of the extensor muscles of the neck) due to licorice-induced hypokalemia.
• Hypertension encephalopathy may occur even at low doses in susceptible patients with 11-beta-HSD deficiency.
• Reduced 11-beta-HSD activity may have a role in increased sodium retention in pre-eclampsia, renal disease and liver cirrhosis. Reduced placental levels may explain the link between reduced birth weight and adult hypertension (the Barker hypothesis).
• Visual disturbance — ingestion of high doses of licorice (110-900 g) has been reported to elicit symptoms of visual disturbance in a case series of five patients. This may be attributed to the possible ability of licorice to ‘stimulate retinal and occipital vasospasm and vasospasm of vessels supplying the optic nerve’.