Licorice

Traditional texts describe the preparations below, and where those texts give specific amounts, the amounts are quoted here as part of that record. This is a record of historical practice, not a dosage recommendation - the figures are what the sources say, not what HerbMate tells you to take. Amounts, potency, and safe use vary enormously by preparation, plant part, and person.

Liquorice appears to diminish the effects of antihypertensives and may have additive effects on potassium depletion if given in large quantities with laxatives and corticosteroids. Iron absorption may be decreased by liquorice, whereas antibacterials may diminish the effects of liquorice. A case report describes raised digoxin levels and toxicity in a patient taking liquorice. Although it has been suggested that liquorice may enhance the effects of warfarin, there appears to be no evidence to support this. Note that liquorice is a constituent of a number of Chinese herbal medicines.

Laxatives

Liquorice may cause additive hypokalaemia if given in large quantities with laxatives.

Ulcer healing drugs

The interaction between liquorice and ulcer-healing drugs is based on experimental evidence only.

Antihypertensives

Liquorice may cause fluid retention and therefore reduce the effects of antihypertensives. Additive hypokalaemia may also occur with loop and thiazide diuretics. 4 weeks (equivalent to glycyrrhetinic acid 150 mg daily) increased mean blood pressure by 15.3/9.3 mmHg. Smaller rises (3.5/3.6 mmHg) were seen in 25 normotensive subjects taking the same dose of liquorice. In another study in healthy subjects liquorice 50 to 200mg daily for 2 to 4 weeks (equivalent to glycyrrhetinic acid 75 to 540mg daily) increased systolic blood pressure by 3.1 to 14.4 mmHg. The group taking the largest quantity of liquorice experienced the greatest rise in systolic blood pressure, and was the only group to have a statistically significant rise in diastolic blood pressure. There are many published case reports of serious hypertension occurring in people consuming, often, but not always, excessive doses of liquorice from various sources (confectionery, alcoholic drinks, flavoured chewing tobacco, herbal teas, herbal medicines).

Iron compounds

The interaction between liquorice and iron compounds is based on experimental evidence only.

Warfarin

The interaction between liquorice and warfarin is based on experimental evidence only.

Food

No interactions found. Note that liquorice is consumed as part of the diet.

Corticosteroids

Liquorice, if given in large quantities with corticosteroids, may cause additive hypokalaemia. (a) Dexamethasone In a parallel group study, 6 patients were given glycyrrhizin 225 mg daily for 7 days, and 6 patients were given the same dose of glycyrrhizin and dexamethasone 1.5 mg daily for 7 days. The mineralocorticoid effects of glycyrrhizin were significantly reduced by dexamethasone; cortisol plasma concentrations and urinary excretions were reduced by up to 70%.1 (b) Hydrocortisone Glycyrrhizin slightly increased the AUC of cortisol by 13.6% in 4 patients with adrenocorticol insufficiency taking oral hydrocortisone 20 to 40 mg daily. Note that glycyrrhizin had no effect on endogenous cortisol levels in 7 control subjects without adrenal insufficiency. In a study in 23 healthy subjects, topical glycyrrhetinic acid markedly potentiated the activity of topical hydrocortisone, as assessed by cutaneous vasoconstrictor effect. (c) Prednisolone A study in 6 healthy subjects found that, after taking four 50-mg oral doses of glycyrrhizin at 8-hourly intervals, followed by a bolus injection of prednisolone hemisuccinate 96 micrograms/kg, the AUC of total prednisolone was increased by 50% and the AUC of free prednisolone was increased by 55%. This confirms previous findings in which the glycyrrhizin 200 mg was given by intravenous infusion. Glycyrrhizin slightly increased the AUC of prednisolone by about 16 to 20% in 12 patients who had been taking oral prednisolone 10 to 30 mg daily for at least 3 months.

Digitalis glycosides

An isolated case of digoxin toxicity has been reported in an elderly patient attributed to the use of a herbal laxative containing kanzo (liquorice). An 84-year-old man taking digoxin 125 micrograms daily and furosemide 80 mg daily complained of loss of appetite, fatigue and oedema of the lower extremities 5 days after starting to take a Chinese herbal laxative containing liquorice (kanzo) 400 mg and rhubarb (daio) 1.6 g three times daily. He was found to have a raised digoxin level of 2.9 nanograms/mL (previous level 1 nanogram/mL) with a pulse rate of 30 bpm, and a slightly low potassium level (2.9 mmol/L).

These entries keep the wording of the reference they come from, and three phrases mean three different things. "No interactions found" means the source looked for reports of that pairing and found none. "No data found" means nothing has been published either way. "Based on experimental evidence only" means the effect has been seen in a laboratory or animal study but not in people - a reason for caution, not a report of harm.