Drug interactions between isosorbide and licorice

GENERALLY AVOID: Licorice use has been associated with hypertension and may antagonize the effects of antihypertensive agents. Glycyrrhizic acid, a component of licorice, is hydrolyzed in the intestine to a metabolite (glycyrrhetinic acid) that causes mineralocorticoid and renin-suppressing effects. In one study, licorice was found to increase blood pressure in a dose-dependent manner. Healthy volunteers who consumed licorice 50 to 200 g/day (corresponding to 75 to 540 mg/day of glycyrrhetinic acid) for two to four weeks had a 3.1 to 14.4 mmHg increase in their systolic blood pressure. Even the lowest dosage demonstrated a significant effect. In another study, plasma potassium levels decreased by 0.3 to 1.5 mEq/L in 12 out of 14 healthy volunteers who ingested licorice 100 or 200 g/day (equivalent to 700 to 1400 mg/day of glycyrrhizic acid) for one to four weeks, including four who had to be withdrawn from the study because of hypokalemia. Two more subjects were withdrawn due to edema of the face, hands, and ankles. Other side effects reported include mild, transient generalized edema; headache; sodium retention; and weight gain (1 to 4 kg, mean 1.5 kg). Signs of renin-angiotensin-aldosterone suppression were observed in all subjects, especially plasma renin activity and urinary aldosterone concentrations, which fell to subnormal or undetectable levels in the majority of subjects. There have been various published case reports of refractory hypertension, severe hypokalemia (life-threatening hypokalemic paralysis, myopathy, arrhythmia, or cardiac arrest), and hypertensive encephalopathy in association with licorice intoxication. Hypertension and hypokalemia have also been reported with moderate doses of licorice in the form of licorice-flavored chewing gum or candy, chewing tobacco, or licorice-based foods and beverages consumed on a chronic basis. Prolonged use of licorice has led to a hypermineralocorticoid (pseudohyperaldosteronism) syndrome characterized by hypertension, hypernatremia, hypokalemia, metabolic alkalosis, renin-angiotensin-aldosterone suppression, and edema. In studies and case reports, licorice toxicity has generally been completely reversible within one to several weeks of licorice discontinuation. However, renin-angiotensin-aldosterone axis may be suppressed for up to several months.

MANAGEMENT: Patients receiving antihypertensive therapy should avoid or limit the consumption of licorice-containing products. Even relatively moderate doses of licorice may be problematic in susceptible patients when ingested regularly for prolonged periods.