Furosemide Interactions

Furosemide is a loop diuretic that blocks the sodium-potassium-chloride cotransporter in the kidney, making it one of the most reliable causes of drug-induced low potassium (hypokalemia). Supplementation or potassium-sparing co-therapy is often needed, but adding potassium on your own, especially alongside ACE inhibitors, ARBs, or kidney impairment, can swing levels too high. The combination should always be guided by blood monitoring rather than self-dosing.

Glycyrrhizin in licorice inhibits 11-beta-hydroxysteroid dehydrogenase type 2, allowing cortisol to act on mineralocorticoid receptors and driving renal potassium loss. Combined with furosemide, which already wastes potassium, this can add up to a markedly higher risk of significant hypokalemia, worsening edema, raised blood pressure, and arrhythmia.

Furosemide blocks the Na-K-2Cl cotransporter in the loop of Henle, which removes the electrical gradient that normally helps the kidney reabsorb magnesium. This can increase urinary magnesium loss, especially with high-dose or prolonged use. In most outpatients the kidney's downstream segments compensate, so clinically meaningful hypomagnesemia is less common with loop diuretics than with thiazides; the effect is more relevant during high-dose IV diuresis, critical illness, or poor intake.