Furosemide Interactions

Furosemide blocks the Na-K-2Cl cotransporter in the loop of Henle and is the most potent diuretic class for causing dose-dependent hypokalemia, affecting 25-36% of users. Supplementation or potassium-sparing co-therapy is frequently required, but uncontrolled dosing combined with ACE inhibitors or kidney disease can flip levels into hyperkalemia.

Glycyrrhizin in licorice inhibits 11-beta-hydroxysteroid dehydrogenase type 2, allowing cortisol to act on mineralocorticoid receptors and stimulating renal potassium excretion. Combined with furosemide, this produces additive potassium wasting and a markedly higher risk of severe hypokalemia, edema, hypertension, and arrhythmia.

Furosemide inhibits the Na-K-2Cl cotransporter, which abolishes the lumen-positive voltage driving paracellular magnesium reabsorption in the thick ascending limb. Long-term loop diuretic use causes urinary magnesium wasting and hypomagnesemia, which worsens loop-diuretic hypokalemia and increases arrhythmia risk.