Losartan Interactions

Losartan blocks the angiotensin II receptor, lowering aldosterone and reducing the amount of potassium the kidneys excrete. Adding concentrated potassium supplements or potassium-based salt substitutes can push serum potassium toward the hyperkalemic range, which carries cardiac arrhythmia risk in people with kidney impairment, diabetes, or heart failure. Routine monotherapy raises measured potassium only modestly in people with healthy kidneys, but the safety margin narrows once supplements or other potassium-raising drugs are added.

Glycyrrhizin in licorice mimics aldosterone, causing the kidneys to retain sodium and water while losing potassium. This pseudoaldosteronism raises blood pressure and works against losartan's antihypertensive effect, and the potassium loss can cause weakness and dangerous heart-rhythm problems.

Grapefruit can reduce how much losartan is converted into its active form, which may modestly blunt the drug's blood-pressure-lowering effect.

Hawthorn modestly lowers blood pressure through vasodilation and endothelial effects. Taken with losartan, an angiotensin II receptor blocker, the two can add up and occasionally cause dizziness or lightheadedness, mainly in people who already run low or who take more than one blood pressure medication.