Losartan Potassium/Hydrochlorothiazide (Generic Hyzaar). The combination of hydrochlorothiazide and losartan is used to treat high blood pressure (hypertension) and to reduce the risk of stroke in people with hypertension.

Hydrochlorothiazide is a thiazide diuretic (water pill) that helps prevent your body from absorbing too much salt, which can cause fluid retention.

Losartan is in a group of drugs called angiotensin II receptor antagonists. Losartan keeps blood vessels from narrowing, which lowers blood pressure and improves blood flow.