What is losartan potassium hydrochlorothiazide?

HYZAAR 50-12.5 (losartan potassium-hydrochlorothiazide), HYZAAR 100-12.5 (losartan potassium-hydrochlorothiazide) and HYZAAR 100-25 (losartan potassium-hydrochlorothiazide) combine an angiotensin II receptor (type AT1)antagonist and a diuretic, hydrochlorothiazide.