This drug is used to treat high blood pressure (hypertension). lowering high blood pressure helps prevent strokes, heart attacks, and kidney problems. this product contains two medications: olmesartan and hydrochlorothiazide. olmesartan is an angiotensin receptor blocker (arb) and works by relaxing blood vessels so that blood can flow more easily. hydrochlorothiazide is a "water pill" (diuretic) that causes you to make more urine, which helps your body get rid of extra salt and water.