Metoprolol Succinate is a beta blocker which works specifically on the heart to reduce heart rate and make the heart more efficient at pumping blood throughout the body. Hydrochlorothiazide is a diuretic which lowers blood pressure by removing extra water and certain electrolytes from the body. Over time it also relaxes blood vessels and improves blood flow. Metoprolol blocks beta receptors in your heart. These receptors normally bind to hormones called catecholamines. When catecholamines bind to these receptors, it causes your heart to beat harder and faster. Blocking these receptors helps your heart beat more slowly. These effects can help your heart work better, lower blood pressure, and may reduce your risk for heart attack and stroke.