Metoprolol, sold under the brand names Lopressor and Toprol-XL among others, is a medication used to treat angina, high blood pressure and a number of conditions involving an abnormally fast heart rate. [5] Metoprolol (Lopressor®) is a medication that lowers your blood pressure and heart rate, making it easier for your heart to pump blood to the rest of your body. Read on to learn about the side effects of metoprolol, including common, severe, and long-term side effects, and how to manage them. Metoprolol is used alone or together with other medicines to treat high blood pressure (hypertension). High blood pressure adds to the workload of the heart and arteries. If it continues for a long time, the heart and arteries may not function properly. Learn about the side effects of metoprolol, from common to rare, for consumers and healthcare professionals. Overview: Metoprolol is a beta blocker. It is is used to treat high blood pressure, chest pain, heart failure, and lower the risk of a repeat heart attack. Common side effects include tiredness. Metoprolol is a beta-blocker medication used to treat high blood pressure, chest pain (angina), and heart failure, and to improve survival after a heart attack.