Metoprolol is an anti-hypertensive (high blood pressure) drug classified as a selective beta-1 receptor blocker, also called a beta adrenergic blocker. Metoprolol is sold under the brand names Lopressor and Toprol-XL and is available in immediate-release and prolonged-release formulations. In addition to high blood pressure, metoprolol is prescribed to treat conditions including angina pectoris (chest pain) abnormal heart rhythms, migraine, tremors, congestive heart failure, bleeding from the esophagus, side effects of antipsychotics, and to prevent second heart attacks.
Beta adrenergic blockers like metoprolol work by blocking certain receptors (beta-1 receptors) for adrenaline. Adrenaline is a hormone that causes increased heart rate and blood pressure, and blocking these particular receptors heart rate and especially blood pressure.