Betalucil is the trade name for metoprolol, and unauthorized reduction of the dosage can result in symptoms such as increased heart rate, increased contractility of the heart muscle, and increased blood pressure. Of these, increased heart rate has a greater impact on patients and can be more uncomfortable and dangerous. Metoprolol is a commonly used beta-blocker. Clinically, metoprolol is commonly used in the treatment of hypertension, heart failure, coronary heart disease and other diseases, and has the effect of reducing heart rate, lowering blood pressure, and reducing myocardial contractile load. Contraindications for metoprolol are: atrioventricular block, sick sinus syndrome, sinus bradycardia, severe peripheral vascular disease, bronchial asthma and so on. Its common adverse reactions include: affecting the body’s sugar and lipid metabolism, airway spasm, and triggering bradycardia. Sudden taper application of metoprolol reflexively excites the sympathetic nerves, which leads to symptoms of increased heart rate and rebound elevation of blood pressure. In addition, dosage reduction can lead to enhanced myocardial contraction due to enhanced myocardial oxygen consumption, which is manifested by palpitations (rapid heartbeat, often accompanied by panic) and other uncomfortable symptoms. Metoprolol dosage reduction needs to be gradually and slowly reduced under the guidance of a doctor, otherwise rebound phenomenon may occur, inducing serious consequences.