The main ingredient of Betalucil is metoprolol, and the effect of lowering heart rate is reversible. Metoprolol is a beta-blocker, which can lower blood pressure and heart rate by inhibiting beta receptors. The effect of metoprolol is reversible, after the effect of the drug is gone, the heart rate can be gradually restored, will not lead to permanent bradycardia. Metoprolol can be used for tachyarrhythmias such as sinus tachycardia and frequent premature beats. Metoprolol can cause bradycardia while controlling the heart rate. Be careful to strengthen the monitoring of the heart rate during the course of taking the medicine, and reduce the dosage or stop the medicine in time if the heart rate is too low. Metoprolol belongs to the western prescription drugs, the adverse effects of the drug are dizziness, nausea, dyspnea, bradycardia, cold extremities, etc. Allergy to the drug components, II degree III degree atrioventricular block, cardiogenic shock, severe bradycardia, bronchial asthma, and other patients are prohibited. Clinical oral metoprolol should be used under the guidance of a physician.