Propranolol hydrochloride tablets work to treat hypertension, angina pectoris, arrhythmia, and thyroid crisis. The drug is a non-selective β-adrenergic receptor blocker, which not only plays a role in lowering blood pressure by reducing cardiac output, inhibiting renin release and reducing sympathetic excitation of vasoconstrictor center; but also reduces exercise-induced increase in heart rate, systolic blood pressure and degree of myocardial contraction, and reduces myocardial oxygen consumption; as well as exerts a membrane-stabilizing effect, affecting myocardial action potential. So clinically the drug is used in the treatment of hypertension, exertional angina pectoris, control of supraventricular tachyarrhythmias, ventricular arrhythmias, and thyroid crisis. There are adverse reactions such as headache, dizziness, nausea, diarrhea, rash, fatigue after the use of the drug. Contraindicated in patients with bronchial asthma or risk of bronchospasm; contraindicated in patients with diabetic ketoacidosis, metabolic acidosis; patients with right heart insufficiency due to pulmonary hypertension; contraindicated in patients with congestive heart failure. When using the drug should start from a low dose, long-term use of the drug should be regularly monitored pulse, blood pressure, electrocardiogram, X-ray examination and cardiac function; hyperthyroidism patients should not be suddenly discontinued; athletes, pregnant women and lactating women should be cautious. If you need to use the drug, it should be used under the guidance of a specialist, not self-medication.