Low blood pressure below 90/60 mmHg should not be taken with Betalac. Betalac is a beta-blocker, which also has the effect of slowing down the heart rate and lowering blood pressure. If the patient has low blood pressure, taking betalac will cause the blood pressure to drop further, and in serious cases, syncope and shock may occur. Betalac mainly inhibits sympathetic excitation, which can reduce myocardial oxygen consumption, and is mainly used to treat unstable angina pectoris, acute myocardial infarction, myocardial ischemia, and rapid arrhythmias. Betalactone should not be used if the patient has hypotension, morbid sinus node syndrome, cardiogenic shock, decompensated cardiac insufficiency, or atrioventricular block. In addition, Betalac should not be used in patients with bronchial asthma.