Beta-blockers are very important drugs in therapy of patients of internal medicine, especially in treatment of hypertension and heart disorders.
There are many generations of beta-blockers that are somewhat different in their effects. The common ability is blockage of beta-receptors in the heart. These beta-receptors are normally targeted by stress hormones such as the epinephrine. By blocking these receptors, the beta-blockers decrease the blood pressure, slower the heart rate, reduce load of the heart muscle and decrease myocardial consumption of oxygen. In addition, beta-blockers significantly decrease risk of various arrhythmias. Beta-blockers are divided into cardioselective and non-cardioselective. Cardioselective drugs affects the receptors of the myocardial muscle, while non-selective also affect other organs.
Beta-blockers are used to treat many cardiac diseases. They are used in heart failure, cardiomyopathies and angina pectoris, in chronic medication after a heart attack and in high blood pressure. Thanks to their effect on decreasing the heart rate, beta-blockers may be used in patients with certain rhythm disorders with rapid heart rate (e.g. atrial fibrillation). Some non-cardioselective beta-blockers are also applied in the treatment of portal hypertension and its complications (such as esophageal varices), because they reduce the local blood pressure in the portal vein.
There are many active substances that are used, for example acebutolol, betaxolol, bisoprolol, carvedilol, celiprolol, metoprolol, nebivolol and others.
Beta-blockers may cause too excessive drop of the blood pressure, resulting in overall weakness, vertigo and episodes of unconsciousness. Another possible disadvantage is significant bradycardia that can cause heart failure. Beta-blockers should not be combined with certain calcium channel blockers (verapamil, diltiazem), because their bradycardizing effects potentiate. Other significant side effects of beta-blockers include aggravation of pulmonary diseases such as bronchial asthma, chronic bronchitis and COPD, decreased libido and various digestive disorders.