Since catecholamines play a very important role in physiological and pathological phenomena in the body, drugs that block their receptors and drugs that mimic these substances have very important and widespread effects in the body.
Beta blockers are a very important class of this group of drugs that are used in the treatment of various heart diseases, including; rhythm disorders, hypertension, systolic heart failure, etc.
These drugs:
– Block beta receptors competitively, and their main difference is in whether they block receptors specifically or non-specifically.
– They often have high gastrointestinal absorption and reach maximum therapeutic concentrations within 1-3 hours.
– They are metabolized in large amounts in the liver, which causes them to have low bioavailability following oral administration. Of course, this defect is less common in the use of drugs from this group such as; betaxolol, pindolol, and sotalol.
-They are often distributed rapidly in various tissues.
Propranolol is a drug in this group that is very lipophilic and easily crosses the blood-brain barrier. Most of these drugs have a half-life of between 3 and 10 hours. Esmolol has the shortest half-life and nadolol has the longest half-life. These drugs often exert their effect through complete beta-receptor blockade and rarely through competitive stimulation of beta-receptors. Among the drugs in this group, only drugs that specifically block the β1 receptor and do not affect β2 can be used in pulmonary patients, especially people with asthma.
Treatment of hypertension:
Beta-blockers are often used in combination with diuretics in the treatment of patients with hypertension and control the patient’s blood pressure well.
Ischemic heart disease:
The use of beta-blockers in patients with cardiac ischemia increases survival and reduces disability. Long-term use of these drugs reduces mortality and disability and improves exercise tolerance. Beta-blockers also increase cardiac output in patients with systolic heart failure and ventricular wall thickening.
Cardiac arrhythmias:
Beta-blockers are often used to treat both ventricular and supraventricular cardiac arrhythmias. These drugs reduce ventricular response by prolonging the atrioventricular node refractory period and are used to treat atrial fibrillation and flutter. Among them, esmolol is an antiarrhythmic drug that is used to treat arrhythmias that occur around surgery and has a very short half-life.
Heart failure:
The use of beta-blockers in the treatment of heart failure increases the lifespan of these patients. Although it increases congestion in some patients, this does not mean that these patients should not be treated with beta-blockers. These drugs seem to benefit this group of patients by reducing remodeling and reducing the risk of sudden death. Carvedilol, bisoprolol, and metoprolol are the best candidates for the treatment of these patients.
Hyperthyroidism:
One of the most important disorders that occurs in patients with hyperthyroidism is increased catecholamine activity, which is treated with beta-blockers, especially propranolol.
BISOPROLOL:
Bisoprolol is a selective β1 receptor inhibitor that competitively inhibits this receptor while having very little effect on the β2 receptor (especially at doses less than 20 mg). The specificity of the mode of action of this drug makes it used in cases of heart failure, hypertension, asthma, etc. with very low concerns and side effects. The onset of action of this drug is approximately one to two hours after administration and it is almost completely absorbed. This drug has high tissue distribution and easily crosses the blood-brain barrier.
The half-life of this drug is between 9-12 hours in normal liver and kidney function, and increases to 27-36 hours if creatinine clearance is less than 40, and increases to 8-22 hours in cirrhosis of the liver.
