Beta blockers, also known as Beta-blockers or Beta-adrenergic antagonists, are a group of drugs that inhibit the effects of the catecholamines adrenaline and noradrenaline in the body.
What are beta blockers?
These two transmitter substances, which are also known as "stress hormones", bind to the ß-receptors of various organs in the body and thereby trigger partly physiologically important and partly pathological processes. Beta blockers have chemical structural components similar to adrenaline and noradrenaline, which means that, as competitive antagonists, they can occupy their receptors without triggering the corresponding effects.
They can be roughly divided into ß1-selective and non-selective beta blockers. The former are characterized by a higher cardiac selectivity, since the density of the receptor subtype ß1 is particularly high in the heart.
This is a desired property for most indications; examples of active ingredients are atenolol, bisoprolol, metoprolol and nebivolol. The non-selective beta blockers such as propranolol, timolol and sotalol have proven themselves in other areas of application.
Medical effect & application
The most common medical use of the Beta blockers refers to the cardiovascular system. By blocking the ß-receptors, beta blockers reduce the contraction force and excitability of the heart as well as its beat frequency, which leads to a drop in blood pressure. For arterial high blood pressure, beta blockers are often prescribed in combination with other antihypertensive drugs, such as diuretics.
In contrast to the active ingredient groups of ACE inhibitors, diuretics and AT1 antagonists, ß1-selective beta blockers such as metoprolol can also be used during pregnancy. Beta blockers are also prescribed for coronary heart disease, heart failure, cardiac arrhythmias and for heart attack prophylaxis.
Beta blockers also reduce the production of aqueous humor in the eye by lowering the secretion of aqueous humor and can therefore also be used to treat glaucoma (timolol). Metoprolol and propranolol are also used as the first choice for migraine prophylaxis. Further indications are hyperthyroidism, tremor and pheochromocytoma, a catecholamine-producing tumor of the adrenal gland.
Interactions
Most of the interactions of the Beta blockers concern their antihypertensive effects and their amplification by other means. If acetylcholinesterase inhibitors such as rivastigmine, donepezil and galantamine (agents for the treatment of Alzheimer's dementia) are taken during beta blocker therapy, the mutual reinforcement of their effects can lead to bradycardia (decreased heart rate) and bronchial constriction with shortness of breath.
Simultaneous treatment with other antihypertensive agents and the antiarrhythmics amiodarone and dronedarone can also result in an increased drop in blood pressure and bradycardia. If co-medication with the mentioned agents cannot be avoided, the heart rate and blood pressure should be monitored and the dosages adjusted if necessary.
Diabetics who are treated with insulin or sulphonylureas such as glibenclamide can experience increased hypoglycaemia. It also masks the warning symptoms of hypoglycaemia, such as restlessness, headache, tremors and tachycardia. In particular, the non-selective beta blockers can partially cancel out the bronchodilator effects of theophylline and its derivatives, which can lead to shortness of breath.
Risks & side effects
Beta blockers should always be dosed gradually in and out to avoid side effects. This means that at the beginning of the therapy, the dose is low and the dose slowly increased, and abrupt discontinuation should also be avoided.
Possible side effects occur primarily when starting treatment with beta blockers and include an excessive drop in blood pressure, dizziness, fatigue, nervousness, sleep disorders, bradycardia, sweating, gastrointestinal complaints, muscle weakness, edema and impotence. Beta blockers should not be used in severe peripheral circulatory disorders, severe asthma, low blood pressure and bradycardia; special monitoring is necessary in diabetes mellitus and renal insufficiency.
After careful risk-benefit assessment, beta blockers can be used during pregnancy, but should be discontinued 72 hours before the due date to avoid bradycardia in the newborn. Athletes should note that beta blockers are assigned to the substance classes on the doping list that are prohibited for certain sports.
