Beta-blockers (β- adrenolytics ) are medicines that temporarily block β- adrenergic receptors that are sensitive to adrenal hormones (adrenaline, norepinephrine). These receptors are localized in the heart, kidneys, skeletal muscles, liver, adipose tissue, and blood vessels. The drugs are usually used in cardiology to relieve symptoms in diseases of the heart and blood vessels.

How adrenaline receptor blockers work

The mechanism of action of β – blockers is associated with the temporary blocking of adrenergic receptors . The drugs limit the effects of adrenal hormones by reducing the sensitivity of target cells. β- adrenergic receptors respond to epinephrine and norepinephrine. They are found in different body systems:

• myocardium;
• adipose tissue;
• liver;
• blood vessels;
• kidneys;
• bronchi;
• the muscle layer of the uterus.

Reception of adrenergic blockers leads to the reversible deactivation of receptors that are sensitive to catecholamines. These are bioactive substances that provide intercellular interactions in the body. This leads to the following effects:

• expansion of the inner diameter of the bronchi;
• lowering blood pressure;
• expansion ( vasodilation ) of blood capillaries;
• decrease in the severity of arrhythmia;
• increased release of oxygen from blood cells by cells;
• decreased heart rate (HR);
• stimulation of myometrium contractions ;
• lowering the concentration of sugar in the blood;
• decrease in the rate of conduction of impulses to the myocardium;
• increased peristalsis of the digestive tract;
• slowing down the synthesis of thyroxine by the thyroid gland;
• decrease in myocardial oxygen demand;
• acceleration of lipid breakdown in the liver, etc.

Adrenergic blockers acting on beta- adrenergic receptors are used mainly in the treatment of diseases of the cardiovascular, respiratory and digestive systems.

Classification of drugs

β- adrenolytics are a large group of medicines that are used in the symptomatic treatment of various diseases. They are conventionally divided into 2 categories:

• Selective beta-1-blockers are drugs that block β1-adrenergic receptors in the kidneys and myocardium. They increase the resistance of the heart muscle to oxygen starvation, and reduce its contractility. With the timely administration of adrenergic blockers , the load on the cardiovascular system decreases, as a result of which the likelihood of death from myocardial insufficiency decreases . New generation drugs practically do not cause undesirable effects. They eliminate bronchospasm and prevent hypoglycemia. Therefore, they are prescribed to people suffering from chronic diseases of the bronchi, diabetes mellitus.
• Non-selective beta-blockers – drugs that reduce the sensitivity of all types of β- adrenergic receptors located in the bronchioles, myocardium, liver, kidneys. They are used to prevent arrhythmias, reduce renin synthesis by the kidneys, and improve the rheological properties of blood. Beta-2-blockers prevent the production of fluid in the sclera of the eye, therefore, they are recommended for the symptomatic treatment of glaucoma.

The higher the selectivity of adrenergic blockers , the lower the risk of complications. Therefore, drugs of the latest generation are much less likely to provoke adverse reactions.

Selective adrenergic blockers inhibit exclusively β1-receptors. They have almost no effect on β2-receptors in the uterus, skeletal muscles, capillaries, bronchioles. Such drugs are safer, therefore they are used in the treatment of heart disease with serious accompanying problems.

Classification of drugs depending on solubility in lipids and water:

• Lipophilic ( Timolol , Oxprenolol ) – dissolve in fats, easily overcome tissue barriers. More than 70% of the drug’s components are absorbed in the intestine. Recommended for severe heart failure.
• Hydrophilic ( Sotalol , Atenolol ) – poorly soluble in lipids, therefore only 30-50% absorbed from the intestine. The decay products of adrenergic blockers are excreted mainly by the kidneys, therefore they are used with caution in renal failure.
• Amphiphilic ( Celiprolol , Acebutolol ) – easily soluble in fats and water. When ingested, they are absorbed in the intestine by 55-60%. The drugs are approved for compensated kidney or liver failure.

Some adrenergic blockers have a sympathomimetic effect – the ability to stimulate β-receptors. Other drugs have a mild dilating effect on the capillaries.

List of drugs-beta- blockers

There are adrenomimetics that have a complex effect on the organs of the cardiovascular system. Metipranolol is an antihypertensive agent from the group of beta- blockers , which not only expands the capillaries, but also affects the contractile activity of the myocardium. Therefore, drugs to eliminate cardiac, pulmonary and other pathologies should be selected exclusively by a doctor.

Selective and non-selective beta-blockers

Group of adrenergic blockers	With sympathomimetic activity	Without sympathomimetic activity
cardioselective	CeliprololVasakorMetoprololAcebutololTalinololKordanumSectral	AtenololLocrenNipertenDilatorAtramCoriolNevotenzBisoprololCoriolNebivatorCarvedilolBetalocKardivasNebivololBetaxolol
noncardioselective	DelevalolTrazicorBetapressinLevatolAptinPenbutololPindololSandonormCarteololOxprenololWhisken	SotagexalKorgardNadololTimololObzidanTenzenePropranololNipradilolSotalolBlockardenAnaprilin
with the properties of α- blockers	BucindololCarvedilolLabetalol	–

If the drug belongs to beta-blockers, it is taken only on the recommendation of a doctor in the prescribed dosage. Abuse of this type of medication is dangerous with a sharp drop in blood pressure, asthma attacks, slow heartbeat.

To whom and when are adrenergic blockers prescribed ?

Selective and non-selective β- adrenolytics are recommended for the symptomatic treatment of many diseases. They have a different spectrum of action, so the indications for their reception are different.

Indications for the use of non-selective adrenergic blockers :

• tremor;
• hypertension;
• painful heart palpitations;
• mitral valve prolapse;
• tense angina pectoris;
• cholecystocardial syndrome;
• high intraocular pressure;
• cardiomyopathy ;
• prevention of ventricular arrhythmia;
• prevention of the risk of recurrent myocardial infarction.

Selective adrenergic blockers act on the myocardium, almost without affecting the capillaries. Therefore, such means are used to treat heart pathologies:

• heart attack;
• paroxysmal arrhythmia;
• ischemic heart disease;
• neurocirculatory dystonia;
• atrial tachycardia;
• atrial fibrillation;
• left valve prolapse.

Beta-blockers with the properties of α- adrenolytics are used in combination therapy:

• glaucoma;
• myocardial insufficiency;
• hypertension and hypertensive crisis; 
• arrhythmias.

Drugs that affect the contractile activity of the myocardium cannot be used for self-medication. Irrational therapy is fraught with an increase in the load on the vascular system and cardiac arrest.

Features and rules of admission

If a cardiologist prescribes adrenergic blockers , you should inform him about the systematic use of prescription and non-prescription drugs. It is necessary to notify a specialist about serious concomitant pathologies – emphysema, sinus rhythm disturbances, bronchial asthma.

To avoid side reactions and complications, adrenergic blockers are used in accordance with the instructions:

• tablets are taken after meals;
• during therapy, monitor the heart rate;
• if the state of health worsens, they consult a doctor;
• therapy is not stopped without the recommendation of a specialist.

The dosage and duration of treatment depends on the type of disease and is determined by the doctor. Do not combine adrenergic blockers with other drugs or alcohol. Violation of the rules for the use of β- adrenolytics is fraught with aggravation of the state of health.

How blockers interact with other drugs

When treating drugs of several groups at once, the doctor takes into account their selectivity, the ability to enhance or weaken the effect of other medications. If necessary, beta-blockers are combined with the following drugs:

• Nitrates. The vasodilating effect on the capillaries is enhanced, bradycardia is leveled by tachycardia.
• Alpha blockers. Medicines mutually reinforce each other’s action. This leads to a more powerful hypotensive effect, a decrease in peripheral vascular resistance.
• Diuretics Adrenergic blockers prevent the release of renin from the kidneys. Because of this, the period of action of diuretics increases.

It is strictly forbidden to combine adrenergic blockers with calcium antagonists. This is dangerous with cardiac complications – a decrease in heart rate and the strength of myocardial contractions.

Without a doctor’s recommendation, beta-blockers are not combined with such medications:

• Cardiac glycosides. The risk of bradyarrhythmia , a decrease in myocardial contractions, increases .
• Antihistamines. The antiallergic effect is weakened.
• Sympatholytics . The sympathetic effect on the heart muscle decreases, which is fraught with cardiac complications.
• MAO inhibitors. The risk of an excessive increase in blood pressure and hypertensive crisis increases.
• Antidiabetic drugs. The hypoglycemic effect increases several times.
• Indirect coagulants. The antithrombotic activity of drugs is reduced.
• Salicylates. Adrenolytics reduce their anti-inflammatory activity.

Any combination of adrenergic blockers with other antiarrhythmic drugs is potentially dangerous. Therefore, before changing the therapy regimen, be sure to consult a cardiologist.

Undesirable consequences

Adrenolytic agents have an irritating effect on the gastrointestinal mucosa. This is why they need to be taken with or after meals. Overdose and prolonged use of β-blockers adversely affect the functioning of the genitourinary, digestive, respiratory and endocrine systems. Therefore, it is extremely important to comply with the dosage prescribed by the doctor.

Possible side effects:

• hyperglycemia;
• an attack of angina pectoris;
• bronchospasm ;
• decreased libido;
• decreased renal blood flow;
• depressive state;
• emotional lability;
• violation of taste perception;
• bradycardia;
• abdominal pain;
• decreased visual acuity;
• asthma attacks;
• stool disorders;
• sleep disturbance.

Insulin-dependent patients should be aware of the increased risk of hypoglycemic coma while taking antidiabetic drugs and adrenolytics .

Contraindications

β1- and β2-adrenolytics have similar contraindications for admission. Drugs are not prescribed for:

• atrioventricular block;
• bradycardia;
• orthostatic hypotension;
• sinoatrial blockade;
• left ventricular failure;
• terminal cirrhosis of the liver;
• obstructive pulmonary disease;
• decompensated kidney failure;
• chronic pathologies of the bronchi;
• vasospastic angina pectoris;
• acute myocardial insufficiency.

Selective adrenergic blockers are not taken in case of impaired peripheral circulation, pregnancy and lactation.

Withdrawal syndrome and how to prevent it

A sharp refusal from therapy after prolonged use of adrenergic blockers leads to a withdrawal syndrome, which manifests itself:

• arrhythmia;
• increased heart rate;
• attacks of angina pectoris;
• heartbeat.

Untimely help with withdrawal syndrome is fraught with cardiac arrest and death.

The group of beta-blockers reduces the sensitivity of receptors to adrenal hormones. The body tries to compensate by increasing the number of target cells for adrenaline and norepinephrine. Additionally, drugs of this group prevent the transformation of thyroxine into triiodothyronine . Therefore, refusal of pills leads to a sharp increase in thyroid hormones in the blood.

To prevent withdrawal symptoms, you must:

• gradually reduce the dose of adrenergic blockers over 1.5-2 weeks;
• temporarily limit loads;
• include antianginal agents in therapy ;
• limit the intake of drugs that lower blood pressure.

Beta-blockers are drugs, an overdose of which is fraught with cardiac complications and even cardiac arrest. Therefore, before taking pills and increasing the dosage, be sure to consult a doctor. Competent treatment reduces the risk of adverse reactions and unwanted consequences.