The mechanism of action, the benefits and harms of beta-blockers in bronchial asthma

Bronchial asthma is a serious illness, accompanied by damage to the respiratory tract. To maintain a decent standard of living, the patient needs constant supervision from the attending physician. For emergency relief of a beginning attack, the patient must always carry a can of medicine with him.

Most often, this is a drug from the beta2-agonist group that can expand the bronchi and alleviate the condition. But these drugs are not selective. By helping relieve asthma symptoms, they increase the risk of heart disease, which is especially common in older people.

For the treatment of cardiovascular diseases, beta-blockers are most often prescribed, which in bronchial asthma can cause narrowing of the bronchi.

The task of the attending physician in this case is to choose the right drugs to ensure an improvement in the condition, while simultaneously arresting the symptoms of both diseases.

Beta blockers: mechanism of action

There are beta1 and beta2 adenoreceptors, which are affected by beta blockers.

Beta1 receptors are found in the heart, intestines, adipose tissue, kidneys and in small amounts in the lungs. Beta2-adenoreceptors can be found in the smooth muscles of the vessels and bronchi, in the gastrointestinal tract, in the pancreas and in small amounts in the heart.

Medicines that activate the work of adrenergic receptors are usually called beta-agonists, and those with the opposite effect are called beta-blockers.

Drugs with the described properties can be either non-selective (affecting all receptors) and selective action. It is important to understand that selectivity in this case is conditional. Large doses of the drug affect both types of receptors.

Beta blockers are structurally similar to catecholamines. That is why they are their competitive antagonists. The effect of beta-blockers directly depends on the concentration of catecholamines in the human blood.

Once in the human body, beta-blockers:

  1. They have a beneficial effect on the work of the heart, reducing arrhythmias.
  2. Reduce the activity of the renin- angiotensin system.
  3. Affect the sympathetic activity of the vasoconstrictor nerves, which leads to a decrease in cardiac output.
  4. Stimulates vasodilation.
  5. Decrease calcium content in heart cells.

In this case, the following positive effects are observed:

  • decreased heart rate;
  • a decrease in the heart’s need for oxygen supply;
  • lowering blood pressure;
  • minimizing the risk of aortic dissection;
  • reducing the likelihood of developing a heart attack;
  • normalization of the heart rhythm.

Bronchial asthma and diseases of the cardiovascular system

Cardiovascular disease and asthma have different risk factors and developmental mechanisms. In practice, however, these diseases often occur together. This is what prompted scientists to study the relationship between asthma and heart disease in more detail.

Common signs were established that unite patients suffering from two diseases at the same time. These include:

  • old age of the patient;
  • overweight;
  • taking medications, the side effect of which is the development of hypertension.

Considering hypertension, its characteristic feature should be highlighted. Against the background of asthma, the risk of developing circulatory disorders (cerebral and coronary) is increased. It was also noted that during the night, when the patient falls asleep, the pressure remains unacceptably high. And when an acute asthmatic attack occurs, a hypertensive crisis may develop simultaneously with it.

One of the reasons explaining this condition is bronchospasm, in which there is a deterioration in oxygen supply to the body. In this case, a significant amount of vasoconstrictor substances are released into the blood. Constantly repeating, this condition leads to damage to the walls of blood vessels, deterioration of their tone and elasticity.

It has been established that long-term use of beta- adrenomimetics in bronchial asthma adversely affects the state of the cardiovascular system, causing a persistent increase in blood pressure. For example, drugs containing fenoterol and salbutamol , often prescribed to patients with asthma, do not cause side effects only at the very beginning of treatment and in small doses. With an increase in blood concentration, their selectivity of action drops sharply.

This increases the heart rate and blood pressure. All this negatively affects the work of the cardiovascular system, leads to impaired blood circulation.

The main signs indicating the development of high blood pressure against the background of bronchial asthma include:

  • headache that does not have a clear localization or is concentrated in the temples and the back of the head;
  • heaviness in the head:
  • weakness and fatigue;
  • nausea;
  • sleep problems;
  • increased heart rate;
  • excessive sweating;
  • trembling and numbness of the limbs.

The appearance of one or more of these signs for a BA patient should be a signal to urgently consult a doctor.

Beta blockers for bronchial asthma

It is important to note that beta-blockers are required to treat cardiovascular disease. Their action is aimed at reducing the oxygen demand of the heart muscle. At the same time, a decrease in blood pressure is observed, the risk of developing angina pectoris or arrhythmia is significantly reduced.

But if the patient has bronchial asthma, taking non-selective beta-blockers can be fatal, because they cause a narrowing of the bronchial lumen. This leads to impaired ventilation, shortness of breath, and other breathing problems.

A side effect of taking some drugs is a cough that worsens the general condition of the patient. When prescribing treatment, a cardiologist must know about all the patient’s comorbidities in order to choose the right medications.

Treatment of cardiovascular disease in asthma

If you have problems with the cardiovascular system, asthmatics are usually prescribed beta-blockers that act on only one type of receptor. The pharmaceutical industry produces a fairly wide range of drugs that meet these requirements.

To cause minimal damage to the respiratory system, drugs that affect beta1-blockers are required, since they are found mainly in the heart muscle and are almost never found in the bronchi.

For the treatment of hypertension, if the patient has a history of asthma, drugs of the following groups are prescribed:

  1. Calcium antagonists.
  2. Alpha blockers .
  3. Angiotensin-2 antagonists.

When prescribing beta-blockers, it must be borne in mind that they in any case narrow the lumen of the bronchi, causing them to spasm. Difficulty breathing and shortness of breath may appear. Even minor symptoms of respiratory failure require immediate discontinuation of the drug.

Selective drugs prescribed in small doses are most easily tolerated by patients.

If the patient has mild asthma, a good solution for the treatment of cardiovascular diseases is the use of cardioselective drugs containing bisoprolol .

If an angiotensin – converting enzyme inhibitor is prescribed , dry cough may develop in BA patients. Despite the fact that there is no direct effect on the tone of the bronchi, sometimes shortness of breath and shortness of breath develop.

In severe asthma, a complication called cor pulmonale may develop. This is often accompanied by severe heart rhythm disturbances. At the same time, it is forbidden to prescribe calcium antagonists, as they can provoke a serious deterioration in the patient’s condition.


Despite the different mechanisms of development, bronchial asthma and diseases of the cardiovascular system often occur simultaneously.

Medicines that relieve asthma conditions, at high doses and long-term use, negatively affect the state of the heart and blood vessels. The risk of developing arterial hypertension is also increased.

Treatment of patients is complicated because beta-blockers, which are good for heart disease, cause bronchial constriction, provoking an asthma attack. The use of selective drugs with selective action partially solves the problem. But this does not completely exclude the development of complications.

It is important for asthma patients who regularly use inhalers to monitor their pulse rate and blood pressure on a daily basis. At the slightest deviation from the norm, you should immediately consult a doctor to adjust the treatment.

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