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Class II Antiarrhythmic Drugs

Q: What are the absolute contraindications for prescribing propranolol?

Contraindications for prescribing propranolol include: Bronchial asthma — risk of bronchospasm.Conduction disturbances — atrioventricular block.Pronounced bradycardia.Acute and severe chronic heart failure.Arterial hypotension.Vasospastic angina.Peripheral artery occlusive disease.Pregnancy — risk of premature labor and adverse fetal effects.

Q: Which non-selective beta-blockers are used in antiarrhythmic therapy?

In antiarrhythmic therapy, propranolol is used among non-selective beta-blockers. Propranolol — a non-selective beta-blocker blocking β1- and β2-receptors. Class II beta-blockers are effective for both ventricular and supraventricular tachyarrhythmias. Propranolol, as a non-selective beta-blocker, is characterized by specific side effects: bronchospasm and peripheral vasospasm.

*Beta-adrenoblocatores*

For medical students2 min readUpdated 2026-10-10

Class II antiarrhythmic drugs comprise beta-blockers, which modulate cardiac electrophysiology. They are utilized for various rhythm disorders and exhibit important differences in cardioselectivity.

Targetsβ₁-receptors of pacemakers and cardiomyocytes

DrugsMetoprolol, atenolol, propranolol

IndicationsVentricular and supraventricular tachyarrhythmias

RisksBradycardia and AV block

Target Localization and Electrophysiology

The primary sites of action for beta-blockers are β₁-receptors, located in the cardiac pacemaker cells and working ventricular cardiomyocytes.

Blockade of these receptors induces several electrophysiological effects in the heart:

Decreased automaticity.
Suppressed conduction velocity.
Decreased excitability.
Prolongation of the effective refractory period (ERP) throughout all myocardial regions.

Classification and Clinical Spectrum

In clinical practice, these drugs are divided into two main categories:

Cardioselective (selectively acting on β₁-receptors): metoprolol, atenolol, talinolol.
Non-selective (blocking both β₁- and β₂-receptors): propranolol.

Due to their electrophysiological properties, these medications demonstrate high efficacy in treating both types of tachyarrhythmias — supraventricular and ventricular.

Adverse Effects

Therapy with beta-blockers may lead to adverse reactions. Common side effects for the entire class relate to the suppression of cardiac activity:

Bradycardia.
Conduction disturbances, such as atrioventricular block.
Decreased myocardial contractility (negative inotropic effect).

Non-selective agents like propranolol are associated with specific complications due to extra-cardiac blockade of β₂-receptors: bronchospasm and peripheral vasospasm.

Mnemonic

Beta-blockers slow down the heart: decreased rate (bradycardia), lower conduction (AV block), and weaker contractility. Non-selective agents (propranolol) also "choke" the bronchi (bronchospasm).

Frequently asked questions

Which cardioselective beta-blockers belong to Class II antiarrhythmic drugs?

Cardioselective beta-blockers belonging to Class II antiarrhythmics include atenolol, talinolol, metoprolol, bisoprolol, nebivolol, and betaxolol. These medications have a selective effect on cardiac beta-1 receptors, decreasing myocardial automaticity, conduction, and excitability.

Atenolol (atenolol) — cardioselective beta-blocker
Metoprolol (metoprolol) — cardioselective beta-blocker
Bisoprolol (bisoprolol) — cardioselective beta-blocker

What are the absolute contraindications for prescribing propranolol?

Contraindications for prescribing propranolol include:

Bronchial asthma — risk of bronchospasm.
Conduction disturbances — atrioventricular block.
Pronounced bradycardia.
Acute and severe chronic heart failure.
Arterial hypotension.
Vasospastic angina.
Peripheral artery occlusive disease.
Pregnancy — risk of premature labor and adverse fetal effects.

Which non-selective beta-blockers are used in antiarrhythmic therapy?

In antiarrhythmic therapy, propranolol is used among non-selective beta-blockers.

Propranolol — a non-selective beta-blocker blocking β1- and β2-receptors.

Class II beta-blockers are effective for both ventricular and supraventricular tachyarrhythmias. Propranolol, as a non-selective beta-blocker, is characterized by specific side effects: bronchospasm and peripheral vasospasm.

Which heart structures are the targets for Class II drugs?

The targets are β₁-receptors located in pacemaker cells and working ventricular cardiomyocytes.

For which types of tachyarrhythmias are beta-blockers effective?

These agents are effective for both types of tachyarrhythmias: supraventricular and ventricular.

What causes bronchospasm during propranolol administration?

Bronchospasm occurs due to the blockade of bronchial β₂-receptors, which is a specific effect of non-selective agents.

Go deeper

Impact of β₁-receptor blockade on the action potential
Comparison of cardioselective and non-selective blockers
Mechanisms of the negative inotropic effect
Causes of atrioventricular block during therapy
Pharmacological properties of metoprolol and atenolol