Bêtabloquants

Bêtabloquants are a class of medications that block beta-adrenergic receptors, thereby reducing the effects of the sympathetic nervous system on the heart, vessels and other tissues. By antagonizing beta-1 receptors in the heart, they decrease heart rate, myocardial contractility and conduction velocity, and they reduce renin release from the kidneys. Nonselective agents also block beta-2 receptors, which can affect bronchial smooth muscle and glucose metabolism.

Bêtabloquants are categorized as cardioselective (beta-1 selective) and nonselective (beta-1 and beta-2 blocking). Cardioselective agents include metoprolol, bisoprolol and atenolol, while nonselective drugs include propranolol and nadolol. Some agents, such as carvedilol and labetalol, have additional alpha-adrenergic blocking activity, contributing to blood pressure lowering.

Common indications include hypertension, angina pectoris and other ischemic heart diseases, various arrhythmias for rate control, and heart failure with reduced ejection fraction (especially carvedilol, metoprolol succinate and bisoprolol). They may also be used for preventive treatment of migraines, essential tremor, and, in some cases, performance anxiety or certain perioperative scenarios.

Contraindications and cautions cover severe bradycardia, AV block without a pacemaker, decompensated heart failure, cardiogenic shock, and significant hypotension. Caution is advised in asthma or COPD (especially with nonselective agents), diabetes, peripheral vascular disease, and during withdrawal, which should be gradual to avoid rebound tachycardia and hypertension.

Adverse effects include fatigue, dizziness, bradycardia, and sexual dysfunction; bronchospasm can occur with nonselective agents in susceptible individuals. Drug interactions include concurrent use with non-dihydropyridine calcium-channel blockers, insulin or other antihyperglycemic agents, and certain antiarrhythmics.