bètablockers

Bètablockers are a class of medicines that antagonize beta-adrenergic receptors, primarily beta-1 receptors in the heart and kidney, and beta-2 receptors in the lungs and vascular smooth muscle. By blocking sympathetic stimulation, they lower heart rate, decrease myocardial contractility, and reduce renin release, resulting in lower blood pressure and reduced myocardial oxygen demand.

Common indications include essential hypertension, angina pectoris, certain arrhythmias (such as atrial fibrillation with rapid ventricular response), and heart failure with reduced ejection fraction. They are also used after myocardial infarction to improve survival, and in some conditions such as migraine prophylaxis and essential tremor. Some agents are selective for beta-1 receptors (metoprolol, atenolol, bisoprolol), while non-selective agents (propranolol, nadolol, carvedilol) block both beta-1 and beta-2 receptors. Carvedilol and labetalol also have alpha-blocking activity.

Administration can be oral or injectable; some are long-acting, allowing once-daily dosing. Topical beta-blockers such as timolol are used in glaucoma.

Adverse effects include fatigue, bradycardia, hypotension, and sexual dysfunction. Non-selective agents may cause bronchospasm in asthma or COPD. They can mask signs of hypoglycemia in diabetes. Abrupt withdrawal after prolonged use can lead to rebound hypertension or angina. Contraindications include severe bradycardia, advanced AV block, decompensated heart failure, and severe reactive airway disease for non-selective agents.

History notes that beta-blockers were developed in the 1960s, notably propranolol by James W. Black. They have since become a cornerstone of cardiovascular therapy and are used for a range of other conditions as well.