Atenolol

• Hypertension (High Blood Pressure)
• Angina Pectoris
• Heart Attack (Acute MI)
• Atrial Fibrillation

Atenolol is a cardioselective beta-1 adrenergic receptor blocker (beta-blocker) used in the treatment of hypertension, angina pectoris, and certain cardiac arrhythmias. This medication is one of the most widely prescribed beta-blockers due to its selectivity, long duration of action, and favorable side effect profile.

Mechanism of Action

Atenolol competitively blocks beta-1 adrenergic receptors located primarily in the heart. By blocking these receptors, atenolol reduces the effects of catecholamines (epinephrine and norepinephrine), resulting in decreased heart rate (negative chronotropic effect), reduced force of cardiac contraction (negative inotropic effect), decreased cardiac output, and lower blood pressure. The medication also reduces myocardial oxygen demand, making it effective for angina. At therapeutic doses, atenolol has minimal effects on beta-2 receptors in the lungs and blood vessels, reducing the risk of bronchospasm and peripheral vasoconstriction.

Available Formulations

Atenolol is available as oral tablets in 25 mg, 50 mg, and 100 mg strengths. Generic formulations are widely available. The medication can be taken with or without food, though taking with food may help reduce gastrointestinal upset. An intravenous formulation is available for acute situations but is rarely used.

Medical Uses

Atenolol is approved for the management of hypertension (alone or in combination with other antihypertensives), long-term management of angina pectoris, and acute myocardial infarction in hemodynamically stable patients. Off-label uses include rate control in atrial fibrillation, prevention of migraine headaches, essential tremor, and performance anxiety. However, some guidelines no longer recommend atenolol as first-line therapy for hypertension due to concerns about efficacy in stroke prevention.

Dosing Guidelines

For hypertension, the initial dose is typically 50 mg once daily, which may be increased to 100 mg daily after 1-2 weeks if needed. For angina, dosing typically starts at 50 mg once daily and may be increased to 100-200 mg daily in divided doses. For acute MI, treatment begins with IV dosing followed by oral maintenance. Patients with renal impairment require dose adjustment: CrCl 15-35 mL/min should receive a maximum of 50 mg daily; CrCl less than 15 mL/min should receive 25-50 mg daily or every other day. Atenolol should not be discontinued abruptly; doses should be tapered over 1-2 weeks.

Important Safety Information

Beta-blockers should not be withdrawn abruptly, especially in patients with coronary artery disease, due to risk of exacerbating angina, myocardial infarction, or arrhythmias. Atenolol is contraindicated in patients with sinus bradycardia, greater than first-degree heart block (without pacemaker), cardiogenic shock, uncompensated heart failure, and sick sinus syndrome. Use with caution in patients with bronchospastic disease, diabetes (may mask hypoglycemia symptoms), peripheral vascular disease, and myasthenia gravis.

Drug Interactions

Calcium channel blockers (particularly verapamil and diltiazem) may potentiate bradycardia and heart block. Clonidine withdrawal after concurrent use with beta-blockers may cause rebound hypertension. NSAIDs may reduce the antihypertensive effect of atenolol. Catecholamine-depleting drugs (reserpine, MAO inhibitors) may cause additive effects. Ampicillin and aluminum-containing antacids may reduce atenolol absorption.

Special Populations

Atenolol crosses the placenta and may cause fetal bradycardia and hypoglycemia; use during pregnancy only if clearly needed. It is excreted in breast milk; caution is advised during breastfeeding. Safety and efficacy have not been established in pediatric patients. Elderly patients may be more sensitive to the effects and may require lower doses. Significant dose reduction is required in renal impairment. No adjustment is needed for hepatic impairment as atenolol undergoes minimal hepatic metabolism.