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Atenolol

Atenolol

Tenormin Atecard Atelol Betacard Noten

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Updated: December 06, 2025

Overview

Atenolol is a selective beta-1 adrenergic receptor blocker primarily used in cardiovascular conditions. It reduces heart rate, myocardial contractility, and blood pressure by inhibiting sympathetic nervous system effects on the heart. Unlike non-selective beta-blockers, atenolol has less effect on bronchial and vascular smooth muscle at therapeutic doses. This cardioselective beta-blocker is particularly useful for hypertension, angina pectoris, and acute myocardial infarction management. It offers the advantage of once-daily dosing in most cases and has fewer CNS side effects compared to lipid-soluble beta-blockers due to its low lipophilicity.

Drug Class

Cardioselective beta-1 adrenergic antagonist Therapeutic category: Antihypertensive, Antiarrhythmic, Antianginal

Mechanism of Action

Competitively blocks beta-1 adrenergic receptors in cardiac tissue: • Reduces sinus node automaticity • Decreases AV node conduction velocity • Lowers myocardial contractility • Suppresses renin release from kidneys Has no intrinsic sympathomimetic activity (ISA) or membrane-stabilizing properties.

Pharmacokinetics

Absorption: ~50% oral bioavailability; food has minimal effect Distribution: Low protein binding (6-16%); limited CNS penetration Metabolism: <10% hepatic metabolism; primarily excreted unchanged Excretion: Renal elimination (85-100% unchanged drug) Half-life: 6-7 hours (prolonged in renal impairment)

Pharmacodynamics

Primary cardiovascular effects: • Reduces resting heart rate by 15-25% • Lowers systolic/diastolic blood pressure • Decreases myocardial oxygen demand • Increases exercise tolerance in angina Onset: Oral hypotensive effect within 1 hour Peak effect: 2-4 hours Duration: 24 hours with chronic dosing

Indications

• Hypertension: Management of essential hypertension as monotherapy or combination therapy • Angina pectoris: Chronic stable angina prophylaxis • Acute myocardial infarction: Early intervention to reduce mortality • Arrhythmias: Management of supraventricular tachycardias and ventricular rate control in atrial fibrillation/flutter

Contraindications

Absolute: • Severe bradycardia (<50 bpm) • Second- or third-degree heart block • Cardiogenic shock • Sick sinus syndrome Relative: • Bronchospastic diseases (asthma/COPD) • Diabetes mellitus (may mask hypoglycemia) • Peripheral vascular disease • Pheochromocytoma (requires alpha-blockade first)

Dosage & Administration

Hypertension: Initial 25-50 mg once daily; may increase to 100 mg/day Angina: Initial 50 mg once daily; may increase to 100-200 mg/day Acute MI: 5 mg IV over 5 minutes, repeat after 10 minutes if tolerated, followed by 50 mg oral after 15 minutes Arrhythmias: 25-50 mg once daily; titrate to response

Special Populations

Pediatric: Safety not established for children <6 years Geriatric: Start with lower doses due to reduced renal function Renal impairment: • CrCl 15-35 mL/min: Max 50 mg/day • CrCl <15 mL/min: Max 25 mg/day • HD: Give post-dialysis Hepatic impairment: No significant adjustment needed

Adverse Effects

Common (>10%): • Bradycardia • Fatigue • Dizziness • Cold extremities Serious (<1%): • Heart block • Bronchospasm • Worsening heart failure • Severe hypotension • Depression (less common than with lipophilic beta-blockers)

Drug Interactions

• Calcium channel blockers (verapamil/diltiazem): Increased risk of bradycardia/AV block • Insulin/oral hypoglycemics: Masked hypoglycemia symptoms • Digoxin: Additive bradycardia • NSAIDs: Reduced antihypertensive effect • Clonidine: Rebound hypertension if stopped concurrently

Warnings & Precautions

• Abrupt withdrawal may precipitate angina/MI - taper over 1-2 weeks • May reduce exercise tolerance in athletes • Can mask thyrotoxicosis symptoms • Caution in peripheral vascular disease (may worsen symptoms) • May increase serum triglycerides and decrease HDL cholesterol

Pregnancy & Lactation

Pregnancy: FDA Category D • May cause fetal bradycardia, hypoglycemia, and IUGR • Avoid especially in 2nd/3rd trimesters Lactation: Excreted in breast milk (infant dose ~6-19% of maternal dose) • Consider alternative agents or monitor infant for bradycardia/hypotension

Monitoring Parameters

• Blood pressure and heart rate at each visit • ECG for patients with arrhythmias • Renal function tests (BUN/creatinine) • Blood glucose in diabetics • Signs of heart failure exacerbation • Peripheral circulation in PVD patients

Patient Counseling

• Do not stop suddenly - may cause rebound hypertension/angina • Rise slowly from sitting/lying position to prevent dizziness • Monitor pulse daily and report <50 bpm • May cause cold hands/feet - keep extremities warm • Inform dentists/surgeons about beta-blocker use • Carry medical alert if diabetic

Storage & Stability

Store at 20-25°C (68-77°F) Protect from light and moisture Keep container tightly closed Tablets stable for 24 months

Clinical Pearls

• Preferred beta-blocker in asthma/COPD patients (but still use cautiously) • First-line for hypertension with tachycardia • Less likely than propranolol to cause CNS side effects • Combine with diuretics for enhanced BP control • Consider switching to longer-acting agents in non-adherent patients

References

• UpToDate: Atenolol drug information • AHFS Drug Information 2023: Atenolol monograph • FDA Prescribing Information: Tenormin (atenolol) • Goodman & Gilman's: The Pharmacological Basis of Therapeutics, 14th ed • ESC Guidelines on Hypertension Management (2023)