Atenolol

Generic Name

Atenolol

Brand Names

Tenormin

Apo-Atenol

Noten

Betacard

Tenbless

Atenix

Atenova

Available globally under numerous generic and branded names in tablet and injectable forms

Drug Class

Beta-adrenergic receptor antagonist

Cardioselective beta-blocker (selective for β1 receptors at low doses)

Antihypertensive agent

Class II antiarrhythmic (Vaughan-Williams classification)

Mechanism of Action

Atenolol blocks β1-adrenergic receptors predominantly in the heart

Reduces heart rate, cardiac output, and myocardial contractility

Decreases renin release from the juxtaglomerular cells of the kidney

Leads to reduction in blood pressure and oxygen demand

Slows atrioventricular (AV) conduction and prolongs sinus node recovery

Exhibits no intrinsic sympathomimetic activity or membrane-stabilizing effects

At higher doses, cardioselectivity diminishes and β2 blockade may occur

Indications

Approved Uses

Hypertension

Chronic stable angina pectoris

Post-myocardial infarction secondary prevention

Supraventricular arrhythmias (e.g. atrial fibrillation, atrial flutter)

Ventricular arrhythmias

Thyrotoxicosis symptoms (adjunctive treatment)

Migraine prophylaxis

Anxiety (somatic symptoms like tachycardia, palpitations)

Essential tremor (non-selective beta-blockers are preferred)

Off-label or Investigational Uses

Hypertrophic obstructive cardiomyopathy

Prevention of variceal bleeding (not first-line)

Pheochromocytoma (with alpha-blocker co-administration)

Perioperative cardiac protection

Postural orthostatic tachycardia syndrome (POTS)

Alcohol or drug withdrawal symptoms

Tachycardia due to stimulant toxicity (e.g. thyrotoxicosis, amphetamines)

Dosage and Administration

Adults (Oral)

Hypertension: 25–50 mg once daily initially; maintenance dose 25–100 mg once daily

Angina: 50 mg once daily; may increase to 100 mg once daily or in divided doses

Post-MI: 100 mg daily in single or divided doses

Arrhythmias: 50–100 mg daily

Migraine prophylaxis: 25–100 mg once daily

Anxiety: 25–50 mg daily off-label

Children

Not commonly used; pediatric dose is individualized based on weight

Typically 0.5–1 mg/kg/day in divided doses (max 2 mg/kg/day or 100 mg/day)

Injectable (IV use in hospital settings)

Arrhythmias or acute MI: 2.5–10 mg slow IV push, may repeat every 5 minutes up to 10 mg

Transition to oral therapy once stable

Elderly

Start at lower dose due to increased sensitivity

Titrate slowly with regular monitoring

Renal Impairment

Excreted primarily by kidneys

Dose adjustment required

CrCl 15–35 mL/min: give 50% of usual dose

CrCl <15 mL/min: 25% of usual dose

Hemodialysis patients: administer after dialysis

Pharmacokinetics

Bioavailability: ~50% (oral)

Time to peak plasma: 2–4 hours

Protein binding: ~5–10%

Metabolism: minimal hepatic metabolism

Half-life: ~6–9 hours (prolonged in renal impairment)

Excretion: primarily renal (85–90% unchanged)

Contraindications

Sinus bradycardia

Second- or third-degree AV block (unless paced)

Overt cardiac failure (acute decompensation)

Cardiogenic shock

Severe peripheral arterial disease with ischemia

Hypersensitivity to atenolol or excipients

Untreated pheochromocytoma (must be pretreated with alpha-blocker)

Sick sinus syndrome (without pacemaker)

Warnings and Precautions

Do not stop abruptly—may precipitate angina, MI, or arrhythmias

Use caution in heart failure—can worsen symptoms during initiation

Can mask symptoms of hypoglycemia (tachycardia, tremor) in diabetics

Avoid in patients with asthma or bronchospasm unless necessary (prefer cardioselective beta-blockers)

May exacerbate peripheral vascular disease or Raynaud's phenomenon

Caution in thyrotoxicosis—can mask clinical signs

Monitor renal function in long-term therapy

May worsen depression or fatigue in susceptible individuals

Crosses placenta—may cause fetal bradycardia or growth restriction

Adverse Effects

Very Common

Bradycardia

Fatigue

Cold extremities

Dizziness

Hypotension

Common

Sleep disturbances (insomnia, vivid dreams)

Depression

Nausea

Diarrhea

Peripheral vasoconstriction

Exercise intolerance

Erectile dysfunction

Lightheadedness

Uncommon

Bronchospasm (particularly in asthmatics)

AV block

Heart failure exacerbation

Raynaud's phenomenon

Alopecia

Rash

Visual disturbances

Rare but Serious

Severe bradyarrhythmias

Worsening angina or MI on abrupt withdrawal

Acute decompensated heart failure

Psoriasiform skin reactions

Anaphylaxis (very rare)

Confusion or hallucinations in elderly

Pregnancy and Lactation

Pregnancy

Category D (old FDA system)

Crosses placenta—may cause fetal bradycardia, intrauterine growth restriction, and hypoglycemia

Use only if potential benefit outweighs risk

Avoid use near delivery

Lactation

Excreted in breast milk in small amounts

Generally considered safe with infant monitoring for bradycardia or hypoglycemia

Monitor neonate if mother is breastfeeding

Drug Interactions

Verapamil and diltiazem

Additive effect on AV node suppression—risk of bradycardia, heart block

Avoid IV verapamil in patients on atenolol

Clonidine

Additive hypotensive effect

Abrupt withdrawal of clonidine while on atenolol may cause rebound hypertension

Insulin or oral hypoglycemics

May mask hypoglycemia symptoms

Monitor glucose closely

NSAIDs

May reduce antihypertensive effect of atenolol

Amiodarone

Additive risk of bradycardia and AV block

Digoxin

Enhanced bradycardia and AV nodal block

Catecholamine-depleting drugs (reserpine, guanethidine)

Potentiate beta-blockade—risk of profound bradycardia

Monitoring Parameters

Resting heart rate (target 55–60 bpm)

Blood pressure (supine and standing)

ECG in arrhythmia treatment

Signs of heart failure (dyspnea, edema)

Renal function in chronic use

Blood glucose in diabetics

Fatigue and mood changes in long-term therapy

Counseling Points

Take at the same time each day, with or without food

Do not stop suddenly—consult doctor first

May cause fatigue during early weeks—usually improves

Avoid activities requiring alertness if dizziness or tiredness occurs

Monitor blood pressure and heart rate regularly

May mask low blood sugar symptoms in diabetics

Inform your physician about asthma or respiratory symptoms

Store tablets at room temperature and protect from moisture

Report symptoms like chest pain, slow heartbeat, or wheezing immediately

Comparative Notes

Atenolol vs Metoprolol

Atenolol more renally excreted; metoprolol more hepatically metabolized

Metoprolol crosses the blood-brain barrier more—greater CNS effects

Metoprolol is preferred in heart failure (succinate formulation)

Atenolol vs Propranolol

Atenolol is cardioselective; propranolol is non-selective

Propranolol more effective in essential tremor and migraine

Atenolol has longer duration and simpler dosing

Atenolol vs Bisoprolol

Bisoprolol is more β1-selective, longer half-life, better tolerated in HF

Bisoprolol preferred in heart failure and chronic use

Regulatory and Legal Status

Prescription-only medication

Approved by FDA (1981)

Available globally in tablet form: 25 mg, 50 mg, 100 mg

Also available as IV injection for acute use

Included in WHO Model List of Essential Medicines

Guideline-approved for hypertension, arrhythmia, and post-MI care