1. Pharmacology

Atenolol is a selective β1-adrenergic receptor blocker. It primarily affects the heart and reduces heart rate, cardiac output, and blood pressure. It does not have intrinsic sympathomimetic or membrane-stabilizing activity. Unlike propranolol, atenolol has minimal penetration of the blood-brain barrier, which results in fewer CNS-related side effects.

2. Indications

  • Hypertension

  • Angina pectoris

  • Acute myocardial infarction (AMI)

  • Arrhythmias (especially supraventricular tachycardias)

  • Long-term management post-MI

  • Migraine prophylaxis (off-label)

3. Dosage & Administration

Adults:

  • Hypertension: 25–50 mg once daily; may increase to 100 mg once daily or in divided doses.

  • Angina: 50–100 mg/day in 1–2 divided doses.

  • AMI: Initially 5–10 mg IV, then 50 mg orally 6–12 hours later, followed by 50–100 mg daily.

  • Arrhythmias: 50–100 mg/day orally.

Elderly or Renal Impairment: Dose adjustment required based on creatinine clearance.

Pediatrics: Safety and efficacy not well established.

4. Drug Interactions

  • Calcium channel blockers (e.g., verapamil, diltiazem): Risk of bradycardia and heart block.

  • Clonidine: Rebound hypertension upon withdrawal.

  • NSAIDs: May reduce antihypertensive effects.

  • Insulin/Oral hypoglycemics: May mask symptoms of hypoglycemia.

  • Anesthesia drugs: Additive hypotensive effects.

5. Contraindications

  • Sinus bradycardia

  • Heart block > first degree

  • Overt cardiac failure

  • Cardiogenic shock

  • Hypersensitivity to atenolol

  • Severe peripheral arterial circulatory disturbances

6. Side Effects

Common:

  • Bradycardia

  • Hypotension

  • Cold extremities

  • Fatigue

  • Dizziness

Less common:

  • Depression

  • GI disturbances (nausea, diarrhea)

  • Erectile dysfunction

  • Sleep disturbances

Rare:

  • Bronchospasm (especially in asthmatics)

  • AV block

  • Thrombocytopenia

7. Pregnancy & Lactation

  • Pregnancy Category D: Evidence of human fetal risk, but benefits may warrant use in serious situations.

  • May cause fetal bradycardia, hypoglycemia, and growth retardation.

  • Lactation: Excreted in breast milk. Use caution or consider alternatives if breastfeeding.

8. Precautions & Warnings

  • Avoid abrupt withdrawal; taper gradually to prevent rebound hypertension or angina.

  • Use cautiously in patients with asthma, diabetes, renal impairment, or peripheral vascular disease.

  • May mask hypoglycemia symptoms in diabetics.

  • Caution during anesthesia due to risk of severe hypotension.

9. Overdose Effects

Symptoms:

  • Severe bradycardia

  • Hypotension

  • Bronchospasm

  • Acute heart failure

Management:

  • Supportive care

  • Atropine for bradycardia

  • IV fluids, vasopressors for hypotension

  • Glucagon as a specific antidote

  • Hemodialysis may help due to low protein binding

10. Therapeutic Class

  • Beta-adrenergic receptor antagonists (Beta-blockers) – Selective for β1 receptors

11. Storage Conditions

  • Store below 25°C.

  • Protect from light and moisture.

  • Keep out of reach of children.

12. Chemical Structure

Chemical Formula: C14H22N2O3
IUPAC Name: 4-[2-hydroxy-3-(isopropylamino)propoxy]phenylacetamide

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