Atenolol

Atenolol is a cardioselective beta1-adrenergic receptor antagonist (beta-blocker) used to treat hypertension, angina pectoris, arrhythmia, and acute myocardial infarction. It also helps prevent migraine.

Atenolol specifically works on beta1 receptors in the heart. It slows the heart rate and reduces contractility, decreasing the heart's workload and oxygen demand. This lowers blood pressure and reduces the risk of angina and heart attack.

The initial dose is usually 50 mg daily, which can be increased to 100 mg if needed. Common side effects include fatigue, slow heart rate, dizziness, and diarrhea.

• Hypertension - alone or with thiazide diuretics
• Angina pectoris - long-term management
• Acute myocardial infarction - to reduce cardiovascular mortality
• Arrhythmia
• Migraine prevention

Atenolol is a competitive cardioselective beta1-blocker. It competitively blocks beta1 (cardiac) receptors but has no effect on beta2-receptors except in high doses. It has no membrane-stabilizing or partial agonist activity.

Atenolol is the most hydrophilic of currently available beta-blockers, thus it poorly penetrates cell membrane lipids. It reduces resting and exercise-induced heart rate and myocardial contractility.

Atenolol blocks beta1-adrenergic receptors in the heart. These receptors are normally stimulated by catecholamines (e.g., adrenaline, noradrenaline) to increase heart rate and contractility. Atenolol blocks this stimulation, slowing the heart rate, reducing contractility, and decreasing myocardial oxygen demand. This lowers blood pressure and reduces the risk of angina and heart attack.

Hypertension: 50 mg once daily. May increase to 100 mg once daily if needed. Doses above 100 mg are unlikely to provide additional benefit.

Angina Pectoris: 50 mg once daily. May increase to 100 mg once daily if needed. Some patients may require 200 mg once daily for optimal effect.

Acute Myocardial Infarction (IV + Oral): 5 mg IV over 5 minutes, followed by another 5 mg IV 10 minutes later. If tolerated, 50 mg oral 10 minutes after last IV dose, then another 50 mg oral 12 hours later. Then 100 mg once daily or 50 mg twice daily for 6-9 days.

Renal Dose: CrCl 15-35 mL/min: max 50 mg/day; CrCl <15 mL/min: max 25 mg/day; Hemodialysis: 25-50 mg after each dialysis.

Take this medicine in the dose and duration as advised by your doctor. Swallow the tablet whole - do not chew, crush or break. May be taken with or without food, but take at a fixed time. Do not stop suddenly.

If you miss a dose, take it as soon as you remember. If it is almost time for your next dose, skip the missed dose and continue with your regular schedule. Do not double the dose. Do not stop suddenly.

• Cold extremities
• Fatigue
• Bradycardia
• Nausea
• Diarrhea
• Dizziness
• Orthostatic hypotension

Rare: Agranulocytosis, allergic fever, laryngospasm, respiratory distress, reversible mental depression, skin rash, dry eyes

Serious Precautions:

• Do not stop suddenly - may cause rebound hypertension, increasing risk of heart attack and stroke
• Caution in diabetic patients - may mask hypoglycemia symptoms (tachycardia)
• May aggravate peripheral arterial circulatory disorders
• Dose adjustment needed in renal impairment
• Pregnancy Category D - risk to fetus in third trimester
• Caution during breastfeeding - neonatal bradycardia reported
• Caution with clonidine - withdraw atenolol several days before clonidine

• Sinus bradycardia
• Heart block >1st degree
• Cardiogenic shock
• Overt cardiac failure
• Hypersensitivity to atenolol or any component
• Bronchospastic diseases
• Peripheral vascular diseases

• Catecholamine-depleting drugs (reserpine): Additive hypotension and bradycardia
• Calcium channel blockers (verapamil, diltiazem): Additive negative inotropic and chronotropic effects
• Disopyramide: Severe bradycardia, asystole, heart failure
• Amiodarone: Additive negative chronotropic effects
• Clonidine: Withdraw atenolol before clonidine to avoid rebound hypertension
• Indomethacin (PG synthase inhibitors): May decrease hypotensive effects
• Digitalis glycosides: Additive bradycardia and AV conduction slowing

[UNSAFE] Alcohol with Atenolol may cause excessive drowsiness. Avoid alcohol.

[CONSULT YOUR DOCTOR] Atenolol is unsafe during pregnancy (Category D). There is definite evidence of risk to the developing baby. Use only if potential benefit justifies the risk.

[CONSULT YOUR DOCTOR] Atenolol is excreted in breast milk. Clinically significant bradycardia has been reported in breast-fed infants. Premature infants or those with renal impairment are at higher risk.

Safety and efficacy in children have not been established.

Elderly patients should start at the lower end of the dosing range. Dose adjustment based on creatinine clearance.

[CAUTION] Use with caution in renal impairment. Dose adjustment needed:

• CrCl 15-35 mL/min: max 50 mg/day
• CrCl <15 mL/min: max 25 mg/day
• Hemodialysis: 25-50 mg after each dialysis

[CONSULT YOUR DOCTOR] Limited information available on use in liver disease.

Symptoms: Lethargy, respiratory drive disorder, wheezing, sinus pause, bradycardia, congestive heart failure, hypotension, bronchospasm, hypoglycemia.

Treatment: Induced emesis, gastric lavage, activated charcoal. Atenolol can be removed by hemodialysis. Cardiac and respiratory support may be required.

Do not use after expiry date. Keep out of reach of children. Dispense only on prescription of a registered physician.

Atenolol (C₁₄H₂₂N₂O₃)