Tenormin (atenolol) is a cardioselective beta-blocker prescribed for the management of hypertension (high blood pressure) and angina pectoris (chest pain). As a cornerstone in cardiovascular therapy, it works by blocking the effects of adrenaline on the heart and blood vessels, thereby reducing heart rate, cardiac output, and blood pressure. Its high selectivity for β1-adrenergic receptors minimizes impact on bronchial and vascular smooth muscle, making it a preferred choice for many patients under expert medical supervision. This profile provides a comprehensive, evidence-based overview for healthcare professionals.

Features

• Active Ingredient: Atenolol
• Pharmacological Class: Cardioselective beta-1-adrenergic receptor blocking agent
• Standard Formulations: 25 mg, 50 mg, and 100 mg film-coated tablets
• Bioavailability: Approximately 50% following oral administration
• Protein Binding: Low (6-16%)
• Half-life: 6-7 hours (permits once-daily dosing)
• Primary Route of Elimination: Renal (excreted unchanged in urine)
• Onset of Action: Within 1 hour
• Peak Effect: 2-4 hours post-administration

Benefits

• Effective Blood Pressure Reduction: Provides consistent 24-hour control of hypertension, reducing the long-term risk of stroke, myocardial infarction, and kidney damage.
• Angina Symptom Management: Decreases the frequency and severity of angina attacks by reducing myocardial oxygen demand through lowered heart rate and contractility.
• Cardioprotective Post-MI: When administered in the acute phase and continued long-term, it reduces mortality and the risk of reinfarction in post-myocardial infarction patients.
• Favorable Safety Profile: Its cardioselectivity offers a superior side effect profile compared to non-selective beta-blockers, particularly for patients with co-morbidities like respiratory issues.
• Once-Daily Dosing: Supports high patient adherence and consistent therapeutic coverage, simplifying treatment regimens.

Common use

Tenormin is primarily indicated for the management of essential hypertension, either as monotherapy or in combination with other antihypertensive agents such as diuretics or calcium channel blockers. It is also approved for the long-term management of chronic stable angina pectoris. Furthermore, it is a standard component of secondary prevention protocols following an acute myocardial infarction to improve survival and reduce cardiovascular morbidity. Off-label uses may include the management of certain cardiac arrhythmias (e.g., supraventricular tachycardias), situational anxiety, and prophylaxis for migraine headaches, though these applications require careful individual risk-benefit assessment by a physician.

Dosage and direction

Dosage must be individualized based on the patient’s clinical condition and therapeutic response.

• Hypertension: The usual initial dose is 50 mg administered orally once daily. The full effect of a given dose may not be apparent for 1-2 weeks. The dosage may be increased to 100 mg once daily. Doses exceeding 100 mg per day are unlikely to produce further benefit.
• Angina Pectoris: The initial recommended dose is 50 mg orally once daily. If optimal response is not achieved within one week, the dosage should be increased to 100 mg once daily. Some patients may require a divided dose (e.g., 50 mg twice daily) for optimal 24-hour effect.
• Acute Myocardial Infarction: A specific IV-to-oral protocol is used. Following initial IV administration (5 mg over 5 minutes, followed by another 5 mg 10 minutes later), oral therapy is initiated with 50 mg 10 minutes after the last IV dose, followed by another 50 mg 12 hours later. Thereafter, maintenance dosing is 100 mg once daily or 50 mg twice daily for at least 6-9 days post-infarction.
• Renal Impairment: Dosage adjustment is necessary. For patients with a creatinine clearance of 15-35 mL/min/1.73m², the maximum recommended dose is 50 mg daily. For patients with a clearance below 15 mL/min/1.73m², the maximum recommended dose is 25 mg daily or 50 mg every other day.
• Administration: Can be taken with or without food. The tablet should be swallowed whole with a glass of water.

Precautions

• Abrupt Cessation: Therapy should not be discontinued abruptly, as this may exacerbate angina symptoms, precipitate ventricular arrhythmias, or cause a rebound hypertensive crisis. Dosage should be tapered gradually over a period of 1-2 weeks under close medical supervision.
• Ischemic Heart Disease: Patients with angina should be warned against interruption or sudden discontinuation of therapy due to the risk of severe exacerbation of angina.
• Bronchospastic Disease: Although cardioselective, Tenormin should be used with caution in patients with chronic obstructive pulmonary disease (COPD) or asthma, as it may still cause bronchospasm. It is not absolutely contraindicated but requires a compelling indication and ready availability of a beta2-agonist.
• Diabetes and Hypoglycemia: May mask certain signs of hypoglycemia (e.g., tachycardia, palpitations) and may potentiate insulin-induced hypoglycemia. It does not mask sweating or dizziness.
• Thyrotoxicosis: May mask the clinical signs of developing or continuing hyperthyroidism (e.g., tachycardia).
• Peripheral Vascular Disease: May precipitate or aggravate symptoms of arterial insufficiency (e.g., Raynaud’s phenomenon, cold extremities).
• Anesthesia: The heart’s ability to respond to reflex stimuli is impaired. Anesthesiologists must be made aware of beta-blocker therapy prior to any surgical procedure.
• Pheochromocytoma: Should not be used unless an alpha-blocker has been initiated first, to avoid unopposed alpha-adrenergic activity leading to severe hypertension.

Contraindications

Tenormin is contraindicated in patients with:

• Sinus bradycardia (heart rate <50 bpm)
• Second- or third-degree heart block (without a permanent pacemaker)
• Cardiogenic shock
• Overt cardiac failure (unless the failure is secondary to a tachyarrhythmia treatable with atenolol)
• Hypersensitivity to atenolol or any component of the formulation
• Severe peripheral arterial circulatory disorders
• Untreated pheochromocytoma
• Sick sinus syndrome

Possible side effect

Like all medications, Tenormin can cause side effects, although not everybody gets them. The most common are related to its pharmacological action.

• Very Common (≥1/10): Bradycardia, cold extremities, fatigue, dizziness.
• Common (≥1/100 to <1/10): Depression, shortness of breath (dyspnea), gastrointestinal disturbances (nausea, diarrhea, constipation), headache, sleep disorders.
• Uncommon (≥1/1,000 to <1/100): Heart failure deterioration, heart block, postural hypotension, rash, pruritus, impotence/erectile dysfunction.
• Rare (≥1/10,000 to <1/1,000): Alopecia, dry eyes, visual disturbances, psoriasiform skin reactions or exacerbation of psoriasis.
• Very Rare (<1/10,000): Hallucinations, nightmares, confusion, thrombocytopenia.

Drug interaction

Concomitant use of Tenormin with other drugs requires careful monitoring due to potential pharmacodynamic and pharmacokinetic interactions.

• Other Antihypertensives: Concomitant use with other blood pressure-lowering agents (e.g., calcium channel blockers like verapamil or diltiazem, alpha-blockers, diuretics) may lead to additive hypotensive and/or bradycardic effects.
• Antiarrhythmics: Concomitant use with Class I antiarrhythmic drugs (e.g., disopyramide) or amiodarone may have additive negative inotropic and chronotropic effects, increasing the risk of bradycardia and heart block.
• Insulin and Oral Hypoglycemics: May enhance the hypoglycemic effect and mask tachycardia as a sign of hypoglycemia.
• NSAIDs: Non-Steroidal Anti-Inflammatory Drugs (e.g., ibuprofen, naproxen) may reduce the antihypertensive effect of atenolol.
• Clonidine: Potentiates the rebound hypertension effect if clonidine is withdrawn during concurrent beta-blocker therapy.
• Sympathomimetics: Drugs like adrenaline (epinephrine) may lead to unopposed alpha-adrenergic activity, causing severe hypertension and bradycardia.
• Digoxin: Concomitant use increases the risk of bradycardia.

Missed dose

If a dose is missed, it should be taken as soon as the patient remembers. However, if it is almost time for the next scheduled dose, the missed dose should be skipped, and the regular dosing schedule resumed. The patient should not take a double dose to make up for a forgotten one. Maintaining a consistent schedule is crucial for stable therapeutic effect.

Overdose

Symptoms of overdose are primarily extensions of the drug’s beta-blocking activity and include severe bradycardia, heart failure, hypotension, hypoglycemia, bronchospasm, and loss of consciousness. In cases of severe overdose, cardiogenic shock and cardiac arrest may occur.

• Management: Treatment is primarily supportive and symptomatic.
  • Bradycardia & Heart Block: Administer atropine sulfate IV. If there is no response to vagal blockade, administer isoproterenol cautiously. Refractory cases may require transvenous cardiac pacing.
  • Hypotension & Shock: Administer vasopressors with alpha-adrenergic agonist effects (e.g., epinephrine, norepinephrine). Glucagon has been used successfully due to its positive inotropic and chronotropic effects that are not mediated by beta-receptors.
  • Bronchospasm: Administer a beta2-stimulating agent and/or a theophylline derivative.
  • Hypoglycemia: Administer intravenous glucose.
  • Gastric lavage may be considered if ingestion was recent. Atenolol can be removed from the circulation by hemodialysis due to its low protein binding.

Storage

• Store below 30°C (86°F).
• Keep the blister strips in the outer carton to protect from light and moisture.
• Keep out of sight and reach of children.
• Do not use after the expiration date printed on the packaging.

Disclaimer

This information is intended for educational purposes and for use by healthcare professionals only. It is a summary and does not contain all possible information about this product. It does not constitute medical advice. The prescribing physician is responsible for determining the appropriate dosage and monitoring therapy for each individual patient based on their specific medical condition, concomitant medications, and other factors. Patients must not alter or stop their medication without first consulting their doctor.

Reviews

• Clinical Consensus: “Atenolol remains a well-established, effective, and generally well-tolerated first-line option for hypertension and angina, particularly valued for its cardioselectivity and once-daily dosing regimen. Its role in post-MI management is firmly supported by decades of clinical evidence.” – Cardiology Today
• Meta-Analysis Findings: “In large-scale meta-analyses, beta-blocker therapy with drugs like atenolol has demonstrated significant reductions in cardiovascular events and mortality in hypertensive patients, especially those with a history of coronary artery disease.” – Journal of the American College of Cardiology
• Real-World Evidence: “Patient adherence is high with Tenormin due to its simple dosing schedule. While newer agents exist, its cost-effectiveness and proven track record ensure its continued place in formularies and treatment guidelines worldwide.” – Clinical Pharmacist Review