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# Beta Blockers ## Overview Beta-adrenergic blocking agents (beta blockers) antagonize the effects of catecholamines (epinephrine and norepinephrine) at beta-adrenergic receptors. They are classified as selective (beta-1 selective) or non-selective. Some also possess intrinsic sympathomimetic activity (ISA) or alpha-blocking properties. ## Primary Indications * Hypertension * Angina Pectoris * Myocardial Infarction (secondary prevention) * Heart Failure (certain agents) * Arrhythmias (e.g., supraventricular tachycardia, atrial fibrillation rate control) * Migraine Prophylaxis * Essential Tremor * Glaucoma (topical) * Hyperthyroidism (symptomatic control) * Pheochromocytoma (adjunct therapy) * Anxiety (situational) ## Adult Dosing Dosing varies significantly by specific agent and indication. Titration is typically required. * **Hypertension:** * Metoprolol tartrate: 25-100 mg twice daily. Max: 400 mg/day. * Metoprolol succinate: 25-100 mg once daily. Max: 400 mg/day. * Atenolol: 25-50 mg once daily. Max: 100 mg/day. * Propranolol: 40-80 mg twice daily. Max: 640 mg/day. * Carvedilol: 3.125-6.25 mg twice daily. Titrate upwards. Max: 81 mg twice daily. * Labetalol: 100-200 mg twice daily. Max: 2400 mg/day. * **Heart Failure (HFrEF):** * Metoprolol succinate: Initiate at 12.5-25 mg once daily, titrate every 2-4 weeks to target dose (e.g., 200 mg once daily). * Carvedilol: Initiate at 3.125 mg twice daily, titrate every 2-4 weeks to target dose (e.g., 25 mg twice daily for < 85 kg, 50 mg twice daily for > 85 kg). * Bisoprolol: Initiate at 1.25 mg once daily, titrate every 2-4 weeks to target dose (e.g., 10 mg once daily). * **Post-MI:** * Metoprolol tartrate: 50 mg every 6 hours for 24 hours, then 100 mg twice daily. * Propranolol: 40-80 mg three times daily. * **Angina:** Dosing is individualized to control symptoms and exercise tolerance. ## Pediatric Dosing Dosing is often weight-based and requires careful titration. Pediatric dosing recommendations are less standardized than adult dosing and may depend on local protocols or specialist guidance. * **Hypertension (e.g., Atenolol):** 0.5-1 mg/kg/day divided once or twice daily. Max: 2 mg/kg/day (or 100 mg/day). * **Arrhythmias (e.g., Propranolol):** 0.1-0.5 mg/kg/dose every 6-8 hours. ## Dose Adjustments * **Renal Impairment:** Dose reduction may be necessary for renally eliminated agents (e.g., atenolol, nadolol). Metoprolol and propranolol require less adjustment unless severe. * **Hepatic Impairment:** Dose reduction may be necessary for agents with significant first-pass metabolism (e.g., propranolol, metoprolol). ## Contraindications * Severe bradycardia * Second or third-degree heart block (without a pacemaker) * Sick sinus syndrome * Cardiogenic shock * Decompensated heart failure * Severe peripheral arterial disease * Asthma or bronchospastic disease (relative contraindication for non-selective agents) * Known hypersensitivity ## Adverse Effects Common: Bradycardia, hypotension, fatigue, dizziness, cold extremities, bronchospasm (non-selective), masking of hypoglycemia symptoms (especially in diabetics), erectile dysfunction. Less common: Depression, nightmares, heart failure exacerbation, peripheral vasoconstriction. ## Key Drug Interactions * **Calcium Channel Blockers (verapamil, diltiazem):** Additive negative chronotropic and inotropic effects, risk of severe bradycardia, heart block, and heart failure. * **Antiarrhythmics (amiodarone, flecainide):** Additive negative effects on cardiac conduction and contractility. * **Digoxin:** May increase digoxin levels; additive bradycardia. * **Insulin/Oral Hypoglycemics:** Beta blockers can mask symptoms of hypoglycemia; monitor blood glucose closely. * **CYP450 Inhibitors/Inducers:** May alter concentrations of metoprolol and propranolol (e.g., cimetidine, fluoxetine, rifampin). * **Alpha-Blockers (e.g., prazosin):** Increased risk of orthostatic hypotension. ## Monitoring * Blood pressure and heart rate * Signs and symptoms of heart failure (weight gain, edema, dyspnea) * Electrolytes * Blood glucose (in diabetic patients) * Signs of bronchospasm * Signs of peripheral ischemia ## Clinical Pearls * Beta blockers are generally not first-line therapy for hypertension unless there is a compelling indication (e.g., post-MI, heart failure, angina, atrial fibrillation). * Initiate beta blockers at low doses and titrate slowly, especially in patients with heart failure, to minimize adverse effects. * Abrupt discontinuation can lead to rebound hypertension, angina, or myocardial infarction. Taper dose over 1-2 weeks. * Cardioselective (beta-1 selective) agents are preferred in patients with reactive airway disease, but caution is still advised. * Non-selective beta blockers with alpha-blocking activity (carvedilol, labetalol) are particularly useful in heart failure and hypertensive emergencies. *** *Disclaimer: This information is intended for educational purposes only and does not constitute medical advice. Always consult the most current prescribing information and clinical guidelines, and verify doses with available resources before making any treatment decisions.*