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# Beta Blockers ## Overview Beta-adrenergic blocking agents competitively antagonize catecholamines at beta-1 (cardiac) and/or beta-2 (bronchial/vascular) receptors. They are categorized by selectivity (cardioselective vs. non-selective) and intrinsic sympathomimetic activity (ISA). ## Primary Indications Hypertension, stable angina pectoris, post-myocardial infarction (MI), heart failure with reduced ejection fraction (HFrEF), atrial fibrillation/flutter rate control, and migraine prophylaxis (propranolol). ## Adult Dosing * **Metoprolol Succinate (ER):** Start 25–50 mg daily. Target dose for HFrEF: 200 mg daily. * **Bisoprolol:** Start 1.25–2.5 mg daily. Target dose for HFrEF: 10 mg daily. * **Carvedilol:** Start 3.125 mg twice daily. Target dose (weight-dependent): 25 mg BID (<85kg) to 50 mg BID (>85kg). * **Atenolol:** 25–100 mg daily for hypertension/angina. * **Propranolol (Immediate Release):** 40–160 mg daily in 2–4 divided doses for hypertension. ## Pediatric Dosing * **Propranolol:** 0.5–4 mg/kg/day divided BID–QID for hypertension; up to 8 mg/kg/day for portal hypertension. * **Atenolol:** 0.5–1 mg/kg/day once daily. * *Note:* Pediatric dosing varies by indication (e.g., infantile hemangioma vs. hypertension); always consult pediatric-specific guidelines (e.g., Lexicomp/Harriet Lane). ## Dose Adjustments * **Renal Impairment:** Generally no adjustment for lipophilic agents (e.g., metoprolol, propranolol). Atenolol and bisoprolol may require dose reduction in severe renal impairment (CrCl <30 mL/min). * **Hepatic Impairment:** Mandatory dose reduction for lipophilic agents as they rely on extensive hepatic metabolism. ## Contraindications * Severe bradycardia (<50 bpm). * Second or third-degree AV block (without a pacemaker). * Cardiogenic shock. * Decompensated heart failure. * Severe reactive airway disease (non-selective agents like propranolol should be used with extreme caution/avoided in severe asthma). ## Adverse Effects * Bradycardia, hypotension, AV block. * Fatigue and exercise intolerance. * Masking of hypoglycemia symptoms (except sweating). * Bronchospasm (non-selective). * Cold extremities and erectile dysfunction. ## Key Drug Interactions * **CYP2D6 Inhibitors:** (e.g., fluoxetine, paroxetine) increase levels of metoprolol and carvedilol. * **Non-DHP CCBs:** (Diltiazem, Verapamil) significant risk of severe bradycardia or heart block. * **Digoxin:** Additive slowing of AV conduction. ## Monitoring * Heart rate (prior to every dose if unstable) and blood pressure. * Symptoms of heart failure exacerbation (weight gain, edema, dyspnea). * Blood glucose in diabetic patients. * ECG for PR interval prolongation. ## Clinical Pearls * **Do not discontinue abruptly:** Must taper over 1–2 weeks to prevent "rebound" tachycardia, hypertension, or myocardial ischemia. * **Selective vs. Non-selective:** Cardioselective agents (Bisoprolol, Metoprolol, Atenolol) are preferred in patients with mild-to-moderate reactive airway disease. * **Carvedilol:** Exhibits alpha-1 blocking activity, providing additional vasodilation; must be taken with food to minimize orthostatic hypotension. * **Titration:** In HFrEF, start low and double the dose no more frequently than every 2 weeks as tolerated. *** *Disclaimer: This information is for educational purposes only. Clinical protocols vary; always verify current prescribing information, contraindications, and dose-specific guidelines via institutional pharmacy resources or up-to-date clinical databases like Lexicomp or Micromedex before prescribing.*