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# Beta Blockers ## Overview Beta-adrenergic blocking agents competitively antagonize catecholamines at beta-receptors. They are categorized by selectivity (beta-1 cardioselective vs. non-selective) and intrinsic sympathomimetic activity (ISA). Common examples include Metoprolol (succinate/tartrate), Atenolol, Propranolol, and Carvedilol. ## Primary Indications * Hypertension * Heart failure (HFrEF) * Post-myocardial infarction (secondary prevention) * Atrial fibrillation/flutter (rate control) * Angina pectoris * Essential tremor (Propranolol) * Migraine prophylaxis (Propranolol) ## Adult Dosing * **Metoprolol Succinate (ER):** Start 25–50 mg daily; titrate to max 200 mg daily. * **Metoprolol Tartrate (IR):** 25–100 mg twice daily; max 400 mg daily (divided). * **Carvedilol:** Start 3.125–6.25 mg twice daily; titrate to max 25 mg twice daily (HF), or 50 mg twice daily (HTN). * **Propranolol (IR):** 40 mg twice daily; titrate up to 240–320 mg/day (for tremor or angina). * **Atenolol:** 25–50 mg daily; max 100 mg daily. ## Pediatric Dosing * *Note: Dosing is highly weight-based and indication-dependent; verify via local institutional or pediatric formulary (e.g., Lexicomp/Harriet Lane).* * **Propranolol:** Hypertension: 0.5–1 mg/kg/day divided twice daily; max 4 mg/kg/day or 160 mg/day. * **Atenolol:** Hypertension: 0.5–1 mg/kg/dose once daily; max 2 mg/kg/day. ## Dose Adjustments * **Renal Impairment:** Atenolol requires significant adjustment (reduce frequency/dose); lipophilic agents (Metoprolol/Carvedilol) generally do not require dose adjustment in renal impairment. * **Hepatic Impairment:** Reduce starting doses for agents undergoing extensive hepatic metabolism (Carvedilol, Propranolol). ## Contraindications * Second or third-degree heart block (without a pacemaker). * Severe sinus bradycardia (usually <50 bpm). * Overt, decompensated heart failure. * Cardiogenic shock. * Severe reactive airway disease (non-selective agents like Propranolol). ## Adverse Effects * Bradycardia and hypotension. * Fatigue and exercise intolerance. * Cold extremities (peripheral vasospasm). * Masking of hypoglycemic symptoms (except sweating). * Erectile dysfunction. * Bronchospasm (in susceptible individuals). ## Key Drug Interactions * **CYP2D6 inhibitors:** (e.g., Fluoxetine, Paroxetine) increase levels of Metoprolol and Carvedilol. * **Non-dihydropyridine CCBs:** (Diltiazem, Verapamil) pose severe risk of synergistic bradycardia and heart block. * **Insulin/Sulfonylureas:** May potentiate hypoglycemia and mask symptoms. * **Clonidine:** Risk of rebound hypertension if beta-blocker is withdrawn before clonidine. ## Monitoring * Heart rate and blood pressure (pre-dose/titration). * Electrocardiogram (if high risk for conduction disturbances). * Respiratory status (in patients with history of asthma/COPD). * Blood glucose (in diabetics). ## Clinical Pearls * **Tapering:** Never stop abruptly; withdrawal can cause sympathetic "rebound" (tachycardia, hypertension, cardiac ischemia). Taper over 1–2 weeks. * **Metoprolol conversion:** Metoprolol tartrate has a short half-life and requires twice-daily dosing for stable control; Metoprolol succinate is once daily. * **Selective vs. Non-selective:** Use cardioselective (B1-selective, e.g., Metoprolol, Bisoprolol) in patients with mild COPD or diabetes to minimize airway or metabolic side effects. * **Carvedilol:** Has additional alpha-1 blocking activity, which provides vasodilation benefits but carries a higher risk of orthostatic hypotension during initiation. *** **Educational Disclaimer:** This information is for educational purposes only. Always cross-reference with official product labeling (FDA-approved package inserts) and local institutional protocols before prescribing or administering any medication.