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# Beta Blockers ## Overview Beta-adrenergic blocking agents competitively antagonize catecholamines at beta-adrenergic receptors. They are categorized by receptor selectivity (β1-selective vs. non-selective) and intrinsic sympathomimetic activity (ISA). ## Primary Indications * Hypertension * Heart failure with reduced ejection fraction (HFrEF) * Atrial fibrillation/flutter (rate control) * Post-myocardial infarction (secondary prevention) * Angina pectoris * Essential tremor (propranolol) * Migraine prophylaxis (propranolol) ## Adult Dosing *Dosing varies significantly by agent; examples provided for common drugs:* * **Metoprolol Succinate (ER):** Start 25–50 mg daily; titrate to max 200 mg/day (Heart Failure target dose: 200 mg/day). * **Metoprolol Tartrate (IR):** 25–100 mg twice daily. * **Carvedilol:** Start 3.125–6.25 mg twice daily; titrate to max 25 mg twice daily (patient weight <85 kg) or 50 mg twice daily (patient weight >85 kg). * **Bisoprolol:** Start 1.25–2.5 mg daily; titrate to max 10 mg/day. * **Propranolol (ER):** 80 mg daily; titrate based on indication (max 240–320 mg/day for angina/migraine). ## Pediatric Dosing *Requires provider-specific protocol; highly weight-dependent.* * **Propranolol:** Hypertension: 0.5–1 mg/kg/day divided BID–QID; max 8 mg/kg/day. * **Atenolol:** 0.5–1 mg/kg/day; max 2 mg/kg/day (divided daily or BID). * **Note:** Always verify weight-based calculations using institutional or current pediatric formularies (e.g., Lexicomp/Harriet Lane). ## Dose Adjustments * **Renal Impairment:** Generally unnecessary for lipophilic agents (e.g., metoprolol, propranolol). Atenolol and bisoprolol may require reduction in severe renal impairment (CrCl <30 mL/min). * **Hepatic Impairment:** Required for highly metabolized agents (e.g., propranolol, carvedilol); initiate at lower doses. ## Contraindications * Bradycardia (<50–60 bpm) or heart block (second- or third-degree) without a pacemaker. * Decompensated heart failure (unless stable). * Cardiogenic shock. * Severe reactive airway disease (asthma/COPD) for non-selective agents (use β1-selective with caution at low doses). * Sick sinus syndrome. ## Adverse Effects * **Common:** Bradycardia, hypotension, fatigue, dizziness, cold extremities. * **Specific:** Metabolic masking of hypoglycemia symptoms (except sweating), bronchospasm, erectile dysfunction, depression. ## Key Drug Interactions * **CYP2D6 Inhibitors:** May increase levels of metoprolol and carvedilol. * **Non-DHP Calcium Channel Blockers (Diltiazem/Verapamil):** Synergistic effects on AV conduction; high risk of profound bradycardia/heart block. * **Digoxin:** Additive slowing of AV conduction. * **Clonidine:** Risk of rebound hypertension upon abrupt withdrawal if taken concomitantly. ## Monitoring * Heart rate and blood pressure (pre-dose and during titration). * Signs of fluid overload/decompensated heart failure. * Blood glucose in patients with diabetes. * Signs of respiratory distress in patients with baseline reactive airway disease. ## Clinical Pearls * **Heart Failure titration:** Always start low and titrate slowly (q2–4 weeks) to avoid acute worsening of HF symptoms. * **Abrupt Cessation:** Avoid abrupt discontinuation after chronic use; this can cause beta-receptor upregulation leading to rebound tachycardia, hypertension, or myocardial ischemia. Taper over 1–2 weeks. * **Selectivity:** In patients with mild asthma/COPD, β1-selective agents (e.g., bisoprolol, metoprolol succinate) are preferred but should still be used with caution. * **Food:** Metoprolol is better absorbed with food; consistency is key. *** *Disclaimer: This information is for educational purposes and does not supersede local institutional protocols. Always consult the most current prescribing information or a clinical pharmacist before calculating or administering drug doses.*