Beta%2520blockers

# Beta Blockers ## Overview Beta-adrenergic blocking agents competitively antagonize catecholamine binding to beta-receptors. They are categorized as non-selective (e.g., propranolol), cardioselective ($\beta_1$-selective; e.g., metoprolol, bisoprolol, atenolol), or vasodilatory (e.g., carvedilol, nebivolol). ## Primary Indications Hypertension, stable angina pectoris, post-myocardial infarction (MI), heart failure with reduced ejection fraction (HFrEF; specifically carvedilol, metoprolol succinate, bisoprolol), and rate control for atrial fibrillation/flutter. ## Adult Dosing * **Metoprolol Succinate (ER):** Start 25–50 mg daily; titrate every 1–2 weeks. Max: 400 mg/day. * **Metoprolol Tartrate (IR):** 25–100 mg twice daily. Max: 450 mg/day (for angina/HTN). * **Carvedilol:** Start 3.125–6.25 mg twice daily for HFrEF. Target: 25 mg twice daily (or 50 mg if >85 kg). * **Bisoprolol:** 5–10 mg daily. Max: 20 mg/day. * **Atenolol:** 25–100 mg daily. Max: 200 mg/day (Note: less effective for HFrEF). * **Propranolol (IR):** 40 mg twice daily; titrate as needed. Max: 320–480 mg/day. *Note: Dosing for specific indications such as migraine prophylaxis or hyperthyroidism will differ significantly; ensure indication-specific prescribing.* ## Pediatric Dosing * **Propranolol:** 0.5–4 mg/kg/day in 2–4 divided doses for hypertension. * **Atenolol:** 0.5–1 mg/kg/day (once daily). * **Metoprolol Tartrate:** 1–2 mg/kg/day in 2 divided doses. *Note: Pediatric dosing is highly weight/indication-dependent. Confirm via Harriet Lane Handbook or institutional guidelines.* ## Dose Adjustments * **Renal Impairment:** Generally unnecessary for lipophilic agents (e.g., metoprolol, propranolol) as they undergo hepatic metabolism. Dose reduction may be required for hydrophilic agents (e.g., atenolol) in severe renal failure. * **Hepatic Impairment:** Use caution with hepatically cleared drugs (propranolol, carvedilol); reduce starting doses, as clearance is significantly decreased leading to increased bioavailablity. ## Contraindications * Second or third-degree AV block (without a pacemaker). * Severe bradycardia (typically <50 bpm). * Decompensated heart failure (unless stable/chronic HFrEF after optimization). * Cardiogenic shock. * Severe, uncontrolled reactive airway disease (asthma). ## Adverse Effects Bradycardia, hypotension, fatigue, sexual dysfunction, masking of hypoglycemia symptoms (tachycardia remains masked, but sweating/tremor may persist). Abrupt withdrawal can trigger rebound tachycardia or hypertension. ## Key Drug Interactions * **CYP2D6 Inhibitors (e.g., fluoxetine, paroxetine):** Increases levels of metoprolol, carvedilol, and propranolol. * **Non-DHP Calcium Channel Blockers (verapamil, diltiazem):** Synergistic effects on AV conduction and negative inotropy; high risk of severe bradycardia or heart block. * **Antidiabetic Agents:** Beta-blockers may mask hypoglycemia symptoms and decrease insulin secretion. ## Monitoring Heart rate and blood pressure at baseline and after any dose titration. Periodic assessments for peripheral edema, weight gain (worsening HF), and dyspnea. ## Clinical Pearls * **Heart Failure:** Initiate "low and go slow" in stable patients only. Do not initiate during acute decompensation. * **Selectivity:** Cardioselectivity is lost at higher doses; non-selective agents should be used with extreme caution in patients with asthma or COPD. * **Switching:** Metoprolol succinate and tartrate are NOT mg-for-mg interchangeable. * **Withdrawal:** Always taper over 1–2 weeks to prevent "rebound" effect. *** *Disclaimer: This information is for educational purposes and does not replace medical judgment. Always verify current, indication-specific dosing and contraindications using institutional protocols, the package insert, or resources like Lexicomp or Micromedex before prescribing.*