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# Beta Blockers ## Overview Beta-blockers (β-adrenergic blocking agents) competitively inhibit catecholamine binding to beta-receptors. They are categorized by selectivity (β1-selective vs. non-selective) and intrinsic sympathomimetic activity (ISA). ## Primary Indications * Hypertension * Heart failure (HFrEF - carvedilol, metoprolol succinate, bisoprolol) * Post-myocardial infarction * Angina pectoris * Atrial fibrillation/flutter (rate control) * Migraine prophylaxis (propranolol) * Essential tremor (propranolol) ## Adult Dosing (Common Examples) * **Metoprolol Succinate:** Start 25–50 mg daily; titrate to max 200 mg/day. * **Atenolol:** 25–50 mg daily; titrate to max 100 mg/day. * **Carvedilol:** Start 3.125 mg BID; titrate to target 25 mg BID (or 50 mg BID for stable patients >85kg). * **Propranolol (ER):** 80 mg daily; titrate to max 240 mg/day (varies by indication). * **Bisoprolol:** 5 mg daily; titrate to target 10 mg/day. ## Pediatric Dosing * **Hypertension (e.g., Propranolol):** Start 0.5–1 mg/kg/day divided BID; max 8 mg/kg/day. * **Atenolol:** 0.5–1 mg/kg/dose once daily; max 2 mg/kg/day. * *Note: Pediatric dosing is highly variable based on weight and specific indication; always consult institutional protocols or specialized resources (e.g., Harriet Lane).* ## Dose Adjustments * **Renal Impairment:** Most do not require adjustment (except atenolol, which requires reduction in CrCl <35 mL/min). * **Hepatic Impairment:** Reduce dose for drugs with high first-pass metabolism (e.g., propranolol, carvedilol). * **Geriatric:** Initiate at the lowest dose and titrate slowly due to increased sensitivity and risk of bradycardia. ## Contraindications * Second or third-degree heart block (without a pacemaker). * Severe bradycardia (typically <50–60 bpm). * Cardiogenic shock. * Decompensated heart failure. * Severe, uncontrolled reactive airway disease (asthma) for non-selective agents. ## Adverse Effects * Bradycardia, hypotension, heart block. * Fatigue, dizziness, depression. * Cold extremities (peripheral vasoconstriction). * Masking of hypoglycemia symptoms (tachycardia/tremor). * Sexual dysfunction. ## Key Drug Interactions * **CYP2D6 Inhibitors:** May increase levels of metoprolol and carvedilol (e.g., fluoxetine, paroxetine). * **Non-DHP Calcium Channel Blockers:** (Diltiazem, Verapamil) High risk of additive bradycardia and heart block. * **Digoxin:** Additive AV nodal conduction slowing. * **Insulin/Sulfonylureas:** Masking of hypoglycemia and potential blunting of recovery from hypoglycemia. ## Monitoring * Heart rate and blood pressure prior to increases. * Electrocardiogram (if conduction abnormalities suspected). * Symptom assessment for heart failure (weight gain, edema, dyspnea). * Blood glucose in diabetic patients. ## Clinical Pearls * **Sudden Withdrawal:** Avoid abrupt discontinuation to prevent "rebound hypertension" or tachyarrhythmias; taper over 1–2 weeks. * **Selectivity:** β1-selective blockers (Atenolol, Metoprolol, Bisoprolol) are preferred in patients with mild COPD or diabetes to minimize pulmonary and metabolic side effects. * **Heart Failure titration:** Patients must be hemodynamically stable at a low dose before any upward titration. * **Lipophilicity:** Propranolol is highly lipophilic and crosses the blood-brain barrier, making it effective for tremors/anxiety but increasing risk of CNS side effects (nightmares). *** **Disclaimer:** This information is for educational purposes only. Prescribing information, dosing, and safety profiles can change. Always verify current prescribing information via official pharmacy references (e.g., Lexicomp, Clinical Pharmacology) or institutional drug formularies before administration.