β-blockers — selectivity, ISA, ABCs of side effects

Cardioselective vs non-selective, with the indications and contraindications that matter.

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◆Classes

•β1-selective (cardioselective): metoprolol, atenolol, bisoprolol, esmolol, nebivolol — preferred in COPD, DM, PAD
•Non-selective (β1+β2): propranolol, nadolol, timolol — useful in migraine, essential tremor, performance anxiety
•Mixed α+β: labetalol, carvedilol — labetalol for hypertensive emergency (incl pregnancy), carvedilol for HFrEF
•ISA (intrinsic sympathomimetic activity): pindolol, acebutolol — less bradycardia; avoid post-MI

•HFrEF: carvedilol, metoprolol succinate (NOT tartrate), bisoprolol → mortality benefit
•Post-MI: any β-blocker × at least 1 yr
•Rate control AFib: metoprolol or atenolol
•Migraine prophylaxis: propranolol, metoprolol
•Essential tremor: propranolol
•Performance anxiety: propranolol PRN (short-acting)
•Hyperthyroidism (until antithyroid takes effect): propranolol
•Variceal bleeding prophylaxis (cirrhosis): nadolol, propranolol
•Pheochromocytoma: AFTER α-blockade (phenoxybenzamine) — never first

•Asthma / bronchospasm (especially non-selective)
•Bradycardia, heart block
•Claudication / cold extremities (worsen PAD)
•Depression, fatigue, sexual dysfunction
•Erectile dysfunction; masks hypoglycemia symptoms (sweating preserved; tachycardia masked) in diabetics

•Asthma: avoid non-selective; cardioselective at low dose OK in COPD
•Decompensated HF: hold; restart slowly when euvolemic
•2nd/3rd degree AV block (without pacer)
•Cocaine intoxication: unopposed α → AVOID β-blockers; use benzos, phentolamine if HTN crisis
•Pheochromocytoma: phenoxybenzamine first, then β-blocker

•Bradycardia + hypotension; hypoglycemia, seizures
•Treatment: IV fluids, atropine, glucagon (drug of choice), high-dose insulin / euglycemia, calcium, lipid emulsion in severe
•Pacing if refractory bradycardia

◆HFrEF: only carvedilol, metoprolol SUCCINATE, and bisoprolol have mortality benefit
◆Cocaine chest pain: NO β-blocker (use benzos + nitrate); 'unopposed α' risk historically taught — modern evidence less clear, board answer = avoid
◆Pheochromocytoma needs α-blockade FIRST (phenoxybenzamine), then β to prevent hypertensive crisis
◆Glucagon is the antidote for β-blocker AND calcium-channel blocker overdose (via cAMP)

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