STEPTRACKERPHARMACOLOGY | AUTONOMIC | HIGH-YIELD REVIEW

β-Blockers

One class with many uses — slowing the heart, lowering demand and blocking catecholamine effects — and a predictable list of who shouldn't take them.

FOCUS ON
β1-selective: atenolol, metoprolol, esmolol (ultrashort IV), bisoprolol, betaxolol, acebutolol. Nonselective: propranolol, nadolol, timolol, pindolol. Mixed α + β: carvedilol, labetalol. Partial agonists (ISA): pindolol, acebutolol. Vasodilating: nebivolol (NO), carvedilol, labetalol. Uses: angina (↓ HR and contractility → ↓ O₂ demand), post-MI and HFrEF (only metoprolol succinate, carvedilol, bisoprolol ↓ mortality), rate control in AF, hypertension, HCM, thyrotoxicosis symptoms, aortic dissection, glaucoma (timolol), essential tremor, migraine prophylaxis, performance anxiety, portal hypertension (nonselective), variceal bleed prevention. Adverse: bradycardia, AV block, bronchospasm (nonselective), fatigue, erectile dysfunction, masked hypoglycemia, ↑ triglycerides, worsened acute HF. Overdose → glucagon.
GROUP
DRUGS
DISTINCT FEATURE
BEST USE
β1-selective
Metoprolol, atenolol, bisoprolol, betaxolol, esmolol
Less bronchospasm (selectivity lost at high doses)
Angina, post-MI, HFrEF (metoprolol, bisoprolol), COPD patients
Esmolol
IV, very short half-life (RBC esterases)
Titratable
Aortic dissection, perioperative tachycardia, SVT
Nonselective
Propranolol, nadolol, timolol
β1 + β2 block
Portal hypertension, essential tremor, migraine, thyrotoxicosis, glaucoma (timolol)
Propranolol extras
Lipophilic, membrane stabilizing
Blocks T4 → T3 conversion
Thyroid storm, infantile hemangioma, performance anxiety
Mixed α1 + β
Carvedilol, labetalol
Vasodilation plus β block
Carvedilol: HFrEF · labetalol: pregnancy, hypertensive emergency
Partial agonists (ISA)
Pindolol, acebutolol
Less resting bradycardia
Avoid post-MI and in angina
Nebivolol
β1-selective + NO-mediated vasodilation
—
Hypertension
Cardiac adverse effects
Bradycardia, AV block, hypotension, acute HF decompensation
—
Caution with verapamil or diltiazem
Noncardiac adverse effects
Bronchospasm, fatigue, depression, sexual dysfunction, cold extremities, ↑ TG
Masks tremor and tachycardia of hypoglycemia
Caution in insulin users
Withdrawal
Upregulated receptors
Rebound tachycardia, angina, MI
Taper
Overdose
Bradycardia, hypotension, hypoglycemia, seizures (propranolol)
—
Glucagon (↑ cAMP via its own receptor), atropine, high-dose insulin
Contraindications
Asthma (nonselective), cocaine-related chest pain, acute decompensated HF, severe bradycardia or high-grade AV block
—
Prinzmetal angina (unopposed α)

Mechanism — why β-blockers relieve angina

Block β1
→
↓ HR, ↓ contractility
→
↓ O₂ demandLonger diastole → more coronary filling
→
Fewer ischemic episodes

Which β-blocker

SITUATION
CHOICE
REASON
HFrEF
Metoprolol succinate, carvedilol, bisoprolol
Mortality benefit
Pregnancy HTN
Labetalol
Safe, α + β
Varices
Propranolol, nadolol
↓ portal pressure
Dissection
Esmolol IV
↓ shear, titratable
COPD
β1-selective
Less bronchospasm

How it's tested

COMMON CONFUSIONStart β-blockers in stable, euvolemic HFrEF — they help long-term — but don't start or uptitrate in acute decompensated failure.
THE TRAPA diabetic on insulin with a β-blocker may not feel hypoglycemia (tremor, palpitations masked); sweating persists (cholinergic).
YOUR APPROACHCheck selectivity (lungs), α activity (vasodilation, pregnancy), ISA (post-MI) and the specific mortality drugs in HF.

If you see… think…

β-blocker overdose with bradycardia and hypotension → glucagon
Wheezing after starting propranolol → β2 blockade
β-blockers that lower mortality in HFrEF → metoprolol succinate, carvedilol, bisoprolol
IV β-blocker for aortic dissection → esmolol
Topical drug for glaucoma ↓ aqueous production → timolol
Essential tremor → propranolol
Thyroid storm symptom control → propranolol
β-blockers with α1 activity → carvedilol, labetalol
Avoid post-MI because of ISA → pindolol, acebutolol
Rebound angina after stopping → receptor upregulation