Chapter 5  ·  Module 5  ·  Visual Summary

Beta-Adrenergic Antagonists

Classification · Cardiovascular Uses · Adverse Effects · Contraindications

Classification by Generation and Selectivity

First Generation

Non-Selective

BlocksBeta-1 AND beta-2 receptors equally
DrugsPropranolol, nadolol, timolol
Beta-2 SEBronchoconstriction, peripheral vasoconstriction
PropranololThyroid storm (also inhibits T4→T3 conversion); essential tremor; migraine prophylaxis

Second Generation

Cardioselective (Beta-1)

BlocksBeta-1 preferentially; spares beta-2 at standard doses
DrugsMetoprolol, atenolol, bisoprolol
BenefitLess bronchoconstriction and peripheral vasoconstriction
NoteSelectivity is dose-dependent. Asthma still contraindicated.

Third Generation

Vasodilatory

CarvedilolBeta-1/2 + alpha-1 blockade → vasodilation; HFrEF (approved); take with food
LabetalolBeta-1/2 + alpha-1 blockade; hypertensive emergency; drug of choice in pregnancy
BenefitReduces cardiac output AND peripheral vascular resistance; no reflex tachycardia

HFrEF-Approved Agents

Three Only

AgentsCarvedilol, bisoprolol, metoprolol succinate (extended-release) ONLY
MechanismReverse sympathetic remodeling → receptor resensitization → improved ejection fraction over months
RuleStart ONLY when euvolemic and stable. Never during acute decompensation. Start low, double every 2 weeks.

Adverse Effects & Absolute Contraindications

Cardiac

Bradycardia, AV block. Contraindicated: Mobitz II or 3rd-degree AV block, sick sinus syndrome (without pacemaker), cardiogenic shock.

Pulmonary

Bronchospasm from beta-2 blockade. Contraindicated: Asthma — ALL beta-blockers including cardioselective agents. COPD without reversibility is relative.

Metabolic

Masks hypoglycemia (tachycardia blunted; sweating preserved). Non-selective agents also raise triglycerides. Use cardioselective in diabetes.

Withdrawal

Never stop abruptly. Taper over 1–2 weeks. Rebound tachycardia, angina, and myocardial infarction risk in coronary artery disease patients.

Key Drug Interactions

Interacting Drug Consequence and Management
Verapamil / Diltiazem (intravenous) Severe AV block, asystole. Never give intravenous verapamil to a patient on a beta-blocker. Use with extreme caution even orally.
Epinephrine (with non-selective beta-blocker) Beta-2 vasodilation blocked → unopposed alpha-1 vasoconstriction → severe diastolic hypertension. Risk in anaphylaxis on propranolol — use glucagon.
Insulin / sulfonylureas Hypoglycemia warning signs masked (tachycardia, tremor). Sweating preserved. Non-selective agents also prolong hypoglycemia. Use cardioselective agents.
Non-steroidal anti-inflammatory drugs Blunt antihypertensive efficacy of beta-blockers through prostaglandin-mediated sodium retention. Monitor blood pressure when NSAIDs added.