the sympatholytic
Competitive antagonists at beta-adrenergic receptors. They blunt the chronic sympathetic nervous system activation that drives heart failure progression and arrhythmias.
- Mechanism: Blocks (cardiac: rate/contractility) and (bronchial/vascular) receptors.
- Dosing: “Start low, go slow.” Titrate every 2-4 weeks.
- PK: Lipophilicity varies (Propranolol > Metoprolol > Atenolol), affecting CNS penetration (anxiety/nightmares).
evidence & mortality benefits
Not all beta blockers are equal. Evidence is specific to the agent and the condition.
heart failure with reduced ejection fraction (HFrEF)
Only three agents have proven mortality benefit in large RCTs.
- Bisoprolol (CIBIS-II): selective.
- Carvedilol (COPERNICUS): Non-selective blocker. Additional afterload reduction.
- Metoprolol Succinate (MERIT-HF): selective. Note: Metoprolol Tartrate (short acting) is NOT evidence-based for HF mortality.
ischemic heart disease
- Post-MI: Reduces mortality and re-infarction (CAPRICORN).
- Angina: First-line anti-anginal (reduces myocardial oxygen demand).
specific non-cardiac indications
Some beta blockers have unique properties making them suitable for non-cardiac conditions.
| Indication | Preferred Agent | Mechanism |
|---|---|---|
| Thyrotoxicosis | Propranolol | Non-selective block controls tremor/palpitations. High doses block T4T3 conversion. |
| Migraine Prophylaxis | Propranolol / Metoprolol | CNS penetration (Lipophilic). |
| Essential Tremor | Propranolol | Central and peripheral blockade. |
| Esophageal Varices | Propranolol / Carvedilol | Splanchnic vasoconstriction ( block) lowers portal pressure. |
| Performance Anxiety | Propranolol | Blunts autonomic arousal. |
adverse effects & cautions
- Bradycardia / Heart Block: Dose-limiting.
- Hypotension: Particularly with Carvedilol (alpha-blockade).
- Bronchospasm: In asthma/COPD. Prefer selective agents (Bisoprolol/Metoprolol) if strictly necessary.
- Metabolic: Can mask hypoglycemia symptoms (except sweating).
- Acute Decompensation: Negative inotropy can worsen acute heart failure. Do not start in “wet & cold” shock.