Beta-adrenoceptor blockers remain one of the most important drug classes in clinical pharmacology. For postgraduates, mastering them means understanding not just their uses but the subtle differences between agents.
Classification
- Cardioselectivity: β1-selective (metoprolol, atenolol, bisoprolol) vs non-selective (propranolol, carvedilol)
- Intrinsic sympathomimetic activity (ISA): pindolol, oxprenolol
- Additional properties: carvedilol (α1 block), nebivolol (NO release), labetalol (α1 + β block)
Mechanism & effects
- ↓ Heart rate, contractility and AV conduction
- ↓ Renin release from juxtaglomerular cells
- ↓ Aqueous humour production (relevant in glaucoma)
Exam tip: nebivolol causes vasodilation via NO release — the answer when asked for the most selective beta blocker with additional vasodilatory action.
Contraindications
Asthma/COPD (non-selective agents), high-degree AV block, severe bradycardia, and Prinzmetal’s angina (risk of coronary spasm).