Beta-blockers
also: β-blocker · -olol
Overview
Negative chronotropes/inotropes for rate control, angina, prognostic heart failure and post-MI. Cardioselective (β₁) vs non-selective matters for safety.
Mechanism
Competitive antagonism of β-adrenoceptors. β₁ blockade → ↓heart rate, ↓contractility, ↓renin (Gs–cAMP pathway). Non-selective agents also block β₂ (bronchial + vascular smooth muscle → bronchoconstriction risk). Class II antiarrhythmic.
Indications
- AF rate control
- Stable angina
- Heart failure (bisoprolol/carvedilol/nebivolol — start low, go slow)
- Post-MI secondary prevention
- Hypertension (no longer first-line)
The agents
OD
HF + rate control workhorse.
renal
Hydrophilic; renally cleared.
short t½
IV for acute rate control.
lipophilic
Migraine, thyrotoxicosis tremor, anxiety, portal HTN. Crosses BBB.
BD
HF; added vasodilation.
IV/PO
Pregnancy hypertension + hypertensive emergency.
renal
Antiarrhythmic; prolongs QT.
Adverse effects
Non-selective agents; caution even with cardioselective in asthma.
Blunts adrenergic warning signs in diabetes.
Lipophilic agents (propranolol).
Cautions & contraindications
β₂ blockade → bronchoconstriction. Non-selective absolutely; cardioselective with caution if essential.
Additive AV block → asystole.
Start only when euvolaemic/stable.
Unopposed α → hypertensive crisis; α-block first.
Interactions
- Verapamil/diltiazem → bradycardia/asystole
- Other rate-limiting drugs (digoxin, amiodarone) → bradycardia
Monitoring & kinetics
Heart rate, BP,HF: symptoms/weight during uptitration
Never stop abruptly in ischaemic heart disease (rebound angina/MI) — taper.
Source: BNF — Beta-adrenoceptor blocking drugs