Available Intravenous Beta Blockers
The intravenous beta blockers available for clinical use are esmolol, metoprolol, propranolol, atenolol, and labetalol. 1
Specific IV Beta Blockers and Their Characteristics
Esmolol
- Ultra-short-acting, cardioselective (beta-1) agent with rapid onset and offset 1
- Administered as continuous infusion at 50-300 mcg/kg/min 1
- Loading dose: 0.5 mg/kg over 2-5 minutes, followed by infusion of 0.10-0.20 mg/kg/min (maximum 0.3 mg/kg/min) 1
- Elimination half-life of approximately 9 minutes, with return to baseline hemodynamics within 30 minutes of discontinuation 2, 3
- Preferred agent when testing beta-blocker tolerance in patients with potential contraindications (bronchial asthma, bradycardia, heart failure) due to its short half-life 1
- Maximum concentration is only 10 mg/mL, so maximal infusion constitutes substantial volume load 1
Metoprolol
- Cardioselective (beta-1) agent commonly used for acute rate control 1
- Given as 5 mg increments by slow IV push over 1-2 minutes, repeated every 5 minutes for total initial dose of 15 mg 1, 4
- Longer half-time than esmolol 1
- After tolerating full 15 mg IV dose, transition to oral therapy (25-50 mg every 6 hours for 48 hours, then 100 mg twice daily maintenance) 1
Propranolol
- Non-selective beta blocker (blocks both beta-1 and beta-2 receptors) 1
- Initial IV dose: 0.5-1.0 mg, followed by transition to oral 40-80 mg every 6-8 hours 1
- Alternative dosing: 0.05-0.15 mg/kg every 4-6 hours 1
- No cardioselectivity, so greater risk of bronchospasm in reactive airway disease 1
Atenolol
- Cardioselective (beta-1) agent with longer half-time than metoprolol 1
- Available for IV administration but less commonly used than metoprolol 1
- Effective for rate control in atrial fibrillation 1
Labetalol
- Combined alpha and beta blocker (blocks both alpha and beta-adrenergic receptors) 1, 5
- Initial dose: 20 mg (0.25 mg/kg for 80 kg patient) by slow IV injection over 2 minutes 5
- Additional injections of 40-80 mg can be given at 10-minute intervals until desired blood pressure achieved or total of 300 mg administered 5
- Alternative continuous infusion: 200 mg in 200 mL (1 mg/mL) at 2 mL/min, or 200 mg in 250 mL at 3 mL/min 5
- Maximum effect occurs within 5 minutes of each injection 5
- Particularly useful in hypertensive emergencies and aortic dissection 1
Clinical Context for Selection
Atrial Fibrillation Rate Control
- Esmolol, metoprolol, propranolol, or atenolol are all effective for acute ventricular rate control 1
- Beta blockers particularly useful in high adrenergic states 1
- Achieve better exercise rate control than digoxin alone 1
Acute Coronary Syndromes
- Oral beta blockers now preferred over IV in hemodynamically stable patients within first 24 hours 1
- IV beta blockers should be avoided in patients with heart failure, hypotension, or hemodynamic instability due to increased risk of cardiogenic shock 1
- Risk factors for shock include older age, female sex, higher Killip class, lower blood pressure, higher heart rate, and previous hypertension 1
Aortic Dissection
- IV beta blockers are first-line therapy to reduce force of left ventricular ejection (dP/dt) 1
- Target systolic blood pressure 100-120 mmHg 1
- Esmolol preferred in patients with potential intolerance (bronchial asthma, bradycardia, heart failure) due to short half-life 1
Critical Monitoring Requirements During IV Administration
- Frequent heart rate and blood pressure checks 1
- Continuous ECG monitoring 1
- Auscultation for rales and bronchospasm 1
- Patients should remain supine during IV administration, especially with labetalol 5