What beta blockers are available for intravenous (IV) administration?

Intravenous Beta Blockers Available for Clinical Use

The intravenous beta blockers available for clinical use include esmolol, metoprolol, propranolol, and labetalol. 1

Available IV Beta Blockers and Their Properties

1. Esmolol

• Selectivity: Beta-1 selective
• Dosing: 50-300 mcg/kg/min by continuous infusion 1
• Key features:
  • Ultra-short-acting (elimination half-life ~9 minutes) 2, 3
  • Rapidly metabolized by blood esterases 4
  • Effects dissipate within 30 minutes after discontinuation 3
  • Ideal for situations requiring tight control and quick reversibility 5
  • Loading dose of 0.5 mg/kg over 2-5 minutes followed by infusion 1

2. Metoprolol

• Selectivity: Beta-1 selective
• Dosing: 5 mg increments by slow IV administration (over 1-2 min), repeated every 5 min for total initial dose of 15 mg 1
• Key features:
  • Can be followed by oral therapy (25-50 mg every 6h) 15 minutes after last IV dose 1
  • Maintenance oral dose up to 100 mg twice daily 1

3. Propranolol

• Selectivity: Non-selective (blocks both beta-1 and beta-2 receptors)
• Dosing: Initial dose of 0.5-1.0 mg IV, followed in 1-2 hours by oral dosing 1
• Key features:
  • Longer duration of action compared to esmolol 4
  • Oral follow-up dosing: 40-80 mg every 6-8 hours 1

4. Labetalol

• Selectivity: Non-selective with alpha-blocking properties
• Dosing: Two administration methods 6:
  • Repeated IV injection: Initial dose of 20 mg over 2 minutes, with additional doses of 40-80 mg at 10-minute intervals (max total 300 mg)
  • Slow continuous infusion: 2 mg/min (diluted solution)
• Key features:
  • Combined alpha and beta blockade 1
  • Particularly useful in hypertensive emergencies 1
  • Maximum effect usually occurs within 5 minutes of each injection 6

Clinical Considerations for IV Beta Blocker Selection

Monitoring Requirements

• Frequent checks of heart rate and blood pressure
• Continuous ECG monitoring
• Auscultation for rales and bronchospasm 1

Contraindications

• Marked first-degree AV block (PR interval >0.24 sec)
• Second or third-degree AV block without functioning pacemaker
• History of asthma
• Severe LV dysfunction or heart failure
• Cardiogenic shock or high risk for shock
• Hypotension (systolic BP <90 mmHg) 1

Caution in Special Populations

• Elderly patients may require lower doses 7
• Patients with hepatic dysfunction may require dose adjustments for metoprolol 7
• In patients with bronchial asthma, if beta blockade is necessary, consider a cardioselective agent like esmolol to test tolerance 1

Selection Algorithm Based on Clinical Scenario

1. Need for ultra-short duration of action:

   • Choose esmolol when rapid reversibility is critical or in patients with uncertain tolerance to beta blockade 3, 5

2. Acute coronary syndromes:

   • Metoprolol or propranolol are commonly used 1
   • Start with oral therapy within first 24 hours unless specific indication for IV therapy exists 1

3. Aortic dissection:

   • Labetalol or esmolol are preferred to reduce force of left ventricular ejection 1
   • Target systolic BP between 100-120 mmHg 1

4. Hypertensive emergencies:

   • Labetalol offers combined alpha and beta blockade 6
   • Esmolol provides rapid titratability and offset if needed 4

Common Pitfalls and Caveats

• Early aggressive beta blockade poses substantial hazard in hemodynamically unstable patients 1
• Risk factors for cardiogenic shock with IV beta blockers include: older age, female sex, higher Killip class, lower BP, higher heart rate, and ECG abnormalities 1
• If vasodilators are needed with beta blockers, always administer the beta blocker first to avoid reflex tachycardia 1
• Abrupt discontinuation can precipitate angina, MI, or ventricular arrhythmias 7
• Hypotension is more common with esmolol at higher doses and requires careful titration 8, 4

By understanding the specific properties of each available IV beta blocker, clinicians can make informed choices based on the clinical scenario, desired onset and duration of action, and patient-specific factors.