What is the dosing regimen for metoprolol (beta-blocker) in patients with atrial fibrillation?

Metoprolol Dosing for Atrial Fibrillation

For atrial fibrillation rate control, metoprolol tartrate should be administered at 25-100 mg twice daily orally, or metoprolol succinate (XL) at 50-400 mg once daily orally. 1

Intravenous Administration

• For acute rate control, metoprolol tartrate can be given as 2.5-5.0 mg IV bolus over 2 minutes, with up to 3 doses 1
• IV metoprolol is particularly effective in β-blocker-naive patients, with higher treatment response compared to those on chronic β-blocker therapy 2

Oral Maintenance Dosing

• Metoprolol tartrate: Start with 25 mg twice daily and titrate up to maximum 100 mg twice daily 1, 3
• Metoprolol succinate (XL): Start with 50 mg once daily and titrate up to maximum 400 mg once daily 1, 3
• Titration should be gradual, based on heart rate response and patient tolerance 3

Rate Control Targets

• Standard rate control strategy: Target resting heart rate <80 bpm 3
• Lenient rate control strategy: Target resting heart rate <110 bpm in asymptomatic patients with preserved left ventricular function 3
• Heart rate should be assessed both at rest and during exercise to ensure adequate control throughout daily activities 3

Combination Therapy

• If rate control remains inadequate despite maximum tolerated dose of metoprolol, consider adding:
  • Non-dihydropyridine calcium channel blocker (diltiazem or verapamil) 3
  • Digoxin (particularly useful in patients with heart failure) 3, 4
• Early studies showed that adding metoprolol to digoxin therapy provides better rate control than digoxin alone, especially during exercise 4

Cautions and Contraindications

• Avoid metoprolol in patients with:
  • Decompensated heart failure 3
  • Severe bradycardia or high-degree AV block without a pacemaker 3
• Monitor for common adverse effects:
  • Hypotension
  • Bradycardia
  • Worsening heart failure 3

Alternative Beta-Blockers

• If metoprolol is not tolerated or contraindicated, consider:
  • Atenolol: 25-100 mg once daily 1, 3
  • Carvedilol: 3.125-25 mg twice daily 1, 3
  • Bisoprolol: 2.5-10 mg once daily 1, 3
  • Propranolol: 10-40 mg three to four times daily 1, 3

Clinical Pearls

• Metoprolol CR/XL has been shown to be effective not only for rate control but also for maintaining sinus rhythm after cardioversion of persistent atrial fibrillation 5
• A higher initial heart rate tends to show a more pronounced reduction with metoprolol therapy 4
• In patients with mitral stenosis and atrial fibrillation, verapamil may provide better symptomatic improvement than metoprolol, while in those with normal sinus rhythm, metoprolol may be more effective 6
• For patients with coexisting heart failure, careful dose titration is essential to avoid worsening heart failure symptoms 3