What is the starting dose of beta blockers (e.g. metoprolol) for atrial fibrillation (AFib)?

Beta Blocker Starting Dose for Atrial Fibrillation

For atrial fibrillation rate control, metoprolol tartrate should be started at 25-50 mg twice daily or metoprolol succinate at 25-50 mg once daily, with careful titration based on heart rate response and patient tolerance. 1, 2

Beta Blocker Selection and Initial Dosing

Starting Doses by Formulation

• Metoprolol tartrate: 25-50 mg twice daily
• Metoprolol succinate (extended release): 25-50 mg once daily
• Bisoprolol: 1.25-2.5 mg once daily
• Carvedilol: 3.125 mg twice daily
• Nebivolol: 2.5 mg once daily

Dosing Considerations Based on Left Ventricular Function

• LVEF ≥40%: Any beta-blocker can be used at starting doses listed above
• LVEF <40%: Use the smallest dose of beta-blocker to achieve rate control; metoprolol, carvedilol, or bisoprolol are preferred 1

Titration Protocol

1. Initial assessment: Start with lower doses in elderly patients, those with renal impairment, or history of bradycardia
2. Follow-up: Reassess heart rate and symptoms after 1-2 weeks
3. Dose adjustments:
   • If heart rate remains elevated and medication is tolerated, increase by 25-50% increments
   • For metoprolol tartrate: Increase to 50 mg twice daily, then 100 mg twice daily as needed
   • For metoprolol succinate: Increase to 50 mg, then 100 mg, then 200 mg once daily as needed

Target Heart Rate Goals

• Resting heart rate: 60-80 beats per minute
• With moderate activity: <110 beats per minute 2

Alternative Agents When Beta Blockers Are Contraindicated

• Calcium channel blockers (if LVEF >40%):
  • Diltiazem: 60 mg three times daily initially (120-360 mg daily total dose)
  • Verapamil: 40-120 mg three times daily (120-480 mg daily total dose) 1
• Digoxin: 0.0625-0.125 mg daily (especially useful in heart failure patients)

Special Considerations

Heart Failure Patients

• In patients with heart failure and AF, beta-blockers remain first-line therapy despite lack of mortality benefit 1
• Start at lower doses (metoprolol tartrate 12.5-25 mg twice daily or metoprolol succinate 12.5-25 mg once daily)
• Titrate more gradually (every 2 weeks) to avoid decompensation

Acute Rate Control

• For acute management, intravenous metoprolol can be given as 2.5-10 mg bolus (repeated as needed) 1
• Target the smallest dose needed to achieve rate control in patients with heart failure 1

Common Pitfalls to Avoid

1. Starting with too high a dose in elderly or heart failure patients
2. Failing to monitor for bradycardia when increasing beta-blocker dose
3. Using calcium channel blockers in patients with LVEF <40% (contraindicated)
4. Inadequate follow-up during dose titration phase
5. Overly aggressive rate control which may lead to symptomatic bradycardia

Beta blockers are effective for rate control in AF and should be titrated to the minimum effective dose that achieves target heart rate while minimizing side effects 1, 2.