What is the recommended dose of metoprolol (beta blocker) for rate control in atrial fibrillation (A Fib) with rapid ventricular response (RVR)?

Metoprolol Dosing for Atrial Fibrillation with RVR

For atrial fibrillation with rapid ventricular response (RVR), the recommended dose of metoprolol is 2.5-5 mg IV bolus over 2 minutes (up to 3 doses) for acute management, followed by oral maintenance therapy of 25-100 mg twice daily. 1

Acute Management (IV Administration)

• Initial IV dosing: 2.5-5 mg IV bolus administered over 2 minutes 1
• Maximum IV dosing: Up to 3 doses (total 15 mg) with 5-minute intervals between doses 1, 2
• Onset of action: Approximately 5 minutes 1
• Monitoring: Continuous ECG monitoring, frequent blood pressure checks, and heart rate assessment during administration 2

Alternative IV options when metoprolol fails or is contraindicated:

• Diltiazem: 0.25 mg/kg IV over 2 minutes (onset 2-7 minutes) 1
• Esmolol: 500 mcg/kg IV over 1 minute, followed by 60-200 mcg/kg/min infusion 1

Transition to Oral Therapy

After successful IV rate control:

• Begin oral metoprolol 15 minutes after the last IV dose 2
• Start with 25 mg orally every 6 hours for 48 hours 2
• Then transition to maintenance dosing 2

Oral Maintenance Therapy

• Initial oral dose: 25-50 mg twice daily 1, 2
• Titration: Increase dose at 2-week intervals, doubling if heart rate remains above target 2
• Maximum oral dose: 100 mg twice daily (200 mg/day) 1, 2
• Target heart rate: 50-60 beats per minute 2

Efficacy Considerations

• Metoprolol has been shown to be effective for rate control in AF with RVR, with a lower adverse event profile (10%) compared to diltiazem (19%) 3
• In critical care settings, metoprolol has demonstrated lower failure rates compared to amiodarone and better rate control at 4 hours compared to diltiazem 4

Special Populations

Heart Failure Patients:

• HFpEF: Beta blockers (including metoprolol) are recommended first-line 1
• HFrEF: IV beta blockers should be used with caution in patients with overt congestion or hypotension 1
• In acute decompensated heart failure, consider starting with lower doses (12.5-25 mg) 2

Elderly Patients:

• Start with lower doses (12.5-25 mg) 2
• Use caution in patients >70 years 2

Contraindications:

• Marked first-degree AV block
• Second or third-degree AV block without pacemaker
• Severe bradycardia
• Hypotension
• Decompensated heart failure
• Cardiogenic shock
• Severe bronchospastic disease 2

Monitoring and Follow-up

• Initial follow-up 2 weeks after starting therapy 2
• Monitor heart rate, blood pressure, symptom improvement, and side effects 2
• ECG monitoring at baseline and with significant dose changes 2
• Target resting heart rate: 50-60 beats per minute (a more lenient rate control strategy of <110 bpm may be reasonable for asymptomatic patients with preserved LV function) 2

Common Pitfalls to Avoid

1. Avoid in WPW syndrome: Beta blockers are contraindicated in patients with AF and Wolff-Parkinson-White syndrome as they can facilitate antegrade conduction along the accessory pathway, potentially accelerating ventricular rate 1

2. Caution with concurrent nodal blocking agents: Avoid using with other drugs that have SA/AV nodal blocking properties 2

3. Abrupt discontinuation: Advise patients against suddenly stopping metoprolol as this can lead to rebound tachycardia 2

4. Inadequate dose titration: Benefits may develop slowly over 3-6 months; temporary symptom worsening may occur during initiation 2