Bisoprolol Equivalent Dose for 75 mg Metoprolol Succinate Daily in AFib
For a patient with atrial fibrillation taking 75 mg metoprolol succinate daily, the equivalent bisoprolol dose is approximately 3.75 mg daily, which should be rounded to either 2.5 mg or 5 mg daily based on clinical response and tolerability. 1
Dose Conversion Rationale
The conversion between metoprolol and bisoprolol is not straightforward because:
- Metoprolol succinate 75 mg daily falls between the typical starting dose (50 mg) and mid-range therapeutic doses (50-400 mg daily) for AFib rate control 1
- Bisoprolol dosing range for AFib is 2.5-10 mg daily, with most patients responding to 2.5-5 mg daily 1
- The approximate potency ratio is 1:5 to 1:10 (bisoprolol:metoprolol), meaning bisoprolol is roughly 5-10 times more potent than metoprolol on a milligram-per-milligram basis 1
Practical Conversion Approach
Start with bisoprolol 2.5 mg daily as the initial equivalent dose: 1
- This represents a conservative conversion that minimizes risk of excessive bradycardia or hypotension
- Bisoprolol 2.5 mg daily produces significant heart rate reduction (approximately 12 beats/min) in AFib patients 2
- The longer half-life of bisoprolol (9-12 hours) compared to metoprolol succinate (3-7 hours) provides more consistent 24-hour coverage 1
Titrate to bisoprolol 5 mg daily if needed: 1, 2
- If heart rate control is inadequate after 2 weeks on 2.5 mg daily, increase to 5 mg daily
- Bisoprolol 5 mg produces dose-responsive additional heart rate reduction (approximately 17 beats/min total) 2
- Target resting heart rate should be <80 bpm for symptomatic management 3
Monitoring After Conversion
Assess the following parameters within 1-2 weeks of switching: 1
- Resting heart rate (target <80 bpm for symptomatic patients, <110 bpm may be acceptable if asymptomatic with preserved LV function) 3
- Blood pressure (watch for hypotension, particularly systolic BP <90 mmHg) 4
- Symptoms of bradycardia (dizziness, fatigue, syncope)
- Heart rate during exertion, not just at rest 3
Key Advantages of Bisoprolol Over Metoprolol
- Higher beta-1 selectivity reduces risk of bronchospasm in patients with mild reactive airway disease 1
- Longer half-life (9-12 hours vs 3-7 hours) provides more consistent rate control throughout the day 1
- Once-daily dosing improves medication adherence 1
- More effective heart rate reduction in AFib patients compared to other beta-blockers in some studies 2, 5
Common Pitfalls to Avoid
Do not use a 1:1 dose conversion - this would result in severe bradycardia and hypotension, as bisoprolol is significantly more potent than metoprolol 1
Avoid in decompensated heart failure - ensure the patient is euvolemic before switching, as beta-blockers can worsen acute decompensation 1, 3
Do not combine with other AV nodal blocking agents without careful monitoring, as this can cause profound bradycardia 4
Avoid in pre-excited AFib (WPW syndrome with AFib) - beta-blockers may paradoxically accelerate ventricular response 3, 4
Monitor renal function - while bisoprolol is not primarily renally eliminated like atenolol, dose adjustments may be needed in severe renal impairment 1