What are the differences between bisoprolol and metoprolol?

Key Differences Between Bisoprolol and Metoprolol

Bisoprolol offers greater beta-1 selectivity than metoprolol, which may provide clinical advantages in patients with respiratory conditions, while both medications effectively reduce mortality in heart failure patients when used at appropriate doses. 1, 2

Pharmacological Properties

Selectivity

• Bisoprolol: Higher beta-1 selectivity (12.2 times more selective for beta-1 than beta-2 receptors) 2
• Metoprolol: Moderate beta-1 selectivity (9.0 times more selective) 2

Pharmacokinetics

• Bisoprolol:

  • Longer half-life allowing once-daily dosing
  • Target dose: 10 mg once daily 1
  • Less affected by CYP2D6 metabolism

• Metoprolol:

  • Available in immediate-release (tartrate) and extended-release (succinate) formulations
  • Target doses:
    • Metoprolol tartrate: 50 mg twice daily (total 100 mg/day)
    • Metoprolol succinate: 200 mg once daily 1
  • Higher exposure in women (50-100% higher) due to slower CYP2D6 clearance 1

Clinical Efficacy

Heart Failure

• Both medications reduce mortality in heart failure with reduced ejection fraction (HFrEF) when used at appropriate doses 1

• Bisoprolol:

  • CIBIS-II trial showed 34% reduction in all-cause mortality
  • NNT of 23 patients to prevent one death 1

• Metoprolol:

  • MERIT-HF trial showed 34% reduction in all-cause mortality (using metoprolol succinate)
  • NNT of 27 patients to prevent one death 1
  • Note: Formulation matters - immediate-release metoprolol tartrate has not shown the same mortality benefits as succinate 1

Sex-Related Differences

• Women may experience greater adverse effects with metoprolol due to higher drug exposure
• Women may benefit from lower-than-standard doses of metoprolol to reduce adverse reaction risk 1
• Bisoprolol showed significantly greater reduction in mortality in women compared to men in the CIBIS II trial 1

Safety Profile

Respiratory Effects

• Bisoprolol: Higher beta-1 selectivity may provide advantages in patients with respiratory conditions like asthma or COPD 2
• Metoprolol: Moderate beta-1 selectivity, but still preferable to non-selective beta-blockers in patients with respiratory issues

Adverse Effects

• Both can cause cold extremities, bradycardia, and fatigue
• Metoprolol may cause more pronounced adverse reactions in women due to higher plasma concentrations 1

Practical Considerations

Dosing

• Bisoprolol: Once-daily dosing (starting 1.25 mg, target 10 mg) 1
• Metoprolol succinate: Once-daily dosing (starting 12.5-25 mg, target 200 mg) 1
• Metoprolol tartrate: Twice-daily dosing (starting 5 mg, target 50 mg twice daily) 1

Special Populations

• Elderly patients: Both medications can be used, but careful dose titration is essential
• Women: Consider lower doses of metoprolol due to higher plasma concentrations 1
• Patients with respiratory conditions: Bisoprolol may be preferred due to higher beta-1 selectivity 2

Clinical Decision Making

When choosing between bisoprolol and metoprolol:

1. Consider patient characteristics:

   • For patients with respiratory conditions: Prefer bisoprolol due to higher beta-1 selectivity
   • For women: Either bisoprolol or lower doses of metoprolol may be appropriate

2. Consider formulation:

   • If choosing metoprolol, prefer the succinate (extended-release) formulation for heart failure
   • Metoprolol tartrate has not demonstrated the same mortality benefits as succinate in heart failure 1

3. Consider dosing convenience:

   • Bisoprolol: Once daily
   • Metoprolol succinate: Once daily
   • Metoprolol tartrate: Twice daily

4. Consider cost and availability:

   • Both medications are widely available as generics
   • Local formulary restrictions may influence choice

Common Pitfalls to Avoid

1. Using inadequate doses: Titrate to target doses shown to be effective in clinical trials
2. Confusing metoprolol formulations: Succinate (extended-release) and tartrate (immediate-release) are not interchangeable
3. Overlooking sex-related differences: Women may need lower doses of metoprolol
4. Abrupt discontinuation: Always taper beta-blockers to avoid rebound effects