What can be used as an alternative to metoprolol succinate (Extended Release) if it is unavailable?

Alternatives to Metoprolol Succinate Extended Release

When metoprolol succinate ER is unavailable, metoprolol tartrate immediate release is the most appropriate alternative, but must be administered twice daily instead of once daily to maintain therapeutic effect. 1

Comparison of Metoprolol Formulations

Metoprolol Tartrate (Immediate Release)

• Dosing: 25-100 mg twice daily 1
• Administration: Must be given twice daily due to shorter half-life (3-4 hours)
• Peak effect: Reaches peak concentration quickly with more pronounced peaks and troughs 2
• Bioequivalence: 100 mg metoprolol tartrate is equivalent to 95 mg metoprolol succinate 3

Metoprolol Succinate (Extended Release)

• Dosing: 50-400 mg once daily 1
• Administration: Once-daily dosing due to controlled release over 20 hours 2
• Peak effect: Provides relatively constant plasma concentrations over 24 hours 2

Conversion Protocol

1. Calculate equivalent daily dose:

   • Determine current total daily dose of metoprolol succinate ER
   • Use same total daily dose of metoprolol tartrate, but divide into twice daily dosing 1

2. Example conversion:

   • Metoprolol succinate 100 mg once daily → Metoprolol tartrate 50 mg twice daily
   • Metoprolol succinate 200 mg once daily → Metoprolol tartrate 100 mg twice daily

3. Timing of administration:

   • Administer doses approximately 12 hours apart to maintain consistent beta-blockade

Alternative Beta-Blockers

If metoprolol tartrate is also unavailable, consider these alternatives based on indication:

For Heart Failure with Reduced Ejection Fraction:

• Carvedilol: 3.125-25 mg twice daily (preferred alternative) 1, 4

  • Offers superior mortality benefits compared to metoprolol in heart failure
  • Start at 3.125 mg twice daily and titrate gradually

• Bisoprolol: 1.25-10 mg once daily 1

  • Evidence-based beta-blocker for heart failure
  • Once-daily dosing similar to metoprolol succinate

For Atrial Fibrillation Rate Control:

• Atenolol: 25-100 mg once daily 1
• Bisoprolol: 2.5-10 mg once daily 1
• Carvedilol: 3.125-25 mg twice daily 1, 4

Clinical Considerations

1. Heart failure patients:

   • Carvedilol may be preferred over metoprolol tartrate due to 17% greater mortality reduction 4
   • Only three beta-blockers (bisoprolol, carvedilol, and metoprolol succinate) have proven mortality benefits in heart failure 1

2. Monitoring requirements:

   • Monitor heart rate and blood pressure more frequently after switching from extended-release to immediate-release formulation
   • Target similar heart rate control as achieved with metoprolol succinate

3. Common pitfalls:

   • Underdosing: Failure to divide the daily dose into twice-daily administration can result in inadequate beta-blockade between doses
   • Abrupt discontinuation: Never abruptly stop beta-blockers; this can precipitate rebound tachycardia or angina
   • Inappropriate substitution: Not all beta-blockers have the same indications or evidence base for specific conditions

4. Special populations:

   • For patients with renal impairment: Atenolol requires dose adjustment, while metoprolol does not 1
   • For patients with hepatic impairment: Consider lower initial doses of carvedilol 4

By following this approach, you can effectively substitute metoprolol tartrate immediate release for metoprolol succinate extended release while maintaining therapeutic efficacy and minimizing adverse effects.