What is the preferred choice between atenolol and metoprolol succinate (beta blockers) for patients requiring beta-blockade?

Metoprolol Succinate vs. Atenolol for Beta-Blockade

Metoprolol succinate is preferred over atenolol for patients requiring beta-blockade due to its superior 24-hour blood pressure control, proven mortality benefits in heart failure, and more consistent plasma concentrations throughout the day.

Pharmacokinetic Differences

• Metoprolol succinate (extended-release):

  • Provides near-constant drug delivery for approximately 20 hours 1
  • Produces even plasma concentrations over a 24-hour period without marked peaks and troughs
  • Maintains consistent beta1-blockade over 24 hours while preserving cardioselectivity at doses up to 200 mg daily 1
  • Once-daily dosing (50-200 mg daily) 2

• Atenolol:

  • Typically requires twice-daily dosing (25-100 mg) 2
  • Less effective in sustaining 24-hour and early morning BP reductions 3
  • Shows more variable blood pressure control, particularly during early morning hours when cardiovascular risk is highest

Clinical Evidence Supporting Metoprolol Succinate

A randomized study comparing the two medications found that metoprolol succinate was more effective in sustaining 24-hour and early morning blood pressure reductions compared to atenolol in hypertensive patients. The early morning systolic BP differences were 3±14 mm Hg with atenolol versus -7±8 mm Hg with metoprolol succinate (P=.03) 3.

Guideline Recommendations

The ACC/AHA guidelines specifically recommend only three beta-blockers as having proven mortality benefits:

1. Metoprolol succinate (extended-release)
2. Carvedilol
3. Bisoprolol 2, 4

Notably, atenolol is not included in this list of beta-blockers with proven mortality benefits.

Heart Failure Considerations

For patients with heart failure with reduced ejection fraction (HFrEF):

• Metoprolol succinate is one of only three beta-blockers proven to reduce mortality (Class I, Level of Evidence: A) 2
• Atenolol lacks robust evidence for mortality reduction in heart failure
• The 2020 ACC/AHA clinical performance measures specifically recommend bisoprolol, carvedilol, or sustained-release metoprolol succinate for HFrEF patients 2

Perioperative Beta-Blockade

In the perioperative setting, there is some evidence suggesting long-acting beta-blockers like atenolol might be superior to short-acting metoprolol tartrate (not succinate) for reducing perioperative MI or death 2. However, this was based on retrospective data with methodological limitations, and clinical trial evaluation was recommended to confirm this finding.

Dosing Considerations

• Metoprolol succinate:

  • Starting dose: 25-50 mg once daily
  • Target dose: 200 mg once daily
  • Gradual titration at 2-week intervals 4

• Atenolol:

  • Typical dosing: 25-100 mg twice daily 2

Clinical Pitfalls and Caveats

1. Underdosing: Beta-blockers are frequently underdosed in clinical practice. Data from the OPTIMIZE-HF registry showed that the mean daily doses were less than half the recommended target doses, with only 7.9% of patients receiving target doses of metoprolol succinate at 60-90 days post-discharge 5.

2. Abrupt discontinuation: Never stop beta-blockers abruptly as this may precipitate rebound hypertension or worsening angina 4.

3. Monitoring requirements: Regular monitoring of heart rate, blood pressure, and signs of worsening heart failure is essential when using either agent 4.

4. Contraindications: Both drugs are contraindicated in second- or third-degree heart block, sick sinus syndrome, severe bradycardia, and severe hypotension 4.

Conclusion

Based on the most recent and highest quality evidence, metoprolol succinate is preferred over atenolol for patients requiring beta-blockade due to:

• Superior 24-hour blood pressure control, especially during high-risk early morning hours
• Proven mortality benefits in heart failure patients
• More consistent plasma concentrations with once-daily dosing
• Specific recommendation in current ACC/AHA guidelines

For patients with heart failure, the choice is even clearer, as metoprolol succinate is one of only three beta-blockers with proven mortality benefits.