Why is metoprolol succinate (Metoprolol) preferred over metoprolol tartrate for Heart Failure (HF)?

Metoprolol Succinate vs. Tartrate in Heart Failure Management

Metoprolol succinate is strongly preferred over metoprolol tartrate for heart failure management due to proven mortality benefits in clinical trials. 1

Why Metoprolol Succinate is Preferred

• Only three beta-blockers have demonstrated mortality reduction in heart failure with reduced ejection fraction (HFrEF): metoprolol succinate, carvedilol, and bisoprolol 1
• Metoprolol tartrate has not shown the same mortality benefits in heart failure clinical trials and should not be used in preference to evidence-based beta-blockers 1
• The Metoprolol CR/XL Randomized Intervention Trial in Heart Failure (MERIT-HF) specifically used metoprolol succinate (not tartrate) and demonstrated a 34% reduction in mortality 1
• The European Society of Cardiology explicitly states that "metoprolol tartrate should not be used in preference to an evidence-based beta-blocker in HF" 1

Key Differences Between Formulations

• Metoprolol succinate is an extended-release formulation that provides more consistent blood levels over 24 hours 2
• Metoprolol tartrate is immediate-release and requires more frequent dosing, leading to fluctuating blood levels 1, 2
• The Carvedilol or Metoprolol European Trial (COMET) directly compared carvedilol to metoprolol tartrate and found a 17% greater mortality reduction with carvedilol 1, 3
• This suggests that the specific formulation matters significantly for clinical outcomes in heart failure 2, 3

Clinical Evidence Supporting Succinate Formulation

• The MERIT-HF trial used metoprolol succinate at target doses of up to 200 mg daily and demonstrated significant mortality benefits 1
• When comparing beta-blockers, the American College of Cardiology Foundation/American Heart Association guidelines specifically note that the benefits seen with metoprolol succinate should not be extrapolated to metoprolol tartrate 1
• A study comparing carvedilol to metoprolol succinate found similar effectiveness in real-world clinical practice, suggesting both are appropriate choices for HFrEF 4
• In contrast, metoprolol tartrate performed worse than carvedilol in the COMET trial 1, 3

Practical Considerations for Clinical Use

• Target dose for metoprolol succinate in heart failure is 200 mg once daily, whereas metoprolol tartrate would require twice-daily dosing 5
• When initiating therapy, start with a low dose of metoprolol succinate (12.5-25 mg daily) and titrate gradually over weeks 5
• Treatment benefit appears proportional to the magnitude of heart rate reduction, so the target dose should be the maximum tolerated for adequate bradycardia 5
• If a patient is currently on metoprolol tartrate for heart failure, they should be switched to either metoprolol succinate or carvedilol for improved outcomes 6, 2

Common Pitfalls and Caveats

• Avoid abrupt discontinuation of any beta-blocker in heart failure patients, as this can precipitate acute decompensation 1, 6
• If switching from tartrate to succinate formulation, ensure appropriate dose conversion and monitoring for heart rate and blood pressure changes 6
• Some clinicians incorrectly assume all metoprolol formulations are equivalent for heart failure management 1, 3
• Even in decompensated heart failure, beta-blockers are not absolutely contraindicated, though the dose may need to be reduced or temporarily withheld 1, 5

In summary, metoprolol succinate has proven mortality benefits in heart failure based on rigorous clinical trials, while metoprolol tartrate has not demonstrated the same benefits and performed worse than carvedilol in direct comparison. For optimal heart failure management, metoprolol succinate should be used instead of metoprolol tartrate.