What is the difference between metoprolol (beta-blocker) tartrate and metoprolol succinate?

Differences Between Metoprolol Tartrate and Metoprolol Succinate

Metoprolol succinate is superior to metoprolol tartrate for most cardiovascular conditions due to its once-daily dosing, consistent 24-hour beta-blockade, and proven mortality benefits in heart failure. 1

Formulation Differences

Metoprolol Tartrate

• Dosing frequency: Twice daily dosing (12-hour duration of action) 2
• Release mechanism: Immediate release (IR) or sustained release (SR) with monolith matrix type 3
• Typical dosing: 25-100 mg twice daily for hypertension 2
• Heart failure dosing: Starting at 6.25-12.5 mg twice daily, target 50 mg twice daily 1

Metoprolol Succinate

• Dosing frequency: Once daily dosing (24-hour duration of action) 1
• Release mechanism: Controlled release/extended-release (CR/XL) using multiple pellet system 3
• Typical dosing: 50-400 mg once daily for hypertension 1
• Heart failure dosing: Starting at 12.5-25 mg once daily, target 200 mg once daily 1
• Tablet composition: A 100 mg tablet contains 95 mg of metoprolol succinate, equivalent to 100 mg metoprolol tartrate 4

Pharmacokinetic Differences

• Metoprolol succinate: Designed to provide relatively constant plasma concentrations over approximately 20 hours 4
• Release mechanism: After ingestion, succinate tablets disintegrate into individual pellets with each pellet acting as a diffusion cell releasing drug at a constant rate 4
• Bioequivalence: 95 mg of metoprolol succinate is considered bioequivalent to 100 mg of metoprolol tartrate 4

Clinical Efficacy Differences

• Heart failure outcomes: Metoprolol succinate (CR/XL) demonstrated a 34% reduction in all-cause mortality in heart failure patients in the MERIT-HF trial 5
• Consistency of effect: Metoprolol succinate provides more consistent beta-blockade over 24 hours compared to the more variable levels with tartrate 1
• Proven mortality benefit: Metoprolol succinate is one of only three beta-blockers (along with bisoprolol and carvedilol) proven to reduce mortality in heart failure 1

Hemodynamic Differences

• Despite different formulations, both produce similar hemodynamic effects when dosed appropriately 6
• When full doses are administered during chronic therapy, both formulations show comparable effects on:
  • Cardiac index (decrease by 0.5-0.6 L/min/m²)
  • Systemic vascular resistance (increase by 250-270 dyne-sec-cm⁻⁵)
  • Stroke volume index (decrease by 6.5-7.0 ml/m²) 6

Clinical Applications

• Hypertension: Both formulations are effective, but succinate offers convenience of once-daily dosing 2, 1
• Heart failure: Metoprolol succinate is preferred due to proven mortality benefits in large clinical trials 1, 5
• Post-MI: Both formulations have shown benefits, but succinate provides more consistent 24-hour coverage 3

Important Considerations

• Initiation: Both formulations should be started at low doses and gradually uptitrated to avoid hemodynamic compromise 1
• Discontinuation: Abrupt discontinuation of either formulation may precipitate angina, myocardial infarction, or arrhythmias 1
• Tapering: Gradual tapering is essential, with recommended reduction in dose by half every week for 3 weeks 1

Conclusion

While both metoprolol formulations contain the same active beta-blocker, the succinate formulation offers significant advantages in terms of dosing convenience, consistent beta-blockade, and proven mortality benefits in heart failure, making it the preferred choice for most cardiovascular conditions.