What is the difference between metoprolol (beta-blocker) succinate and tartrate in terms of dosing and patient management?

Metoprolol Succinate vs Tartrate: Key Differences in Dosing and Patient Management

Formulation and Dosing Equivalence

Metoprolol succinate 100 mg once daily is equivalent to metoprolol tartrate 100 mg total daily dose (50 mg twice daily). 1

• Metoprolol tartrate is an immediate-release formulation requiring twice-daily administration 1
• Metoprolol succinate is an extended-release formulation administered once daily 1
• When switching formulations, metoprolol tartrate 25-50 mg BID (total 50-100 mg daily) equals metoprolol succinate 50-100 mg once daily 1

Critical Pharmacokinetic Differences

The extended-release succinate formulation provides relatively constant plasma concentrations over 20 hours, avoiding the peak-trough fluctuations seen with tartrate. 2, 3

• After ingestion, succinate tablets disintegrate into individual pellets that release drug at a constant rate over approximately 20 hours 3
• The avoidance of high peak plasma concentrations with succinate is associated with fewer adverse effects and may improve compliance 2
• Despite these differences, both formulations produce similar hemodynamic and clinical effects when dosed appropriately 4

Evidence-Based Formulation Selection

For heart failure with reduced ejection fraction, metoprolol succinate is the only formulation with proven mortality benefit and FDA approval. 5, 6

• Sustained-release metoprolol succinate reduces mortality in chronic heart failure 5
• Short-acting metoprolol tartrate showed lesser effectiveness in clinical trials and should NOT be considered equivalent for heart failure management 5
• In the COMET trial, carvedilol reduced all-cause mortality compared to metoprolol tartrate, but this finding cannot be extrapolated to metoprolol succinate due to different pharmacokinetic and pharmacodynamic profiles 6

Practical Dosing Protocols

For Heart Failure (HFrEF):

• Metoprolol succinate only: Start 12.5-25 mg once daily, target 200 mg once daily 7
• Mean effective dose: 159 mg daily 7
• Metoprolol tartrate is NOT recommended for this indication 5

For Hypertension:

• Metoprolol tartrate: 25-50 mg twice daily initially, maximum 200 mg daily 7
• Metoprolol succinate: 50-200 mg once daily, maximum 400 mg daily 7

For Atrial Fibrillation Rate Control:

• Metoprolol tartrate: 25-100 mg twice daily 7
• Metoprolol succinate: 50-400 mg once daily 7

Common Prescribing Pitfalls

Always specify the salt form when prescribing—confusion between formulations is a major medication error risk. 1

• Metoprolol tartrate is marketed as Lopressor 1
• Metoprolol succinate is marketed as Toprol-XL 1
• Never assume interchangeability: The dose and formulation of metoprolol tartrate commonly prescribed (50 mg twice daily) differs from the dose and formulation proven to reduce mortality in heart failure trials (metoprolol succinate) 5

Initiation Advantages

Metoprolol succinate may offer distinct advantages for more rapid initiation in heart failure due to readily available starting doses. 4

• Studies used a fourfold greater starting dose of succinate (25 mg) compared to tartrate (6.25 mg) with similar hemodynamic effects 4
• Both formulations produce parallel adverse hemodynamic effects when readministered during chronic therapy, with similar decreases in cardiac index and stroke volume 4

Clinical Context for Selection

For patients requiring beta-blockade for coronary disease, hypertension, or arrhythmias without heart failure, either formulation is appropriate at equivalent doses. 1

• The once-daily convenience of succinate may improve adherence 2
• The twice-daily tartrate formulation allows more flexible titration in some clinical scenarios 1

For heart failure patients specifically, metoprolol succinate is mandatory—this is not a matter of preference but of evidence-based outcomes. 5, 6