What is the difference between metoprolol succinate and metoprolol tartrate?

Differences Between Metoprolol Succinate and Metoprolol Tartrate

Metoprolol succinate is an extended-release formulation designed for once-daily dosing, while metoprolol tartrate is an immediate-release formulation requiring twice-daily dosing, with succinate providing more consistent plasma concentrations and beta-blockade over 24 hours. 1

Formulation Differences

Metoprolol Succinate

• Extended-release (ER) formulation
• Designed to deliver medication at a near-constant rate for approximately 20 hours 1
• After ingestion, the tablet disintegrates into individual pellets with each pellet acting as a diffusion cell releasing drug at a relatively constant rate 2
• Provides even plasma concentrations over 24 hours without marked peaks and troughs 1
• Dosed once daily (QD)
• 95 mg of metoprolol succinate is equivalent to 100 mg of metoprolol tartrate 2
• Listed in guidelines as "metoprolol succinate extended release (metoprolol CR/XL)" 3

Metoprolol Tartrate

• Immediate-release (IR) formulation
• Produces characteristic peaks and troughs in plasma concentration 1
• Requires twice-daily (BID) dosing for optimal effect
• More rapid onset of action
• More pronounced fluctuations in beta-blockade throughout the day 1

Clinical Implications

Dosing

• Metoprolol Succinate: 12.5-25 mg QD initially, titrated up to 200 mg QD 3
• Metoprolol Tartrate: 25-50 mg BID initially, titrated up to 100 mg BID 3

Heart Failure Applications

• Metoprolol succinate is specifically indicated for heart failure with reduced ejection fraction (HFrEF) based on clinical trials 3, 4
• The MERIT-HF study demonstrated that extended-release metoprolol succinate reduced all-cause mortality by 34% versus placebo in heart failure patients 4
• Metoprolol tartrate has not been proven to have the same mortality benefit in heart failure 3
• Guidelines specifically list metoprolol succinate (not tartrate) as one of the three beta-blockers proven to reduce mortality in HFrEF 3

Hemodynamic Effects

• Both formulations produce similar hemodynamic effects when at steady state 5
• When comparing equivalent doses (100 mg once daily succinate vs. 50 mg twice daily tartrate):
  • Both decrease cardiac index by approximately 0.5-0.6 L/min/m²
  • Both increase systemic vascular resistance by approximately 250-270 dyne-sec-cm⁻⁵
  • Both decrease stroke volume index by approximately 6.5-7.0 ml/m² 5

Pharmacokinetic Differences

• Metoprolol Succinate:

  • Provides consistent beta₁-blockade over 24 hours 1
  • Maintains cardioselectivity at doses up to 200 mg daily 1
  • More pronounced and even beta₁-blockade over a 24-hour period compared to IR formulation 1
  • Independent of food intake and gastrointestinal pH 1

• Metoprolol Tartrate:

  • Shorter half-life requiring more frequent dosing 6
  • More variable plasma concentrations throughout the day 1
  • May provide more rapid onset of action when needed 6

Clinical Selection Considerations

• Choose metoprolol succinate when:

  • Once-daily dosing is preferred for adherence
  • Patient has heart failure with reduced ejection fraction (HFrEF)
  • More consistent beta-blockade is desired over 24 hours
  • Patient is at risk for missed doses (succinate provides more forgiveness)

• Choose metoprolol tartrate when:

  • More rapid titration or dose adjustment is needed
  • Cost is a significant factor (tartrate is generally less expensive)
  • Immediate beta-blockade effect is required
  • Patient has bradycardia concerns (easier to adjust with shorter-acting formulation) 7

Practical Equivalence

• 100 mg metoprolol succinate (extended-release) ≈ 100 mg metoprolol tartrate (immediate-release) in total daily dose, but with different pharmacokinetic profiles 2
• When switching between formulations, the total daily dose remains the same, but the dosing frequency changes 2

Both formulations are selective beta₁-adrenergic antagonists, but their different release characteristics create important clinical distinctions that should guide selection based on the specific patient scenario and treatment goals.