Can metoprolol succinate and metoprolol tartrate be taken together?

Combining Metoprolol Succinate and Metoprolol Tartrate

Metoprolol succinate and metoprolol tartrate should not be taken together as they are different formulations of the same medication and combining them could lead to excessive beta-blockade with potential adverse effects on morbidity and mortality. 1

Understanding the Formulations

Metoprolol comes in two distinct formulations with different pharmacokinetic properties:

• Metoprolol tartrate:

  • Immediate-release formulation
  • Requires twice-daily dosing (100-200 mg/day in divided doses)
  • Half-life of 3-7 hours with rapid absorption and elimination 2

• Metoprolol succinate:

  • Extended-release formulation
  • Once-daily dosing (50-200 mg once daily)
  • Controlled release over approximately 20 hours 2
  • 100 mg of metoprolol succinate is equivalent to 100 mg of metoprolol tartrate 3

Rationale Against Combination

1. Redundant Mechanism of Action: Both formulations are the same active drug (metoprolol) targeting the same beta-1 receptors. The ACC/AHA guidelines explicitly state that "drug combinations that have similar mechanisms of action or clinical effects should be avoided" and specifically note that "2 drugs from the same class should not be administered together" 1.

2. Risk of Excessive Beta-Blockade: Combining both formulations could lead to excessive beta-blockade, potentially causing:

   • Bradycardia
   • Hypotension
   • Heart block
   • Worsening heart failure

3. Pharmacokinetic Overlap: Metoprolol succinate is designed to provide consistent plasma concentrations over 24 hours 3. Adding metoprolol tartrate would create unpredictable peaks in plasma concentration, defeating the purpose of the extended-release formulation.

Appropriate Clinical Use

Instead of combining these formulations, clinicians should choose one based on the clinical indication:

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

  • Metoprolol succinate is specifically recommended at a target dose of 200 mg once daily 2
  • Metoprolol tartrate is not recommended for heart failure based on inferior outcomes 2

• For hypertension:

  • Either formulation is effective 2
  • Metoprolol succinate offers better adherence with once-daily dosing and more consistent blood pressure control 2

• For angina or post-MI:

  • Both formulations are effective when used appropriately 1

Important Clinical Considerations

• If transitioning between formulations, ensure equivalent dosing (100 mg metoprolol succinate = 100 mg metoprolol tartrate) 3
• Never abruptly discontinue either formulation due to risk of rebound hypertension or worsening angina 2
• Metoprolol succinate tablets must be swallowed whole, not crushed or chewed, to maintain their controlled-release properties 2

If higher doses of metoprolol are needed, the appropriate approach is to increase the dose of a single formulation rather than combining both formulations.