Metoprolol Tartrate to Succinate Conversion
For a patient taking metoprolol tartrate 50 mg twice daily (total daily dose 100 mg), convert to metoprolol succinate 100 mg once daily. This represents a 1:1 total daily dose equivalence between the immediate-release and extended-release formulations 1.
Pharmacological Equivalence
The conversion between metoprolol formulations is straightforward based on total daily dose:
- Metoprolol tartrate 50 mg twice daily (100 mg total daily) = Metoprolol succinate 100 mg once daily 1
- The American College of Cardiology and American Heart Association confirm this 1:1 equivalence, where 100 mg metoprolol succinate extended-release once daily provides equivalent beta-blockade to 100 mg total daily dose of metoprolol tartrate 1
Key Formulation Differences
- Metoprolol tartrate is an immediate-release formulation requiring twice-daily administration for sustained effect 1
- Metoprolol succinate is an extended-release formulation designed for once-daily dosing, providing relatively constant plasma concentrations over 20-24 hours 1, 2
- A 100 mg metoprolol succinate tablet contains 95 mg of the succinate salt but is considered bioequivalent to 100 mg metoprolol tartrate in terms of clinical activity 2
Practical Conversion Guidelines
When switching formulations:
- Calculate the total daily dose of metoprolol tartrate currently being taken 1
- Convert to the same total daily dose of metoprolol succinate, administered once daily 1
- For your specific case: 50 mg BID tartrate (100 mg total) → 100 mg QD succinate 1
The extended-release formulation maintains more stable plasma concentrations throughout the 24-hour period, with lower peak concentrations but higher trough levels compared to immediate-release tablets 3.
Critical Prescribing Considerations
Always specify the salt form (tartrate vs. succinate) when prescribing to avoid medication errors 1:
- Metoprolol tartrate is also known by the brand name Lopressor 1
- Metoprolol succinate is also known by the brand name Toprol-XL 1
- Confusion between formulations can lead to dosing errors and inadequate beta-blockade 1
Timing of Administration
- Metoprolol succinate should be taken once daily at the same time each day 1
- Metoprolol tartrate requires twice-daily dosing (typically every 12 hours) for equivalent 24-hour beta-blockade 1
- The extended-release formulation provides more consistent heart rate and blood pressure control throughout the dosing interval compared to twice-daily immediate-release dosing 3, 4