Metoprolol Tartrate to Succinate Conversion
Metoprolol tartrate 12.5 mg is equivalent to metoprolol succinate 12.5 mg in terms of clinical effect, though the succinate formulation is designed for once-daily dosing while tartrate requires twice-daily administration.
Pharmacological Equivalence
- Metoprolol tartrate (Lopressor) and metoprolol succinate are different salt forms of the same active ingredient (metoprolol)
- The dosing equivalence is 1:1 in terms of labeled strength, but with different release characteristics:
- 12.5 mg metoprolol tartrate = 12.5 mg metoprolol succinate
- 25 mg metoprolol tartrate = 25 mg metoprolol succinate
Formulation Differences
Metoprolol Tartrate (Lopressor)
- Immediate-release formulation
- Typically dosed twice daily
- Produces peaks and troughs in plasma concentration
- Available in 25 mg, 50 mg, and 100 mg tablets
Metoprolol Succinate
- Extended-release formulation
- Once-daily dosing
- Provides more consistent plasma concentrations over 24 hours 1
- Each pellet in the tablet acts as a separate drug delivery unit designed to release metoprolol continuously over approximately 20 hours 2, 3
Clinical Applications
Heart Failure
- For heart failure, metoprolol succinate is specifically indicated based on clinical trials 4
- Initial dose: 12.5-25 mg once daily
- Target dose: 200 mg once daily 4
- The MERIT-HF trial used metoprolol succinate with initial doses of 12.5-25 mg once daily, gradually increased to target dose of 200 mg once daily 5
Hypertension/Angina
- Both formulations are effective for hypertension management
- Typical dosing:
Important Considerations
When switching between formulations:
- Total daily dose remains the same (e.g., metoprolol tartrate 12.5 mg twice daily would convert to metoprolol succinate 25 mg once daily)
- For a patient on metoprolol tartrate 12.5 mg once daily, the equivalent metoprolol succinate dose would be 12.5 mg once daily
Metoprolol succinate offers advantages:
- Improved adherence with once-daily dosing
- More consistent beta-blockade over 24 hours
- Fewer peak-related side effects 6
Common Pitfalls to Avoid
- Don't confuse the total daily dose with the per-dose amount when converting
- Remember that metoprolol succinate is specifically indicated for heart failure based on clinical evidence, while both formulations can be used for hypertension
- Avoid abrupt discontinuation of either formulation to prevent rebound effects
- Monitor for bradycardia, hypotension, and heart block when initiating or titrating either formulation
When initiating beta-blocker therapy in heart failure patients, start with low doses and titrate gradually (every 1-2 weeks) to target doses, monitoring for signs of worsening heart failure, hypotension, or bradycardia 4.