What is the equivalent dose of metoprolol succinate (extended-release formulation) for a patient taking metoprolol tartrate (immediate-release formulation) 100mg twice daily (bid)?

Metoprolol Tartrate to Succinate Conversion

Metoprolol tartrate 100mg twice daily is equivalent to metoprolol succinate 200mg once daily. 1, 2

Pharmacological Basis for Conversion

Metoprolol comes in two formulations with different pharmacokinetic properties:

• Metoprolol tartrate: Immediate-release formulation requiring twice daily dosing
• Metoprolol succinate: Extended-release formulation allowing once daily dosing

The extended-release formulation (succinate) is designed to provide relatively constant plasma concentrations over approximately 20 hours, with consistent beta1-blockade over a 24-hour period, without the marked peaks and troughs seen with the immediate-release formulation (tartrate). 3

Conversion Ratio

The conversion is straightforward and based on total daily dose:

• Metoprolol tartrate 100mg BID = 200mg total daily dose
• Equivalent metoprolol succinate dose = 200mg once daily 1, 2

According to the 2022 AHA/ACC/HFSA guidelines for heart failure management, metoprolol succinate extended-release has a target dose of 200mg once daily, which corresponds to the total daily dose of metoprolol tartrate when given as 100mg twice daily. 1

Clinical Considerations

Benefits of Switching to Succinate Formulation

• Improved adherence: Once-daily dosing may improve medication adherence 2
• More consistent beta-blockade: Succinate provides more even plasma concentrations over 24 hours 3
• Proven mortality benefits: Metoprolol succinate is one of only three beta-blockers (along with bisoprolol and carvedilol) proven to reduce mortality in heart failure patients 1, 2

Practical Implementation

When converting from tartrate to succinate:

1. Switch directly from metoprolol tartrate 100mg twice daily to metoprolol succinate 200mg once daily
2. No dose titration is needed when making this direct conversion in a stable patient
3. Monitor heart rate and blood pressure after conversion to ensure adequate response

Special Populations

• Heart failure patients: Metoprolol succinate is specifically recommended in heart failure guidelines with a target dose of 200mg daily 1
• Elderly patients: May benefit from the more stable plasma levels of the succinate formulation to reduce orthostatic hypotension risk 2

Potential Pitfalls

• Do not confuse the two formulations when prescribing, as they are not interchangeable on a milligram-per-milligram basis
• Ensure patients understand the change in dosing frequency to prevent medication errors
• Remember that a 100mg metoprolol succinate tablet contains 95mg of metoprolol succinate and is equivalent to 100mg of metoprolol tartrate 4

In summary, when converting from metoprolol tartrate 100mg twice daily, the appropriate equivalent dose is metoprolol succinate 200mg once daily, which provides similar clinical efficacy with the advantage of once-daily dosing.