Equivalent Dosing of Metoprolol Tartrate and Metoprolol Succinate
A 100-mg metoprolol succinate (extended-release) tablet is considered equivalent to 100 mg of metoprolol tartrate (immediate-release), but the key difference is in dosing frequency: metoprolol tartrate requires twice-daily administration while metoprolol succinate is given once daily. 1
Pharmacokinetic Basis for Equivalency
The equivalency is based on the total daily dose of active metoprolol delivered, not on the salt form itself:
- A 100-mg metoprolol controlled/extended-release tablet contains 95 mg of metoprolol succinate and is considered to have equivalent activity to 100 mg metoprolol tartrate 1
- The extended-release formulation disintegrates into individual pellets that release drug at a relatively constant rate over approximately 20 hours, providing even plasma concentrations without the marked peaks and troughs seen with immediate-release formulations 1, 2
Clinical Dosing Conversion
When converting between formulations, use the following approach:
For Heart Failure with Reduced Ejection Fraction (HFrEF):
- Metoprolol tartrate: Start at 6.25 mg twice daily (12.5 mg total daily dose), titrate to target of 50 mg twice daily (100 mg total daily dose) 3
- Metoprolol succinate: Start at 25 mg once daily, titrate to target of 200 mg once daily 4, 3
Note the fourfold greater starting dose of metoprolol succinate (25 mg vs 6.25 mg) produces similar hemodynamic and clinical effects as metoprolol tartrate, allowing for more rapid initiation 3
For Hypertension and Other Indications:
- Metoprolol tartrate: 25-100 mg twice daily (50-200 mg total daily dose) 5
- Metoprolol succinate: 50-200 mg once daily 5
The total daily dose remains equivalent between formulations 1, 6
Key Clinical Differences Beyond Dosing
While the total daily doses are equivalent, important pharmacodynamic differences exist:
- Once-daily metoprolol succinate 12.5-200 mg produces even plasma concentrations over 24 hours, leading to consistent beta1-blockade without peaks and troughs 2
- Both formulations produce similar hemodynamic effects acutely and chronically, with parallel changes in cardiac index, systemic vascular resistance, and stroke volume index 3
- At 200 mg daily dosing, the extended-release preparation may provide superior exercise tolerance over 24 hours compared to conventional tablets given as 100 mg twice daily 6
Common Pitfalls to Avoid
- Do not assume you can simply give half the daily dose of metoprolol succinate twice daily—the formulations are designed for different dosing frequencies and the extended-release mechanism requires once-daily administration 1, 2
- When initiating therapy in heart failure patients, metoprolol succinate allows for a higher starting dose (25 mg vs 6.25 mg) with similar tolerability, potentially offering advantages in treatment initiation 3
- Metoprolol tartrate requires twice-daily dosing to maintain adequate beta-blockade over 24 hours in most patients, as once-daily conventional metoprolol provides inferior 24-hour coverage compared to atenolol 7