Switching from Metoprolol Tartrate to Metoprolol Succinate
When switching from metoprolol tartrate to metoprolol succinate, patients should be started on an equivalent dose to their current metoprolol tartrate regimen rather than the lowest available dose.
Dose Equivalence and Conversion
- Metoprolol succinate (extended-release) 100 mg once daily is equivalent to metoprolol tartrate 100 mg given twice daily 1
- The conversion follows a 1:1 total daily dose ratio:
- Metoprolol tartrate 50 mg twice daily (100 mg total) = Metoprolol succinate 100 mg once daily
- Metoprolol tartrate 100 mg twice daily (200 mg total) = Metoprolol succinate 200 mg once daily
Pharmacokinetic Considerations
- Metoprolol succinate is designed to release medication at a relatively constant rate over approximately 20 hours, providing more consistent plasma concentrations 2
- The extended-release formulation eliminates the peaks and troughs seen with immediate-release tartrate formulation, providing consistent beta1-blockade over 24 hours 2
- A 100 mg metoprolol succinate tablet contains 95 mg of metoprolol succinate and is considered to have equivalent activity to 100 mg metoprolol tartrate 3
Clinical Rationale for Equivalent Dosing
- Starting at an equivalent dose maintains therapeutic effect without interruption in beta-blockade
- Abrupt reduction in beta-blocker dose could potentially lead to rebound effects, including tachycardia, increased blood pressure, or exacerbation of angina in patients with coronary artery disease 4
- The ACC/AHA guidelines specifically warn against abrupt cessation of beta-blockers as this can precipitate angina, myocardial infarction, or ventricular arrhythmias 1
Special Considerations
- Elderly patients or those with hepatic dysfunction may require dose adjustment, but this should be based on their current stable dose of metoprolol tartrate 1
- Women may experience higher drug exposure and may require lower doses than men, but this adjustment should have already been made with the tartrate formulation 1
- For patients with heart failure, the hemodynamic effects of equivalent doses of both formulations are similar despite the different dosing schedule 5
Monitoring After Conversion
- Monitor heart rate and blood pressure within 1-2 weeks after switching formulations
- Watch for signs of excessive beta-blockade (bradycardia, hypotension, fatigue) or inadequate beta-blockade (tachycardia, uncontrolled hypertension)
- Adjust dose as needed based on clinical response, but maintain the once-daily dosing schedule with the succinate formulation
Common Pitfalls to Avoid
- Do not start at the lowest dose when converting from an established tartrate regimen, as this may lead to inadequate beta-blockade
- Do not exceed the maximum recommended daily dose of metoprolol succinate (400 mg daily) 4
- Do not split or crush extended-release metoprolol succinate tablets as this would destroy the controlled-release mechanism
By maintaining equivalent total daily dosing when switching from metoprolol tartrate to succinate, you ensure continuous therapeutic effect while gaining the benefits of once-daily dosing and more consistent plasma levels throughout the day.