Metoprolol SR Dosing Frequency
Metoprolol succinate (sustained-release) should be dosed once daily, not twice daily, as this formulation was specifically designed for 24-hour coverage and is the only metoprolol formulation proven to reduce mortality in heart failure. 1, 2
Critical Distinction Between Formulations
The formulation of metoprolol matters significantly for both dosing frequency and clinical outcomes:
- Metoprolol succinate (SR/ER) is designed for once-daily administration with a maximum recommended dose of 200 mg once daily 2
- Metoprolol tartrate (immediate-release) requires twice-daily dosing, typically 25-100 mg twice daily 2
- The sustained-release metoprolol succinate formulation was the specific preparation that demonstrated mortality reduction in clinical trials, while short-acting metoprolol tartrate showed lesser effectiveness 1
Evidence-Based Dosing Recommendations
Heart Failure
- Initial dose: 12.5-25 mg once daily 2
- Target dose: 200 mg once daily 2
- Titration: Double the dose every 1-2 weeks if well tolerated 2
- The mean dose achieved in clinical trials was 159 mg daily 2
Hypertension
- Dose range: 50-400 mg once daily 2
- Studies demonstrate that metoprolol SR maintains effective blood pressure control for 24 hours after a single daily dose 3, 4
Post-Myocardial Infarction
- After initial IV therapy, maintenance dosing is 100 mg twice daily—but this refers to metoprolol tartrate, not the sustained-release formulation 2
Why Once-Daily Dosing Works
The controlled-release delivery system releases metoprolol at a relatively constant rate over 24 hours, producing sustained plasma concentrations and consistent beta-1 blockade 4, 5. This design:
- Maintains clinically effective plasma concentrations within a narrow therapeutic range over the entire 24-hour interval 4
- Avoids high peak plasma concentrations that can reduce beta-1 selectivity 4, 5
- Provides more consistent antihypertensive effect at 24 hours compared to twice-daily immediate-release formulations 3
Common Pitfall to Avoid
Do not confuse metoprolol succinate SR with metoprolol tartrate. The ACC/AHA guidelines specifically note that although metoprolol tartrate dosed at 50 mg twice daily is commonly prescribed, this was neither the dose nor formulation used in trials that showed mortality reduction 1. Using metoprolol succinate twice daily would be inappropriate dosing that deviates from evidence-based practice and potentially wastes medication.
Monitoring During Titration
During dose escalation, monitor for: