Why is metoprolol succinate (Extended-Release) prescribed twice a day (BID) when it's an extended-release formulation?

Metoprolol Succinate ER Should NOT Be Dosed Twice Daily

This prescription is incorrect—metoprolol succinate extended-release is specifically designed and FDA-approved for once-daily dosing only, and prescribing it twice daily contradicts evidence-based practice and the formulation's pharmacokinetic design. 1

Why This Prescription Is Wrong

The Critical Formulation Error

• Metoprolol succinate ER is engineered to release medication continuously over approximately 20 hours, providing stable plasma concentrations with once-daily administration. 2, 3

• The American College of Cardiology and American Heart Association explicitly state that using metoprolol succinate twice daily is inappropriate dosing that deviates from evidence-based practice—this was neither the dose nor formulation used in mortality-reduction trials. 1

• The extended-release formulation contains controlled-release pellets that each act as separate drug delivery units, designed specifically to maintain consistent beta-1 blockade over 24 hours with a single daily dose. 2, 3

What the Provider Likely Intended

The provider may have confused two different formulations:

• Metoprolol tartrate (immediate-release) requires twice-daily dosing due to its shorter half-life and is typically dosed at 25-100 mg twice daily. 1

• Metoprolol succinate (extended-release) should be dosed once daily, with typical dosing of 25-200 mg once daily depending on the indication. 1, 4

Correct Dosing Recommendations

For Most Indications

• Start metoprolol succinate ER at 25-50 mg once daily in the morning, not divided into twice-daily doses. 1

• The maximum recommended daily dose is 200 mg once daily for heart failure, or up to 400 mg once daily for hypertension. 1, 4

• Titrate gradually by doubling the dose every 1-2 weeks if the preceding dose was well tolerated. 1

Condition-Specific Guidance

For heart failure with reduced ejection fraction:

• Start at 12.5-25 mg once daily, targeting 200 mg once daily as the goal dose. 1, 5
• Only metoprolol succinate (not tartrate) has proven mortality benefit in heart failure—a 34% reduction in mortality in the MERIT-HF trial. 1, 5

For hypertension:

• Start at 50 mg once daily, with a usual range of 50-200 mg once daily (maximum 400 mg daily). 1, 4

For atrial fibrillation rate control:

• Dose range is 50-400 mg once daily for metoprolol succinate. 4

Critical Clinical Pitfalls

Common Prescribing Errors to Avoid

• Never split or crush metoprolol succinate ER tablets, as this destroys the extended-release mechanism and can cause dangerous peaks in drug levels. 6

• Do not substitute metoprolol tartrate for metoprolol succinate in heart failure patients—only the succinate formulation has mortality benefit. 1, 5

• Avoid abrupt discontinuation of either formulation, as this can precipitate angina, myocardial infarction, or arrhythmias. 1

What to Do About This Prescription

The prescription should be corrected to metoprolol succinate ER 25 mg once daily (total daily dose remains 25 mg, not 50 mg split twice daily). 1

If the provider specifically needs twice-daily dosing for clinical reasons:

• Switch to metoprolol tartrate (immediate-release) 25 mg twice daily instead, which is the appropriate formulation for BID dosing. 1
• Note that for heart failure, this would be suboptimal as tartrate lacks the mortality benefit of succinate. 5

Monitoring Parameters

• Check heart rate and blood pressure at each visit during titration, targeting a resting heart rate of 50-60 beats per minute unless limiting side effects occur. 4

• Monitor for signs of worsening heart failure symptoms, fluid retention, hypotension, and symptomatic bradycardia during dose adjustments. 1

• If symptoms worsen during titration, increase diuretics or ACE inhibitors first before reducing the beta-blocker dose. 1