A patient on metoprolol succinate 25 mg twice daily for arrhythmia now has a resting heart rate of 60–65 bpm; what are the appropriate next steps?

Management of Bradycardia in Patient on Metoprolol Succinate for Arrhythmia

A resting heart rate of 60-65 bpm in a patient on metoprolol succinate 25 mg twice daily is generally acceptable and does not require immediate intervention, but the twice-daily dosing of metoprolol succinate is incorrect and should be corrected to once-daily administration. 1, 2

Critical Dosing Error to Address First

Your patient is receiving metoprolol succinate on an incorrect dosing schedule. Metoprolol succinate is an extended-release formulation designed for once-daily administration, not twice-daily dosing. 1, 2 The current regimen of 25 mg twice daily (total 50 mg/day) should be consolidated to 50 mg once daily. 1, 2 This formulation-specific dosing is critical because metoprolol succinate was the preparation proven to reduce mortality in clinical trials when dosed once daily. 2

Assessment of Current Heart Rate

Is This Bradycardia Problematic?

The current heart rate of 60-65 bpm falls into a gray zone that requires symptom assessment:

• Asymptomatic bradycardia at 60-65 bpm does not constitute an absolute contraindication to continued beta-blocker therapy. 1 Guidelines define symptomatic bradycardia requiring intervention as heart rate <50-60 bpm accompanied by dizziness, syncope, or signs of hypoperfusion. 1

• Target resting heart rate for patients on beta-blockers is 50-60 bpm unless limiting side effects occur. 1 Your patient's heart rate of 60-65 bpm is actually within or just above the therapeutic target range.

• Assess for symptoms: Check specifically for dizziness, lightheadedness, syncope, fatigue, or altered mental status. 1 If any of these symptoms are present, the bradycardia becomes clinically significant and requires intervention.

Management Algorithm

If Patient is Asymptomatic:

1. Correct the dosing schedule immediately: Switch from metoprolol succinate 25 mg twice daily to 50 mg once daily. 1, 2 This maintains the same total daily dose but uses the correct administration schedule for the extended-release formulation.

2. Monitor closely for the next 1-2 weeks: Check heart rate, blood pressure, and symptoms at follow-up. 1 The once-daily dosing may actually provide more stable heart rate control throughout the 24-hour period.

3. Continue current dose if well-tolerated: A heart rate of 60-65 bpm without symptoms represents adequate rate control for arrhythmia management. 3, 1

If Patient Has Symptoms (Dizziness, Fatigue, Syncope):

1. Reduce the metoprolol dose by 50%: Switch to metoprolol succinate 25 mg once daily. 1 This maintains some beta-blockade benefit while reducing bradycardic risk.

2. Do NOT abruptly discontinue metoprolol, especially if the arrhythmia being treated is atrial fibrillation or if the patient has underlying coronary disease. 1, 4 Abrupt discontinuation is associated with a 2.7-fold increased risk of 1-year mortality and can precipitate severe exacerbation of angina, myocardial infarction, and ventricular arrhythmias. 1, 4

3. Hold the dose only if: 1

   • Heart rate consistently <45 bpm
   • Heart rate 45-49 bpm with severe symptoms
   • Systolic blood pressure <100 mmHg with symptoms of hypoperfusion
   • Evidence of high-grade AV block on ECG

4. Reassess within 1-2 weeks after dose reduction to determine if symptoms have resolved and heart rate has improved. 1

What Type of Arrhythmia is Being Treated?

This matters for your next steps:

If Atrial Fibrillation:

• Rate control target is 60-80 bpm at rest, so the current heart rate is appropriate. 3 The goal is lenient rate control (<110 bpm during moderate exercise), which your patient likely achieves. 3

• Alternative rate-control agents if metoprolol must be reduced or discontinued: 3, 1

  • Diltiazem 120-360 mg daily (does not cause bradycardia as readily)
  • Verapamil 120-360 mg daily
  • Digoxin 0.125-0.25 mg daily (though less effective as monotherapy)

If Frequent PVCs or Other Ventricular Arrhythmia:

• Beta-blockers remain first-line therapy, and the current heart rate is acceptable. 1 Consider maintaining the corrected dose (50 mg once daily) if asymptomatic.

• If symptomatic bradycardia develops, alternatives include: 1

  • Calcium channel blockers (diltiazem or verapamil) starting at 120 mg daily
  • Class IC agents (flecainide or propafenone) only if no structural heart disease or coronary disease is present

Monitoring Parameters Going Forward

After correcting the dosing schedule, monitor: 1

• Heart rate and blood pressure at each visit during the adjustment period
• Symptoms: Specifically ask about dizziness, lightheadedness, fatigue, syncope, or near-syncope
• Signs of worsening heart failure: Increased dyspnea, edema, weight gain (if heart failure is present)
• ECG if symptoms develop: To rule out high-grade AV block or other conduction abnormalities

Common Pitfalls to Avoid

1. Never give metoprolol succinate twice daily. 1, 2 This is the most common prescribing error with this formulation and deviates from evidence-based practice.

2. Do not assume all bradycardia requires intervention. 1 Heart rates of 60-65 bpm are often therapeutic targets in patients on beta-blockers for arrhythmia control.

3. Never abruptly stop metoprolol without a tapering plan, especially in patients with coronary disease or heart failure. 1, 4 If discontinuation is necessary, reduce by 25-50% every 1-2 weeks. 1

4. Do not confuse metoprolol tartrate (immediate-release, dosed twice daily) with metoprolol succinate (extended-release, dosed once daily). 2 These are not interchangeable formulations, and metoprolol succinate is the evidence-based choice for heart failure and long-term arrhythmia management. 2