How should metoprolol succinate be dosed and used as first‑line oral therapy for recurrent paroxysmal supraventricular tachycardia in adults?

Metoprolol Succinate for Recurrent PSVT: Dosing and First-Line Oral Therapy

Metoprolol succinate is a reasonable option for ongoing management of recurrent PSVT, but catheter ablation should be strongly considered as first-line therapy given its superior efficacy (94-98% success rate) and potential for cure without lifelong medication. 1, 2

When to Use Oral Metoprolol for PSVT

Oral beta blockers including metoprolol are recommended (Class I) for ongoing management in patients with symptomatic PSVT who are not candidates for, or prefer not to undergo, catheter ablation. 1 This applies specifically to patients without ventricular pre-excitation during sinus rhythm. 1

Critical Contraindications to Verify First

Before initiating metoprolol, you must exclude:

• Decompensated heart failure or signs of low cardiac output 3
• Second or third-degree AV block without a functioning pacemaker 3
• Active asthma or severe reactive airway disease 3, 4
• Symptomatic bradycardia (heart rate <50-60 bpm with symptoms) 3
• Systolic blood pressure <100 mmHg with symptoms 3

Dosing Protocol for Metoprolol Succinate

Initial Dosing

Start with metoprolol succinate 50 mg once daily. 3 For patients with concerns about beta-blocker tolerance or elderly patients, consider starting at 25 mg once daily. 3

Titration Strategy

• Increase the dose every 1-2 weeks based on heart rate and blood pressure response 3
• Target dose is 50-200 mg once daily 3
• Maximum dose is 400 mg once daily if needed for symptom control 3
• Target resting heart rate of 50-80 bpm unless limiting side effects occur 3

Monitoring Parameters

At each visit during titration:

• Check blood pressure (maintain systolic ≥100 mmHg) 3
• Assess heart rate (target 50-80 bpm) 3
• Monitor for symptomatic bradycardia, hypotension, or worsening heart failure symptoms 3
• Watch for bronchospasm, particularly in patients with any history of reactive airway disease 3

Evidence for Efficacy

The evidence for oral beta blockers in PSVT is limited but supportive. One small randomized trial compared propranolol 240 mg/day to verapamil 480 mg/day and digoxin, showing similar reductions in PSVT episodes and duration, with all three medications well tolerated. 1 However, these doses are higher than typically used in current practice. 1

A more recent study of metoprolol specifically showed that oral therapy (50-100 mg twice daily) successfully prevented PSVT recurrences in most patients over several months of follow-up, with intravenous testing correctly predicting oral response in 7 of 8 patients. 5

Alternative First-Line Options

If metoprolol is contraindicated or not tolerated:

• Diltiazem 120-360 mg daily or verapamil up to 480 mg daily are reasonable alternatives (Class I recommendation) 1
• Flecainide or propafenone are reasonable (Class IIa) in patients without structural heart disease or ischemic heart disease 1

A head-to-head trial showed flecainide (median 200 mg/day) had 30% of patients complete >270 days without symptomatic attacks versus 13% on verapamil (median 240 mg/day), though both were effective and well tolerated. 6

Common Pitfalls to Avoid

• Never abruptly discontinue metoprolol—this can precipitate severe angina, myocardial infarction, and ventricular arrhythmias with a 2.7-fold increased mortality risk 3
• Do not use metoprolol in patients with pre-excited atrial fibrillation (WPW syndrome), as it may paradoxically accelerate ventricular response 3
• Avoid initiating during acute decompensation—wait until clinical stabilization 3
• Do not overlook catheter ablation as the preferred definitive therapy, especially in younger patients or those requiring lifelong medication 1, 2

"Pill-in-the-Pocket" Approach

Self-administered acute doses of oral beta blockers may be reasonable (Class IIb) for infrequent, well-tolerated PSVT episodes, though safety data are limited and episodes of syncope have been observed. 1 Patients should be instructed to seek medical attention if oral therapy fails to terminate the arrhythmia. 1

Why Catheter Ablation Should Be Discussed

Catheter ablation achieves >95% success rates with <1% risk of AV block and is recommended as first-line therapy (Class I) for symptomatic PSVT. 1 Meta-analyses show single-procedure success rates of 94.3-98.5%. 2 This should be presented as the preferred option, with pharmacotherapy reserved for patients who decline ablation, have contraindications, or lack access to an electrophysiologist. 1