What is the recommended dose and administration of metoprolol (beta-blocker) for a patient with Supraventricular Tachycardia (SVT)?

Metoprolol for Supraventricular Tachycardia

For acute SVT treatment, administer intravenous metoprolol 2-15 mg (typically starting at 2.5-5 mg) given slowly over 1-2 minutes, with repeat doses every 5 minutes as needed based on heart rate and blood pressure response, up to a maximum of 15 mg total. 1

Acute Intravenous Administration

Dosing Protocol

• Initial dose: 2.5-5 mg IV push over 1-2 minutes 2, 3
• Repeat dosing: Additional 2.5-5 mg boluses every 5 minutes as needed based on ventricular rate and blood pressure 2
• Maximum total dose: 15 mg over approximately 10-25 minutes 2, 3
• Mean effective dose in clinical studies: 9.5 mg (range 2-15 mg) 2

Expected Response

• Onset of action: 10 minutes after administration 2
• Peak effect: 48 minutes after initiation 2
• Success rate: 81% for rate control in supraventricular tachyarrhythmias 2
• Conversion to sinus rhythm: 50% in paroxysmal SVT, 43% in atrial flutter, 13% in atrial fibrillation 3
• Duration of effect: 40-320 minutes without additional therapy 2

Clinical Positioning

When to Use Metoprolol

Intravenous beta blockers (including metoprolol) are reasonable for acute treatment in hemodynamically stable patients with AVNRT when vagal maneuvers and adenosine have failed or are contraindicated. 1

The treatment algorithm for SVT follows this sequence:

1. Vagal maneuvers first (Valsalva, carotid massage) 1
2. Adenosine 6 mg rapid IV push (then 12 mg x2 if needed) 1
3. IV metoprolol or other beta blocker if adenosine fails 1
4. Synchronized cardioversion if hemodynamically unstable or medications fail 1

Advantages Over Other Agents

• Cardioselectivity allows use in selected patients with chronic obstructive pulmonary disease where non-selective beta blockers are contraindicated 2
• Excellent safety profile compared to calcium channel blockers 1
• Can be used in pregnant patients when adenosine is ineffective (Class IIa recommendation) 1

Ongoing Oral Management

Chronic Dosing

• Standard dose: 50-100 mg orally twice daily for prophylaxis of recurrent SVT 4
• Dose range: 100-200 mg total daily dose divided into 2-3 administrations 4, 5
• For multifocal atrial tachycardia: 25-50 mg orally with reassessment in 1-3 hours 5

Efficacy for Prevention

• Prophylactic success: 45% remain arrhythmia-free on chronic oral therapy 4
• Rate control achieved in most patients who continue to have breakthrough episodes 4
• Particularly effective for MAT: 100% conversion to sinus rhythm in one study of 11 patients with serious pulmonary disease 5

Critical Safety Considerations

Major Adverse Effect

Hypotension is the most frequent side effect, occurring in approximately 31% of patients, but is typically transient and readily managed. 2

Contraindications and Precautions

• Avoid in acute decompensated heart failure or hemodynamic instability 1
• Avoid in severe bronchospastic pulmonary disease during acute respiratory decompensation 1
• Avoid in severe conduction abnormalities or sinus node dysfunction 1
• Ensure SVT is not pre-excited atrial fibrillation (WPW syndrome), as AV nodal blockade can be dangerous 1
• Confirm absence of ventricular tachycardia before administration 1

Safe Administration in Pulmonary Disease

Metoprolol can be safely used in patients with serious pulmonary disease after correction of hypoxia and acute decompensation, with no adverse effects on arterial blood gases. 5

This cardioselective property distinguishes metoprolol from non-selective beta blockers and makes it particularly useful when beta blockade is indicated but pulmonary concerns exist 2, 5

Special Populations

Pregnancy

IV metoprolol is reasonable for acute SVT treatment in pregnant patients when adenosine is ineffective or contraindicated (Class IIa). 1

• Slow infusion preferred to minimize risk of maternal hypotension 1
• Extensive safety data from decades of use for various maternal conditions 1
• First-line pharmacologic option after adenosine failure 1

Multifocal Atrial Tachycardia

Intravenous metoprolol can be useful for acute treatment of MAT (Class IIa), particularly after correction of underlying metabolic derangements. 1

• Correct hypoxia, hypercarbia, acidosis, and electrolyte abnormalities first 5
• Effective even in patients on therapeutic theophylline and digoxin 5
• Oral metoprolol reasonable for ongoing management (Class IIa) 1

Monitoring Requirements

During IV Administration

• Continuous cardiac monitoring for heart rate and rhythm 2
• Blood pressure measurement every 2-5 minutes during dosing 2
• Assess for hypotension requiring intervention (systolic BP <90 mmHg) 2, 3
• Target ventricular rate reduction: >15% or decrease of 26-60 beats/min 2

Clinical Pitfall

Do not withhold metoprolol in patients with baseline systolic blood pressure >100 mmHg without acute myocardial infarction, as the risk of treatment-requiring hypotension is small. 3