What is the exact dose of metoprolol (beta blocker) for intravenous (IV) push administration in supraventricular tachycardia (SVT)?

Metoprolol IV Push Dosing for Supraventricular Tachycardia

For supraventricular tachycardia (SVT), metoprolol should be administered intravenously at 5 mg over 1-2 minutes, which can be repeated at 5-minute intervals up to a maximum total dose of 15 mg. 1

Detailed Administration Protocol

• Initial dose: 5 mg IV push over 1-2 minutes
• Repeat dosing: Can repeat 5 mg IV bolus in 10 minutes if inadequate response
• Maximum total dose: 15 mg (three 5 mg doses)
• Administration rate: Slow IV push over 1-2 minutes (2 minutes in elderly patients)
• Monitoring: Continuous ECG monitoring is essential during administration

Clinical Considerations

Mechanism of Action

Metoprolol is a cardioselective beta-1 blocker that slows AV nodal conduction and increases AV nodal refractoriness, making it effective for rate control in SVT by interrupting reentry circuits that depend on AV nodal conduction.

Efficacy

• Metoprolol IV has shown 69-81% efficacy in controlling ventricular rate in patients with SVT 2
• Reduces ventricular rate by >15% in most patients with supraventricular tachyarrhythmias
• Maximum effect typically occurs approximately 48 minutes after administration 2

Contraindications

• AV block greater than first degree (unless pacemaker present)
• Sinus node dysfunction
• Cardiogenic shock
• Decompensated heart failure
• Severe bradycardia
• Hypotension (use with caution if systolic BP <100 mmHg)

Potential Adverse Effects

• Hypotension: Most common side effect, occurring in approximately 30% of patients 2
• Bradycardia
• Bronchospasm (less likely than with non-selective beta blockers, but still possible)
• Worsening heart failure in patients with ventricular dysfunction

Alternative Options

If metoprolol is contraindicated or ineffective, consider:

1. Adenosine: 6 mg rapid IV bolus followed by saline flush; if ineffective, 12 mg can be given, repeated once if necessary 1

2. Other beta blockers:

   • Esmolol: 500 mcg/kg IV bolus over 1 minute, followed by infusion at 50-300 mcg/kg/min 1
   • Propranolol: 1 mg IV over 1 minute, repeatable at 2-minute intervals up to 3 doses 1

3. Calcium channel blockers:

   • Diltiazem: 0.25 mg/kg IV over 2 minutes, followed by infusion at 5-10 mg/hour 1
   • Verapamil: 5-10 mg IV over 2 minutes, with possible additional 10 mg after 30 minutes 1

Important Cautions

• Avoid in pre-excited atrial fibrillation/flutter: Beta blockers can potentially accelerate ventricular response in patients with accessory pathways 1
• Avoid combining with other AV nodal blocking agents with longer half-lives due to risk of profound bradycardia 1
• Use with caution in patients with reactive airway disease, although metoprolol's cardioselectivity makes it safer than non-selective beta blockers
• Monitor blood pressure closely during administration due to risk of hypotension

Metoprolol's cardioselectivity makes it particularly useful in patients with chronic obstructive pulmonary disease who require beta blockade, though it should still be used with caution in these patients 2.