Metoprolol Dosing for Supraventricular Tachycardia
For acute SVT, administer metoprolol 5 mg IV over 1-2 minutes, which can be repeated every 5 minutes as needed up to a maximum total dose of 15 mg. 1
Intravenous Administration Protocol
The standard IV dosing regimen consists of 5 mg boluses given slowly over 1-2 minutes, repeated at 5-minute intervals based on heart rate and blood pressure response, not exceeding 15 mg total. 2, 1 This approach allows for titration while monitoring for adverse effects, particularly hypotension and bradycardia.
Clinical Evidence for IV Metoprolol
- In clinical studies, the mean effective dose was 9.5 mg (range 2-15 mg), with 81% of patients responding with adequate ventricular rate control 3
- Ventricular rate decreased from a mean of 134 to 106 beats/min within 10 minutes of administration, with maximum effect at 48 minutes 3
- Rate reduction of >15% (26-60 beats/min decrease) occurred in 69% of patients overall and 82% of those with atrial fibrillation 3
Transition to Oral Therapy
After successful IV administration, oral metoprolol can be initiated 15 minutes after the last IV dose at 25-50 mg every 6 hours for 48 hours, then transitioned to twice-daily dosing. 1 For ongoing management, the maintenance dose ranges from 25 mg twice daily up to 200 mg twice daily for metoprolol tartrate, or 50 mg once daily up to 400 mg once daily for metoprolol succinate extended-release. 2, 1
Critical Contraindications and Precautions
Do not administer metoprolol IV in the following situations: 2, 1
- Signs of heart failure, low output state, or increased risk for cardiogenic shock
- PR interval >0.24 seconds, second- or third-degree heart block without a pacemaker
- Active asthma or reactive airways disease
- Systolic BP <100-120 mmHg with symptoms
- Heart rate <60 bpm with symptoms or >110 bpm (paradoxical risk factor for shock)
- Pre-excited atrial fibrillation or flutter (WPW syndrome) 2
Common Pitfall to Avoid
AV nodal blocking agents like metoprolol should never be used for pre-excited atrial fibrillation conducting via an accessory pathway, as this may paradoxically accelerate the ventricular response and precipitate ventricular fibrillation. 2 Always obtain a 12-lead ECG before administration to identify delta waves suggesting WPW.
Monitoring During IV Administration
Continuous ECG monitoring is mandatory during IV metoprolol administration, with frequent blood pressure and heart rate checks. 1 Specifically monitor for:
- Symptomatic bradycardia (HR <60 bpm with dizziness or lightheadedness) 1
- Hypotension (systolic BP <100 mmHg with symptoms like dizziness or blurred vision) 1
- New or worsening bronchospasm, particularly in patients with any history of reactive airway disease 1
- Signs of heart failure (rales on auscultation) 1
Management of Hypotension
Hypotension is the most frequent side effect, occurring in approximately 30% of patients, but is typically transient and readily managed with IV fluids or temporary Trendelenburg positioning. 3 If severe hypotension with hypoperfusion occurs, immediate intervention is required. 1
Alternative Beta-Blocker Considerations
While metoprolol is effective, other IV beta-blockers including atenolol, propranolol, esmolol, and labetalol can also be used for SVT, though metoprolol and esmolol are most commonly employed in acute settings. 2 The cardioselective properties of metoprolol may offer advantages in patients with mild chronic obstructive pulmonary disease, though caution is still warranted. 3
Oral Dosing for Chronic SVT Management
For ongoing oral therapy to prevent SVT recurrence:
- Metoprolol tartrate: Start 25 mg twice daily, titrate up to 200 mg twice daily as needed 2
- Metoprolol succinate (extended-release): Start 50 mg once daily, titrate up to 400 mg once daily as needed 2
Target a resting heart rate of 50-60 beats per minute unless limiting side effects occur. 1 Dose adjustments should be made gradually every 1-2 weeks based on clinical response. 1