What is the difference between metoprolol (beta-blocker) tartrate and metoprolol succinate for supraventricular tachycardia (SVT)?

Metoprolol Tartrate vs Succinate for SVT

Direct Answer

Both metoprolol tartrate and metoprolol succinate are equally effective for treating supraventricular tachycardia, with the primary difference being pharmacokinetic rather than clinical—tartrate is the immediate-release formulation used for acute IV treatment and short-acting oral therapy (dosed twice daily), while succinate is the extended-release formulation for once-daily maintenance therapy. 1

Formulation Differences

Metoprolol Tartrate (Immediate-Release)

• Oral dosing: 25-100 mg twice daily (BID), with maximum maintenance dose of 200 mg BID 1
• IV formulation available: Used for acute SVT treatment in hemodynamically stable patients (Class IIa recommendation) 1
• Bioavailability: Approximately 50% due to first-pass metabolism 2
• Half-life: 3-4 hours in extensive metabolizers; 7-9 hours in poor CYP2D6 metabolizers 2
• Peak effect: Maximum beta-blockade achieved at approximately 20 minutes with IV administration 2

Metoprolol Succinate (Extended-Release)

• Oral dosing: 50-400 mg once daily (QD), starting at 50 mg QD 1
• No IV formulation available 1
• Sustained release: Provides steady-state plasma levels over 24 hours 1

Clinical Application for SVT

Acute SVT Treatment

For acute SVT management, IV metoprolol tartrate is the only option since succinate has no intravenous formulation. 3, 1

• IV metoprolol is reasonable for acute treatment in hemodynamically stable patients with AVNRT (Class IIa, Level B-R) 4
• Dosing for acute treatment: Typically 2-20 mg IV, with mean effective dose of 9.5 mg administered over up to 25 minutes 5
• Efficacy: Reduces ventricular rate by >15% in 69% of patients, with mean rate decreasing from 134 to 106 beats/min within 10 minutes 5
• Duration of effect: Rate control maintained for 40-320 minutes after single IV dose 5
• Conversion to sinus rhythm: Achieved in 50% of patients with paroxysmal SVT, 43% with atrial flutter, and 13% with atrial fibrillation 6

Ongoing/Chronic SVT Management

For maintenance therapy, either formulation works, but succinate offers convenience with once-daily dosing. 1

• Metoprolol tartrate: 25-100 mg BID for ongoing management 1
• Metoprolol succinate: 50-400 mg QD for ongoing management 1
• Both formulations are listed as reasonable options for chronic management of recurrent symptomatic SVT 3

Shared Pharmacology and Precautions

Mechanism of Action

Both formulations contain the same active drug with identical mechanisms: 2

• Beta-1 selective (cardioselective) adrenergic receptor blockade
• Slows sinus rate and decreases AV nodal conduction
• Reduces heart rate, cardiac output, and myocardial oxygen demand

Critical Contraindications (Apply to Both Formulations)

Avoid metoprolol in: 1, 4

• AV block greater than first degree
• SA node dysfunction
• Decompensated systolic heart failure
• Hypotension
• Reactive airway disease/bronchospasm
• Pre-excited atrial fibrillation/flutter (Wolff-Parkinson-White syndrome)

Important Adverse Effects

Hypotension is the most frequent side effect requiring vigilant monitoring, occurring in approximately 31% of patients receiving IV metoprolol. 5

• Other effects include bradycardia, bronchospasm, and heart failure exacerbation 1
• Hypotension is typically transient and readily managed 5

Special Populations

Pregnant Patients

• IV metoprolol is reasonable for acute SVT treatment when adenosine is ineffective or contraindicated (Class IIa, Level C-LD) 3
• Oral metoprolol is effective for ongoing management in pregnant patients with highly symptomatic SVT (Class IIa, Level C-LD) 3

CYP2D6 Poor Metabolizers

• Poor metabolizers (8% of Caucasians, 2% of other populations) exhibit several-fold higher plasma concentrations and prolonged half-life (7-9 hours vs 3-4 hours) 2
• This decreases cardioselectivity and increases risk of beta-2 blockade effects 2
• Consider lower starting doses in these patients 2

Clinical Decision Algorithm

For acute SVT:

1. Use IV metoprolol tartrate (only available IV formulation)
2. Administer 2-5 mg IV over 2 minutes, may repeat every 5 minutes up to 15-20 mg total
3. Monitor for hypotension and bradycardia continuously

For chronic SVT management:

1. If patient prefers once-daily dosing → metoprolol succinate 50-400 mg QD
2. If patient needs flexible dosing or has compliance concerns → metoprolol tartrate 25-100 mg BID
3. Both achieve equivalent beta-blockade; choice based on convenience and patient preference

Conversion from IV to oral:

• Oral-to-IV dose ratio is approximately 2.5:1 2
• After IV loading, transition to oral formulation at appropriate equivalent dose

Common Pitfalls

• Do not use metoprolol as first-line for acute SVT—vagal maneuvers and adenosine should be attempted first 3
• Do not confuse formulations—succinate cannot be given IV for acute treatment 1
• Do not use in pre-excited atrial fibrillation—may paradoxically increase ventricular response 1, 4
• Monitor for excessive bradycardia when combining with other rate-controlling agents 1