What are the recommended intravenous and oral doses of calcium channel blockers and beta‑blockers for rate or rhythm control in a hemodynamically stable adult with documented supraventricular tachycardia?

Dosing of Calcium Channel Blockers and Beta-Blockers for SVT

For hemodynamically stable adults with documented SVT, intravenous diltiazem 0.25 mg/kg (typically 15-20 mg) over 2 minutes is the preferred calcium channel blocker, with verapamil 5-10 mg IV over 2 minutes as an alternative; for beta-blockers, metoprolol 2.5-5 mg IV over 2 minutes (up to 15 mg total) or esmolol 500 mcg/kg bolus followed by infusion are the recommended options. 1, 2

Intravenous Calcium Channel Blocker Dosing

Diltiazem (Preferred CCB)

• Initial bolus: 0.25 mg/kg (typically 15-20 mg) IV administered over 2 minutes 1, 2
• Second bolus if needed: 0.35 mg/kg (20-25 mg) IV given 15 minutes after the first dose if rhythm remains uncontrolled 1
• Maintenance infusion: 5-15 mg/hour IV, titrated to heart rate control 1, 2
• Efficacy: Achieves conversion in 64-98% of stable SVT cases 2, 3

Verapamil (Alternative CCB)

• Initial bolus: 5-10 mg (0.075-0.15 mg/kg) IV over 2 minutes 1
• Second bolus if needed: Additional 10 mg (0.15 mg/kg) given 30 minutes after first dose if no response 1
• Maintenance infusion: 0.005 mg/kg/min 1
• Efficacy: Similar conversion rates to diltiazem (64-98%) 2, 3

Intravenous Beta-Blocker Dosing

Metoprolol (Most Common)

• Dosing: 2.5-5 mg IV bolus over 1-2 minutes 1
• Repeat dosing: Can repeat 2.5-5 mg every 5-10 minutes up to maximum total dose of 15 mg 1, 3
• Evidence level: Class IIa recommendation (reasonable option) 3

Esmolol (Preferred for Titratability)

• Loading dose: 500 mcg/kg (0.5 mg/kg) IV over 1 minute 1
• Maintenance infusion: Start at 50 mcg/kg/min (0.05 mg/kg/min) 1
• Titration: If inadequate response, give second 0.5 mg/kg bolus and increase infusion to 100 mcg/kg/min; can escalate up to maximum 300 mcg/kg/min 1
• Advantage: Ultra-short half-life (2-9 minutes) allows rapid titration and reversal 1

Propranolol (Alternative)

• Dosing: 0.5-1 mg IV over 1 minute 1
• Repeat dosing: Can repeat 1 mg at 2-minute intervals up to total dose of 0.1 mg/kg (approximately 3 doses) 1

Atenolol (Less Common)

• Dosing: 5 mg IV over 5 minutes 1
• Repeat dosing: Can repeat 5 mg in 10 minutes if arrhythmia persists 1

Comparative Efficacy: CCBs vs Beta-Blockers

Calcium channel blockers are significantly more effective than beta-blockers for acute SVT termination. 2, 3

• Diltiazem and verapamil achieve 64-98% conversion rates 2, 3
• Beta-blockers have limited evidence and lower efficacy compared to CCBs 3
• In head-to-head trials, diltiazem was superior to esmolol for terminating SVT 2

Critical Treatment Algorithm

Step 1: Assess Hemodynamic Stability

• Unstable patients (hypotension, altered mental status, chest pain, acute heart failure): Proceed directly to synchronized cardioversion 1, 2, 3
• Stable patients: Proceed with pharmacologic therapy 1, 2

Step 2: First-Line Pharmacologic Therapy

1. Attempt vagal maneuvers first (Valsalva, carotid massage if no contraindications) 2, 3
2. Adenosine 6 mg rapid IV push, then 12 mg if needed (95% effective for AVNRT) 1, 2

Step 3: Second-Line Pharmacologic Therapy (If Adenosine Fails)

• Preferred: IV diltiazem 0.25 mg/kg over 2 minutes 1, 2
• Alternative: IV verapamil 5-10 mg over 2 minutes 1
• If CCB contraindicated: IV metoprolol 2.5-5 mg or esmolol 500 mcg/kg bolus 1, 3

Absolute Contraindications to Calcium Channel Blockers

Never administer CCBs in the following scenarios: 1, 2, 3

• Second- or third-degree AV block without functioning pacemaker 1, 2
• Wolff-Parkinson-White syndrome with atrial fibrillation or flutter (can precipitate ventricular fibrillation) 1, 2, 3
• Decompensated systolic heart failure or severe left ventricular dysfunction 1, 2
• Hypotension or cardiogenic shock 1, 2
• Wide-complex tachycardia of uncertain etiology (may be ventricular tachycardia) 2

Absolute Contraindications to Beta-Blockers

Avoid beta-blockers in: 1, 3

• Second- or third-degree AV block without pacemaker 1
• Decompensated heart failure or cardiogenic shock 1
• Severe reactive airway disease or active asthma 1
• Pre-excited atrial fibrillation (WPW with AF/flutter) 3

Critical Safety Pitfall: Combined AV Nodal Blockade

Concomitant use of beta-blockers with calcium channel blockers markedly increases risk of severe bradyarrhythmias, profound AV block, and heart failure exacerbation; avoidance is strongly advised. 2 If co-administration is unavoidable, intensive monitoring of heart rate and PR interval is required 2.

Oral Maintenance Dosing (For Chronic Management)

Oral Diltiazem

• Starting dose: 120 mg extended-release once daily 2
• Titration: Gradually increase over several weeks 2
• Target range: 120-360 mg daily based on symptom control 2, 3

Oral Verapamil

• Dose range: 360-480 mg/day for reducing episode frequency 3

Oral Beta-Blockers

• Metoprolol tartrate: Start 25 mg twice daily, maximum 200 mg twice daily 3
• Other options: Propranolol, atenolol, nadolol (Class I recommendation) 3

Special Clinical Scenarios

SVT with Transient ST Elevations (Ischemia)

Beta-blockers are preferred over calcium channel blockers when ischemia is present. 3

• Use IV metoprolol 2.5-5 mg every 2-5 minutes up to 15 mg total 3
• Beta-blockers reduce myocardial oxygen demand by decreasing heart rate, contractility, and blood pressure 3
• This takes priority even if ejection fraction is unknown 3

Systolic Heart Failure

• Avoid calcium channel blockers (negative inotropic effect) 1, 2, 3
• Beta-blockers are preferred for rate control in this population 3
• Consider IV amiodarone if beta-blockers contraindicated 3

Renal Dysfunction

• Beta-blocker doses require reduction in severe renal impairment 3
• Diltiazem requires caution due to hepatic and renal metabolism 1