What is the dosage of Verapamil (calcium channel blocker) for treating supraventricular tachycardia (SVT)?

Verapamil Dosage for Supraventricular Tachycardia (SVT)

For SVT treatment, verapamil should be administered as a 2.5-5 mg IV bolus over 2 minutes (over 3 minutes in older patients), with additional doses of 5-10 mg every 15-30 minutes to a maximum total dose of 20-30 mg if needed. 1, 2

Initial Management Algorithm

• First attempt vagal maneuvers in hemodynamically stable patients with SVT 1
• Adenosine is the preferred first-line pharmacological agent for acute termination of PSVT due to its rapid action and short half-life 3
• If adenosine fails or is contraindicated, verapamil is an appropriate second-line agent 1, 3

Verapamil Dosing Protocol

Adult Dosing

• Initial dose: 2.5-5 mg IV bolus administered over 2 minutes (3 minutes in elderly patients) 1, 2
• If no response: Additional doses of 5-10 mg may be given every 15-30 minutes 1
• Maximum total dose: 20 mg (alternative regimen allows up to 30 mg) 1
• FDA-approved dosing: 5-10 mg (0.075-0.15 mg/kg) IV bolus over at least 2 minutes 2
• Repeat dose: 10 mg (0.15 mg/kg) 30 minutes after first dose if initial response inadequate 2

Special Populations

• Elderly patients: Administer over at least 3 minutes to minimize risk of hypotension 2
• Pediatric patients (not first-line therapy):
  • 0-1 year: 0.1-0.2 mg/kg (usual range: 0.75-2 mg) 2
  • 1-15 years: 0.1-0.3 mg/kg (usual range: 2-5 mg, not to exceed 5 mg as single dose) 2

Administration Requirements

• Administer ONLY by slow intravenous injection 2
• Continuous ECG and blood pressure monitoring is mandatory during administration 2
• Inspect solution visually for particulate matter before administration 2
• Do not dilute with Sodium Lactate Injection in polyvinyl chloride bags 2

Important Precautions and Contraindications

• Do NOT administer verapamil for wide-complex tachycardias unless known with certainty to be supraventricular in origin 1, 4, 5
• Verapamil is contraindicated in:
  • Wolff-Parkinson-White syndrome with atrial fibrillation/flutter 1, 3
  • Impaired ventricular function or heart failure 1, 3
  • AV block greater than first degree 3
  • SA node dysfunction (without pacemaker) 3
  • Hypotension or cardiogenic shock 3, 4
  • Patients who have recently received β-blockers (risk of profound bradycardia and hypotension) 1

Potential Adverse Effects

• Hypotension is the most common adverse effect 3, 4
• Severe hypotension requiring immediate cardioversion has been reported in patients with ventricular tachycardia misdiagnosed as SVT 4, 5
• Worsening heart failure in patients with pre-existing ventricular dysfunction 3
• Bradycardia and pulmonary edema in patients with hypertrophic cardiomyopathy 3

Clinical Pearl

• Consider calcium pretreatment (1g IV calcium chloride) before verapamil administration to minimize hypotensive effects without compromising antiarrhythmic efficacy 6, 7
• After successful termination of SVT with verapamil, the arrhythmia may still be reinducible, suggesting the need for maintenance therapy 8