What is the recommended dose of Calaptin SR (verapamil) for a patient with paroxysmal supraventricular tachycardia (PSVT)?

Recommended Dosing of Calan SR (Verapamil) for PSVT Patients

For patients with paroxysmal supraventricular tachycardia (PSVT), the recommended oral dose of Calan SR (verapamil) is 120 mg daily initially, which can be titrated up to a maximum of 480 mg daily in divided doses or as a single dose with long-acting formulations. 1

Acute Management of PSVT

First-Line Treatment

• Adenosine is the preferred first-line agent for acute termination of PSVT in hemodynamically stable patients due to its rapid action and short half-life 1
• For intravenous verapamil (acute setting), the recommended dose is 5-10 mg (0.075-0.15 mg/kg) IV bolus over 2 minutes 1
• If no response, an additional 10 mg (0.15 mg/kg) can be given 30 minutes after the first dose 1

Second-Line Treatment

• If adenosine fails or is contraindicated, calcium channel blockers like verapamil are effective second-line options 1
• For verapamil, the American Heart Association recommends giving a 2.5-5 mg IV bolus over 2 minutes (over 3 minutes in older patients) 1
• If there is no therapeutic response, repeated doses of 5-10 mg may be administered every 15-30 minutes to a total dose of 20 mg 1
• An alternative dosing regimen is to give a 5 mg bolus every 15 minutes to a total dose of 30 mg 1

Long-Term Oral Management

Initial Dosing

• Start with Calan SR (verapamil sustained-release) at 120 mg daily in divided doses or as a single dose with long-acting formulations 1

Maintenance Dosing

• Titrate up to a maximum of 480 mg daily in divided doses or as a single dose with long-acting formulations 1
• Effectiveness has been demonstrated in randomized controlled trials with verapamil at doses up to 480 mg/day 1

Efficacy

• Verapamil has been shown to significantly reduce the frequency and duration of PSVT episodes 2
• In a long-term, double-blind randomized trial, verapamil reduced PSVT episodes from 0.7 to 0.3 episodes per day and decreased duration from 67 minutes to just 1 minute per day 2

Important Precautions and Contraindications

Contraindications

• Verapamil should not be given to patients with:
  • AV block greater than first degree or SA node dysfunction (in absence of pacemaker) 1
  • Decompensated systolic heart failure or severe LV dysfunction 1
  • Hypotension 1
  • Wolff-Parkinson-White (WPW) syndrome with atrial fibrillation/flutter 1
  • Cardiogenic shock 1

Side Effects to Monitor

• Hypotension is the most common adverse effect 1
• Worsening heart failure in patients with pre-existing ventricular dysfunction 1
• Bradycardia 1
• Pulmonary edema in patients with hypertrophic cardiomyopathy 1
• Constipation (reported in 5 of 11 patients in one study) 2

Comparative Efficacy

• In a randomized comparison between flecainide and verapamil for PSVT, both medications were effective and well-tolerated for prevention of recurrences 3
• Verapamil has been shown to be superior to placebo for conversion of PSVT to sinus rhythm 4
• In one study, 14 of 29 patients converted to sinus rhythm after low-dose verapamil (0.075 mg/kg) and 9 of 15 after high-dose verapamil (0.15 mg/kg), compared to only 1 of 24 after placebo 4

Clinical Pearls

• Verapamil works by slowing AV node conduction and increasing AV node refractoriness 5
• Resuscitation equipment should always be available when administering IV verapamil 5
• For patients who cannot undergo or are not candidates for radiofrequency ablation, verapamil is a reasonable choice for long-term prophylaxis 3