What is the recommended dose of calcium channel blockers (CCBs) for managing paroxysmal supraventricular tachycardia (PSVT)?

Recommended Dosing of Calcium Channel Blockers for PSVT Management

For verapamil, administer 2.5-5 mg IV bolus over 2 minutes (3 minutes in older patients), with repeated doses of 5-10 mg every 15-30 minutes to a maximum total dose of 20 mg if needed. 1

Initial IV Calcium Channel Blocker Dosing

Verapamil

• Initial dose: 2.5-5 mg IV bolus over 2 minutes (3 minutes in older patients)
• Repeat dose: 5-10 mg every 15-30 minutes if no response
• Maximum total dose: 20 mg
• Alternative regimen: 5 mg bolus every 15 minutes to a total dose of 30 mg 1

Diltiazem

• Initial dose: 15-20 mg (0.25 mg/kg) IV over 2 minutes
• Repeat dose: 20-25 mg (0.35 mg/kg) after 15 minutes if needed
• Maintenance infusion: 5-15 mg/hour, titrated to heart rate 1

Administration Considerations

• Administer as a slow IV injection under continuous ECG and blood pressure monitoring 2
• Inspect solution visually for particulate matter before administration
• Use only if solution is clear and vial seal is intact
• Discard unused solution immediately after withdrawal 2

Patient Selection and Contraindications

Calcium channel blockers should be avoided in:

• Pre-excited atrial fibrillation or flutter (may accelerate ventricular response) 1, 3
• Patients with ventricular tachycardia
• Significant LV dysfunction
• Increased risk for cardiogenic shock
• PR interval >0.24 seconds
• Second or third-degree AV block without pacemaker 3

Treatment Algorithm for PSVT

1. First-line treatment (hemodynamically stable patients):

   • Vagal maneuvers (43% effective) 4
   • IV adenosine (91% effective) 4

2. Second-line treatment (if adenosine fails):

   • Non-dihydropyridine calcium channel blockers (verapamil or diltiazem) 1
   • Beta blockers (metoprolol, esmolol) 1

3. For hemodynamically unstable patients:

   • Immediate synchronized cardioversion 3, 4

Efficacy Considerations

• Calcium channel blockers have shown high efficacy rates (98%) in terminating PSVT 5
• Slow infusion of calcium channel blockers has demonstrated comparable safety to adenosine with higher conversion rates (98% vs 86.5%) 5
• Diltiazem has shown superior efficacy compared to esmolol in terminating PSVT (100% vs 25%) 6

Safety Considerations

• Avoid combination with other AV nodal blocking agents with longer half-lives (can cause profound bradycardia) 1
• Monitor for hypotension, especially with rapid administration
• Use caution in patients with asthma, obstructive pulmonary disease, or congestive heart failure 1
• Dihydropyridine CCBs (like nifedipine) should be avoided for PSVT treatment 3

Long-term Management

For patients with recurrent PSVT requiring ongoing management:

• Oral beta blockers, calcium channel blockers (verapamil/diltiazem), or class IC antiarrhythmics 3
• Consider "pill-in-the-pocket" approach with oral beta blockers, diltiazem, or verapamil for infrequent, well-tolerated episodes 1
• Catheter ablation is highly effective (94-98% success rate) for definitive treatment 4

By following these dosing recommendations and treatment algorithm, clinicians can effectively manage PSVT while minimizing risks of adverse events.