What is the oral dose of verapamil (calcium channel blocker) for maintenance therapy in patients with supraventricular tachycardia?

Oral Verapamil Dosage for Maintenance Therapy in SVT

The recommended oral maintenance dose of verapamil for supraventricular tachycardia (SVT) is 120-480 mg daily in divided or single doses with long-acting formulations. 1

Dosing Guidelines

According to the 2015 ACC/AHA/HRS guideline for the management of adult patients with supraventricular tachycardia, verapamil dosing should follow this pattern:

• Initial daily dose: 120 mg daily in divided or single dose with long-acting formulations
• Maintenance dose: Up to 480 mg daily in divided or single dose with long-acting formulations 1

Clinical Evidence and Recommendations

Verapamil is a first-line medication for ongoing management of SVT, particularly in patients who are not candidates for or prefer not to undergo catheter ablation. The ACC/AHA/HRS guidelines give oral verapamil a Class I, Level B-R recommendation for ongoing management of AVNRT (atrioventricular nodal reentrant tachycardia), which is a common form of SVT. 1

Clinical studies have demonstrated that:

• Verapamil is well-tolerated and effective for long-term management of SVT 2
• In a double-blind randomized trial, verapamil significantly reduced both frequency and duration of paroxysmal SVT episodes 2
• The median effective dose in comparative studies was approximately 240 mg/day 3

Administration Considerations

• Verapamil can be administered as a single daily dose using long-acting formulations, or divided into multiple doses
• When initiating therapy, start with the lower recommended dose (120 mg daily) and titrate based on response
• For patients with infrequent, well-tolerated episodes, a "pill-in-the-pocket" approach may be considered 4

Precautions and Contraindications

Verapamil should be used with caution or avoided in patients with:

• AV block greater than first degree or SA node dysfunction (in absence of pacemaker)
• Decompensated systolic heart failure/severe LV dysfunction
• Hypotension
• WPW with atrial fibrillation/flutter
• Concomitant use of dofetilide (contraindicated) 1

Drug Interactions

Verapamil is a moderate CYP3A4 inhibitor and P-glycoprotein inhibitor, potentially interacting with:

• Dofetilide (contraindicated)
• Anticoagulants (dabigatran, edoxaban, rivaroxaban)
• Other cardiovascular medications (flecainide, ivabradine, ranolazine)
• Statins (simvastatin)
• Various other medications including immunosuppressants and antineoplastics 1

Alternative Options

If verapamil is not suitable, other options for maintenance therapy include:

• Diltiazem (120-360 mg daily)
• Beta blockers
• Catheter ablation (considered first-line therapy for symptomatic AVNRT with >95% success rate) 1

Monitoring

When initiating verapamil therapy, monitor for:

• Bradyarrhythmias
• Hypotension
• Signs of heart failure exacerbation in patients with pre-existing ventricular dysfunction
• Potential drug interactions

Remember that while pharmacological therapy is effective, catheter ablation offers a potentially curative approach with success rates >95% and should be considered as a first-line option for symptomatic patients 1, 4.