What is the recommended oral dose of verapamil (Calaptin) for supraventricular tachycardia (SVT)?

Recommended Oral Verapamil (Calaptin) Dosage for SVT

For ongoing management of supraventricular tachycardia (SVT), the recommended oral dose of 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

Dosing Protocol and Titration

• Initial oral dose should be 120 mg daily for patients with symptomatic SVT 1, 2
• Dose can be gradually increased based on clinical response and tolerability 1
• Maximum recommended daily dose is 480 mg, which has been demonstrated effective in randomized controlled trials 3, 1
• For sustained-release formulations (Calan SR), once-daily dosing may be appropriate for better patient compliance 4

Mechanism of Action and Efficacy

• Verapamil works by slowing AV node conduction and increasing AV node refractoriness, which helps terminate and prevent SVT 1
• Oral verapamil has been shown to significantly reduce both frequency and duration of SVT episodes in clinical trials 5
• In long-term studies, verapamil reduced SVT episodes from 0.3 to 0.1 episodes per day (by patient diary) and from 0.7 to 0.3 episodes per day (by Holter monitor) 5
• Sustained-release verapamil at 240 mg once daily has demonstrated effectiveness for long-term prophylaxis with better patient compliance 4

Important Contraindications and Precautions

• Verapamil is contraindicated in patients with:

  • AV block greater than first degree 1, 6
  • SA node dysfunction (unless pacemaker present) 1
  • Decompensated heart failure or severe LV dysfunction 1, 6
  • Hypotension 1
  • Wolff-Parkinson-White (WPW) syndrome with atrial fibrillation/flutter 1, 6
  • Cardiogenic shock 1

• Common adverse effects to monitor:

  • Hypotension (most common adverse effect) 1, 2
  • Bradycardia 2
  • Constipation 5
  • Worsening heart failure in patients with pre-existing ventricular dysfunction 1, 6

Alternative Management Options

• For acute termination of SVT, vagal maneuvers should be attempted first before considering medications 1, 2
• If oral therapy is not preferred, EP study with ablation is a definitive treatment option with high success rates 3
• Beta blockers or diltiazem are alternative oral agents for ongoing management of SVT 3
• Note that oral verapamil tablets are not recommended for acute termination of SVT episodes due to poor absorption during tachycardia (gastric emptying is significantly delayed during SVT) 7

Monitoring and Follow-up

• Regular assessment of heart rate and blood pressure is recommended during dose titration 2
• ECG monitoring is advised to ensure effectiveness and detect potential conduction abnormalities 3
• Patients should be educated on how to perform vagal maneuvers as complementary management for acute episodes 3