What is the dosing for diltiazem (a calcium channel blocker) bolus for rapid atrial fibrillation?

Diltiazem Bolus Dosing for Rapid Atrial Fibrillation

The recommended dosing for diltiazem bolus in rapid atrial fibrillation is 0.25 mg/kg IV over 2 minutes, with a possible second dose of 0.35 mg/kg IV over 2 minutes if response is inadequate after 15 minutes. 1

Initial Bolus Dosing

• First dose: 0.25 mg/kg IV administered over 2 minutes (approximately 20 mg for average adult) 2, 1
• If inadequate response after 15 minutes, administer second dose: 0.35 mg/kg IV over 2 minutes (approximately 25 mg for average adult) 1
• Some patients may respond to a lower initial dose of 0.15 mg/kg, though duration of action may be shorter 1

Continuous Infusion Following Bolus

After successful rate control with bolus administration:

• Start infusion at 5-15 mg/hour 2, 1
• Recommended initial rate: 10 mg/hour 1
• May increase in 5 mg/hour increments up to maximum of 15 mg/hour as needed 1
• Infusion can be maintained for up to 24 hours 1

Efficacy and Safety Considerations

• Recent research suggests that lower doses (≤0.2 mg/kg) may be as effective as standard doses (>0.2 to ≤0.3 mg/kg) with significantly lower rates of hypotension (18% vs 34.9%) 3
• Higher doses (≥0.13 mg/kg) achieve heart rate control more quickly than lower doses (<0.13 mg/kg) - 169 minutes vs 318 minutes 4
• Diltiazem shows dose-dependent, non-linear pharmacokinetics with an elimination half-life of approximately 6.8-6.9 hours 5

Monitoring During Administration

• Continuous ECG monitoring
• Frequent blood pressure measurements
• Heart rate assessment
• Monitor for signs of heart failure, especially in patients with reduced ejection fraction

Contraindications and Precautions

• Avoid in patients with:
  • Decompensated heart failure 2
  • Pre-excitation syndrome with atrial fibrillation 2
  • Hypotension
  • Severe left ventricular dysfunction
  • Cardiogenic shock

Transition to Oral Therapy

• Oral long-acting diltiazem (120-360 mg daily in divided doses) can be initiated while IV infusion continues 2
• IV infusion can be discontinued approximately 4 hours after first oral dose 6
• Approximately 77% of patients maintain heart rate control during transition from IV to oral therapy 6

Common Pitfalls to Avoid

1. Administering diltiazem too rapidly (faster than over 2 minutes), increasing risk of hypotension
2. Using diltiazem in patients with pre-excitation syndromes (e.g., WPW) and atrial fibrillation
3. Failing to monitor blood pressure closely during administration
4. Using in patients with decompensated heart failure or severe left ventricular dysfunction

Diltiazem is a Class I, Level of Evidence B recommendation for heart rate control in atrial fibrillation without accessory pathway 2, and has been associated with improved quality of life and exercise tolerance compared to other rate control agents 2.