What is the appropriate dosage of Diltiazem for rate control in atrial flutter?

Diltiazem Dosage for Rate Control in Atrial Flutter

For rate control in atrial flutter, diltiazem should be administered intravenously at an initial dose of 0.25 mg/kg (approximately 15-20 mg) over 2 minutes, followed by an additional 0.35 mg/kg (approximately 20-25 mg) after 15 minutes if needed, and then maintained with a continuous infusion of 5-15 mg/hour titrated to heart rate response. 1, 2

Initial Bolus Dosing

• Initial IV bolus: 0.25 mg/kg (typically 15-20 mg) administered over 2 minutes 2
• If response is inadequate after 15 minutes, a second bolus of 0.35 mg/kg (typically 20-25 mg) can be administered over 2 minutes 2
• For patients with low body weight, strict adherence to weight-based dosing (mg/kg) is recommended 2

Continuous Infusion

• Begin at 10 mg/hour immediately following successful bolus administration 2
• Some patients may respond to a lower initial rate of 5 mg/hour 2
• Titrate in 5 mg/hour increments up to a maximum of 15 mg/hour as needed for adequate rate control 2
• Infusion can be maintained for up to 24 hours (longer durations have not been studied) 2

Efficacy and Response

• Overall response rate with IV diltiazem is approximately 93-94% of patients with atrial flutter 3
• Median time to maximal heart rate reduction is approximately 4.3 minutes 3
• A plasma diltiazem concentration of approximately 172 ng/ml is required to produce a 30% reduction in heart rate 4

Transition to Oral Therapy

• For continued rate control beyond 24 hours, transition to oral diltiazem CD (long-acting)
• Typical oral dosing is 180-360 mg daily, with 300 mg/day being the median effective dose 5
• Administer oral diltiazem 4 hours before discontinuing IV infusion to ensure smooth transition 5
• Approximately 77% of patients maintain adequate rate control during transition from IV to oral therapy 5

Precautions and Monitoring

• Monitor blood pressure closely as hypotension is a common side effect (occurs in approximately 7% of patients) 3
• Avoid in patients with:
  • Pre-excited atrial flutter (risk of accelerated ventricular rates) 1
  • Decompensated heart failure 1
  • Severe hypotension (systolic BP <90 mmHg)
• Beta blockers are generally preferred for rate control in patients with heart failure 6
• QT interval monitoring is essential, especially when combining with other antiarrhythmic medications 6

Alternative Rate Control Agents

• Beta blockers (if diltiazem is contraindicated):
  • Esmolol: 500 mcg/kg bolus over 1 minute, followed by 50-300 mcg/kg/min infusion 1
  • Metoprolol: 2.5-5 mg IV bolus over 2 minutes, up to 3 doses 1
• Verapamil: 2.5-5 mg IV over 2 minutes, may repeat 5-10 mg every 15-30 minutes to total dose of 20-30 mg 1

Common Pitfalls

• Overdosing is common in emergency settings and can lead to hypotension 7
• Failure to adjust dose based on patient weight can lead to adverse effects
• Inadequate monitoring during transition from IV to oral therapy
• Using diltiazem in patients with pre-excited atrial flutter or decompensated heart failure
• Exceeding the maximum recommended infusion rate of 15 mg/hour or duration of 24 hours 2

Remember that while rate control is an important strategy for managing atrial flutter, catheter ablation of the cavotricuspid isthmus is often the preferred definitive treatment for symptomatic or refractory atrial flutter 1.