What is the dosing range for diltiazem (calcium channel blocker) infusion in rapid atrial fibrillation?

Diltiazem Infusion Dosing for Rapid Atrial Fibrillation

For rapid atrial fibrillation, diltiazem infusion should be initiated with a bolus dose of 0.25 mg/kg (15-20 mg) IV over 2 minutes, followed by a continuous infusion of 5-15 mg/hour, which can be maintained for up to 24 hours. 1, 2

Initial Bolus Dosing

• Initial bolus: 0.25 mg/kg (15-20 mg) IV over 2 minutes
• If inadequate response after 15 minutes: Second bolus of 0.35 mg/kg (20-25 mg) IV over 2 minutes 1, 2
• Lower initial dose of 0.15 mg/kg may be considered in patients at risk for hypotension 2, 3

Continuous Infusion Protocol

1. Start at 5-10 mg/hour immediately following bolus administration
2. Titrate in 5 mg/hour increments as needed for heart rate control
3. Maximum recommended infusion rate: 15 mg/hour 1, 2
4. Maximum duration: 24 hours (longer durations have not been studied) 2

Monitoring During Infusion

• Target heart rate: <100 beats/min or ≥20% reduction from baseline 4
• Blood pressure: Monitor for hypotension (more common with higher doses) 3
• Continuous cardiac monitoring is essential 5
• Assess for signs of heart failure exacerbation 1

Pharmacokinetics and Dose Considerations

• Elimination half-life: 6.8-6.9 hours 6
• Diltiazem shows dose-dependent, non-linear pharmacokinetics 2, 6
• Pharmacodynamic studies show strong correlation between plasma concentration and heart rate reduction 6

Important Cautions and Contraindications

• Avoid in patients with:
  • Decompensated heart failure 1
  • Pre-excited atrial fibrillation (Wolff-Parkinson-White syndrome) 1
  • Severe hypotension
• Consider lower doses (≤0.2 mg/kg) in elderly patients or those at risk for hypotension, as efficacy remains similar with fewer adverse effects 3

Transition to Oral Therapy

• After achieving rate control with IV diltiazem, transition to oral therapy
• Oral diltiazem can maintain rate control in approximately 77% of patients 7
• Typical oral maintenance dose: 120-360 mg daily (extended release) 1

Remember that diltiazem infusion is effective for rate control but does not convert atrial fibrillation to normal sinus rhythm in most patients. The primary goal is to achieve adequate ventricular rate control while maintaining hemodynamic stability.