What is the recommended dose of diltiazem for a patient with atrial fibrillation (Afib) with rapid ventricular response (RVR)?

Diltiazem Dosing for Atrial Fibrillation with Rapid Ventricular Response

The recommended dose of diltiazem for atrial fibrillation with rapid ventricular response is an initial bolus of 0.25 mg/kg actual body weight administered over 2 minutes (approximately 20 mg for an average patient), followed by a continuous infusion starting at 10 mg/hour, titrated up to 15 mg/hour as needed. 1

Initial Bolus Administration

• For initial control, administer diltiazem 0.25 mg/kg actual body weight as an intravenous bolus over 2 minutes (20 mg is reasonable for an average-sized patient) 1
• If response is inadequate after 15 minutes, a second bolus dose of 0.35 mg/kg actual body weight (approximately 25 mg) may be administered 1
• Some patients may respond to a lower initial dose of 0.15 mg/kg, though the duration of action may be shorter 1, 2
• Recent research suggests that lower doses (≤0.2 mg/kg) may be as effective as standard doses while reducing the risk of hypotension 2

Continuous Infusion

• Following bolus administration, begin a continuous infusion at 10 mg/hour 1
• The infusion rate may be increased in 5 mg/hour increments up to 15 mg/hour as needed for heart rate control 1, 3
• Some patients may maintain response to a lower initial infusion rate of 5 mg/hour 1
• The infusion should not exceed 24 hours, and rates greater than 15 mg/hour are not recommended 1

Monitoring and Target Heart Rate

• Monitor heart rate and blood pressure continuously during administration 3
• Target heart rate should be 60-80 beats per minute at rest 3
• Clinical improvement is defined as a heart rate decrease by 20% or to less than 100 bpm 4
• Overall efficacy of diltiazem in controlling ventricular response is approximately 94% with appropriate dosing 5

Precautions and Contraindications

• Avoid diltiazem in patients with:

  • Heart failure with reduced ejection fraction (LVEF ≤40%) due to negative inotropic effects 6
  • AV block greater than first degree or SA node dysfunction (in absence of pacemaker) 7
  • Hypotension 7
  • Wolff-Parkinson-White (WPW) syndrome with AF/atrial flutter 7

• Use with caution when combined with:

  • Beta-blockers due to additive effects on heart rate and blood pressure 3
  • Medications that are CYP3A4 substrates, as diltiazem is a moderate CYP3A4 inhibitor 7

Alternative Agents

• In patients with heart failure with reduced ejection fraction, use:
  • Beta-blockers (metoprolol, esmolol, propranolol) as first-line agents 6
  • Digoxin as an alternative for patients with heart failure 7
  • Amiodarone for patients with hemodynamic instability or severely reduced LVEF 6

Clinical Pearls

• Strict adherence to dosing protocols is associated with better outcomes and fewer adverse events 4
• Weight-based dosing (≥0.13 mg/kg) has been shown to achieve heart rate control more quickly than fixed low doses 8
• Hypotension is the most common adverse effect, occurring in 18-42% of patients depending on the dose used 2
• For patients with thyrotoxicosis and AF, a beta blocker is first-line therapy, with diltiazem as an alternative when beta blockers are contraindicated 7