What is the dose of Cardizem (diltiazem) bolus for atrial fibrillation (AFib) with rapid ventricular response (RVR)?

Diltiazem Bolus Dosing for Atrial Fibrillation with Rapid Ventricular Response

The recommended diltiazem bolus dose for atrial fibrillation with rapid ventricular response is 0.25 mg/kg actual body weight administered over 2 minutes (approximately 20 mg for an average patient). 1

Initial Bolus Dosing

• Initial dose: 0.25 mg/kg actual body weight over 2 minutes
• If response is inadequate after 15 minutes, a second dose of 0.35 mg/kg over 2 minutes may be administered (approximately 25 mg for an average patient) 1
• Some patients with low body weight should be dosed strictly on a mg/kg basis
• 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 bolus administration and heart rate reduction:

1. Begin continuous IV infusion at 10 mg/hour
2. Dose may be increased in 5 mg/hour increments up to 15 mg/hour as needed
3. Some patients may maintain response at a lower rate of 5 mg/hour
4. Infusion may be maintained for up to 24 hours 1

Efficacy and Safety Considerations

• Studies show that diltiazem is effective for rate control in AF with RVR, achieving the specified heart rate endpoints in approximately 54% of patients 2
• Low-dose diltiazem (≤0.2 mg/kg) may be as effective as standard dose (0.25 mg/kg) with potentially lower risk of hypotension 3
• Response to diltiazem is defined as:
  • Heart rate <100 beats/min
  • ≥20% decrease in heart rate from baseline
  • Conversion to sinus rhythm 4

Monitoring During Administration

• Monitor heart rate, blood pressure, and ECG during and after administration
• Watch for hypotension, which occurs more frequently with higher doses
• Target heart rate: 60-80 bpm at rest, <110 bpm with moderate activity 5

Potential Adverse Effects

• Hypotension (most common side effect)
• Heart block
• Heart failure exacerbation 2
• Use cautiously or avoid in patients with heart failure due to systolic dysfunction 2

Alternative Agents if Diltiazem is Ineffective or Contraindicated

• Beta blockers (IV esmolol, metoprolol, propranolol)
  • Esmolol: 500 mcg/kg IV over 1 min, then 50-200 mcg/kg/min 2
  • Metoprolol: 2.5-5 mg IV bolus over 2 min; up to 3 doses 2
• Verapamil: 0.075-0.15 mg/kg IV over 2 min 2
• Amiodarone: 150 mg IV over 10 min, then 1 mg/min for 6 hours, then 0.5 mg/min 2

Clinical Pearls

• Diltiazem has a short duration of action when given as a bolus, often requiring continuous infusion to maintain rate control
• Non-dihydropyridine calcium channel antagonists like diltiazem are the only agents associated with improved quality of life and exercise tolerance in AF patients 2
• Diltiazem shows dose-dependent, non-linear pharmacokinetics 1
• Recent research suggests that lower doses (0.13-0.2 mg/kg) may be effective while potentially reducing hypotension risk 6, 7

By following these evidence-based dosing recommendations, you can effectively manage atrial fibrillation with rapid ventricular response while minimizing the risk of adverse effects.