What is the recommended dose of diltiazem (calcium channel blocker) for rate control of atrial fibrillation (AFib) in the Emergency Room (ER)?

Diltiazem Dosing for Rate Control of Atrial Fibrillation in the Emergency Room

The recommended dose of diltiazem for rate control of atrial fibrillation in the ER is an initial IV bolus of 0.25 mg/kg actual body weight administered over 2 minutes, followed by a second dose of 0.35 mg/kg after 15 minutes if needed, and then a continuous infusion of 5-15 mg/hour for ongoing rate control. 1

Initial Bolus Dosing

• For the average patient, 20 mg is a reasonable initial bolus dose (equivalent to 0.25 mg/kg) administered over 2 minutes 1
• If response is inadequate after 15 minutes, a second bolus dose of 0.35 mg/kg (approximately 25 mg for the average patient) should be administered over 2 minutes 1, 2
• Some patients may respond to a lower initial dose of 0.15 mg/kg, although duration of action may be shorter with this dose 1
• Low-dose diltiazem (≤0.2 mg/kg) has been shown to be as effective as standard dosing (0.25 mg/kg) with potentially lower rates of hypotension (18% vs 34.9%) 3

Continuous Infusion

• Following successful bolus administration, begin a continuous IV infusion at 10 mg/hour 1, 2
• Some patients may maintain response to a lower initial infusion rate of 5 mg/hour 1
• The infusion rate can be increased in 5 mg/hour increments up to a maximum of 15 mg/hour as needed for further heart rate reduction 1
• Continuous infusion can be maintained for up to 24 hours; infusion duration exceeding 24 hours and rates exceeding 15 mg/hour are not recommended 1

Monitoring and Efficacy Assessment

• Target heart rate should be <80 bpm (strict control) or <110 bpm (lenient control) depending on the patient's symptoms 2
• Monitor heart rate, blood pressure, and symptoms during administration 2
• Diltiazem has been shown to be highly effective, with response rates of 93-94% in clinical studies 4
• The median time to maximal decrease in heart rate is approximately 4.3 minutes after administration 4

Important Precautions

• Diltiazem should not be used in patients with:
  • Decompensated heart failure 2
  • Pre-excitation syndromes (e.g., Wolff-Parkinson-White) 2
  • Severe hypotension (systolic BP <90 mmHg) 4
• Monitor for hypotension, which occurs in approximately 18-42% of patients depending on dosing 3
• Weight-based dosing (≥0.13 mg/kg) has been associated with improved time to heart rate control compared to fixed low doses without significant differences in hypotension rates 5

Dilution for IV Administration

• For continuous infusion, diltiazem can be prepared in various concentrations:
  • 125 mg in 100 mL (1 mg/mL)
  • 250 mg in 250 mL (0.83 mg/mL)
  • 250 mg in 500 mL (0.45 mg/mL) 1
• Diluted solution should be refrigerated until use and used within 24 hours 1

Alternative Rate Control Options

• If diltiazem is contraindicated or ineffective, consider:
  • IV beta-blockers (e.g., metoprolol 2.5-5 mg IV bolus over 2 min, up to 3 doses) 2
  • IV verapamil (0.075-0.15 mg/kg IV bolus over 2 min) 2
  • IV amiodarone (300 mg IV over 1 hour, then 10-50 mg/hour) for critically ill patients without pre-excitation 2