Initial Dosing of IV Diltiazem for Atrial Fibrillation with Rapid Ventricular Response
The initial dose of IV diltiazem for atrial fibrillation with rapid ventricular response is 0.25 mg/kg actual body weight administered over 2 minutes (approximately 15-20 mg for an average patient). 1
Dosing Protocol
Initial Bolus
- 0.25 mg/kg actual body weight administered over 2 minutes 1, 2
- For a typical adult, this translates to approximately 15-20 mg
Follow-up Dosing
If the initial dose is inadequate after 15 minutes:
- Second bolus: 0.35 mg/kg actual body weight over 2 minutes (approximately 25 mg) 1, 2
- Some patients may respond to a lower initial dose of 0.15 mg/kg, though duration of action may be shorter 1
Continuous Infusion
If continued rate control is needed:
- Start at 5-15 mg/hour IV infusion 2, 1
- Typical starting rate: 10 mg/hour 1
- May titrate in 5 mg/hour increments up to 15 mg/hour as needed 1
- Infusion may be maintained for up to 24 hours 1
Efficacy and Safety Considerations
Efficacy
- Response rates to initial bolus dosing are high, with approximately 94% of patients achieving >20% reduction in heart rate, conversion to sinus rhythm, or heart rate <100 beats/min 3
- Target heart rate is generally considered controlled when ventricular response is between 60-80 bpm at rest and 90-115 bpm during moderate exercise 2
Safety Considerations
- Monitor for hypotension, which is a common side effect 2
- Lower doses (≤0.2 mg/kg) may provide similar efficacy with reduced risk of hypotension compared to standard doses 4
- Avoid in patients with heart failure with reduced ejection fraction (HFrEF) 2, 5
- Use caution in patients with impaired ventricular function 2
Special Populations and Considerations
Elderly or Low Body Weight
- Patients with low body weights should be dosed strictly on a mg/kg basis 1
- Consider starting at the lower end of the dosing range
Transition to Oral Therapy
- For continued rate control, oral diltiazem can be started while IV infusion is maintained
- Oral maintenance dose: 120-360 mg daily in divided doses 2
- IV infusion can be discontinued 4 hours after the first oral dose 6
Important Cautions
- Do not use in patients with pre-excited atrial fibrillation (with accessory pathway) as it may accelerate ventricular response 2
- Avoid in patients with severe hypotension, cardiogenic shock, or acute heart failure 2
- Monitor blood pressure and heart rate continuously during administration
- Have resuscitation equipment readily available due to risk of significant hypotension
By following this evidence-based dosing protocol, you can effectively manage patients with atrial fibrillation and rapid ventricular response while minimizing adverse effects.