Diltiazem Initial Dosing for Rate Control
The initial intravenous dose of diltiazem for rate control is 0.25 mg/kg (actual body weight) administered over 2 minutes, which typically translates to 15-20 mg for most adults. 1
Dosing Protocol for IV Diltiazem
- Initial bolus dose: 0.25 mg/kg IV over 2 minutes
- If inadequate response after 15 minutes, may give an additional dose of 0.35 mg/kg IV over 2 minutes
- Follow with continuous infusion of 5-15 mg/hour if needed for ongoing rate control
Clinical Applications
Diltiazem is indicated for:
- Stable narrow-complex tachycardias unresponsive to adenosine or vagal maneuvers
- Control of ventricular rate in atrial fibrillation or atrial flutter
- Management of supraventricular tachycardias
Efficacy Considerations
Recent evidence suggests that weight-based dosing is important for efficacy:
- Doses ≥0.13 mg/kg achieve heart rate control significantly faster than lower doses 2
- Heart rate control (defined as HR <100 bpm) was achieved in 61% of patients receiving ≥0.13 mg/kg compared to only 36% in those receiving <0.13 mg/kg 2
Safety Considerations
Contraindications
- Heart failure with reduced ejection fraction (HFrEF)
- Pre-excited atrial fibrillation/flutter (e.g., WPW syndrome)
- AV block greater than first degree
- Sinus node dysfunction without pacemaker
- Hypotension
- Concomitant use of other AV nodal blocking agents
Adverse Effects
- Hypotension (more common with higher doses)
- Bradycardia
- Heart block
- Worsening heart failure in patients with ventricular dysfunction
Monitoring
- Continuous cardiac monitoring during administration
- Blood pressure monitoring every 5-15 minutes during initial administration
- ECG monitoring for development of heart block
Practical Considerations
Low-dose strategy: Some evidence suggests that lower doses (≤0.2 mg/kg) may provide similar efficacy with reduced risk of hypotension 3
Transition to oral therapy:
Alternative agents if diltiazem is contraindicated:
- Beta-blockers (metoprolol, esmolol)
- Digoxin (particularly in heart failure patients)
- Amiodarone (in critically ill patients or when other agents fail)
Common Pitfalls to Avoid
- Using diltiazem in patients with heart failure with reduced ejection fraction
- Administering too rapidly (should be given over full 2 minutes)
- Failure to adjust dose based on patient weight
- Not monitoring blood pressure closely during administration
- Using in patients with accessory pathways (can precipitate ventricular fibrillation)
Remember that the recommended initial dose of 0.25 mg/kg IV over 2 minutes provides the optimal balance of efficacy and safety for most patients requiring acute rate control.