Duration of Action of Diltiazem Bolus
The duration of action of an intravenous diltiazem bolus typically lasts 1-3 hours, with maximal heart rate reduction occurring within 2-7 minutes after administration. 1
Pharmacokinetics and Pharmacodynamics
- Initial onset: Following IV bolus administration, the response usually occurs within 3 minutes 1
- Peak effect: Maximal heart rate reduction generally occurs in 2-7 minutes 1
- Duration: Heart rate reduction typically lasts 1-3 hours 1
- Plasma half-life: Approximately 3.4 hours 1
- Clearance: Diltiazem exhibits systemic clearance of approximately 65 L/h in healthy individuals, but this decreases to approximately 36 L/h in patients with atrial fibrillation or flutter 1
Clinical Applications
Atrial Fibrillation/Flutter Management
- Diltiazem is administered as a 0.25 mg/kg (typically 15-20 mg) IV bolus over 2 minutes 2, 3
- If inadequate response after 15 minutes, a second bolus of 0.35 mg/kg (20-25 mg) IV can be administered 2, 3
- Following bolus administration, a continuous infusion (5-15 mg/hour) is typically started to maintain rate control 2, 3
Supraventricular Tachycardia Management
- For PSVT, diltiazem is highly effective with a success rate of up to 100% in some studies 4
- When the first bolus is ineffective, a second bolus given after 5 minutes often succeeds 4
Important Considerations
Monitoring Requirements
- Continuous ECG monitoring is essential during and after diltiazem bolus administration 3, 1
- Blood pressure should be monitored frequently as hypotension may occur and can last 1-3 hours 1
Potential Adverse Effects
- Hypotension: If it occurs, it is generally short-lived but may last from 1-3 hours 1
- Bradycardia: Due to AV nodal blocking properties 2
- Heart failure exacerbation: In patients with pre-existing ventricular dysfunction 2, 5
Contraindications
- Avoid in patients with:
Transitioning to Oral Therapy
After achieving rate control with IV diltiazem, transition to oral therapy is often necessary:
- Oral long-acting diltiazem maintains heart rate control in approximately 77% of patients when transitioned from IV therapy 6
- Typical oral maintenance dose is 120-360 mg daily (extended release) 3
Comparison to Other Rate Control Agents
- Diltiazem acts more rapidly than digoxin, with significant heart rate reduction within 5 minutes compared to 3 hours for digoxin 7
- Unlike beta-blockers, diltiazem has direct effects on the AV node without significant effects on His-Purkinje tissue 8
In emergency situations, having a clear understanding of diltiazem's duration of action is critical for appropriate dosing and monitoring. The 1-3 hour duration of a single bolus explains why continuous infusion is typically required for sustained rate control in clinical practice.