Maximum Dose of Cardizem (Diltiazem) Drip
The maximum recommended intravenous infusion rate for Cardizem (diltiazem) drip is 15 mg/hour, with a maximum duration of 24 hours and a total dose not exceeding 2.2 g over 24 hours. 1, 2
Dosing Protocol for IV Diltiazem
Initial Bolus Dose
- Start with 0.25 mg/kg actual body weight administered over 2 minutes (approximately 20 mg for average patient) 1
- If response is inadequate after 15 minutes, administer second bolus of 0.35 mg/kg over 2 minutes (approximately 25 mg for average patient) 1
- Some patients may respond to a lower initial dose of 0.15 mg/kg, though duration of action may be shorter 1
Continuous Infusion
- Initial infusion rate: 10 mg/hour 1
- Some patients may maintain response at 5 mg/hour 1
- Titration: Increase in 5 mg/hour increments as needed 1
- Maximum infusion rate: 15 mg/hour 1
- Maximum duration: 24 hours 1
- Maximum total dose over 24 hours: 2.2 g 2
Dilution Guidelines
| Diluent Volume | Quantity of Diltiazem | Final Concentration | Infusion Rate for 10 mg/h | Infusion Rate for 15 mg/h |
|---|---|---|---|---|
| 100 mL | 125 mg (25 mL) | 1 mg/mL | 10 mL/h | 15 mL/h |
| 250 mL | 250 mg (50 mL) | 0.83 mg/mL | 12 mL/h | 18 mL/h |
| 500 mL | 250 mg (50 mL) | 0.45 mg/mL | 22 mL/h | 33 mL/h |
Monitoring During Infusion
- Continuous cardiac monitoring is necessary to assess for bradycardia or conduction abnormalities 3
- Monitor blood pressure for hypotension 3
- Watch for signs of fluid retention (edema) 3
- Monitor for common side effects: hypotension, dizziness, flushing, bradycardia 3
Important Precautions and Contraindications
Diltiazem is contraindicated in patients with:
- Left ventricular dysfunction (LVEF <40%)
- Decompensated heart failure
- AV block greater than first degree
- Sick sinus syndrome
- Cardiogenic shock
- Pre-excitation syndromes (e.g., Wolff-Parkinson-White syndrome) 3
Avoid using diltiazem in combination with beta-blockers due to increased risk of bradycardia and heart block 3
Clinical Pearls
- Lower doses of diltiazem (≤0.2 mg/kg) may be as effective as standard doses while reducing the risk of hypotension 4
- Diltiazem shows dose-dependent, non-linear pharmacokinetics, which means higher doses may result in disproportionately higher plasma concentrations 1, 5
- For transition to oral therapy, the median oral dose of diltiazem CD is 300 mg/day after IV infusion at 10 mg/hour 6
Remember that exceeding the maximum recommended infusion rate of 15 mg/hour or duration beyond 24 hours has not been studied and is not recommended due to potential safety concerns 1.