From the Guidelines
The dose of Cardizem (Diltiazem) for atrial fibrillation (afib) is 15 mg to 20 mg (0.25 mg/kg) IV over 2 minutes, with an additional dose of 20 mg to 25 mg (0.35 mg/kg) if needed, and a maintenance infusion dose of 5 mg/hour to 15 mg/hour, titrated to heart rate.
Diltiazem Dosing
- The initial dose is given as an IV bolus over 2 minutes, with a possible additional dose in 15 minutes if needed 1.
- The maintenance infusion dose is titrated to heart rate, with a range of 5 mg/hour to 15 mg/hour 1.
Important Considerations
- Diltiazem should be used with caution in patients with impaired ventricular function or heart failure, as it can have negative inotropic effects and reduce cardiac output 1.
- Caution is advised when encountering pre-excited atrial fibrillation or flutter, as treatment with AV nodal blocking agents, including diltiazem, is unlikely to slow the ventricular rate and may accelerate the ventricular response 1.
From the Research
Diltiazem Dosing for Atrial Fibrillation
- The dose of Cardizem (Diltiazem) for atrial fibrillation (afib) can vary depending on the patient's condition and the dosing strategy used.
- According to a study published in 2019 2, a 0.25mg/kg dose of diltiazem (maximum of 20mg) was used for stable, symptomatic patients in AFIB with RVR at a rate of >150 beats per minute (bpm) with a narrow complex.
- Another study published in 2018 3 compared the incidence of treatment failure between oral (PO) immediate release and IV continuous infusion diltiazem after an initial IV diltiazem loading dose in patients in AFIB with RVR, and found that the median dose of PO diltiazem and IV continuous infusion diltiazem at four hours was 30 mg and 10 mg/h, respectively.
- A study published in 2016 4 compared weight-based dose vs. standard dose diltiazem in patients with atrial fibrillation presenting to the emergency department, and found that the standard dose of 10 mg was noninferior to the weight-based dose of 0.2-0.3 mg/kg.
- A more recent study published in 2021 5 investigated diltiazem administration in a community ED and found that patients treated with ≥ 0.13 mg/kg diltiazem achieved an HR < 100 bpm at a mean time of 169 minutes compared to 318 minutes for < 0.13 mg/kg.
- An older study published in 1995 6 examined the efficacy of various doses of intravenous diltiazem to control the ventricular response during atrial fibrillation or atrial flutter, and found that 94% of patients responded to the bolus dose with a > 20% reduction in heart rate from baseline, a conversion to sinus rhythm, or a heart rate < 100 beats/min.
Key Findings
- Weight-based dosing of diltiazem may be more effective than standard dosing in achieving heart rate control in patients with AFIB with RVR.
- The optimal dose of diltiazem for AFIB with RVR is still a matter of debate, and may depend on individual patient factors and the specific clinical context.
- Intravenous diltiazem can be effective in controlling the ventricular response during atrial fibrillation or atrial flutter, with response rates ranging from 47% to 76% depending on the dose and infusion rate used.