What is the appropriate dosing of Diltiazem (diltiazem) for atrial fibrillation (afib)?

From the Guidelines

Diltiazem is commonly used for rate control in atrial fibrillation, with initial IV dosing of 0.25 mg/kg (typically 15-20 mg) administered over 2 minutes, as recommended by the most recent guidelines 1.

Key Points

• If the response is inadequate after 15 minutes, a second bolus of 0.35 mg/kg (typically 20-25 mg) can be given.
• Following the bolus, a continuous infusion may be started at 5-15 mg/hour, titrated to achieve a heart rate of 60-100 beats per minute.
• For oral maintenance therapy, immediate-release diltiazem is typically started at 30 mg four times daily or 60 mg three times daily, while extended-release formulations range from 120-360 mg once daily, depending on the specific product.
• Dosing should be individualized based on heart rate response and blood pressure, with careful monitoring for hypotension and bradycardia, as noted in the guidelines 1.

Mechanism of Action

Diltiazem works by blocking L-type calcium channels in the heart, which slows conduction through the AV node and reduces heart rate.

Special Considerations

This medication is particularly useful in patients with contraindications to beta-blockers such as those with asthma or COPD, as supported by the evidence 1.

From the FDA Drug Label

DOSAGE AND ADMINISTRATION Direct Intravenous Single Injections (Bolus) The initial dose of diltiazem hydrochloride injection should be 0. 25 mg/kg actual body weight as a bolus administered over 2 minutes (20 mg is a reasonable dose for the average patient). If response is inadequate, a second dose may be administered after 15 minutes. The second bolus dose of diltiazem hydrochloride injection should be 0. 35 mg/kg actual body weight administered over 2 minutes (25 mg is a reasonable dose for the average patient). Continuous Intravenous Infusion For continued reduction of the heart rate (up to 24 hours) in patients with atrial fibrillation or atrial flutter, an intravenous infusion of diltiazem hydrochloride injection or diltiazem hydrochloride for injection may be administered... The recommended initial infusion rate of diltiazem hydrochloride injection or diltiazem hydrochloride for injection is 10 mg/h.

The appropriate dosing of Diltiazem for atrial fibrillation (afib) is:

• Initial dose: 0.25 mg/kg actual body weight as a bolus administered over 2 minutes
• Second dose (if response is inadequate): 0.35 mg/kg actual body weight administered over 2 minutes
• Continuous intravenous infusion: initial rate of 10 mg/h, which may be increased in 5 mg/h increments up to 15 mg/h as needed 2

From the Research

Dosing of Diltiazem for Atrial Fibrillation

• The recommended starting dose of diltiazem for atrial fibrillation (AF) with rapid ventricular response is an intravenous bolus of 0.25 mg/kg over 2 minutes 3.
• However, a lower dose of diltiazem (≤ 0.2 mg/kg) may be as effective as the standard dose in controlling rapid AF and reduce the risk of hypotension 3.
• A study found that patients treated with ≥ 0.13 mg/kg diltiazem achieved an heart rate (HR) < 100 bpm at a mean time of 169 minutes compared to 318 minutes for < 0.13 mg/kg 4.
• Another study compared the efficacy of oral immediate-release and intravenous continuous infusion diltiazem after an initial intravenous diltiazem loading dose, and found that oral immediate-release diltiazem was associated with a lower rate of treatment failure at four hours 5.
• The safety and efficacy of intravenous diltiazem in AF or atrial flutter has been studied, with 94% of patients responding 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 6.
• A comparison of weight-based dose vs. standard dose diltiazem in patients with AF presenting to the emergency department found that standard dose diltiazem was noninferior to weight-based dosing in the initial treatment of AF with rapid ventricular response 7.

Key Findings

• Diltiazem dosing strategies for AF with rapid ventricular response vary, but a lower dose (≤ 0.2 mg/kg) may be as effective as the standard dose in controlling rapid AF and reduce the risk of hypotension 3, 4.
• Oral immediate-release diltiazem may be associated with a lower rate of treatment failure at four hours compared to intravenous continuous infusion diltiazem 5.
• The safety and efficacy of intravenous diltiazem in AF or atrial flutter has been established, with a high response rate to the bolus dose 6.
• Standard dose diltiazem may be noninferior to weight-based dosing in the initial treatment of AF with rapid ventricular response 7.