What is the duration of effect of intravenous (IV) diltiazem (Cardizem)?

From the Guidelines

Intravenous diltiazem has a duration of effect of approximately 1-3 hours after administration. When given as a bolus dose, the onset of action occurs within 2-5 minutes, with peak effects typically seen within 7-15 minutes. For continuous infusions, steady-state plasma concentrations are generally achieved after 6-11 hours of administration. The relatively short duration of action is due to diltiazem's pharmacokinetic profile, including its distribution half-life of about 6-11 minutes and elimination half-life of 3-5 hours 1. This calcium channel blocker works by inhibiting calcium influx through L-type calcium channels in vascular smooth muscle and cardiac tissue, resulting in vasodilation and decreased cardiac conduction.

Some key points to consider when using IV diltiazem include:

• Monitoring for hypotension, bradycardia, and heart block, especially during the first few hours of administration 2
• Transition to oral diltiazem formulations for patients requiring longer calcium channel blockade, as these provide more sustained effects through extended-release preparations that can last 12-24 hours depending on the specific formulation 3
• Individualized dosing and careful consideration of patient factors, such as heart failure and pre-excited AF or flutter, to minimize adverse effects 1, 2, 3

Overall, IV diltiazem is a useful agent for acute rate control in patients with atrial fibrillation or flutter, but its relatively short duration of action and potential for adverse effects require careful monitoring and consideration of alternative therapies.

From the FDA Drug Label

Following administration of one or two intravenous bolus doses of diltiazem hydrochloride injection, response usually occurs within 3 minutes and maximal heart rate reduction generally occurs in 2 to 7 minutes. Heart rate reduction may last from 1 to 3 hours. A 24-hour continuous infusion of diltiazem hydrochloride injection in the treatment of atrial fibrillation or atrial flutter maintained at least a 20% heart rate reduction during the infusion in 83% of patients. Upon discontinuation of infusion, heart rate reduction may last from 0. 5 hours to more than 10 hours (median duration 7 hours).

The duration of effect of intravenous (IV) diltiazem (Cardizem) is as follows:

• Bolus administration: Heart rate reduction may last from 1 to 3 hours.
• Continuous infusion: Heart rate reduction may last from 0.5 hours to more than 10 hours (median duration 7 hours) after discontinuation of the infusion. 4

From the Research

Duration of Effect of Intravenous Diltiazem

• The duration of effect of intravenous (IV) diltiazem can vary depending on the dose and individual patient response 5, 6.
• A study published in 1995 found that after a bolus dose of IV diltiazem, 94% of patients responded with a > 20% reduction in heart rate from baseline, and 47% of patients maintained response with a 5 mg/hour infusion after 10 hours 6.
• Another study published in 2018 found that after an initial IV diltiazem loading dose, oral immediate-release diltiazem was associated with a lower rate of treatment failure at four hours than IV continuous infusion in patients with atrial fibrillation with rapid ventricular response 5.
• The median dose of PO diltiazem and IV continuous infusion diltiazem at four hours was 30 mg and 10 mg/h, respectively 5.
• A study published in 2021 found that the mean time to achieve heart rate < 100 bpm was 270 minutes for the entire cohort, and 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 7.

Factors Affecting Duration of Effect

• The dose of IV diltiazem can affect the duration of its effect, with higher doses resulting in longer durations of action 6, 7.
• Individual patient response to IV diltiazem can also vary, with some patients experiencing a longer duration of effect than others 5, 6.
• The route of administration, whether oral or intravenous, can also impact the duration of effect, with oral administration resulting in a longer duration of action in some studies 5.