How to transition from a diltiazem (calcium channel blocker) intravenous (IV) drip to oral diltiazem?

From the Guidelines

To transition from intravenous (IV) diltiazem to oral diltiazem, first ensure the patient is hemodynamically stable with controlled heart rate or blood pressure, then convert the IV dose to an equivalent oral dose by multiplying the hourly IV rate (mg/hr) by 3 to 4 to determine the total daily oral dose, as recommended by guidelines 1. When transitioning, consider the following key points:

• Ensure the patient's stability before initiating the transition
• Calculate the equivalent oral dose based on the IV rate
• Start with immediate-release diltiazem given three to four times daily
• Consider switching to extended-release formulations for better compliance once stability is confirmed
• Administer the first oral dose 1-2 hours before discontinuing the IV infusion
• Monitor the patient closely for 24-48 hours after the transition The conversion factor accounts for diltiazem's significant first-pass metabolism, resulting in about 40% bioavailability of the oral formulation compared to IV administration 1. Adjust the dose based on individual patient response, renal function, hepatic function, and concomitant medications that might interact with diltiazem. For example, if a patient is receiving diltiazem IV at 10 mg/hr, the equivalent oral dose would be approximately 30-40 mg every 8 hours or 240-320 mg total daily dose, as per the guidelines for heart rate control in patients with atrial fibrillation 1. It is crucial to prioritize the patient's hemodynamic stability and adjust the dose accordingly to minimize potential side effects such as hypotension, bradycardia, and heart failure 1.

From the FDA Drug Label

Diltiazem is well absorbed from the gastrointestinal tract and is subject to an extensive first-pass effect, giving an absolute bioavailability (compared to intravenous dosing) of about 40%. Single oral doses of 30 to 120 mg of diltiazem hydrochloride tablets result in detectable plasma levels within 30 to 60 minutes and peak plasma levels 2 to 4 hours after drug administration.

To transition from a diltiazem intravenous (IV) drip to oral diltiazem, consider the following key points:

• Bioavailability: Oral diltiazem has an absolute bioavailability of about 40% compared to intravenous dosing 2.
• Onset of action: Detectable plasma levels of oral diltiazem are achieved within 30 to 60 minutes, and peak plasma levels are reached 2 to 4 hours after administration 2.
• Dosing: The dose of oral diltiazem may need to be adjusted to account for the difference in bioavailability between IV and oral administration.

When transitioning from IV to oral diltiazem, monitoring of the patient's condition and adjustment of the oral dose as needed is crucial to ensure therapeutic effectiveness and minimize potential adverse effects.

From the Research

Transitioning from Diltiazem Drip to Oral Diltiazem

To transition from a diltiazem intravenous (IV) drip to oral diltiazem, several factors should be considered, including the patient's heart rate control, the dosage of IV diltiazem, and the formulation of oral diltiazem.

• The study 3 tested whether patients with atrial fibrillation (AF) or flutter (AFl) could maintain control of heart rate while transferring from IV diltiazem to oral long-acting diltiazem, and found that 77% of patients maintained heart rate control during the transition.
• The median infusion rate of IV diltiazem was 10 mg/hour, and the median dose of oral diltiazem was 300 mg/day 3.
• Another study 4 compared the incidence of treatment failure between oral immediate-release and IV continuous infusion diltiazem after an initial IV diltiazem loading dose, and found that oral immediate-release diltiazem was associated with a lower rate of treatment failure at four hours.

Considerations for Transition

When transitioning from IV to oral diltiazem, the following considerations should be taken into account:

• The patient's heart rate should be stable and controlled before transitioning to oral diltiazem 3.
• The dosage of oral diltiazem should be adjusted based on the patient's response to the medication and their heart rate control 3, 4.
• The formulation of oral diltiazem, such as long-acting or immediate-release, should be chosen based on the patient's individual needs and medical history 3, 4.

Potential Interactions and Side Effects

When using diltiazem, either IV or oral, potential interactions and side effects should be considered, including:

• Interactions with other medications, such as beta-blockers and direct oral anticoagulants 5, 6, 7.
• Side effects, such as hypotension, bradycardia, and constipation 5, 6.