What is the dosing of diltiazem (Calcium Channel Blocker) for therapeutic use?

From the Guidelines

Diltiazem dosing should be initiated with a dose of 15 mg to 20 mg (0.25 mg/kg) IV over 2 minutes, followed by an additional 20 mg to 25 mg (0.35 mg/kg) IV in 15 minutes if needed, and a maintenance infusion of 5 mg/hour to 15 mg/hour, titrated to heart rate, as recommended by the 2010 American Heart Association guidelines for cardiopulmonary resuscitation and emergency cardiovascular care 1.

Key Considerations

• The dosing of diltiazem varies by formulation and indication, with IV dosing being used for acute rate control in atrial fibrillation or flutter.
• For oral formulations, the typical starting dose is 120 mg daily in divided or single dose with long-acting formulations, which can be increased gradually to 360 mg daily, as outlined in the 2015 ACC/AHA/HRS guideline for the management of adult patients with supraventricular tachycardia 1.
• Diltiazem works by blocking calcium channels in vascular smooth muscle and cardiac tissue, reducing peripheral vascular resistance and myocardial contractivity.
• Dose adjustments should be made gradually, usually at 7-14 day intervals, to allow assessment of clinical response and minimize side effects like hypotension, bradycardia, or heart block.

Important Precautions

• Diltiazem should not be given to patients with wide-complex tachycardias, impaired ventricular function, or heart failure, as it can worsen these conditions.
• Caution is advised when using diltiazem in patients with pre-excited atrial fibrillation or flutter, as it can accelerate the ventricular response.
• The combination of AV nodal blocking agents, including diltiazem, should be avoided due to the risk of profound bradycardia.

Clinical Application

• In clinical practice, diltiazem is often used for rate control in atrial fibrillation or flutter, and its dosing should be individualized based on the patient's response and clinical status.
• The maintenance infusion dose of 5 mg/hour to 15 mg/hour should be titrated to achieve the desired heart rate, while minimizing the risk of side effects.
• Elderly patients and those with hepatic or renal impairment should start at lower doses, typically 50% of the standard dose, and be closely monitored for adverse effects 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). 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. DOSAGE AND ADMINISTRATION Exertional Angina Pectoris Due to Atherosclerotic Coronary Artery Disease or Angina Pectoris at Rest Due to Coronary Artery Spasm: Dosage must be adjusted to each patient’s needs Starting with 30 mg four times daily, before meals and at bedtime, dosage should be increased gradually (given in divided doses three or four times daily) at 1- to 2-day intervals until optimum response is obtained.

The dosing of diltiazem is as follows:

• Intravenous (IV) dosing:
  • Initial dose: 0.25 mg/kg actual body weight as a bolus administered over 2 minutes
  • Second dose (if needed): 0.35 mg/kg actual body weight administered over 2 minutes
  • Continuous infusion: initial rate of 10 mg/h, which may be increased in 5 mg/h increments up to 15 mg/h as needed
• Oral (PO) dosing:
  • Initial dose: 30 mg four times daily
  • Dosage should be increased gradually at 1- to 2-day intervals until optimum response is obtained
  • Average optimum dosage range: 180 to 360 mg/day 2 3

From the Research

Dosing of Diltiazem

• The dosing of diltiazem can vary depending on the condition being treated, with studies suggesting different approaches for atrial fibrillation with rapid ventricular rate (RVR) and hypertension 4, 5.
• For atrial fibrillation with RVR, a weight-based dose of diltiazem (≥ 0.13 mg/kg) has been associated with improved heart rate control compared to a standard dose (≤ 10 mg) 4.
• However, another study found that a standard dose of diltiazem (10 mg) was noninferior to a weight-based dose (0.2-0.3 mg/kg) in achieving successful treatment of atrial fibrillation with RVR 5.
• In the treatment of hypertension, diltiazem has been shown to have a heart rate-lowering effect, particularly at higher initial heart rates 6.
• A study on the effects of diltiazem retard on ambulatory blood pressure and heart rate variability in patients with essential hypertension found that it significantly decreased 24-hour average blood pressure and heart rate, and had favorable effects on the autonomic nervous system 7.

Key Findings

• Diltiazem dosing strategies may vary depending on the specific condition and patient population.
• Weight-based dosing may be more effective for achieving heart rate control in atrial fibrillation with RVR, but standard dosing may also be effective in certain cases.
• Diltiazem has been shown to have a heart rate-lowering effect in hypertension, particularly at higher initial heart rates.
• The choice of diltiazem dose should be individualized based on patient characteristics and response to treatment 4, 8, 5, 6, 7.