When should a diltiazem (calcium channel blocker) drip be avoided?

From the Guidelines

A diltiazem drip should be avoided in patients with severe hypotension, decompensated heart failure, cardiogenic shock, sick sinus syndrome, second or third-degree heart block (without a pacemaker), and severe left ventricular dysfunction (ejection fraction <40%). This is based on the most recent and highest quality study available, which emphasizes the importance of careful patient selection when using diltiazem for rate control in atrial fibrillation or other supraventricular tachycardias 1.

Key Considerations for Avoiding Diltiazem Drip

• Severe hypotension (systolic blood pressure <90 mmHg) because diltiazem can further lower blood pressure, potentially leading to inadequate organ perfusion.
• Decompensated heart failure and cardiogenic shock, as diltiazem's negative inotropic effects can worsen cardiac output in these conditions.
• Sick sinus syndrome and second or third-degree heart block without a pacemaker, due to the risk of exacerbating bradycardia or heart block.
• Severe left ventricular dysfunction (ejection fraction <40%), as the negative inotropic effects of diltiazem can further impair left ventricular function.
• Wolff-Parkinson-White syndrome with atrial fibrillation, because diltiazem can accelerate the ventricular response, potentially leading to ventricular fibrillation.

Additional Precautions

• Caution is advised when using diltiazem in patients taking beta-blockers due to potential additive effects on heart rate and contractility 1.
• Diltiazem should be avoided in pregnancy (category C) unless benefits outweigh risks.
• Continuous monitoring of blood pressure, heart rate, and ECG is necessary when administering diltiazem, with readiness to adjust the dose or discontinue the drug if significant hypotension or bradycardia develops.

Mechanism and Effects

Diltiazem works by blocking calcium channels in cardiac and vascular smooth muscle, which reduces contractility, heart rate, and blood pressure. These effects can be beneficial in controlling the ventricular rate in atrial fibrillation but can worsen conditions where cardiac output is already compromised or where conduction abnormalities exist. Therefore, careful consideration of the patient's clinical status and potential risks is crucial before initiating a diltiazem drip.

From the FDA Drug Label

Diltiazem hydrochloride is contraindicated in: (1) patients with sick sinus syndrome except in the presence of a functioning ventricular pacemaker; (2) patients with second or third degree AV block except in the presence of a functioning ventricular pacemaker; (3) patients with hypotension (less than 90 mmHg systolic); (4) patients who have demonstrated hypersensitivity to the drug; and (5) patients with acute myocardial infarction and pulmonary congestion as documented by X-ray on admission.

A diltiazem drip should be avoided in the following situations:

• Patients with sick sinus syndrome without a functioning ventricular pacemaker
• Patients with second or third degree AV block without a functioning ventricular pacemaker
• Patients with hypotension (less than 90 mmHg systolic)
• Patients with a hypersensitivity to the drug
• Patients with acute myocardial infarction and pulmonary congestion as documented by X-ray on admission 2

From the Research

Conditions to Avoid Diltiazem Drip

• Atrioventricular block grade I, as the risk of developing adverse reactions such as sinus arrest or atrioventricular block may be exacerbated by concomitant beta-adrenergic blocker therapy 3
• Bradycardia, as diltiazem can cause sinus arrest or severe sinus bradycardia, especially when used with beta-blockers 3, 4
• Hypotension, as diltiazem can cause a decrease in blood pressure, and the risk of hypotension is higher when used with beta-blockers 3, 5, 6
• Left ventricular dysfunction, as the combination of diltiazem and beta-blockers may not be suitable for patients with left ventricular dysfunction 3
• Latent cardiac conduction deficits, as the combination of diltiazem and beta-blockers may exacerbate conduction disturbances 3
• Thyrotoxic crisis, as diltiazem can cause hypotension, bradycardia, and asystole cardiac arrest in patients with thyrotoxic storm 7
• Combination with beta-blockers in patients with certain conditions, such as renal or hepatic disease, or those taking other medications that may interact with diltiazem 5, 4

Patient Populations to Exercise Caution

• Hypertensive patients taking beta-blockers, as the combination of diltiazem and beta-blockers can cause severe bradycardia and cardiogenic shock 5
• Patients with coronary heart disease, as the combination of diltiazem and beta-blockers can cause conduction disturbances and exacerbate left ventricular dysfunction 3
• Elderly patients, as they may be more susceptible to the adverse effects of diltiazem, such as hypotension and bradycardia 4