When should Cardizem (Diltiazem) not be given?

When Cardizem (Diltiazem) Should Not Be Given

Diltiazem is absolutely contraindicated in patients with sick sinus syndrome without a pacemaker, second- or third-degree AV block without a pacemaker, hypotension (systolic BP <90 mmHg), acute MI with pulmonary congestion, decompensated heart failure or severe LV dysfunction, and Wolff-Parkinson-White syndrome with atrial fibrillation/flutter. 1, 2, 3

Absolute Contraindications

Cardiac Conduction Abnormalities

• Second- or third-degree AV block without a functioning ventricular pacemaker 1, 2
• Sick sinus syndrome without a functioning ventricular pacemaker 1, 3, 4
• First-degree AV block with PR interval >0.24 seconds when considering diltiazem for acute coronary syndromes 2

Hemodynamic Instability

• Hypotension with systolic BP <90 mmHg 1, 3
• Cardiogenic shock 3, 4, 5
• Acute myocardial infarction with pulmonary congestion documented by x-ray on admission 1

Ventricular Dysfunction

• Decompensated systolic heart failure 2, 3, 4
• Severe left ventricular dysfunction 2, 3
• Patients with reduced ejection fraction (<0.40) have significantly increased risk of late-onset congestive heart failure when treated with diltiazem (21% vs 12% with placebo, p=0.004) 6

Arrhythmia-Specific Contraindications

• Wolff-Parkinson-White syndrome with atrial fibrillation or flutter 2, 3, 4
• Pre-excited atrial fibrillation or flutter conducting via accessory pathway—AV nodal blocking agents may paradoxically accelerate ventricular response 2

Critical Relative Contraindications (Use With Extreme Caution or Avoid)

Drug Combinations

• Concurrent beta-blocker therapy poses significant risk for symptomatic bradycardia, profound AV block, and heart failure 2, 3, 4
  • Symptomatic bradycardia can occur even with low doses of each drug 7
  • Risk is particularly elevated in elderly patients 7
  • Can present with lethargy, dizziness, syncope, chest pain, or pulmonary edema 7
  • May occur within hours to 2 years after starting combination therapy 7

Wide-Complex Tachycardias

• Do not give diltiazem for wide-complex tachycardias unless the arrhythmia is known with certainty to be supraventricular in origin 2
• This mirrors the contraindication for verapamil in this setting 2

Specific Clinical Scenarios

• Cocaine-associated acute coronary syndromes: Diltiazem should not be used as first-line therapy; reserve only for patients unresponsive to benzodiazepines and nitroglycerin, and avoid in patients with heart failure or LV dysfunction 2
• Obstructive hypertrophic cardiomyopathy with severe outflow tract obstruction: Vasodilatory effects may worsen obstruction and precipitate pulmonary edema 4

Important Clinical Pitfalls

Hepatic and Renal Dysfunction

• Use with caution in hepatic dysfunction as diltiazem is metabolized by the liver 3, 4
• Dose adjustment may be required in renal dysfunction 3

Drug Interactions

• Diltiazem is both a CYP3A4 substrate and moderate CYP3A4 inhibitor 2, 3, 4
• Exercise caution with: apixaban, itraconazole, bosutinib, ceritinib, cilostazol, cyclosporine, everolimus, ibrutinib, simvastatin, rifampin 2, 3
• Reduce warfarin dose by 50% and digoxin dose by 30-50% when initiating diltiazem 2

Age-Related Considerations

• Elderly patients are at higher risk for symptomatic bradycardia when diltiazem is combined with beta-blockers 7
• Frail or elderly patients may experience symptomatic hypotension even at blood pressures that appear adequate 3

Acute Coronary Syndromes

• Short-acting nifedipine (a related calcium channel blocker) should never be used in acute coronary syndromes and showed increased mortality 2
• While diltiazem is safer than short-acting nifedipines, it should not be used routinely in STEMI 2
• In non-STEMI/unstable angina, use only when beta-blockers are contraindicated AND there is no severe LV dysfunction 2

Monitoring Requirements When Diltiazem Is Used

When diltiazem is appropriately prescribed, monitor for:

• Blood pressure and heart rate at each visit during titration 3, 4
• ECG monitoring in patients with any conduction system disease 3, 4
• Signs of heart failure (dyspnea, weight gain, edema) in at-risk patients 3, 4, 7
• Liver function tests if clinically indicated 3, 4