Diltiazem (Cardizem): Uses, Dosing, Contraindications

• Diltiazem (Cardizem) is a non-dihydropyridine calcium channel blocker.
• Primary uses include rate control in atrial fibrillation/flutter, hypertension, and angina.
• This medication class inhibits calcium influx in cardiac and vascular smooth muscle.
• Effects include reduced heart rate, contractility, and vasodilation.

Contraindications

• Severe hypotension (SBP < 90 mmHg)
• Cardiogenic shock
• Second- or third-degree AV block (without a pacemaker)
• Acute decompensated heart failure due to negative inotropic effects

Dosing

• Varies based on indication
• IV boluses: 0.25 mg/kg over 2 minutes, followed by 0.35 mg/kg if needed
• Continuous infusion: 5-15 mg/hr, titrated to heart rate
• Oral forms: Extended-release (e.g., Cardizem CD, Tiazac) once daily
• Immediate-release formulations multiple times per day

Pharmacokinetics

• Onset of action: 2-5 minutes (IV), 30-60 minutes (oral)
• Peak effect: 2-4 hours for oral extended-release
• Half-life: 3-5 hours (up to 9 hours in sustained-release forms)
• Metabolism: Extensively by the liver (CYP3A4)
• Excretion: Renally and in bile
• Caution advised in hepatic impairment
• Renal dose adjustments generally not required

Side Effects

• Common: Bradycardia, hypotension, dizziness, headache, and edema
• Serious: Heart block, worsening heart failure, and severe hypotension

Drug Interactions

• Beta-blockers: Risk of profound bradycardia
• CYP3A4 inhibitors or inducers: Affect diltiazem metabolism
• Statins: Risk of increased statin levels and myopathy

Monitoring

• Requires monitoring of blood pressure, heart rate, and ECG, especially in ICU patients receiving IV infusions

Toxicity

• Symptoms: Profound bradycardia, hypotension, and AV block
• Treatment: IV calcium, fluids, vasopressors, glucagon, or high-dose insulin therapy in severe cases

ACLS and Emergency Use

• Preferred agent for rate control in stable narrow-complex tachycardias (e.g., atrial fibrillation with rapid ventricular response)
• Contraindicated in wide-complex tachycardia

Special Populations

• Pregnancy category C: Use cautiously in pregnancy and lactation

Additional Information

• IV formulations are more expensive than oral versions.
• Widely available in hospital formularies
• Hospitals often have protocols for using diltiazem IV infusions for atrial fibrillation with rapid ventricular response (RVR), requiring titration and nursing monitoring for hypotension and bradycardia.
• Generally avoided in patients with heart failure with reduced ejection fraction (HFrEF)
• ICU physicians must know when and how to use diltiazem for acute rate control, how to transition from IV to oral formulations, and how to manage side effects and interactions in critically ill patients.

Explore Diltiazem, a non-dihydropyridine calcium channel blocker, used for rate control in atrial fibrillation, hypertension and angina. Learn about contraindications such as hypotension and cardiogenic shock. Review IV and oral dosing guidelines, onset, peak effect and half-life.