Diltiazem: Uses, Dosing, and ICU Indications

• Diltiazem is a nondihydropyridine calcium channel blocker (CCB)
• It inhibits calcium influx into cardiac and vascular smooth muscle cells
• Results in negative chronotropic, inotropic, and dromotropic effects
• Leads to heart rate reduction, decreased myocardial contractility, and vasodilation

ICU Indications

• Atrial fibrillation (AF) with rapid ventricular response (RVR)
• Atrial flutter with RVR
• Paroxysmal supraventricular tachycardia (PSVT)
• Off-label uses include hypertension and coronary artery spasm

IV Bolus Dosing

• Initial bolus is 0.25 mg/kg IV over 2 minutes
• A second bolus of 0.35 mg/kg IV over 2 minutes can be given after 15 minutes if the response is inadequate

IV Infusion Dosing

• Start at 5-10 mg/hr, titrate by 2.5 mg/hr every 15–30 minutes
• The maximum rate is typically 15 mg/hr, but some protocols allow up to 20 mg/hr
• Usually given for a maximum duration of 24 hours to avoid excessive hypotension or bradycardia

Transitioning from IV to Oral

• Start oral therapy at least 1 hour before stopping the IV infusion
• IV rate of 5 mg/hr converts to 120 mg PO q12h
• IV rate of 10 mg/hr converts to 180 mg PO q12h
• IV rate of 15 mg/hr converts to 240 mg PO q12h
• Diltiazem Extended-Release (XR) formulations can be dosed once daily

Absolute Contraindications

• Hypotension (SBP < 90 mmHg)
• Severe bradycardia (HR < 50 bpm)
• Advanced heart block (2nd or 3rd degree) without a pacemaker
• Acute decompensated heart failure, especially with reduced EF
• Cardiogenic shock
• Wolff-Parkinson-White (WPW) syndrome with atrial fibrillation
• Hypersensitivity to diltiazem or other calcium channel blockers

Relative Contraindications and Precautions

• Hepatic impairment requires dose adjustments
• Renal impairment may prolong effects
• Use caution with concurrent beta-blocker therapy
• Elderly patients are more sensitive to hypotension and bradycardia

Pharmacokinetics

• Onset: 2-5 minutes
• Peak Effect: 15 minutes
• Duration: 1-3 hours after a single bolus
• Continuous infusion duration depends on the rate

Monitoring Parameters

• Heart rate (HR)
• Blood pressure (BP)
• Signs of heart failure (dyspnea, edema, pulmonary congestion)
• Electrocardiogram (ECG) for bradyarrhythmias or conduction delays
• Liver function tests (LFTs) in long-term use
• Renal function (CrCl, urine output) in critically ill patients

Common Side Effects

• Hypotension (most common ICU concern)
• Bradycardia
• AV block
• Dizziness, headache
• Peripheral edema
• Constipation with oral forms

Managing Hypotension

• Stop the infusion immediately
• Administer IV fluids (normal saline or lactated Ringer’s)
• Consider vasopressors (e.g., norepinephrine) if severe
• Calcium chloride or calcium gluconate can help reverse excessive calcium channel blockade

Managing Severe Bradycardia

• Stop diltiazem immediately
• Administer atropine (0.5 mg IV push, repeat as needed up to 3 mg)
• Consider transcutaneous pacing if necessary
• IV calcium may help if bradycardia is severe and refractory

Drug Interactions

• Beta-blockers: Synergistic bradycardia and hypotension risk
• Digoxin: Increased digoxin levels due to P-glycoprotein inhibition
• Amiodarone: Additive effects on bradycardia and AV block
• CYP3A4 inhibitors (e.g., azole antifungals, macrolides): Increased diltiazem levels
• CYP3A4 inducers (e.g., rifampin, phenytoin): Decreased diltiazem efficacy
• Statins: Increased risk of statin-induced myopathy

Use in Heart Failure

• Contraindicated in heart failure with reduced ejection fraction (HFrEF)
• May be used cautiously in heart failure with preserved ejection fraction (HFpEF) if rate control is necessary

Use in Sepsis

• Use only if tachycardia is due to AFib with RVR and not from compensatory sympathetic response
• Not appropriate if underlying cause is sepsis-induced hypotension

Comparison to Metoprolol for Rate Control in AFib with RVR

• Diltiazem works faster (onset 2-5 min vs. 5-10 min for metoprolol)
• Diltiazem provides better rate control in the first 30 minutes
• Metoprolol may be preferred in patients with heart failure with reduced EF
• Diltiazem may be better tolerated in patients with reactive airway disease

Diltiazem is a calcium channel blocker (CCB) used in the ICU to treat atrial fibrillation, atrial flutter, and PSVT with rapid ventricular response. IV bolus and infusion dosing are used, with careful titration to avoid hypotension or bradycardia. Off-label uses include hypertension and coronary artery spasm.