Diltiazem Dosing for Chronic Heart Failure
Critical Contraindication: Do Not Use Diltiazem in Heart Failure with Reduced Ejection Fraction
Diltiazem is absolutely contraindicated in patients with heart failure and reduced ejection fraction (LVEF ≤40%) due to its negative inotropic effects, which can precipitate hemodynamic decompensation. 1, 2
For Heart Failure with Preserved Ejection Fraction (HFpEF) Requiring Rate Control
If your patient has HFpEF (LVEF ≥50%) and requires rate control for atrial fibrillation or other supraventricular arrhythmias, diltiazem can be used with the following dosing:
Oral Maintenance Dosing for Rate Control
Start with 120 mg daily in divided doses (immediate-release) or as a single dose with extended-release formulations, titrating up to a maximum of 360 mg daily based on heart rate response. 1, 2
- Immediate-release tablets: 120-360 mg daily in divided doses (typically 30-90 mg three to four times daily) 1
- Extended-release formulations: 180-360 mg once daily 2, 3
- Target heart rate: 60-80 bpm at rest or <100 bpm with >20% reduction from baseline 2
- Onset of action: 2-4 hours for oral formulations 1, 4
Acute IV Dosing (If Needed for Rapid Rate Control)
For acute management in the emergency or inpatient setting:
- Initial bolus: 0.25 mg/kg IV over 2 minutes 1, 2
- Second bolus (if needed): 0.35 mg/kg IV 15 minutes after first dose 2
- Continuous infusion: 5-15 mg/hour, titrated to heart rate 1, 2
- Onset: 2-7 minutes 1, 2
Absolute Contraindications Beyond HFrEF
Even in HFpEF patients, avoid diltiazem if any of the following are present:
- Second- or third-degree AV block without a functioning pacemaker 1, 2
- Sick sinus syndrome without a pacemaker 2, 3
- Severe hypotension (systolic BP <90 mmHg) 2
- Pre-excited atrial fibrillation (Wolff-Parkinson-White syndrome with AF) 1, 2
- Cardiogenic shock 2, 3
Critical Drug Interaction: Beta-Blockers
Do not routinely combine diltiazem with beta-blockers due to the high risk of profound bradycardia, complete heart block, and worsening heart failure. 1, 2, 3 If both agents are absolutely necessary, use extreme caution with continuous cardiac monitoring and consider reducing doses of both agents. 2
Monitoring Requirements
- Heart rate and blood pressure continuously during IV administration and at each dose adjustment 2
- ECG monitoring in patients with any conduction system disease 3
- Renal function: Recent evidence suggests increased risk of acute kidney injury in patients with reduced EF receiving IV diltiazem (10% vs 3.6% in normal EF, p=0.002) 5, though this risk appears lower in HFpEF patients 6
- Signs of heart failure decompensation: increased dyspnea, weight gain, edema 1
Common Adverse Effects
- Hypotension (18-42% depending on dose and route) 1, 2
- Bradycardia 1, 2
- Peripheral edema (dose-related, more common in women) 3
- Heart block 1, 2
Alternative Agents for HFrEF
If your patient has HFrEF (LVEF <50%) and requires rate control:
- First-line: Digoxin 0.125-0.375 mg daily orally 1
- Second-line: Amiodarone (if other measures unsuccessful) - 800 mg daily for 1 week, then 600 mg daily for 1 week, then 400 mg daily for 4-6 weeks, then 200 mg daily maintenance 1
- Beta-blockers (carvedilol, metoprolol succinate, bisoprolol) can be used cautiously for rate control in HFrEF but must be initiated at very low doses and titrated slowly 1
Key Clinical Pitfall
The most common error is using diltiazem in patients with unrecognized or undocumented systolic dysfunction. Always verify ejection fraction before initiating diltiazem therapy. 2, 7 A 2024 study found that 17% of hospitalized patients with reduced EF who received diltiazem developed worsening heart failure within 24 hours, compared to only 4.8% with preserved EF (p=0.005). 7
Drug Interactions Requiring Dose Adjustment
Diltiazem is a moderate CYP3A4 inhibitor and substrate: 2, 3