Diltiazem CD Dosing for Supraventricular Tachycardia
For chronic prophylaxis of recurrent SVT, start diltiazem CD at 120 mg daily and titrate up to a maintenance dose of 180-360 mg daily in divided or single doses with long-acting formulations, with a maximum of 360 mg daily. 1
Dosing Algorithm
Initial Dosing
- Starting dose: 120 mg daily (can be given as single dose with controlled-release formulations)
- Begin titration after assessing initial response and tolerability
Maintenance Dosing
- Target range: 180-360 mg daily 1
- Can be administered as:
- Single daily dose with long-acting/CD formulations
- Divided doses if using immediate-release formulations
- Maximum dose: 360 mg daily 1
Titration Strategy
Based on FDA labeling for immediate-release formulations (which informs CD dosing principles), titration should occur gradually at 1-2 day intervals until optimal response is achieved 2. The average optimum dosage range is 180-360 mg/day 2.
Important Clinical Context
Role in Current Guidelines
Diltiazem has been downgraded in recent guidelines for acute management of SVT 3. The 2019 ESC guidelines specifically downgraded verapamil and diltiazem for acute management of narrow-QRS tachycardias and are no longer recommended for chronic treatment of AVNRT 3. However, the 2015 ACC/AHA/HRS guidelines still include diltiazem as an option for chronic rate control and prophylaxis 1.
When to Use Diltiazem CD
Diltiazem CD is appropriate for:
- Chronic prophylaxis of recurrent SVT episodes
- Rate control in patients with recurrent paroxysmal SVT
- Patients who have failed or cannot tolerate beta-blockers
- Not for acute conversion - adenosine remains first-line for acute episodes after vagal maneuvers fail 3
Critical Precautions
Absolute Contraindications
- AV block greater than first-degree or SA node dysfunction (without pacemaker)
- Decompensated systolic heart failure or severe LV dysfunction
- Hypotension
- WPW syndrome with atrial fibrillation/flutter (may precipitate ventricular fibrillation) 3, 1
- Concurrent use with other SA/AV nodal-blocking agents requires extreme caution
Monitoring Requirements
- Blood pressure (watch for hypotension)
- Heart rate and rhythm (bradycardia risk)
- PR interval on ECG (can prolong, but usually doesn't cause abnormal prolongation at doses up to 240 mg/day) 2
- Liver function tests (rare hepatic injury possible) 1
Drug Interactions
Diltiazem is a CYP3A4 substrate and moderate inhibitor 1. Key interactions include:
- Avoid with dofetilide (contraindicated with verapamil, use caution with diltiazem)
- Monitor levels with: cyclosporine, simvastatin, digoxin, other CYP3A4 substrates
- Dose adjustments needed with strong CYP3A4 inhibitors/inducers
Dose Adjustments
Hepatic Impairment
Exercise particular caution - studies show 69% increase in AUC and prolonged half-life in cirrhotic patients 2. Start at lower doses and titrate slowly.
Renal Impairment
No significant pharmacokinetic differences in severe renal impairment 2, but titrate carefully given limited data.
Evidence Quality Note
Research from the 1980s showed oral diltiazem (270 mg in divided doses) prevented induction of SVT in most patients during electrophysiology studies 4, and combination therapy with propranolol showed high efficacy 5. However, more recent guidelines have shifted away from calcium channel blockers toward adenosine for acute management and catheter ablation for definitive treatment 3. The role of diltiazem CD is now primarily for chronic rate control in select patients who are not candidates for ablation or prefer medical management.