What is the starting dose of diltiazem (calcium channel blocker) for treating hypertension (high blood pressure) or angina?

Starting Dose of Diltiazem

Start diltiazem at 120-180 mg once daily using a long-acting formulation for both hypertension and angina, with the understanding that hypertension typically requires higher maintenance doses (up to 360 mg daily) compared to angina (typically 240 mg daily). 1

Initial Dosing Strategy

• Begin with 120 mg once daily using extended-release or controlled-delivery formulations for most patients with hypertension or chronic stable angina 1
• Some guidelines support starting at 180 mg once daily, particularly for hypertension, depending on baseline blood pressure severity 1
• The immediate-release formulation can be used at 30-90 mg doses but requires multiple daily administrations and is less commonly used for chronic management 1

Dose Titration Approach

• Titrate cautiously and progressively over several weeks to achieve blood pressure control or angina relief 1
• Reassess patients 1 month after initiation or dose change to monitor for symptom control and adverse effects 1
• For hypertension, doses can be increased incrementally: 120 mg → 180 mg → 240 mg → 360 mg once daily 1, 2
• Maximum maintenance dose is 360 mg daily for most indications, though doses up to 540 mg have been studied and found safe for hypertension 1, 2

Important Dosing Context

Research demonstrates that diltiazem is commonly underdosed in clinical practice, with 70% of prescriptions for hypertension being 180-240 mg despite evidence showing optimal efficacy at 360 mg daily 3. This underdosing stems from historical use at lower antianginal doses (240 mg) before hypertension approval 3. Studies show a clear linear dose-response relationship through 480-540 mg/day for blood pressure reduction, with 90-120 mg/day being essentially a "no-effect dose" 3.

Critical Contraindications (Must Screen Before Starting)

Absolute contraindications where diltiazem must be avoided: 1

• Second or third-degree AV block without a functioning pacemaker
• Sick sinus syndrome without a pacemaker
• Decompensated systolic heart failure or severe left ventricular dysfunction
• Cardiogenic shock
• Wolff-Parkinson-White syndrome with atrial fibrillation/flutter
• Severe hypotension

Special Clinical Situations

When Beta-Blockers Are Contraindicated

• Diltiazem can substitute for beta-blockers in hypertensive patients with chronic stable angina, but NOT if left ventricular dysfunction is present 4
• This substitution is particularly useful in patients with reactive airway disease or other beta-blocker contraindications 4

Combination Therapy Cautions

• Exercise extreme caution when combining diltiazem with beta-blockers due to increased risk of significant bradyarrhythmias and heart failure 4, 1
• If combining with beta-blockers is necessary, close monitoring of heart rate and ECG is essential 1
• Diltiazem can be safely combined with ACE inhibitors/ARBs and thiazide diuretics for additional blood pressure control 1

Monitoring Requirements

Monitor the following parameters regularly: 1

• Blood pressure and heart rate at each visit during titration
• Signs and symptoms of heart failure in at-risk patients
• ECG monitoring in patients with any conduction system disease
• Liver function tests if clinically indicated (diltiazem is hepatically metabolized)

Common Adverse Effects to Anticipate

• Hypotension is the most common adverse effect, particularly dose-related 1
• Peripheral edema occurs more frequently in women and is dose-dependent; consider adding diuretics if problematic 1
• Bradycardia may be dose-limiting, especially in patients with baseline bradycardia 1
• Constipation is common but usually mild 1

Drug Interaction Alert

• Diltiazem is both a CYP3A4 substrate and moderate CYP3A4 inhibitor 1
• Use caution with: apixaban, cyclosporine, simvastatin, rifampin, and other CYP3A4 substrates/inhibitors 1
• Avoid strong CYP3A4 inhibitors (e.g., itraconazole, ketoconazole) which can significantly increase diltiazem levels 1

Formulation Selection

• Extended-release (ER) or controlled-delivery (CD) once-daily formulations are preferred for improved compliance and consistent 24-hour blood pressure control 1, 5
• Once-daily dosing maintains therapeutic drug levels (≥40 ng/mL) throughout the 24-hour period at doses ≥240 mg 2
• Immediate-release tablets require 2-3 divided doses daily and are generally reserved for specific situations 1