What is the typical dose of diltiazem for an adult patient with no specified medical history?

Diltiazem Dosing

For oral therapy, start diltiazem at 120 mg daily (either divided doses or as a long-acting formulation) and titrate up to a maximum of 360 mg daily, with hypertension typically requiring higher doses (240-360 mg daily) than angina (typically 240 mg daily). 1, 2

Oral Dosing for Chronic Conditions

Initial and Maintenance Dosing

• Start with 120 mg daily in divided doses or as a single dose with long-acting formulations 1, 2
• Maximum dose is 360 mg daily in divided doses or as a single dose with long-acting formulations 1, 2
• For hypertension specifically, doses of 240-360 mg daily are typically required for adequate blood pressure control, as lower doses (90-120 mg/day) represent a "no-effect dose" range 3
• For angina, 240 mg daily is typically sufficient 2, 3

Formulation Options

• Extended-release (ER) or controlled-delivery (CD) formulations: dosed once daily at 120-540 mg 2
• Slow-release tablets: available for divided dosing at 120-360 mg daily in 2-3 divided doses 2
• Immediate-release tablets: doses ranging from 30-90 mg 2

Important Dosing Considerations

• Diltiazem is commonly underdosed in clinical practice, with 70% of hypertension prescriptions being for 180-240 mg strengths, despite evidence showing a clear linear dose-response relationship through 480-540 mg/day 3
• Titrate cautiously and progressively over several weeks to reach effective blood pressure control 2
• The standard dosing range for most indications is 120-360 mg once daily, though doses up to 540 mg/day have been studied and found safe for hypertension 2, 4

Intravenous Dosing for Acute Rate Control

Initial IV Bolus

• First dose: 0.25 mg/kg (approximately 15-20 mg for average adults) IV over 2 minutes 1, 5, 6, 7
• Second dose if needed: 0.35 mg/kg (approximately 20-25 mg) IV over 2 minutes, given 15 minutes after the first dose if inadequate response 5, 6, 7
• Some patients may respond to an initial dose of 0.15 mg/kg, although duration of action may be shorter (experience with this dose is limited) 7
• Low-dose diltiazem (≤0.2 mg/kg) may be as effective as standard dose with significantly lower risk of hypotension (adjusted odds ratio 0.39) 8

Continuous IV Infusion

• Start at 10 mg/hour immediately following bolus administration 7
• Some patients may maintain response to an initial rate of 5 mg/hour 2, 7
• Titrate in 5 mg/hour increments up to a maximum of 15 mg/hour as needed for further heart rate reduction 2, 6, 7
• Maximum infusion duration is 24 hours (infusion duration exceeding 24 hours and rates exceeding 15 mg/hour are not recommended due to lack of study data) 7

Absolute Contraindications

Do not use diltiazem in the following situations:

• Second- or third-degree AV block without a functioning pacemaker 1, 2, 5, 6
• Sick sinus syndrome without a pacemaker 2, 6
• Decompensated systolic heart failure or severe left ventricular dysfunction 1, 2, 5, 6
• Hypotension (systolic BP <90 mmHg) 1, 2, 5, 6
• Cardiogenic shock 2, 6, 7
• Wolff-Parkinson-White (WPW) syndrome with atrial fibrillation/flutter (may accelerate ventricular response and cause hemodynamic collapse) 1, 2, 5, 6

Critical Precautions and Drug Interactions

High-Risk Combinations

• Avoid routine combination with beta-blockers due to increased risk of significant bradyarrhythmias, profound AV block, and heart failure 2, 6
• Use extreme caution when combining with beta-blockers; close monitoring is essential 2
• First-degree AV block with PR interval >0.24 seconds is a contraindication in acute coronary syndromes 2

CYP3A4 Interactions

• Diltiazem is both a CYP3A4 substrate (major) and a moderate CYP3A4 inhibitor 1, 2
• Exercise caution with: apixaban, itraconazole, bosutinib, ceritinib, cilostazol, cyclosporine, everolimus, ibrutinib, idelalisib, ivabradine, lomitapide, olaparib, ranolazine, rifampin, simeprevir, simvastatin 1, 2
• Reduce digoxin dose by 30-50% when initiating diltiazem 2

Monitoring Requirements

For Oral Therapy

• Monitor blood pressure and heart rate regularly during dose titration 2
• Watch for signs and symptoms of heart failure in at-risk patients 2
• Monitor liver function tests if clinically indicated 2
• ECG monitoring in patients with conduction system disease 2
• Reassess patients in 1 month after initiation or dose change 2

For IV Therapy

• Continuous ECG monitoring during administration 6
• Frequent blood pressure measurements throughout the infusion 6
• Have defibrillator and resuscitation equipment immediately available 5, 6

Common Adverse Effects

• Hypotension (most common, especially with IV administration) 1, 2, 5, 8
• Peripheral edema (dose-related, more common in women; consider adding diuretics) 2
• Bradycardia 1, 2, 5
• Worsening heart failure in patients with pre-existing ventricular dysfunction 1, 2, 5
• Constipation 2
• Abnormal liver function studies, acute hepatic injury (rare) 1

Clinical Pearls

• For supraventricular tachycardia, adenosine is first-line; diltiazem is an excellent second-line option when adenosine fails or is contraindicated 5, 6
• Diltiazem is preferred over dihydropyridine calcium channel blockers when resting heart rate is elevated 2
• In hemodynamically unstable patients, skip medications entirely and proceed directly to synchronized cardioversion 5, 6
• Asymptomatic low blood pressure (e.g., 115/60 mmHg) does not usually require any change in therapy 2
• Do not use diltiazem for wide-complex tachycardias unless the arrhythmia is known with certainty to be supraventricular in origin 2