What is the dosage and usage of Diltiazem (calcium channel blocker) for treating hypertension, angina, and heart rhythm disorders?

Diltiazem Dosing for Hypertension, Angina, and Heart Rhythm Disorders

Diltiazem should be dosed at 120-360 mg daily for hypertension (typically requiring higher doses up to 360 mg), 120-240 mg daily for angina, and 0.25 mg/kg IV (approximately 15-20 mg) over 2 minutes for acute supraventricular tachycardia. 1, 2

Indications

• FDA-approved for management of chronic stable angina and angina due to coronary artery spasm 3
• Effective for hypertension, requiring higher doses (typically 360 mg daily) than for angina (typically 240 mg daily) 2, 4
• Second-line agent for paroxysmal supraventricular tachycardia (PSVT) when adenosine fails or is contraindicated 1

Dosing Guidelines

For Hypertension:

• Initial dose: 120 mg daily in divided doses or as single dose with long-acting formulations 2
• Maintenance dose: Up to 360 mg daily 2
• Dose-response relationship is linear through 480-540 mg/day range for blood pressure lowering 4
• Often underdosed in clinical practice (90-120 mg/day is considered a "no-effect dose" for hypertension) 4

For Angina:

• Initial dose: 120 mg daily in divided doses 2, 5
• Maintenance dose: Typically 240 mg daily, though some patients may require up to 360 mg daily 2, 5
• May be used as monotherapy or in combination with nitrates for severe angina 5

For Supraventricular Tachycardia:

• IV bolus: 0.25 mg/kg (approximately 15-20 mg for average adult) administered over 2 minutes 1
• If hypotension is a concern, a slow infusion of 2.5 mg/min for up to 20 minutes may reduce this risk 6

Contraindications and Precautions

• Avoid in patients with: 1, 2, 3

  • AV block greater than first degree (without pacemaker)
  • Sick sinus syndrome
  • Hypotension
  • Decompensated systolic heart failure or severe LV dysfunction
  • Pre-excited atrial fibrillation/flutter (WPW syndrome)

• Use with caution when combined with: 6, 2, 3

  • Beta-blockers (risk of significant bradyarrhythmias and heart failure)
  • Digitalis (additive effects on cardiac conduction)
  • Medications metabolized by CYP3A4 (diltiazem is a moderate CYP3A4 inhibitor)

Adverse Effects

• Hypotension is the most common adverse effect 1, 2, 3
• Bradycardia may occur, particularly with concomitant use of other negative chronotropic agents 1, 3
• Worsening heart failure in predisposed patients 1, 3
• Pedal edema, especially with higher doses 5
• Rare instances of significant elevations in liver enzymes 3

Monitoring

• Blood pressure and heart rate 2
• Signs and symptoms of heart failure in at-risk patients 2
• ECG monitoring in patients with conduction system disease 2
• Liver function tests if clinically indicated 2

Clinical Pearls

• For hypertension in patients with coronary artery disease, if beta-blockers are contraindicated, diltiazem may be substituted, but not if there is LV dysfunction 6
• When diltiazem is used for hypertension with stable angina, it can be combined with an ACE inhibitor/ARB and thiazide diuretic if needed for BP control 6
• Resuscitation equipment should be available when administering IV diltiazem 1
• For severe bradycardia as a side effect, consider atropine or temporary pacing if needed 1