What is the use and dosage of Dilzem (Diltiazem) in clinical practice?

Diltiazem: Clinical Uses and Dosing Guidelines

Diltiazem is recommended for the management of hypertension, angina, and supraventricular tachycardias, with a usual maintenance dose range of 120-360 mg once daily for extended-release formulations, and specific dosing based on the indication. 1

Primary Indications

1. Cardiovascular Conditions

• Angina

  • FDA-approved for chronic stable angina and angina due to coronary artery spasm 2
  • Usual maintenance dose: 240 mg daily for extended-release formulations 1
  • Maximum dose: 360 mg daily 1

• Hypertension

  • Starting dose: 240 mg daily (extended-release) 1
  • Maintenance dose: 120-360 mg once daily 1
  • Note: Evidence suggests hypertension often requires higher doses (360 mg/day) compared to angina (240 mg/day) 3

2. Arrhythmia Management

• Supraventricular Tachycardia (SVT)
  • Intravenous diltiazem is reasonable for acute treatment in hemodynamically stable patients with AVNRT 4
  • Oral diltiazem is recommended for ongoing management in patients with AVNRT who are not candidates for catheter ablation 4
  • Effective in terminating supraventricular tachycardia and controlling ventricular response in atrial fibrillation/flutter 5

Dosage Forms and Administration

Oral Formulations

• Immediate-release tablets:

  • Absorbed to about 98% of reference solution 2
  • Detectable plasma levels within 30-60 minutes 2
  • Peak plasma levels 2-4 hours after administration 2

• Extended-release formulations:

  • Once-daily dosing (CD formulation) is as effective as twice-daily (SR formulation) for hypertension 6
  • Therapeutic plasma levels: 50-200 ng/mL 2

Important Contraindications and Precautions

Absolute Contraindications 1

• Left ventricular dysfunction (LVEF <40%)
• Decompensated heart failure
• AV block greater than first degree
• Sick sinus syndrome
• Cardiogenic shock
• Pre-excitation syndromes (e.g., Wolff-Parkinson-White syndrome)

Drug Interactions

• Avoid combination with beta-blockers when possible due to increased risk of bradycardia and heart block 1
• If combination therapy is necessary, careful monitoring is required 1

Monitoring Parameters

• Blood pressure response
• Heart rate and cardiac conduction
• Signs of fluid retention (edema)
• Symptoms of hypotension or bradycardia 1

Common Side Effects

• Hypotension
• Dizziness
• Flushing
• Bradycardia
• Edema 1

Clinical Pearls

1. Dosing Considerations:

   • Diltiazem is often underdosed for hypertension; optimal antihypertensive effects may require doses up to 360-480 mg/day 3
   • The 90-120 mg/day range is considered a "no-effect dose" for hypertension 3

2. Pharmacokinetics:

   • Subject to extensive first-pass metabolism with absolute bioavailability of about 40% 2
   • Plasma elimination half-life: 3.0-4.5 hours 2
   • 70-80% bound to plasma proteins 2

3. Alternative to Ablation:

   • Oral verapamil or diltiazem is recommended for ongoing management in patients with AVNRT who are not candidates for catheter ablation 4
   • However, catheter ablation has success rates exceeding 95% for AVNRT and should be considered for recurrent SVT 1

4. Cardioprotective Effects:

   • Diltiazem appears to exert cardioprotective effects that may benefit patients undergoing coronary procedures 5
   • Has been shown to reduce subsequent cardiac events in patients with non-Q wave myocardial infarction 5

Remember that diltiazem has minimal negative inotropic effects in patients with normal ventricular function but should be avoided in patients with left ventricular dysfunction where it can have detrimental effects on mortality 1, 7.