When to switch from immediate acting Cardizem (diltiazem) to long acting Cardizem (diltiazem)?

Switching from Immediate-Acting to Long-Acting Diltiazem (Cardizem)

The optimal time to switch from immediate-acting diltiazem to long-acting diltiazem is 4 hours after administering the first dose of long-acting diltiazem, with the long-acting formulation given on a milligram-for-milligram basis or to the next higher available dose.

Conversion Protocol

Timing of Conversion

• When converting from intravenous to oral diltiazem, research shows that administering the first oral long-acting dose and continuing the IV infusion for 4 hours afterward maintains effective heart rate control in 77% of patients 1
• For patients on immediate-release oral diltiazem tablets, direct conversion to the extended-release formulation can be done without a transition period 2

Dosage Conversion

• Convert from immediate-release to extended-release diltiazem on a milligram-for-milligram basis 2
• When an exact equivalent dose is not available, use the next higher available dose of the extended-release preparation 2
• The American College of Cardiology recommends starting with a total daily dose of 240mg of diltiazem given as a once-daily extended-release formulation 3

Monitoring During Transition

Parameters to Monitor

• Heart rate and blood pressure should be closely monitored during the transition period
• For patients with atrial fibrillation or flutter, target heart rate should be <100 beats/min or ≥20% decrease from baseline 1
• Continuous cardiac monitoring is necessary to assess for worsening bradycardia or conduction abnormalities during the transition 3

Duration of Monitoring

• Monitor for at least 48 hours after transitioning to ensure stable heart rate control 1
• Pay particular attention to the morning hours when blood pressure typically surges 4

Special Considerations

Timing of Administration

• Evening dosing of long-acting diltiazem may be more effective than morning dosing for controlling morning blood pressure surges 4
• Evening-dosed long-acting diltiazem has been shown to be more effective than morning-dosed amlodipine in reducing morning diastolic BP in African-Americans 4

Contraindications

• Avoid diltiazem in patients with:
  • Heart failure with reduced ejection fraction (LVEF <40%)
  • Decompensated heart failure
  • AV block greater than first degree
  • Sick sinus syndrome
  • Cardiogenic shock 3

Drug Interactions

• Use caution when combining diltiazem with beta-blockers due to increased risk of bradycardia and heart block 3
• Non-dihydropyridine calcium channel blockers like diltiazem can have a detrimental effect on mortality in patients with LV dysfunction 5

Dosage Range and Adjustments

• The usual oral maintenance dose range for extended-release diltiazem is 120-360mg once daily 3
• Maximum recommended dose is 360mg once daily 3
• Titrate based on blood pressure response, heart rate, and symptoms

Common Pitfalls to Avoid

• Avoid immediate-release nifedipine in patients with acute coronary syndromes without concomitant beta-blockade 5
• Don't discontinue IV diltiazem before the long-acting oral formulation has had time to reach therapeutic levels (approximately 4 hours) 1
• Avoid abrupt discontinuation of diltiazem therapy, which may exacerbate angina symptoms

By following this protocol for switching from immediate-acting to long-acting diltiazem, clinicians can maintain effective control of heart rate and blood pressure while transitioning patients to a more convenient once-daily dosing regimen.