Verapamil to Diltiazem CD Conversion
For a patient taking verapamil XC 240 mg daily, convert to diltiazem CD 240 mg once daily using a 1:1 dose equivalence ratio. 1
Direct Dose Conversion
The American College of Cardiology recommends a 1:1 ratio for converting between verapamil and diltiazem at standard dosing levels, with both medications sharing an initial dose of 120 mg daily. 1
Verapamil 240 mg daily converts directly to diltiazem CD 240 mg once daily, maintaining equivalent therapeutic effect for rate control and blood pressure management. 1
Both extended-release formulations can be administered once daily, making the transition straightforward without requiring dose frequency adjustments. 2, 1
Important Monitoring After Conversion
Monitor blood pressure and heart rate regularly during the first 2-4 weeks after switching to detect any differences in individual patient response. 1
Watch specifically for signs of hypotension, bradycardia, conduction abnormalities, or worsening heart failure in patients with pre-existing ventricular dysfunction. 2, 1
Reassess the patient within 1 month after conversion to ensure adequate symptom control and absence of adverse effects. 2
Critical Drug Interaction Differences
Verapamil has more extensive drug interactions than diltiazem, particularly through P-glycoprotein inhibition in addition to CYP3A4 effects. 1
When switching from verapamil to diltiazem, patients on dabigatran, edoxaban, rivaroxaban, or flecainide may experience decreased drug levels since diltiazem lacks verapamil's P-glycoprotein inhibition. 1
Carefully review the patient's complete medication list before conversion, as dose adjustments of interacting medications may be necessary. 1
Dosing Range Considerations
While the 1:1 conversion applies at standard doses, verapamil can be titrated up to 480 mg daily versus diltiazem's maximum of 360 mg daily, suggesting verapamil may have slightly greater potency at higher dose ranges. 1
If the patient was well-controlled on verapamil 240 mg daily, the equivalent diltiazem CD 240 mg daily should provide comparable efficacy. 1
Contraindications Remain Identical
Both medications share the same contraindications: AV block greater than first degree without a pacemaker, sick sinus syndrome without a pacemaker, decompensated systolic heart failure or severe LV dysfunction (LVEF <40%), hypotension, and Wolff-Parkinson-White syndrome with atrial fibrillation/flutter. 3, 1
Avoid routine combination with beta-blockers due to increased risk of profound bradycardia, AV block, and heart failure with both agents. 2, 1