OBJECT DRUGS

Antiarrhythmics (CYP3A4 Substrates):

• Amiodarone (Cordarone, etc.)
• Disopyramide (Norpace, etc.)
• Dronedarone (Multaq)
• Quinidine (Quinidex)

PRECIPITANT DRUGS

Calcium Channel Blockers:

• Diltiazem (Cardizem, etc.)
• Verapamil (Isoptin, etc.)

Comment:

Although data are limited, any calcium channel blocker that inhibits CYP3A4 could increase the plasma concentrations of these antiarrhythmic drugs. Toxicity including cardiac arrhythmias could result. Assume that all CYP3A4 inhibitors interact until proven otherwise.

Class 3: Assess Risk & Take Action if Necessary

• Consider Alternative:
• Calcium Channel Blockers: Calcium channel blockers other than diltiazem and verapamil are unlikely to inhibit the metabolism of these antiarrhythmics.
• Monitor: Monitor for altered antiarrhythmic response if the CYP3A4 inhibitor is initiated, discontinued, or changed in dosage. Monitor for ECG changes indicating antiarrhythmic toxicity, and measure antiarrhythmic plasma concentrations as needed.