amiodarone and diltiazem

MajorAvoid this combination where possible.

Mechanism

Pharmacodynamic additive inhibition of sinoatrial and atrioventricular node conduction and myocardial contractility; pharmacokinetic interaction with amiodarone inhibiting CYP3A4 and P-glycoprotein, increasing diltiazem concentrations.

What it means clinically

Bradycardia, AV block, hypotension, and heart failure may occur. Risk is highest in patients with pre-existing conduction disease or left ventricular dysfunction.

What to do

Avoid co-prescription where possible. If the combination is necessary, monitor ECG, heart rate, and blood pressure, and consider dose reduction. Advise patients to report palpitations, dizziness, or syncope.

Evidence

Well established; reported in clinical studies and case reports. Cautions in guidelines and formularies.

The two drugs

amiodaroneClass III antiarrhythmicRead the monograph diltiazemCalcium channel blockersRead the monograph

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Other interactions involving amiodarone or diltiazem

Educational reference for students and clinicians in training. It does not replace professional judgement, local protocols or current prescribing information.