Common Cardiovascular Drug Interactions

Question 1

Amiodarone + Warfarin

1. Risk
2. Action by the pharmacist

Answer 1

1. Amiodarone inhibits CYP2C9 (Major warfarin substrate) = DECREASED warfarin metabolism, INCREASED INR, bleeding risk INCREASED
2. Start warfarin at decreased dose, or empirically decrease dose by 30-50%, monitor INR, adjust as needed.

Question 2

Amiodarone + Digoxin

1. Risk
2. Action by the pharmacist

Answer 2

1. Amiodarone inhibits P-gp: Digoxin = P-gp substrate = DECREASED digoxin excretion, INCREASED ADRs/Toxicity