Cardiovascular Drug Interactions

Amiodarone + Warfarin

Amiodarone inhibits CYP2C9 = increases INR

If amiodarone first and then adding warfarin, start at a lower dose < 5 mg. If vice-versa, lower dose by 30-50%.

Amiodarone + Digoxin

Amiodarone inhibits P-gp = increases ADRs/toxicity

Both lowers HR and so, increases risk of bradycardia.

If amiodarone first and then digoxin, start at low dose like 0.125 mg daily. If vice-versa, lower dose by 50%.

Digoxin + Loop diuretic

Loop diuretics lowers K, Mg, Ca, and Na, which can increase Digoxin toxicity.

Caution: HF and renal impairment occur together. Loop can exacerbate renal impairment and prevent digoxin excretion.

Drugs that decrease HR

Additive effects when the following are used together: amiodarone, digoxin, beta-blockers, clonidine, diltiazem, verapamil, and dexmedetomidine.

Statins + Strong CYP3A4 Inhibitors

Levels of lovastatin, atorvastatin, and simvastatin will be increased. Recommend another statin.

Warfarin + CYP2C9 inhibitors and inducers

Inhibitors: Increases warfarin levels.

Inducers: Lowers warfarin level.

Monitor INR.