Anticoagulants (eg, warfarin) Warfarin PT increased by 100% after 3 to 4 days; reduce dose of anticoagulant by one third to one half.
Antihypertensives Use with caution with beta blockers or calcium channel blockers because of the possible potentiation of bradycardia, sinus arrest, and AV block.
Azole antifungals/fluoroquinolones/macrolides Reports of QTc prolongation with or without torsades de pointes may occur when used concomitantly with amiodarone.
Cardiac glycosides (eg, digoxin) Digoxin levels are increased and may result in toxicity. Reduce digoxin dose by approximately 50% or discontinue.
Cholestyramine Cholestyramine increases enterohepatic elimination of amiodarone and may reduce its serum levels and t ½ .
CYP3A4 inducers (eg, rifampin) Amiodarone and the metabolite, desethylamiodarone, plasma levels may be reduced, decreasing the pharmacologic effect.
CYP3A4 inhibitors (eg, cimetidine, ritonavir) Amiodarone plasma concentrations may be elevated, increasing the pharmacologic and adverse reactions.
Fentanyl In combination with amiodarone may cause hypotension, bradycardia, and decreased cardiac output.
Grapefruit juice Amiodarone plasma concentrations may be elevated, increasing the risk of side effects. Patients taking oral amiodarone should avoid grapefruit juice.
HMG-CoA reductase inhibitors (eg, simvastatin) Simvastatin plasma levels may be elevated, increasing the risk of adverse reactions (eg, myopathy, rhabdomyolysis).
Lidocaine Lidocaine plasma concentrations may be elevated, increasing the risk of seizures.
P-glycoprotein and CYP1A2, CYP2C9, CYP2D6, and CYP3A4 (eg, cyclosporine) Plasma concentrations of drugs metabolized by these CYP enzymes or substrates of P-glycoprotein may be elevated, increasing the risk of side effects.
Protease inhibitors (eg, ritonavir) Amiodarone plasma concentrations may be elevated, increasing the pharmacologic and adverse reactions.
St. John's wort Amiodarone plasma levels may be reduced, decreasing the pharmacologic effects.
Trazodone QT interval prolongation and torsade de pointes have been reported with coadministration.
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