AMIODARONE AND WARFARIN AND OTHER ORAL ANTICOAGULANTS
The anticoagulant effects of warfarin, phenprocoumon and acenocoumarol are increased by amiodarone in most patients and bleeding may occur. The onset of this interaction may be slow (up to 2 weeks). (23)
The dosage of warfarin and phenprocoumon should be reduced by one-third to two-thirds if amiodarone is added. The dosage of acenocoumarol should be reduced by between about 30 and 50%. However, these suggested reductions are only broad generalisations and individual patients may need more or less. The INR (or prothrombin times) should be very closely monitored both during and following treatment. One study advises weekly monitoring for the first 4 weeks of concurrent use.