Warfarin potentiation: a review of the "FAB-4" significant drug interactions

Warfarin is an anticoagulant with numerous drug-drug interactions. Four significant drug interactions with warfarin are: fluconazole, amiodarone, sulfamethoxazole/trimethoprim, and metronidazole. Potentially life-threatening interactions with these medications are a common occurrence because they have a broad spectrum of indications in elderly individuals. With the increasing number of elderly individuals, who consume a disproportionate number of medications, cautious monitoring for these drug interactions is essential. Drug interactions often are overlooked despite computer alert systems. Careful analysis of each patient's situation will help in evaluating whether the use of a medication is appropriate. Through knowledge of potential mechanisms of interaction, management options such as dose reductions and/or the use of alternative agents should be used in determining the appropriate drug therapy.