Aspects of anticoagulant action: a review of the pharmacology, metabolism and toxicology of warfarin and congeners.

Warfarin is the most widely used anticoagulant in the treatment of thromboembolism in man. It has also been used extensively as a rodenticidal agent. Insofar as its clinical use is concerned, it is now clear that many of the drug interactions observed in patients are mediated via metabolic or pharmacokinetic factors. An understanding of the disposition of warfarin is therefore essential if one is to predict the likely response in patients undergoing anticoagulant therapy with this compound. Warfarin-resistance has been reported in both man and rodents. Understanding resistance in both man and rodents is important for effective anticoagulant therapy, and in control of resistant strains of rodents. Warfarin resistance in rat strains does not appear to have a metabolic or pharmacokinetic basis; in this species, resistance is thought to be due to differences in permeability to, or affinity for a receptor. Apart from its clinical and rodenticidal uses, warfarin is an excellent substrate for probing the heterogeneity of cytochrome P.450, since its metabolic oxidation is mediated by this mixed function oxidase. This review draws together much of the current published literature on the pharmacology, metabolism and toxicology of warfarin and related congeners.