Mechanisms of drug interactions
Warfarin is well absorbed, is highly bound to the
plasma proteins (99%) and is metabolized via the
cytochrome P450 system.1 It is an indirect anticoagulant,
exerting its effect by preventing the internal
recycling of oxidized vitamin K to reduced
vitamin K. Reduced vitamin K is necessary to
enable carboxylation of the terminal g-glutamic
acid residue of the vitamin K–dependent clotting
factors (factors II, VII, IX and X). The metabolism
of warfarin allows for both pharmacokinetic
and pharmacodynamic mechanisms for drug
interactions.