Rwarfarin

Rwarfarin refers to the R-enantiomer of warfarin, a vitamin K antagonist used as an oral anticoagulant. Warfarin is administered as a racemic mixture containing both R- and S-enantiomers. S-warfarin is more potent at inhibiting vitamin K epoxide reductase (VKORC1) and contributes most of the anticoagulant effect, while R-warfarin is less potent but still contributes to overall activity and variability in response.

Pharmacology and metabolism: Both enantiomers inhibit VKORC1, decreasing the regeneration of reduced vitamin K and thereby impairing the synthesis of vitamin K–dependent clotting factors. R-warfarin is primarily metabolized by cytochrome P450 enzymes such as CYP1A2 and CYP3A4 to hydroxywarfarin metabolites; S-warfarin is mainly metabolized by CYP2C9. These enantiomers can have different pharmacokinetic profiles, influencing onset and duration of action.

Clinical use: There is no separate regulatory indication for R-warfarin as an independent drug; therapeutics rely on the racemate. Genetic variations (eg, VKORC1, CYP2C9) and drug interactions affecting one enantiomer often affect the other, though to different extents.

Safety and monitoring: Warfarin therapy requires regular monitoring of the international normalized ratio (INR) to maintain therapeutic anticoagulation while minimizing bleeding risk. Diet (vitamin K intake), liver function, age, and interactions with other drugs can influence the balance of both enantiomers.

History: Warfarin was developed from earlier anticoagulants and first marketed in the 1950s. R- and S-warfarin refer to its chiral forms, with ongoing pharmacological studies assessing the distinct properties of each enantiomer.