warfarin + rifampin

This is a combination of two small molecule drugs, warfarin and rifampin, used concomitantly rather than as a fixed-dose combination product. Warfarin is an oral anticoagulant that acts as a vitamin K antagonist, inhibiting the synthesis of vitamin K-dependent clotting factors (II, VII, IX, X) in the liver. Rifampin is an antibiotic primarily used to treat tuberculosis and other bacterial infections; it works by inhibiting DNA-dependent RNA polymerase in susceptible bacteria. When administered together, rifampin induces hepatic cytochrome P450 enzymes (notably CYP2C9 and CYP3A4), which accelerates the metabolism of warfarin—especially R-warfarin—leading to reduced anticoagulant effect and necessitating significant increases in warfarin dosage to maintain therapeutic anticoagulation[1][2][5]. This interaction requires close monitoring due to risks of both thrombosis (if under-anticoagulated) and bleeding (if over-anticoagulated after stopping rifampin)[1][2].

Other names

warfarin plus rifampin