Warfarin Therapy

WITH increasing frequency patients receiving warfarin are taking other medications that profoundly influence the response to the anticoagulant. In some cases the patients are rendered more sensitive to warfarin, whereas in others the combination of drugs decreases the effect of warfarin. The often confusing array of interactions of warfarin with other drugs can be more clearly appreciated if the varying steps in the metabolism of warfarin and of vitamin K are considered (Fig. 2). Drugs that bind vitamin K (phytate) or prevent its absorption by trapping the bile salts necessary for its absorption (cholestyramine) will markedly increase the sensitivity of . . .