Case reports describe raised INRs and bleeding when
fluconazole,
ketoconazole, or
itraconazole were given with
warfarin. The anticoagulant effects of acenocoumarol, ethyl biscoumacetate, fluindione, phenindione, phenprocoumon, tioclomarol and
warfarin can be markedly increased if miconazole is given orally, and bleeding can occur. The interaction can occur with buccal gel, intravaginal miconazole, and in one case, with miconazole cream. Voriconazole decreases the
metabolism of
warfarin resulting in a doubling of the prothrombin time. Acenocoumarol appears to interact similarly.
Monitor the INR if an azole is given with an oral anticoagulant and adjust the dose accordingly. Oral miconazole,
fluconazole and
voriconazole interfere with the main metabolic pathway of
warfarin (and acenocoumarol) and are therefore likely to interact more frequently than the other
azoles.