GRISEOFULVIN AND WARFARIN AND OTHER ORAL ANTICOAGULANTS

The anticoagulant effects of warfarin can be reduced by griseofulvin in some patients. In one patient a 41% increase in the dose of warfarin was needed.
Monitor the anticoagulant effect if griseofulvin is added or withdrawn in patients taking warfarin. Note that in one patient the interaction took 12 weeks to develop.