VITAMINS AND WARFARIN AND OTHER ORAL ANTICOAGULANTS

The effects of these anticoagulants can be reduced or abolished by vitamin K. This effect can be used to manage overdosage, but unintentional and unwanted antagon- ism has occurred in patients after taking some proprietary chilblain preparations, health foods, food supplements, enteral feeds or exceptionally large amounts of some green vegetables, seaweed, or green tea, which can contain significant amounts of vitamin K.
The drug intake and diet of any patient who shows warfarin resistance' should be investigated for the possibility of this interaction. It can be accommodated either by increasing the anticoagulant dosage, or by reducing the intake of vitamin K. However, patients taking vitamin K-rich diets should not change their eating habits without at the same time reducing the anticoagulant dosage, because excessive anticoagulation and bleeding may occur.