Does vitamin K supplementation improve vitamin K antagonist therapy? A case report and update of the literature

We report a multi-morbid patient with mechanical aortic valve and unstable and sub-therapeutic levels of international normalized ratio (INR), initially in phenprocoumon and later in warfarin therapy. All efforts, including self-testing using Point of Care Testing with telemedicine support to stabilize the patient's INR within the therapeutic range, were unsuccessful. Since INR fluctuations can occur due to poor or varied dietary vitamin K, 180 μg/day vitamin K was added to the patient's warfarin treatment in an attempt to stabilize INR fluctuations. Three weeks later INR was in therapeutic range and remained within range for two consecutive months suggesting beneficial effect of vitamin K. Our updated literature review demonstrates that vitamin K supplementation can improve the stability of INR without improvement of time therapeutic range.