Medscape - Deep vein thrombosis, pulmonary embolism, recurrent myocardial infarction-specific dosing for Coumadin, Jantoven (warfarin), frequency-based adverse effects, comprehensive interactions, contraindications, pregnancy & lactation schedules, and cost information. A sudden increase or decrease in the amount of vitamin K can change the effect warfarin may have on your blood. Grapefruit juice and cranberry juice are sometimes of concern to patients taking warfarin. However, recent studies indicate that consuming 4 to 6 ounces of cranberry juice doesn't cause significant interactions. However, in regard to grapefruit juice, you may want to be a little more. Warfarin has many drug interactions; always check with an anticoagulation provider before taking any new medications (including over-the-counter medications and dietary supplements) Foods with a lot of vitamin K like broccoli, spinach, and green tea may interfere with warfarin; do not avoid foods with vitamin K, but try to maintain consistent dietary habits Warfarin decreases the amount of clotting proteins that that the liver makes. In addition to treating your atrial fibrillation with warfarin (Coumadin), your doctor probably decided you need aspirin for another reason. Although using two different methods to prevent blood clots does increase the risk of bleeding, it is generally accepted as safe given the potential benefits. These studies, if successful, may herald a new era of personalized medicine, in which the dosage of warfarin, and hence INR control, can be better predicted through the development of algorithms that use environmental and genetic factors as co-variates. The importance of this lies not only in improving the use and safety of warfarin, but because it also serves as a paradigm for introducing. While warfarin can be a lifesaver for patients suffering from atrial fibrillation and other conditions that may cause a fatal blood clot, the drug also has its drawbacks. Bleeding is the most common side effect and is described in a black-box warning on the drug’s label. The side effect can be avoided through frequent blood tests and dose adjustments.