This is given for several months after a person has had a blood clot in a leg vein or the lung and sometimes after a heart attack as well. People with mechanical heart valves and many patients with atrial fibrillation or blood clots in their heart chambers must remain on coumadin chronically to prevent strokes. Some people have unusually thick blood due to abnormal coagulation proteins and also must remain on coumadin permanently. Treatment with coumadin requires periodic monitoring with blood tests. The main side effect with coumadin is an increased risk of bleeding.
Many medications interact with coumadin.
It is prudent to check the INR more frequently when other medications are added or withdrawn. Coumadin works by interfering with the effect of vitamin K. Vitamin K is used by the liver to make some of the coagulation proteins. Excess vitamin K will offset the effect of coumadin. The dose of coumadin can be adjusted for any level of dietary vitamin K intake. However, it is important to eat the same amount of vitamin K containing foods all the time so that the level of blood thinning remains stable.