What is Coumadin? This medicine is used to treat blood clots (eg, deep vein thrombosis-DVT or pulmonary embolism-PE) and/or to prevent new blood clots from forming in the body. Preventing harmful blood clots from forming helps reduce the risk of a stroke or heart attack. The active ingredient in this medicine is warfarin. Warfarin competitively inhibits vitamin K epoxide reductase complex 1 (VKORC1), which is an enzyme required to activate vitamin K in the body. Through this mechanism, warfarin can deplete the functional stores of vitamin K and, consequently, reduce the synthesis of active blood clotting factors. Warfarin entered clinical practice under the trade name Coumadin and was approved for human use in 1954. One of the first recipients of warfarin was US President Dwight D. Eisenhower, who was prescribed the drug after a heart attack in 1955. Warfarin was first registered for use as a rodenticide in the US in 1948 and immediately became popular. Although warfarin was developed by Link, the Wisconsin Alumni Research Foundation funded the research and received a patent. Coumadin is manufactured by Bristol-Myers Squibb. Coumadin is available in the following forms: 1mg, 2mg, 2.5mg, 3mg, 4mg, 5mg, 6mg, 7.5mg, 10mg. Warfarin belongs to a class of drugs called anticoagulants. A drug class is a group of drugs that work in a similar way. These drugs are often used to treat these conditions.