What is warfarin?

Warfarin (Coumadin®) is an anticoagulant that can be taken by mouth. It has been used extensively for more than 50 years to prevent blood clots.

In the early 1930s, Dr. Karl Paul Link, at the University of Wisconsin, identified a component of spoiled sweet clover, dicumarol, that caused a bleeding disease in cattle. In 1939, Link, looking for a better rat poison, synthesized dicumarol and assigned the patents to the Wisconsin Alumni Research Foundation—hence the name “warfarin,” a name derived from the organization’s initials. Warfarin was introduced as a rat poison in 1948 and licensed in 1952.

Warfarin was thought to be unsafe for humans until a U.S. sailor tried to poison himself with this agent in 1955. After this unsuccessful suicide attempt, doctors began to think about using warfarin to treat people. One of the first patients to receive this drug as an anticoagulant was President Dwight Eisenhower, who was treated with warfarin after he suffered a heart attack in 1955. Joseph Stalin, who died with bleeding complications in 1953, may have been poisoned with warfarin, as suggested in the book Stalin’s Last Crime: The Plot Against the Jewish Doctors, 1948–1953.

Since its adoption as medication for humans, warfarin has been widely used to treat and prevent clots. Besides the treatment and prevention of DVT and PE, it is used to prevent recurrent heart attacks and strokes and to prevent clots from forming in individuals with mechanical heart valves or the heart condition known as atrial fibrillation. With more than 20 million prescriptions being written for this drug each year, warfarin is the twentieth most commonly prescribed drug in the United States. At any given time, as much as 1 percent of the U.S. population may be taking warfarin.