The event leading to the discovery of Warfarin started in the early 20th Century by the deaths of cattle in the United States and Canada by severe internal bleeding. In 1922, a specialist in veterinary medicine, Schofield, postulated that these deaths were being caused by the cattle eating spoiled sweet clover hay. It was a mystery as to why this spoilt sweet clover hay had these effects until 1939 when Karl Paul Link and his team at the University of Wisconsin discovered the compound that had caused these effects. It was Dicumarol. This compound was formed from the oxidation of coumarin, which is in fresh sweet clover hay, by fungi in the spoilt hay. Dicumarol was used as an oral anticoagulant once its' effects had been discovered.
Interest was regenerated after the Second World War when in 1946 Link and his team turned their attentions to the development of a rat poison. Dicumarol was ineffective as a rodenticide and they later discovered, 3-phenylacetyl ethyl 4-hydroxycoumain, which was a very potent rodenticide and patents rights were assigned to the Wisconsin Alumni Research Foundation. This lead to the name WARFARIN. In 1948 Warfarin was launched as the perfect rat poison.
Above is a model of WARFARIN
Karl Paul Link in his laboratory early 1950's
The first clinical study of Warfarin for use in humans was carried out in the early 1950's. This had been brought about due to a failed suicide attempt by a navy recruit who had tried to kill himself by taking an overdose of the rat poison, Warfarin. These studies had a great impact on the use of Warfarin and in 1955 Warfarin was even given to President Eisenhower following his heart attack.