It all began in the early 1920s in the farms of Wisconsin, USA. Cattle were mysteriously dying bleeding to death from even the tiniest cuts. Farmers were horrified. Postmortems revealed massive internal hemorrhages, but no known disease explained it.
Desperate, they called in veterinary pathologist Frank Schofield, who noticed a strange pattern: the cows had all eaten spoiled sweet clover hay. But why would hay cause bleeding?
The breakthrough came in 1940 when biochemist Karl Paul Link and his team at the University of Wisconsin isolated the culprit: a chemical compound formed when sweet clover molded dicoumarol. It interfered with vitamin K and stopped blood from clotting.
So what did they do with this discovery?
They weaponized it.
In the 1940s, Link’s team modified dicoumarol into a more potent compound to kill rats. It was named warfarin, after the Wisconsin Alumni Research Foundation (WARF). It was one of the first true anticoagulant rodenticides and yes, it worked very well. Rats bled to death.
But the twist came in 1951.
A young soldier in the US Army tried to take his own life by ingesting a large amount of warfarin rat poison. Shockingly, he survived with no permanent damage after being treated with vitamin K.
That changed everything. If warfarin’s effects were reversible and manageable, maybe it could be used therapeutically.
By 1954, warfarin was approved for human use as an anticoagulant. Ironically, its first major patient? President Dwight D. Eisenhower, who was given warfarin after a heart attack.
From dead cows
To rat poison
To the President’s medicine
Warfarin became one of the most widely prescribed drugs in history, saving millions from strokes, clots, and heart attacks.
Today, it’s a symbol of both caution and innovation—proof that medicine can come from the most unexpected places.