The blood-thinning medication Warfarin is used by millions of patients across the country, and we can trace its origins to a lab at the University of Wisconsin-Madison in the middle of the 20th century.
There, researcher Karl Paul Link and his team isolated the anticoagulating compound that can help prevent strokes and heart attacks. It can also be used — in a different form — as rat poison.
Author Doug Moe dug into the history of the discovery and Link’s unique personality in a new book called “Saving Hearts and Killing Rats: Karl Paul Link and the Discovery of Warfarin.”
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Moe joined WPR’s “Wisconsin Today” to share the story of Warfarin and Link’s legacy with this breakthrough discovery.
The following was edited for clarity and brevity.
Rob Ferrett: Take us through the story of how Karl Paul Link discovered Warfarin.
Doug Moe: A young farmer named Ed Carlson from St. Croix County comes down on a bitterly cold Saturday morning in February of 1933. Carlson has with him a dead cow, a bucket of cow’s blood and a batch of sweet clover hay. He explains that his cows have been hemorrhaging and dying. If they bump up against barbed wire and start bleeding, the blood won’t stop.
Link, who was a carbohydrate chemist, really took on this farmer’s cause. Something really clicked with this visit. For the next six or seven years, Karl and his grad students in the lab worked on that sweet clover hay to find out what was in it that made the cow’s blood not coagulate. They did like 10,000 blood coagulation tests, I found in my research. Eventually, they were able to isolate what it was. It was coumarin in the hay that caused their blood not to coagulate. Link and his team then were able to reproduce that synthetically and came up with a blood thinner.
RF: This substance ended up being used both as a rat poison and a life-saving medication. How did that happen?
DM: You have to jump to the late ’40s or around 1950 or so. A young serviceman who was suffering depression stumbled into a military hospital out East and was not doing well. He had attempted suicide by ingesting large amounts of the rat poison Warfarin. And a light bulb kind of clicked on here in Madison for Karl Paul Link.
He thought, “Well, if Warfarin isn’t lethal, at least in the amounts that this individual took, maybe there’s a way to tweak it a bit, and it can be a better human anticoagulant.” And indeed, that’s what happened. They came up with a water-soluble sodium salt derivative of Warfarin. They called it Warfarin sodium, and eventually that became one of the world’s great human anticoagulants.
RF: You heard different stories about Link being generous with the staff he worked with and yet also having conflict with colleagues. What were these different sides of him like?
DM: The students that I was able to interview did talk about his generosity and how he asked them to do things on their own to gain the confidence that would help their later science. But he did have a few very serious fallings out. One of them was with a grad student of his, a young man named Mark [A.] Stahmann, who is on the Warfarin patent with Karl. As time went on, Karl and Stahmann had a falling out. I worked very hard to try to find out what was behind it. It seems like there was some dispute about proper credit for the discovery. But a definitive answer escaped me.
RF: What do you think Karl Paul Link would say about the kind of cuts we’re seeing to research funding in the U.S. today?
DM: Well, he would be aghast, if I may say that boldly. He devoted his life to research at the university. That research component led to one of the great medical breakthroughs of the 20th century. I have no doubt in my mind that he would be very upset and I’m sure quite vocal about it.