William Henry Howell (1860–1945), Jay McLean (1890–1957), Gordon Murray (1894–1976), Charles Best (1899–1978)
Heparin’s journey from discovery to clinical use was long, tortuous, and controversial. In 1916, Jay McLean, a second-year medical school student working in the laboratory of William Henry Howell, a distinguished Professor of Physiology at Johns Hopkins University, isolated an anticoagulant from a dog liver. Two years later, Howell isolated another distinct anticoagulant from the liver and named it heparin (from Greek hepar, or liver).
Although Howell’s heparin was impure and caused toxic reactions, its promise was recognized. Starting in the late 1920s, Charles Best (of insulin fame) and members of his laboratory at the University of Toronto set out to purify it—a method not accomplished until 1936. In 1937, Gordon Murray, one of Canada’s most famous surgeons, first used heparin to prevent clotting in veins and in kidney-dialysis machines.
Heparin, which retards the ability of blood to clot in blood vessels, is used during open-heart surgery, bypass surgery, kidney dialysis, blood transfusions, and pregnancy. Medically used heparin is prepared from the lungs of cattle and intestines of pigs. Although heparin and related anticoagulants are colloquially referred to as “blood thinners,” they do not thin the blood or dissolve blood clots. Rather, they prevent clots from becoming larger and blocking the flow of blood in blood vessels, which can have lethal consequences.
The anticoagulant effects of heparin begin almost immediately after being injected and continue for several hours. Heparin is a medical “double-edged sword”: It can be lifesaving, but if not used at correct doses and monitored carefully, potentially fatal bleeding can occur. This danger was highlighted in 2007, when the twelve-day-old twins of the actor Dennis Quaid were mistakenly given 1,000 times the recommended dose with near-fatal results.
Credit for the discovery of heparin has shifted over the years and currently remains a subject of active debate among medical historians. Before the 1940s, Howell was overwhelmingly lauded for this honor. After Howell’s death in 1945, McLean aggressively campaigned in national lectures and published articles that it was he who discovered, or at least co-discovered, heparin.
SEE ALSO Aspirin (1899), Insulin (1921), Warfarin (1940), Plavix (1997), Pradaxa (2010).
William Henry Howell (1860–1945) had a career-long passion for the physiology of blood coagulation. This research led to the 1916 discovery of heparin, a substance naturally circulating in the blood that inhibits coagulation within blood vessels. Howell’s studies in the 1930s were instrumental to the introduction of heparin into clinical practice for the treatment of life-threatening clotting disorders.