An early recipient of warfarin was US President Dwight Eisenhower, who was prescribed the drug after having a heart attack in 1955.The exact mechanism of action remained unknown until it was demonstrated, in 1978, that warfarin inhibits the enzyme vitamin K epoxide reductase, and hence interferes with vitamin K metabolism.Lavrenty Beria and I. V. Khrustalyov are thought to have conspired to use warfarin to poison Soviet leader Joseph Stalin. Warfarin is tasteless and colourless, and produces symptoms similar to those that Stalin exhibited. Pest control
Rodents
Coumarins (4-hydroxycoumarin derivatives) are used as rodenticides for controlling rats and mice in residential, industrial, and agricultural areas. Warfarin is both odorless and tasteless, and is effective when mixed with food bait, because the rodents will return to the bait and continue to feed over a period of days until a lethal dose is accumulated (considered to be 1 mg/kg/day over about six days). It may also be mixed with talc and used as a tracking powder, which accumulates on the animals skin and fur, and is subsequently consumed during grooming. The LD50 for warfarin is 50–100 mg/kg for a single dose, after 5–7 days. LD50 1 mg/kg for repeated daily doses for 5 days, after 5–8 days. The IDLH value is 100 mg/m3 (warfarin; various species).The use of warfarin itself as a rat poison is now declining, because many rat populations have developed resistance to it, and poisons of considerably greater potency are now available. Resistance is due to an autosomal dominant on chromosome 1 in Norway rats.
Warfarin, sold under the brand name Coumadin among others, is a medication that is used as an anticoagulant (blood thinner). It is commonly used to prevent blood clots such as deep vein thrombosis and pulmonary embolism, and to prevent stroke in people who have atrial fibrillation, valvular heart disease, or artificial heart valves. Less commonly, it is used following ST-segment elevation myocardial infarction and orthopedic surgery. It is generally taken by mouth, but may also be used intravenously.The common side effect is bleeding. Less common side effects may include areas of tissue damage and purple toes syndrome. Use is not recommended during pregnancy. The effects of warfarin typically should be monitored by checking prothrombin time (INR) every one to four weeks. Many other medications and dietary factors can interact with warfarin, either increasing or decreasing its effectiveness. The effects of warfarin may be reversed with phytomenadione (vitamin K1), fresh frozen plasma, or prothrombin complex concentrate.Warfarin decreases blood clotting by blocking an enzyme called vitamin K epoxide reductase that reactivates vitamin K1. Without sufficient active vitamin K1, clotting factors II, VII, IX, and X have decreased clotting ability. The anticlotting protein C and protein S are also inhibited, but to a lesser degree. A few days are required for full effect to occur, and these effects can last for up to five days.