It used to be known as a rat poison - give rats a lot of Warfarin and they suffer death from internal bleeding. So did Donald Dewar, the most senior government figure in Scotland and member of the Labour Cabinet, who die on 11 October 2000, mourned across Briatin. He suffered a fatal brain haemorrhage following a fall, after recent surgery to replace an aortic heart valve. The Warfarin successfully prevented clots on the valve, but the Warfarin also thinned his blood, probably made the bleed worse and made it even more difficult for surgeons to operate. Warfarin works by blocking the creation of Vitamin K - vital to normal blood clot formation.
Warfarin is usually very safe when used carefully but the level in the blood is critical.
Too much Warfarin and you can bleed to death - as simple as that. The trouble is that Warfarin levels are affected by a huge number of other drugs that people may be taking at the same time. Chloramphenicol Sulphonamides Colchicine Reserpine Mefanamic acid Aspirin Phenytoin Broad spectrum antibiotics Erythromycin Liquid paraffin Clofibrate Warfarin effect is reduced by Barbiturates Rifampicin Oral contraceptives Glutethimide Griseofulvin Weight changes and changes in kidney function can also affect Warfarin levels. A common problem can be if a person is stable for a long time on Warfarin with a combination of other drugs - but then one or two of the other drugs are stopped, perhaps sending Warfarin levels sky high or perhaps far too low. A common early sign of Warfarin overdose is spontaneous bruising - patches of skin discolouration without a history of injury, or even blood in the urine.