User:Ishtaah

Preventing blood clotting Once the immediate danger of a pulmonary embolism caused by DVT is over, thought must be given as to how to stop the same thing happening again. People who are at a very high risk of a thrombosis developing can be given drugs which slow down the blood clotting process. Some of these drugs work as enzyme inhibitors- but in a rather more complicated way than the action of antithrombin on thrombin. The first drug that a person is likely to be given is heparin. This is given by injection directly to a vein. Heparin works by binding to antithrombin. This causes the shape of antithrombin to change in such a way that it binds even more easily and effectively than usual thrombin. This happens almost immediately, so heparin is good for very quickly slowing down the tendency for someone's blood to clot. The patient may be prescribed warfarin. This can be taken by mouth - it doesn't need to be injected. Warfarin actually works in the liver, not in the blood. Warfarin slow down, or stops, the formation of prothrombin in the liver cells. If there is no prothrombin formed in the blood, so fibrinogen won't be changed into fibrin. The formation of prothrombin involves vitamin K. Vitamin K has to bind with some proteins in the liver cell in order for prothrombin to be made. Warfarin competes with Vitamin K for these binding sites. Warfarin takes longer to work than heparin- often around 7 days- but it has a much longer-term effect. Yet another anti-clotting agent is the substance injected by leeches when they begin feeding. This is called hirudin. Hirudin is an inhibitor of thrombin, binding with part of its active site. studies have been undertaken to see if hirudin could perhaps be used instead of heparin, to prevent inappropriate blood-clotting.