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Anticoagulant drugs

In a healthy person, the body is able to protect itself from excessive bleeding, by allowing a part of the blood called plasma to stick together and form clots. These clots are formed at the site of a wound or injury, where blood might otherwise leak out of the body or into the wrong internal organs.

Clotting is a natural mechanism that relies on a number of chemical reactions occurring within the body, in order to produce a substance called thrombin. This substance then acts upon a protein in the body called fibrinogen, and converts it into fibrin. Fibrin creates a number of threads that make the plasma sticky, enabling a clot to form.

The process of forming clots is therefore complicated and relies upon a lot of processes in the body happening correctly. This means that things can go wrong if one or more parts of the process fail to work. Sometimes the blood does not clot easily and there is a risk of excessive bleeding (haemorrhage), and sometimes it clots too much so the patient risks complications such as strokes or heart attacks.

Anticoagulant drugs are used to reduce the ability of the blood to clot. Examples of anticoagulants include aspirin, heparin, and warfarin.