Anticoagulants prevent the clotting of blood. They are administered orally or via injection.
When a blood vessel is damaged, blood oozes out. However, bleeding stops amazingly within a few minutes especially if the wound is small. Persistent loss of blood from the body can lead to shock, hence the natural mechanism is important to preserve life. Two constituents of blood are responsible for this Ė platelets
and clotting factors
. The platelets initially form a plug to stop the flow. This activates some proteins in the blood called clotting factors. The clotting factors undergo a cascade reaction that results in a clot formation that reinforces the platelet plug. Thus it seals the wound and stops the bleeding.
In some conditions such as prolonged immobility, clots may form within blood vessels. Clot formation in deep veins is called deep vein thrombosis
. These clots block the flow of blood in the particular area. They may also dislodge and block blood supply to important organs such as lungs or brain resulting in a stroke or the heart leading to a heart attack. Drugs used to prevent clot formation are called anticoagulants or blood thinners
. They should be differentiated from drugs such as aspirin and clopidogrel that prevent the formation of a platelet plug and are referred to as anti-platelet drugs.
Anticoagulants are of two types depending on their route of administration. Injectable anticoagulants
Ė These include heparin, low molecular weight heparin, fondaparinux, lepirudin, bivalirudin, argatroban, danaparoid and drotrecogin alfa Oral anticoagulant tablets
Ė The main oral anticoagulant tablet used is warfarin.
A number of new drugs are undergoing testing before being introduced into the market.
Some anticoagulants are used to prevent clotting of blood when it is collected either for transfusion or blood tests. These include heparin, sodium citrate, sodium oxalate and sodium edetate.