Blood Coagulation
Mechanism of Action
Side Effects
The Future


Hemostasis is the ability of the body to control blood flow after vascular injury. It is a natural process that allows blood to thicken and form a clot to stop bleeding. Eventually, the clot helps form a protective scab over the healing wound.Without this  protective mechanism, people would bleed to death from even minor cuts.

Sometimes, however, blood clots can form even though a person has not been wounded in any way. Under certain conditions, a clot can form in an artery, which could block the blood flow and cause a heart attack or a stroke. A clot could also form in one of the heart's chambers, travel through the blood stream and lodge itself in an organ or artery, cutting of blood supply from that point and thus causing an embolism.

heart attack

Blood  clots usually form when blood flow becomes sluggish, as when there is roughness or scar tissue along the interior  walls of a blood vessel that slows blood flow. Some underlying conditions that could contribute to  the formation of blood clots include :
  • Atherosclerosis
  • Heart attack
  • Trauma to a blood vessel due to accident or medical procedure
  • Hypertension
  • Atrial fibrillation
  • Congestive heart failure
  • Valvular heart disease

In addition,  there are a number of risk factors that can increase the chances of developing a blood clot. These include :
  • Smoking
  • Obesity
  • Prolonged lack of exercise
  • Genetics
  • Advanced age
  • Oral contraceptive use

Oral anticoagulants such as warfarin are specially indicated for treatment of blood clots resulting from the following :

Deep vein thrombosis (DVT) and its extension : this is the formation of an obstructing blood clot in the deep veins embedded in the muscles, usually in the lower leg and sometimes in the lower abdomen or groin. It causes permanent damage to the vein. There is also a high risk of either the whole or part of the clot breaking off , travelling through the bloodstream and getting lodged in one of the arteries of the lungs, causing a possibly fatal pulmonary embolism.


Pulmonary embolism : An embolism occurs when a clump of material such as a piece of plaque or blood clot travels through the blood stream and becomes lodged in a blood vessel. Pulmonary embolism is a commonly occurring type of embolism, and oral anticoagulants like warfarin are used in their prophylaxis and treatment.

Atrial Fibrillation (AF)
: this is a rapid, irregular heart rhythm (arrythmia) caused by abnormal electrical signals from the upper chambers of the heart (atria).  The normal heart  rate is 60-100 beats per minute. AF is marked by a rapid heart rate of 100-175 beats per minute. Instead of contracting normally, the atria quiver.There is a chance that blood may pool in the atria, which can lead to the formation of blood clots. These can break off and cause emboli or stroke.

Valvular heart disease and heart valve replacement : Valvular heart disease is any dysfunction or abnormality of one or more of the heart's four valves.Heart valves act as gates and  keep blood flowing in one direction Diseased valves which cannot be repaired are replaced by artificial ones. Anticoagulants help prevent the body's natural response of forming blood clots around foreign objects such as the artificial valve. They thus prevent complications associated with blood clots and also reduce risks of valve malfunction.

Post Myocardial Infarction (MI) : A heart attack is an event that results in permanent damage or death to part of the heart muscle. It is also known as a myocardial infarction, because part of the heart muscle (myocardium) may literally die (infarction). A heart attack occurs when one of the coronary arteries becomes severely or totally blocked, usually by a blood clot, and specially when the artery has been narrowed by fatty plaque (atherosclerosis). Following recovery from MI, patients remain at increased risk of sustaining subsequent thromboembolic complications, a recurrent MI, stroke or even death. Anticoagulants such as warfarin and aspirin are generally used to reduce such risks.