Learn about Blood Clot Formation and Anticoagulant Drugs

What Factors Are Involved in the Process? 

1036-Blood Clot Formation by NLMBlood clotting normally occurs when there is damage to a blood vessel. Platelets immediately begin to adhere to the cut edges of the vessel and release chemicals to attract even more platelets. A platelet plug is formed, and the external bleeding stops. Next, small molecules, called clotting factors, cause strands of blood-borne materials, called fibrin, to stick together and seal the inside of the wound. Eventually, the cut blood vessel heals and the blood clot dissolves after a few days.

Source: US National Library of Medicine

Atrial fibrillation and new oral anticoagulant drugs

More than 3 million Americans have atrial fibrillation, a problem with the electrical system of the heart that causes an irregular heart rhythm. Atrial fibrillation can produce palpitations, shortness of breath, lightheadedness, weakness, and chest pain, or may occur without symptoms. The main concern, however, is that atrial fibrillation can lead to the formation of blood clots in the heart, which can travel to the brain and cause a stroke.

There are a number of treatments—drugs and procedures—intended to correct the fundamental heart rhythm problem in patients with atrial fibrillation, but the main focus of treatment is to try to decrease the rate of stroke by preventing the formation of blood clots. This is accomplished with taking anticoagulant drugs or “blood thinners.”

Decreasing stroke risk

Anticoagulants have been known for many years to produce a striking (more than 50%) decrease in the rate of stroke, but they also prevent clotting in locations and situations where clotting is desirable. In other words, they can cause bleeding.

Until recently, warfarin (approved in 1954 and marketed under the brand names Coumadin and Jantoven) had been the only drug approved for the prevention of stroke in patients with atrial fibrillation. But the anticoagulant effect of warfarin must be carefully monitored with periodic blood tests. If the effect is too small, it will fail to prevent strokes; if the effect is too high, it will cause excess bleeding. Thus, the dosage of warfarin must be carefully adjusted to keep the blood thinning effect in the right range.

Since 2010, FDA has approved four new oral anticoagulant drugs – Pradaxa (dabigatran), Xarelto (rivaroxaban), Eliquis (apixaban), and Savaysa (edoxaban). Like warfarin, all four are “blood thinners” that reduce the overall risk of stroke related to atrial fibrillation, but they can also cause bleeding. (read more here).

Last Updated: 2015-12-05

Blood Clot Formation and Anticoagulant Drugs