Anticoagulant medication is used to slow down the blood clotting process.

Anticoagulants can be used to prevent a clot forming in the blood or to help treat existing clots.

Blood they are commonly and incorrectly known do not dissolve existing blood clots though, another class of pharmaceutical drug called a Thrombolytic is required to assist with that process.

However, this class of drugs can help treat existing blood clots by decreasing their expansion...stops them 'growing' in size.

The most well known anticoagulant medication is probably Warfarin with Heparin a close second.

Anticoagulants are used in the treatment of:

  • Deep vein thrombosis blood clot in a large vein (not Artery) of your leg for example.
  • Pulmonary embolus Blood clot that travels to or forms in your lungs
  • Atrial fibrillation - Abnormal heart rhythm in the Atrial pumping chambers of the heart. This condition slows down the passage of blood through this part of the heart which can increase the tendency of blood to clot there. If these clots breakaway, they can become lodged elsewhere and dramatically impair organ function.
  • Mechanical heart valves - Blood clots can form on these valves and impair their function.
  • Surgical procedures - The prevention of blood clot formation during certain surgical procedures such as heart surgery and cardiac catheterization is an important safety consideration.
  • Increased risk of myocardial Infarction In combination with other drug therapies, Anticoagulants can reduce risk in this setting.

Warfarin: Coumadin

Warfarin is an antagonist of vitamin K...Vitamin K being necessary for the production of certain blood clotting factors.The rate of production of blood factors and proteins which are responsible for the clotting process is dependant on vitamin K

A deficiency of Vitamin K produces an environment of increasing Anticoagulation.

K will K will not!

With respect to the name Coumadin, this is derived from Coumarin....a substance from which several anticoagulants are derived and which is present in a number of plants species.

It usually takes several days (up to five) for warfarin to take effect...this is called the lead in time...and the effect of that dose will last about five days...however patients on warfarin usually take daily doses to maintain stability and control of the anticoagulation process.

INR - International Normalised Ratio.

The INR test measures the time it takes for blood to clot and compares it against an average....a bigger number means that your blood is taking longer to clot.

If you don't take warfarin your normal INR should be about 0.9 to 1.2

If you have been prescribed warfarin then your INR will be kept within certain specific ranges. Which range is determined by the condition that requires Anticoagulation.

Examples are

2.0 to 3.0 - treatment and prevention of DVT (Deep Vein Thrombosis)2.5 to 3.5 - mechanical heart valve. Regular blood tests are required to monitor the effect that warfarin is having on your INR and to assist your health care professional in keeping you within a desired range.

Possible side effects of Anticoagulant therapy may include:

  • unexplained severe bruising
  •  prolonged bleeding from small cuts
  •  nose bleeds
  •  bleeding gums
  • blood in urine
  • red or black stoolsIf

you are on warfarin therapy then moderate exercise is fine...but contact sports that could cause physical injury are discouraged as controlling the bleeding from injury may be problematic and require medical assistance.


Heparin is sourced from the mucosal tissues of dead animals....particularly the intestinal tissue of pigs and the lung tissue of cows.

Heparin is also a polysaccharide - a substance containing several sugar molecules found naturally in many cells.

Heparin acts against three different clotting factors by preventing formation of...

  • Prothrombin
  • Fibrin

and...decreasing the availability of...

  • Thrombin

Compared with warfarin, heparin does not dissolve blood clots but can help to prevent them form occurring and from getting larger if they are already present.

Low molecular weight Heparin:

This is a product that like heparin is used in the hospital or clinical setting...but unlike 'plain' Heparin it does not require regular monitoring in the patient for coagulation time...known as APTT or Activated Partial Thromboplastin Time. This is so because its levels in the blood are more predictable than that of 'plain 'Heparin.

Synthetic Pentasaccharide Inhibitors:

Heparin is a five sugar chemical structure. Some products that synthesize the natural heparin molecule such as Fondaparinux inhibit the action of a certain blood factor...factor Xa that is critical to the coagulation process.

Direct Thrombin Inhibitors:

Bivalirudin, trade name Angiomax is another class of anticoagulant drug. It acts as a direct thrombin inhibitor.

Interestingly, Bivilirudin is a synthetic of the naturally occurring Hirudin found in the saliva of the medicinal leech Hirudo medicinalis. Huriden is an anticoagulant also.

Bivalirudin and Hirudin inhibit thrombin formation by binding to thrombin that is circulating in the blood and thrombin that is present in clots already formed.

  • Hirudin is an irreversible inhibitor of thrombin
  • Bivalirudin is a reversible one

Bivalirudin has a low complication rate because it can be well controlled. Bivilirudin is not the kind of drug that a patient takes at home. It is usually found in the clinical setting especially in the cardiac catheterization lab as it has been shown to help reduce the risk of Acute Ischemic Complications.

Acute Ischemic Complications can be present in an acute patient who has come to the emergency room in the process of having a heart attack or occur in someone undergoing a balloon angioplasty (PCI) or Coronary Artery Stent implantation...simply as a result of procedure complications.

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