Coumadin versus Pradaxa

Coumadin (Warfarin) is a blood anticoagulant which prevents clotting by inhibiting Vitamin K dependent clotting factors.  It is taken orally and becomes effective after several days of administration when the Vitamin K dependent clotting factors have been depleted.  It is inexpensive and has been used for years to prevent clots from forming in patients with the irregular heart rhythm known as atrial fibrillation.  These clots can form in the chambers of the heart and break off and travel to the brain causing embolic strokes.

Coumadin is additionally used to prevent recurrent blood clots in patients who have had phlebitis (or inflammation of a blood vessel) and in certain postoperative conditions such as joint replacements. Physicians monitor your ability to clot by drawing blood for a test called “the prothrombin time or INR (International Normalized Ratio).  The blood can be drawn from a vein and sent to a lab or performed by a finger stick method in a doctor’s office.  Based on the blood test result we adjust your medication dose up or down. Coumadin’s effect on blood clotting can be easily affected by certain foods rich in Vitamin K (green leafy vegetables in particular) and by medicines which either enhance or limit Coumadin’s effect on clotting.

The major complication of Coumadin is excessive bleeding. We stop the bleeding by administering Vitamin K and infusing blood products intravenously containing active blood clotting factors.

Pradaxa and the new wave of direct thrombin inhibitors that are now being released are designed to do the same job as Coumadin without requiring monitoring by blood test of your ability to clot. This new class of medications should have many fewer interactions with food and other prescription and over the counter medicines. Its two major drawbacks are bleeding and expense.  The drug was tested extensively in Europe and proved to be safe but it has been on the US market for less than six months. While Coumadin costs pennies per tablet, Pradaxa costs about $300 per month. It requires taking a pill twice per day.

It is clear that thrombin inhibitors like Pradaxa will one day replace Coumadin. For now I prefer to have other physicians’ patients use it and compile a safety record before I try it on my patients. We know the pros and cons of Coumadin.  Let Pradaxa survive the test of use on the US market, and time, and show a clear cut safety advantage before giving it to our patients locally.