COUMADIN (WARFARIN)

Coumadin, known as warfarin by its generic name, is a medication that is commonly prescribed for the management of DVT and PE. It is used in the oral form. The drug needs to be carefully dosed. Too much, and there is a high risk for bleeding. Too little, and it is not efficaceous.

WHAT IS COUMADIN?

Coumadin is a blood thinning medication. The generic name for coumadin is warfarin. It is used primarily for the treatment of deep venous thrombosis (DVT) or pulmonary emboli (PE). It can also be used for other purposes, such as in atrial fibrillation where the uncoordinated movements of one of the heart chambers can lead to the development of blood clots that can lead to a stroke. It has the unfortunate history of being used as a poison for rats years ago. Therefore, it has a stigma attached to it that we still hear about today. (You want me to take rat poison?)

HOW DOES COUMADIN THIN OUT THE BLOOD?

Coumadin acts on certain blood proteins that promote clotting. the blood clotting system is a constant mix of pro and anti clotting mechanisms. Using coumadin tends to tip the mix into the favor of the anti clotting forces. The actual mechanism involves the blocking of vitamin K dependent protein synthesis of Factors II, VII, IX, and X, as well as protein C and protein S. These proteins are formed in the liver, and the process involves the use of vitamin K. Coumadin blocks a specific enzyme that uses Vitamin K to synthesize these proteins.

HOW IS COUMADIN USED FOR BLOOD THINNING?

Coumadin is administered as an oral agent. It is given after blood thinning has been started with another agent such as Lovenox. If Coumadin is given without the cover of another anticoagulant such as lovenox, it might have a paradoxical blood clotting tendency initially. This mechanism of action is because Coumadin also decreases Protein S levels first, which tends to promote clotting before the other factors are affected. Therefore, it is imperative that Coumadin be started after some other agent such as Lovenox has been initiated.

The dose of coumadin is adjusted to maintain a therapeutic PT with INR level. There are numerous factors that can affect the dose of Coumadin needed to maintain a stable and therapeutic INR level. In my opinion, if one is having problems maintaining a therapeutic level of INR, then a Coumadin clinic is an ideal place to follow-up with INR checks and adjustment of dosages. Coumadin clinics specialize in adjusting the dose of Coumadin, and often can solve some of the swings in INR readings that patients can experience with their primary care doctors or surgeons. There are numerous Coumadin clinics in your local areas in the U.S.A. For an example of the beneficial effects of a Coumadin clinic, click on the following link

SIDE EFFECTS OF COUMADIN

Coumadin can have side effects, and it can have serious consequences, even if the blood thinning level is well controlled. These side effects can include the following:
1. Bleeding: one can bleed from numerous sites, some annoying, and some dangerous. Frequent nose bleeds are common, but prolonged and repetative bleeding from the nose needs further evaluation. Bleeding from stomach ulcers might present as dark blood in the stool, or vomiting bright red blood. Bleeding from the lower intestinal tract will cause either bright red blood in the stool, or darker blood depending on the rat of bleeding. Please do not discount blood in the bowel movements as coming from hemorrhoids. Very infrequently, one can bleed into the space between the intestines and the back, the so called "retroperitoneal space." Also, one can notice blood in the urine, which also needs to be addressed.
2. Intracranial hemorrhage: This type if bleeding is a subset that should be discussed seperately, because it is very dangerous. The skull is limited in terms of the space between the brain and inside lining of the skull bone. Therefore, bleeding into this space is very poorly tolerated. Patients with an intracranial bleed with present with headaches and stroke type symptoms. These types of situations are emergencies and need to be assessed immediately with diagnostic work-up and possible CT scans of the head. 3. Warfarin necrosis: Very infrequently, Coumadin can cause suddent onset of gangrene of the skin. It typically presents as a purple discoloration of the skin, that progresses to gangrene. The key is diagnosing it quickly, discontinuing Coumadin, and starting Lovenox.
4. Drug interactions: Coumadin can interact wiht numerous drugs, both prescribed and over the counter. Probably the one I see the most is when someone is taking Coumadin, and is then prescribed an antibiotic such as Cipro or Levaquin. These antibiotics increase the effect of Coumadin, and can elevate the INR significantly in a situation where the INR had been stable for years. The best way of avoiding these types of interactions is to tell you doctor and pharmacist about all the medications you are currently taking, including over the counter medications.
5. Coumadin and Advil, Alleve, Motrin, Ibuprofen etc.: One needs to avoid these latter "non-steroidal anti-inflammatory drugs (NSAIDS)" when taking Coumadin. The NSAIDS affect another part of the clotting mechanism different from the cascade that Coumadin works on. Therefore, by combining these two treatments, one increases the risk of bleeding. For pain or aches while in Coumadin, one can take Tylenol that does not affect any clotting cascades.
6. Allergic reactions, jaundice, brittle hair are all possible reactions to Coumadin.

DURATION OF COUMADIN TREATMENT

Typically, Coumadin is used for 3-6 months, depending on the extent of the DVT or the cause of the DVT. After that time, studies have shown a decreased rate of recurrence of a DVT if one stays on a lower dose of Coumadin, maintaining an INR of 1.5-1.6. The alternative is to start taking an aspirin a day. If there are recurrent signs of a DVT, then repeat testing with a doppler ultrasound should be performed. If one has repeated DVT's or a tendency to clot due to a genetic predisposition, then one might have to take Coumadin lifelong.

Some patients stick to brand name coumadin, while others tend to switch to generic versions that are cheaper. My personal opinion is that is does not matter which one is used, as long as the dose results in a therapeutic response.