Coumadin, an anticoagulant, is the most frequently prescribed oral medication to treat disorders involving blood clots, according to the American Academy of Family Physicians. Coumadin works as a blood thinner by inhibiting the action of vitamin K (ingested in foods such as kale, broccoli and spinach), which in turn blocks the production of clotting factors. Coumadin has a very sensitive dose-response relationship, meaning that a slight change in dose can induce a significant response in the body. Although very effective in preventing strokes, Coumadin can also induce dangerous side effects.
Severe Bleeding
Bleeding is the most common complication of Coumadin. The American Academy of Family Physicians reports that this side effect occurs in 6 to 39 percent of those taking the medication. Because of this risk, patients should be monitored closely and report any unusual bruising to their doctor.
The potential for severe and profuse bleeding is a dangerous side effect. Even a small cut can become a major risk because the bleeding will not cease. Internal bleeding is also a risk. The appearance of black tarry stools is an indicator of bleeding within the intestines. Blood visible in the urine is also a sign that internal bleeding may be present.
Another sign to be aware of is hemoptysis, or coughing up blood. The frequent occurrence of a bloody nose or bleeding gums is also cause for concern.
Necrosis
In rare cases -- only 0.01 to 0.1 percent of patients -- Coumadin may induce necrosis, or the death of skin tissue, according to "Wounds." As the skin cells die, lesions appear on the breasts, buttocks, abdomen or thighs.
This side effect usually begins as a complaint of skin sensitivity to applied pressure. Within 24 to 48 hours, a rash of small red or purple dots may appear, progressing to larger purple lesions. The skin will then change to a full-blown necrotic lesion that is covered with thick, dry, black dead skin.
Necrosis induced by Coumadin may occur due to the initial loading dose of the medication. When therapy begins, the initial doses of Coumadin are larger, in order to produce the wanted antithrombotic (preventing the formation of blood clots) effect sooner. This increased dose can actually temporarily induce the formation of blood clots, blocking tiny blood vessels and resulting in necrosis.
Coumadin Resistance
If patients on Coumadin therapy are administered large doses of vitamin K, they run the risk of becoming resistant to the medication. This is dangerous because for that time period they are susceptible to blood clots that could lead to a stroke.
