Anticoagulants are medications that are used to prevent the blood from coagulating and causing life-threatening clots. Examples of commonly used anticoagulants are heparin and warfarin; heparin is injected and warfarin is taken by mouth. These medications can be very beneficial to patients who are at risk of blood clots; however, they also have several important adverse effects.
Thrombocytopenia
Thrombocytopenia is a term that means that the level of platelets--which are the elements within the blood that are responsible for forming blood clots--is abnormally low. Dr. Stephen Coutre, of Stanford University Medical School, writes in the medical reference "UpToDate" that this is a well-known complication of heparin therapy. It generally develops within five to ten days, and occurs because of formation of antibodies. Heparin-induced thrombocytopenia results in a large drop in platelets. The most serious risk of this complication is that blood clots, called thromboses, will form. Dr. Coutre reports that this phenomenon is not well understood, but it is thought that the platelets release some type of pro-coagulation substance that results in clot formation. Of these, deep venous thromboses, or DVTs, and pulmonary embolisms are especially concerning. DVTs form in the arms or legs; these are dangerous because they can break off and travel to the lungs. Pulmonary embolisms are within the lungs, and are a medical emergency that may be fatal if not treated immediately.
Skin Lesions
When intravenous heparin is used to reduce the clotting activity of blood, patients are at risk for developing skin lesions. These are areas of damaged skin, which, according to a 2009 study published in the "Canadian Medical Association Journal," may occur in up to 7.5 percent of patients receiving low molecular weight heparin anticoagulation. It is not clear why these lesions occur; the authors of the 2009 study suggest that either thrombocytopenia or development of a delayed allergic reaction may be the cause.
Bleeding
Bleeding is one of the most common side effects of anticoagulant therapy. The medical reference UpToDate reports that in a list of medications that result in death from their use, anticoagulants ranked number one. Because of this, the Food and Drug Administration has issued a "black box" warning for anticoagulants. A "black box" warning is the highest level of warning that can be added to a drug's product label; in this case, the warning is accompanied by a medication guide that must be given to patients with their prescription for warfarin.
Risk factors for bleeding include the presence of high blood pressure, diabetes, and advanced age; interestingly, "advanced age" is defined differently by different studies, ranging from older than 60 to older than 80. UpToDate warns patients that bleeding from warfarin may occur nearly everywhere in the body. Bleeding within the brain and bleeding within the digestive system are two examples of potential fatally bleeding that may occur as a side effect of warfarin use.
References
- "Canadian Medical Association Journal;" Incidence and causes of heparin-induced skin lesions; M. Schindewolf et. al.; October 2009
- "UpToDate;" Therapeutic Use of Warfarin; K. Valentine and R. Hull; May 2010
- "American Journal of Medicine;" A 14-year study of heparin-induced thrombocytopenia.; T. M. Warkentin and J.G. Kelton; November 1996
- "UpToDate;" Warfarin: Drug Information; Lexi-Comp, Inc.; 2010
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