Mosby (2002) defines an anticoagulant as a substance that prevents or delays coagulation of the blood. Anticoagulants interfere with the formation of thromboplastin, with the conversion of prothrombin to thrombin, and with the formation of fibrin to fibrinogen (Mosby, 2002). Anticoagulants are usually prescribed for individuals who are suffering from venous and arterial vessel disorders that can cause a high risk for clot formation (Kee and Hayes, 2004). Deep vein thrombosis and pulmonary embolism are the most common venous disorders that are treated with anticoagulants while coronary thrombosis or myocardial infarction, the presence of artificial heart valves, and cerebrovascular accidents are the arterial disorders that are prescribed with this medication (Kee and Hayes, 2004).
Albeit there are different anticoagulant therapies prescribed for each kind of arterial or vascular disease, the action of these therapies are all the same. Described as a thrombosis of the deep rather than the superficial veins, deep vein thrombosis is a type of venous thrombosis that can cause two complications namely pulmonary embolism and post-phlebitic syndrome (Nettina and Mills, 2006). There are three precursors in the development of venous thrombosis and these are believed to be blood stasis, the presence of an injury to the vessel wall and altered blood coagulation (Nettina and Mills, 2006). Conditions that can produce these precursors can be certain operations, childbirth, bed rest or prolonged sitting, and injury to a vein that can be caused by direct trauma or internal trauma (Nettina and Mills, 2006). It can also be caused by an extension of an infection from tissues surrounding the vessels, continuous pressure of a tumor, aneurysm, or excessive weight gain in pregnancy, unusual activity in a person who has been sedentary, and hypercoagulability associated with malignant disease or blood dyscrasias (Nettina and Mills, 2006).
Arterial diseases that could indicate the need for an anticoagulant include myocardial infarction. Myocardial infarction is a type of coronary artery disease. Coronary artery diseases are characterized by the presence of plaque within the layers of the coronary arteries. The plaques present in these disorders are progressively enlarged, thickened, and calcified which causes a narrowing or approximately 75% occlusion of the coronary artery lumen (Nettina and Mills, 2006). This results in a reduction in coronary blood flow and an insufficient oxygen supply to the heart muscle. Myocardial infarction is a process by which regions of the heart undergo a rigorous and lengthened reduction in oxygen supply due to inadequate coronary blood flow (Nettina and Mills, 2006). This will subsequently result in necrosis or death to the myocardial tissue.
Although the aforementioned venous and arterial disorders differ in their pathophysiologies, both conditions are prescribed anticoagulants for their pharmacologic regimen. Anticoagulants can be administered by mouth or parenterally. The first anticoagulant that was used in blood transfusion to prevent clotting and in an open-heart surgery for individuals with disseminated intravascular coagulation or DIC is heparin (Kee and Hayes, 2003).
Heparin works by first binding with antithrombin III. The action of antithrombin III is inactivation of thrombin. When thrombin is inactivated, the conversion of fibrin to fibrinogen does not take place, and thus prevents clot formation (Kee and Hayes, 2003).
Low-molecular-weight heparins are derivatives of the standard heparin, however, research showed that they have lowered the risk for bleeding (Kee and Hayes, 2003). There are five low-molecular-weight heparins namely enoxaparin sodium, dalteparin sodium, ardeparin, danaparoid, and tinzaparin sodium (Kee and Hayes, 2003).
Oral anticoagulants are also widely used today. Examples of these are warfarin, dicumarol, and anisindione (Kee and Hayes, 2003). Warfarin is the most common oral anticoagulant ordered and its action is to inhibit hepatic synthesis of vitamin K and will affect clotting factors II, VII, IX, and X (Kee and Hayes, 2003).
These anticoagulant medications have very specific instructions by the prescribing physician and should be followed precisely because of the drug’s serious side effects. Bleeding or hemorrhage is the major adverse effect of warfarin and individuals taking this medication should be monitored closely for signs of bleeding (Kee and Hayes, 2003). These include petechiae, ecchymosis, and hematemesis among many others. The prothrombin time and thrombin time together with the INR should also be monitored.
Due to the oral anticoagulants being highly protein – bound, drug-to-drug interactions are also common. The patient should be able to take note of the other drugs that he or she is taking and consult with the prescribing physician. Aspirin, non-steroidal anti-inflammatory drugs, sulfonamides, other types of anti-inflammatory drugs, allopurinol, phenytoin, and oral hypoglycemic agents for diabetes can cause interactions with warfarin and can enhance bleeding (Kee and Hayes, 2003). Acetaminophen should be used as a substitute for aspirin when taking warfarin (Kee and Hayes, 2003). In addition, there are antidotes in case warfarin or heparin has been taken in generous amounts. Vitamin K or phytonadione is taken as the antidote for warfarin overdose and protamine sulfate for heparin (Kee and Hayes, 2003).
There are also special considerations in the individual’s diet when taking anticoagulants. This is because vitamin K can be found in our daily food intake and can disturb the drug’s action. Individuals who are taking anticoagulants must be aware of their food intake and which food are high in vitamin K and should eat no more than they used to of those food.
Foods that contain a lot of vitamin K include cooked green leafy vegetables. Examples of which are spinach, collard greens, kale, and turnip greens (Parks, 2008). Broccoli that is raw or cooked, raw parsley, and green tea also have high vitamin K content and should be eaten in little amounts or in moderation (Parks, 2008). There are also green leafy vegetables that contain medium amount of vitamin K and these are green leaf lettuce, endive, Brussels sprouts, cauliflower, and asparagus, among many others (Parks, 2008). The reason for eating these foods with vitamin K in moderation is that eating more than one will reduce the effect of warfarin, forming more blood clots and thus making the medication useless (Parks, 2008). On the other hand, eating lesser amounts of vitamin K than normal will only enhance the effect of warfarin and can increase the risk of bleeding (Parks, 2008).
There are also special considerations for specific conditions when taking anticoagulant medications. Allergic reactions to any anticoagulants taken in the past should be disclosed to the prescribing physician (Flannigan, 2002). In addition, pregnant women who are taking anticoagulants should be warned about the possible problems that can be encountered. Anticoagulants could cause birth defects, severe bleeding in the fetus, and any other problems that could affect the physical or mental development of the fetus (Flannigan, 2002). The risk of severe bleeding of the pregnant woman is also high if she is taking anticoagulants during her pregnancy (Flannigan, 2002).
Even lactating mothers should be warned about taking anticoagulants. This is because some anticoagulant medications may pass into the mother’s breast milk (Flannigan, 2002). Fortunately, blood tests can be conducted to see if the infant is really taking in the anticoagulant drug through the breast milk and antidotes can be prescribed if it does happen (Flannigan, 2002).
The individual being prescribed any anticoagulants should also be able to disclose any other medical treatments he or she is undergoing or underwent to the prescribing physician as this can actually also cause interactions. In addition, they should also let their prescribing physician know if they are seeing another doctor or even a dentist (Flannigan, 2002). The following conditions can affect the anticoagulant regimen and the prescribing physician should be made aware if these are present. These include fever that is present for more than a day, diarrhea, pregnancy or recent childbirth, menstrual bleeding that is unusual in pattern or is heavily bleeding (Flannigan, 2002). In addition, the presence of an IUD, any injuries to the body or to the head, surgeries, even dental ones, anesthesia especially spinal, and radiation treatment should be disclosed to the physician.
Anticoagulants, just like any other medication, disrupt the normal processes inside the body therefore, it is very important to stick to the regimen given by the physicians to avoid unwanted effects and interactions. If we are in doubt, it is still best to consult with the physician who prescribed the medications and full disclosure is necessary.
Flannigan, N. (2002). Anticoagulant and antiplatelet drugs . Retrieved February 16, 2009, from The Gale Group Inc Web site: http://www.healthline.com/galecontent/anticoagulant-and-antiplatelet-drugs
Kee, J., & Hayes, E. (2003). Pharmacology: A Nursing Process Approach. Philadelphia: Elsevier Science Ltd.
Mosby, (2002). Mosby’s Pocte Dictionbart of Medicine, Nursing, and Allied Health. Singapore: Elsevier Science Ltd.
Nettina, S., & Mills, E. (2006). Lippincott Manual of Nursing Practice.Philadelphia: Lippincott Williams and Wilkins.
Parks, R. (2008). Anticoagulants: Vitamin K and your diet. Retrieved February 16, 2009, from WebMD Web site: http://www.webmd.com/a-to-z-guides/eating-a-steady-amount-of-vitamin-k-when-you-take-warfarin-coumadin