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Warfarin (Coumadin) Therapy

Warfarin (Coumadin) Therapy. 

Coumarin anticoagulants (warfarin; eg, Coumadin) are antagonists of vitamin K and therefore interfere with the synthesis of vitamin K–dependent clotting factors. Coumarin anticoagulants bind to albumin, are metabolized in the liver, and have an extremely long half-life. Typically, a patient is initially treated with both heparin (either the unfractionated form or LMWH) and warfarin. When the international normalized ratio (INR) reaches the desired therapeutic range, the heparin is stopped. The dosage required to maintain the thera peutic range (typically using an INR of 2.0 to 3.0) varies widely among patients and even within the same patient. Frequent monitoring of the INR is extremely important so that the dosage of warfarin can be adjusted as needed. Warfarin is affected by many medications; consultation with a pharmacist is important to assess the extent to which concurrently administered medications, herbs, and nutritional supplements may interact with warfarin. It is also affected by many foods, so patients need dietary instruction and may benefit from consultation with a dietitian when receiving warfarin therapy. (See figure) for a listing of agents that interact with warfarin.

Nursing Management Patients with thrombotic disorders should avoid activities that promote circulatory stasis (eg, immobility, crossing the legs). Exercise, especially ambulation, should be performed frequently throughout the day, particularly during long trips by car or plane. Medications that alter platelet aggregation, such as low-strength aspirin, may be prescribed. Some patients require life-long therapy with anticoagulants such as warfarin (eg, Coumadin). Patients with thrombotic disorders, particularly those with thrombophilia, should be assessed for concurrent risk factors for thrombosis and should avoid concomitant risk factors if possible. For example, use of tobacco and nicotine products exacerbates the problem and should be avoided. Just as for other conditions, patients with thrombotic disorders, particularly thrombophilia, should know the name of their specific condition and understand its significance. In many instances, younger patients with thrombophilia may not require prophylactic anticoagulation; however, with concomitant risk factors (eg, pregnancy), increasing age, or subsequent thrombotic events, prophylactic or lifelong anticoagulation therapy may be required. Being able to provide the health care provider with an accurate health history can be extremely useful and can help guide the selection of appropriate therapeutic interventions. 

Patients with hereditary disorders should be encouraged to have their siblings and children tested for the disorder. When patients with thrombotic disorders are hospitalized, frequent assessments should be performed for signs and symptoms of beginning thrombus formation, particularly in the legs (DVT) and lungs (pulmonary embolism). Ambulation or range-of-motion exercises as well as the use of elastic compression stockings should be initiated promptly to decrease stasis. Prophylactic anticoagulants are commonly prescribed.