October 10, 2015
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Pulmonary Embolism (cont.)

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Anticoagulation prevents further growth of the blood clot and preventing more lung tissue from being affected. The body has complex mechanism to form blood clots to help repair blood vessel damage. Under normal conditions, there is a clotting cascade with numerous blood factors that have to be activated for a clot to form.

Medications are available that block the clotting cascade at different places and therefore "thin" or anti-coagulate the blood.

Warfarin (Coumadin) is the classic anti-coagulation medication that acts as a Vitamin K antagonist, blocking blood clotting factors II, VII, IX and X. It is prescribed immediately after diagnosis of a clot or pulmonary embolism, but unfortunately may it take a week or more for the blood to be appropriately thinned. Therefore, low molecular weight heparin (enoxaparin [Lovenox]) is administered at the same time. It thins the blood via a different mechanism and is used as a bridge therapy until the warfarin has reached its therapeutic level. Enoxaparin injections can be given on an outpatient basis. For those patients who have contraindications to the use of enoxaparin (for example, kidney failure does not allow enoxaparin to be appropriately metabolized), intravenous heparin can be used as the first step in association with warfarin. This requires admission to the hospital.

The dosage of warfarin is monitored by blood tests measuring the prothrombin time or INR (international normalized ratio). Therapeutic levels range from 2.0 - 3.0.

Newer anticoagulation medications as treatment options for pulmonary embolus inhibit blood factor X. These act almost immediately to thin the blood and do not need the two step approach of warfarin and heparin. Medications that have been approved for pulmonary embolus treatment include:

  • apixaban (Eliquis),
  • rivaroxaban (Xarelto),
  • dabigatran (Pradaxa) and
  • edoxaban (Savaysa).

These medications do not need blood tests to monitor dosing.

The decision to prescribe a type of anticoagulation medication (Vitamin K antagonist v. Factor X inhibitor) depends upon the patient situation. Patients who take any of these medications are at risk for bleeding. At present there is no antidote approved in the United States to reverse the effects of the Factor X inhibitors, should the need arise. There are reversal strategies available for warfarin and heparin.

The recommended length of treatment for an uncomplicated pulmonary embolism is 3 months. Depending upon the patient situation, a longer duration of anticoagulation may be required.

Medically Reviewed by a Doctor on 2/27/2015

Source: MedicineNet.com

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