NCLEX RN Practice Question # 541

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Warfarin sodium (Coumadin)


  • Warfarin suppresses coagulation by acting as an antagonist of vitamin K by inhibiting four dependent clotting factors (X, IX, VII, and II).
  • Warfarin prolongs clotting time and is monitored by the prothrombin time (PT) and the international normalized ratio (INR).
  • It is used for long-term anticoagulation and is used mainly to prevent thromboembolic conditions such as thrombophlebitis, pulmonary embolism, and embolism formation caused by atrial fibrillation, thrombosis, myocardial infarction, or heart valve damage.

Blood levels

  • The normal PT is 9.6 to 11.8 seconds.
  • Warfarin sodium prolongs the PT; the therapeutic range is 1.5 to 2 times the control value.

International normalized ratio (INR)

  • The normal INR is 1.3 to 2.0.
  • The INR is determined by multiplying the observed PT ratio (the ratio of the client’s PT to a control PT) by a correction factor specific to a particular thromboplastin preparation used in the testing.
  • The treatment goal is to raise the INR to an appropriate value.
  • An INR of 2 to 3 is appropriate for most clients, although for some clients the target INR is 3 to 4.5.
  • If the INR is below the recommended range, warfarin sodium should be increased.

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