Anticoagulants - Warfarin: Nursing Pharmacology

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warfarin (Jantoven)
Vitamin K antagonist
  • Blocks vitamin K epoxide reductase and prevent regeneration of vitamin K epoxide, which is a cofactor for the enzyme gamma-glutamyl carboxylase, which converts the non-functional forms of coagulation factors II, VII, IX, and X and anticoagulation proteins C and S, into their functional forms
  • Inhibits maturation of clotting factors II, VII, IX, X and anti-coagulation proteins C, S
  • Causes an initial period of hypercoagulation (due to protein C depletion) followed by anticoagulation
  • Deep vein thrombosis, pulmonary embolism
  • Ischemic stroke, transient ischemic attack
  • Coronary artery disease
  • Cardiac valve replacement or coronary angioplasty
  • Coagulation disorders like antiphospholipid syndrome and DIC
  • Dialysis
  • Surgical procedures: cardiopulmonary bypass, ECMO, PCI
  • PO
  • Undue bleeding (antidote: Vitamin K1, called phytonadione)
  • Hair loss
  • Fever
  • Bone marrow depression
  • Gastrointestinal effects (anorexia, vomiting, diarrhea, abdominal cramps)
  • Warfarin-induced skin necrosis, purple toe syndrome
  • Teratogenic (fetal hemorrhage, bone deformities, congenital heart defects, brain malformation in the fetus, spontaneous abortion)
  • Active internal bleeding, recent trauma in the past three months, history of intracranial hemorrhage or ischemic stroke, gastrointestinal ulcers, coagulopathies or bleeding disorders
  • Surgery of the eye, brain, or spinal cord
  • Spinal anesthesia or spinal puncture
  • Pregnancy and breastfeeding
  • Vital signs, signs of bleeding
  • Laboratory test results: CBC, PT, INR, renal and hepatic function; negative pregnancy test for female clients of childbearing age

  • INR level
  • Signs of bleeding
  • Therapeutic effect: absence of thromboembolic events
  • Purpose of medication: prevent clots, thromboembolism
  • Take exactly as directed
    • Contact the healthcare provider for a missed dose
  • Need for regular INR testing
  • Main side effect: bleeding
  • Bleeding precautions
    • Soft bristled toothbrush, floss gently
    • Electric razor for shaving
    • Care with sharp objects
    • Avoid hazardous activities; e.g., contact sports
    • Eliminate tripping hazards
    • Wear a helmet when bike riding
  • Treatment for minor bleeding
    • Cuts: hold gauze or clean cloth over the affected area for 15 minutes
    • Nose bleed: tilt their head slightly forward; apply pressure above their nostrils for 15 minutes
  • Immediately notify their healthcare provider if injured, hit their head; experience bleeding longer than 15 minutes; notice blood in their vomit, stool, or urine; new onset of chest or back pain, shortness of breath, weakness, dizziness, or confusion
  • Dietary modifications
    • Avoid large day-to-day variations in the amount of vitamin K
    • Avoid alcohol, nicotine products
  • Wear a medical alert identification at all times
  • Inform all of their healthcare providers they are taking warfarin
  • Consult with healthcare provider before taking over the counter medications or supplements


Anticoagulants are medications that work by interfering with the function of clotting factors in the coagulation cascade, preventing the formation of thrombi, or blood clots. These medications are used to prevent or treat thromboembolic events, such as deep vein thrombosis, pulmonary embolism, ischemic stroke, transient ischemic attack, coronary artery disease or myocardial infarction.

They're also used in clients with coagulation disorders, including antiphospholipid syndrome and disseminated intravascular coagulation; as well as in clients who underwent coronary angioplasty or cardiac valve replacement; and during surgical procedures like cardiopulmonary bypass, percutaneous coronary intervention, extracorporeal membrane oxygenation, and in clients undergoing dialysis.

One of the most important anticoagulants is warfarin, which is given orally, and works as a vitamin K antagonist.

Normally, vitamin K is used by the liver as a cofactor for the synthesis and activation of the clotting factors II, VII, IX, and X, as well as the anticoagulant proteins C and S. During this process, the active form of vitamin K, called vitamin K hydroquinone, is converted into vitamin K epoxide, which is then recycled back into vitamin K hydroquinone by another enzyme called epoxide reductase.

Warfarin antagonizes the function of vitamin K by inhibiting the epoxide reductase enzyme and preventing vitamin K hydroquinone from getting recycled. As a result, there’s no synthesis and activation of the clotting factors II, VII, IX, and X, but also the anticoagulant proteins C and S. Out of all the vitamin K-dependent proteins, protein C has the shortest half-life so it is the first to be depleted in clients taking warfarin. This results in an initial period of hypercoagulation before the anticoagulant effect kicks in. To prevent this, bridging anticoagulation with LMWH is usually prescribed for a short period while starting warfarin therapy.


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