Anticoagulants are drugs that prevent coagulation (clotting) of blood. They can occur naturally in leeches and blood-sucking insects.

• Used as medications:
  • To prevent:
    • DVT
    • PE
    • MI
    • Ischemic stroke
  • To Tx:
    • Atrial fibrillation
    • PE
    • DVT
    • Venous thromboembolism
    • CHF
    • Stroke
    • MI
    • Genetic or acquired hypercoagulability
• Medical equipment (e.g. test tubes, blood transfusion bags, renal dialysis equipment)

• Vitamin K antagonists (derived from coumarin), which inhibits the enzyme vitamin K epoxide reductase [from recycling inactivate vitamin K epoxide back to the active reduced form of vitamin K]. Vitamin K is required for production of certain proteins involved in the clotting process. It includes:
  • Warfarin (see page), the prominent inclusion, which takes at least 2-3 days for warfarin to take effect. Where an immediate effect is required, heparin must be given simultaneously
• Heparin (see page), which activates antithrombin III (which blocks thrombin from activating blood)
• Synthetic factor Xa inhibitors
• NOACS (novel oral anticoagulants, direct oral anticoagulant), which are equivalent or better than coumarins (vitamin K antagonists) with less serious side effects. They are more expensive, and should be used w/ care in Pt's w/ kidney problems. The problem is there is no antidote, so it is difficult to stop it's effects in cases of emergency (accidents, urgent surgery). It includes:
  • Direct factor Xa inhibitors, including:
    • Rivaroxaban (Xarelto)
    • Apixaban
  • Direct thrombin inhibitors, including:
    • Dibigatran (Pradaxa)

• In pregnancy, warfarin is contraindicated → passes through the placental barrier and may cause bleeding in the fetus, and is teratogenic → usually LMWH is used instead

• VTE
• Thrombolytic
• Antiplatelet