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Chapter 7. Anticoagulation/Venous Thromboembolism

KP is 72-year-old woman who presents to the emergency department and reports hematuria for the past 2 days. The patient’s INR is 7.2 and KP reports she may have accidentally taken old 10 mg warfarin tablets instead of her currently prescribed 5 mg tablets for the past week. Which agent is the most appropriate reversal agent to be used in the case of warfarin overdose?

a. Phenprocoumon

b. Protamine sulfate

c. Vitamin K

d. Idarucizumab

Answer c is correct. Vitamin K reverses the anticoagulant effects of vitamin K antagonists (VKAs) such as warfarin. VKAs reduce thrombus formation by inhibiting the activation of the vitamin K-dependent clotting factors II, VII, IX, and X. The anticoagulant effect of VKAs is a fine balance between the amount of vitamin K available to activate the clotting factors and ultimately produce thrombin. Ingestion of additional Vitamin K upsets this equilibrium and reverses the anticoagulant effects.

Answer a is incorrect. Phenprocoumon is a vitamin K antagonist available in countries outside the United States. The addition of this agent would have an additive effect to warfarin and increase the severity of the adverse effects.

Answer b is incorrect. Protamine sulfate is the agent of choice for the reversal of unfractionated heparin (UFH) overdose. The recommended dose for reversal of UFH effects is 1 mg of protamine per 100 U of heparin.

Answer d is incorrect. Idarucizumab reverses the anticoagulant effects of dabigatran for emergent surgery, urgent procedures, or in the instance of life-threatening or uncontrolled bleeding. The manufacturer recommended dose is 5 g (2 vials, each contains 2.5 g) administered intravenously as two consecutive infusions or bolus injection by injecting both vials consecutively one after another via syringe.

JC is a 36-year-old pregnant woman with an active DVT. She takes no other medications and has no significant past medical history. Which agent is the best choice for the initial treatment of her DVT?

a. Enoxaparin

b. Aspirin

c. Warfarin

d. Dabigatran

Answer a is correct. UFH or LMWH are the agents of choice for anticoagulation during pregnancy. LMWHs are the agents of choice for outpatient use due to less monitoring and subcutaneous route of administration. UFH requires close monitoring and is generally given intravenously.

Answer b is incorrect. Aspirin is an antiplatelet medication. Antiplatelet and anticoagulant therapies may often be confused since they both may be used for the prevention of stroke and thrombus formation ...

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