True or False: Warfarin’s anticoagulant effect can be reversed with vitamin K. (True/False)单项选择题
A
True
B
False

Question

True or False: Warfarin’s anticoagulant effect can be reversed with vitamin K. (True/False)

BlackTom AI · Accepted Answer

Vitamin K (phytonadione) is the antidote for warfarin anticoagulation, so the correct answer is True.

Relevant concepts:
- Warfarin inhibits the vitamin K epoxide reductase complex (VKORC1), preventing regeneration of reduced vitamin K needed for gamma-carboxylation of clotting factors II, VII, IX, and X (and proteins C and S). Without gamma-carboxylation these factors are nonfunctional → anticoagulation.
- Reversal requires restoring vitamin K–dependent carboxylation so new functional clotting factors can be produced.

Step-by-step reasoning:
1. Warfarin blocks VKORC1 → decreased reduced vitamin K → decreased gamma-carboxylation → lower active clotting factor levels → prolonged INR and anticoagulation.
2. Administering vitamin K (phytonadione) supplies the reduced vitamin K cofactor. This allows gamma-glutamyl carboxylase to produce functional clotting factors as hepatocytes synthesize new proteins, overcoming warfarin’s effect.
3. Because reversal depends on synthesis of new factors, onset is not instantaneous: factor VII (half-life ≈ 6 hours) is replaced fastest, so partial INR improvement can be seen within 6–12 hours; fuller correction (factor II, half-life ≈ 60–72 hours) occurs over longer periods. For life-threatening bleeding, prothrombin complex concentrate (PCC) or fresh frozen plasma (FFP) is given for immediate factor replacement while vitamin K is given to sustain reversal.
4. Vitamin K can be given orally or IV (IV is faster; very rare anaphylactoid reactions reported with IV preparations).

Why the other option is incorrect:
- “False” would claim vitamin K cannot reverse warfarin; this contradicts the established pharmacologic mechanism and clinical practice where vitamin K reliably lowers INR and reverses warfarin’s effect (with timing caveats and use of PCC/FFP when immediate reversal is needed).

Conclusion: Vitamin K reverses warfarin anticoagulation by restoring the vitamin K–dependent carboxylation of clotting factors; therefore the correct answer is True.

True or False: Warfarin’s anticoagulant effect can be reversed with vitamin K. (True/False)单项选择题

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