Vitamin K INR Reversal Timing — FRCA Final MCQ

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ModeratePreoperative AssessmentVitamin K INR Reversal TimingFRCA Final

A patient on warfarin with INR 3.0 requires urgent surgery in 12-24 hours. IV vitamin K 5 mg is given. Expected time to achieve INR <2.0 is:

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Correct answer: C — 6-12 hours

IV vitamin K begins to reduce INR within 2-4 hours, with maximum effect at 6-12 hours. For truly urgent reversal (<6 hours), PCC is needed in addition. Vitamin K provides sustained reversal lasting 48-72 hours.

Reference: BNF – 2025 – Vitamin K reversal; Association of Anaesthetists – 2025 – Blood components