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Canadian Pharmacist Qualifying Exam Practice · Question

A patient on warfarin therapy reports eating a large amount of spinach recently. What effect might this have on their INR?

Spinach is rich in Vitamin K, which is a cofactor for clotting factors. Increased Vitamin K intake can antagonize warfarin's effect, leading to a decreased INR.

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Question: A patient on warfarin therapy reports eating a large amount of spinach recently. What effect might this have on their INR?

Answer options: ✅ Decrease INR due to increased Vitamin K intake.

  • Increase INR due to increased Vitamin K intake.
  • No significant effect on INR.
  • Increase INR due to interaction with iron in spinach.

Correct answer: Decrease INR due to increased Vitamin K intake.

Explanation: Spinach is rich in Vitamin K, which is a cofactor for clotting factors. Increased Vitamin K intake can antagonize warfarin's effect, leading to a decreased INR.

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