Elevated international normalized ratio from vitamin K supplement discontinuation

Area of Science:

• Pharmacology
• Internal Medicine

Background:

• Warfarin is a common anticoagulant used for stroke prevention in atrial fibrillation.
• Vitamin K supplementation is sometimes used to manage INR variability in patients on warfarin.
• Managing anticoagulation requires careful monitoring of the international normalized ratio (INR).

Observation:

• A patient on warfarin and low-dose vitamin K supplements experienced a subtherapeutic INR after discontinuing the supplement.
• Following protocol, the warfarin dose was increased, but the patient later presented with a critically elevated INR.
• No other contributing factors to the INR elevation were identified.

Findings:

• Discontinuation of vitamin K supplementation was identified as the likely cause of the critically elevated INR.
• The INR elevation occurred despite a protocol-based increase in warfarin dosage.
• The case was classified as a category D error, indicating a significant adverse event.

Implications:

• Clinicians must be aware that discontinuing vitamin K supplements can significantly impact INR levels.
• Close INR monitoring is essential after changes in vitamin K supplementation in patients receiving warfarin.
• This case underscores the complex interplay between vitamin K intake and warfarin efficacy.