ORAL VITAMIN K LOWERS THE INTERNATIONAL NORMALIZED RATIO MORE RAPIDLY THAN SUBCUTANEOUS VITAMIN K IN THE TREATMENT OF WARFARIN-ASSOCIATED COAGULOPATHY. A RANDOMIZED, CONTROLLED TRIAL.

Crowther MA, Det al. Ann Intern Med 2002 Aug 20;137(4):251-4.

BACKGROUND: Excessive anticoagulation due to warfarin use is associated with hemorrhage. Subcutaneously administered vitamin K has not been evaluated for the treatment of warfarin-associated coagulopathy, yet it is widely used.

OBJECTIVE: To show that oral vitamin K is more effective than subcutaneous vitamin K in the treatment of warfarin-associated coagulopathy.

DESIGN: Randomized, controlled trial.

SETTING: Two teaching hospitals.

PATIENTS: Patients with an international normalized ratio (INR) between 4.5 and 10.0.

INTERVENTION: Warfarin therapy was withheld, and 1 mg of vitamin K was given orally or subcutaneously. MEASUREMENTS: The primary outcome measure was the INR on the day after administration of vitamin K. Secondary outcome measures were hemorrhage and thrombosis during a 1-month follow-up period.

RESULTS: 15 of 26 patients receiving oral vitamin K and 6 of 25 patients receiving subcutaneous vitamin K had therapeutic INRs on the day after study drug administration (P = 0.015; odds ratio, 4.32 [95% CI, 1.13 to 17.44]).

CONCLUSION: Oral vitamin K lowers INR more rapidly than subcutaneous vitamin K in asymptomatic patients who have supratherapeutic INR values while receiving warfarin.

COMMENTS: While PO vitamin K is preferred over sub-Q vitamin K, the better question to be asked is, "Is vitamin K therapy necessary in asymptomatic patients with supratherapeutic INR?"