This is excerpted from AL Lodwick's site
www.warfarinfo.com/vitamin-K.htm
Note that Jody C was administered a Vitamin K injection due to having an INR of 7.1. She was released from the hospital with an INR of 1.5. I has now plumetted to 1.1
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The Journal American Family Physician published a case study where the author conceded that there was an overly aggressive response to a bloody nose. The patient was a man with mechanical heart valve who had a bloody nose of two hours duration. His INR was found to be 4.7, The bleeding was controlled by packing the nose and including bacitracin, oxymetazolone and cocaine. (Not that the bleeding was controlled at this point.) Then they injected him with vitamin K 2.5 mg subcutaneously, administered 2 units of fresh frozen plasma and held his warfarin for 5 days. Ten days later his INR was only 1.7. He was put at high risk for a thrombus by using vitamin K, fresh frozen plasma and holding warfarin all after the bleeding was controlled. Holding the warfarin for one day should have been sufficient in this case after the bleeding was controlled.
When there is no bleeding, just an elevated INR, I use the approach advocated by Witt et al. They state that at INRs of 4.5 to 10.0, the risk of major bleeding is not high enough to warrant rapid INR reversal with vitamin K. I do not have prescribing authority, so I must request that a physician order vitamin K therapy. I seldom request this if a patient is not bleeding. The only exceptions I can think of are when patients live many miles from health care. Then I have asked for a prescription to be used only if the patient begins to experience bleeding. For patients who are healthy enough to come into an outpatient clinic and live near the hospital, the chances of a life-threatening bleed are very small. As Witt et al state, "We believe that the INR overcorrection frequently seen after vitamin K administration is worrisome in non-bleeding patients with INRs between 4.5 and 10.0, especially when the underlying thromboembolic risk is high."
Patel et al conducted a randomized, double-blind, placebo-controlled study of using vitamin K 2.5 mg orally. They studied patients who had INRs between 6 an 10 and gave them either a single dose of vitamin K 2.5 mg or a placebo. Warfarin was stopped until the INR fell back to below 4.0. The people who took the vitamin K had their INRs come down faster, but they also came down farther and dropped too low more often than the others. Neither group had significant warfarin resistance when they restarted warfarin.
How long should you hold warfarin? I think that it depends upon the dose of warfarin. The average dose of warfarin seems to be about 4 or 5 mg per day. This is the average dose because these people are about average in their metabolism of warfarin. With this dose, the INR should decline to about half of its previous level in about 48 hours. So if someone taking 3 to 6 mg of warfarin per day has an INR of less than 8, their INR should be back below 4 in two days. (A statistical analysis of about 2,500 visits to my clinic found no additional risk of bleeding with an INR less than 5.0.) Therefore, I feel confident in having these people rechecked in two days. When someone who takes less than 3 mg of warfarin daily (a slow metabolizer), they will usually not have their INR decrease by half in 48 hours. I will check this person again in 48 hours to be sure that they have not developed bleeding. However, if they had a INR of near 8, their INR will usually still be above 4 after 48 hours. They often need to be checked again in another 48 hours. When someone takes more than 6 mg of warfarin daily (a rapid metabolizer), I am reluctant to hold warfarin for more than one day. They will usually have their reduced by more than half in 48 hours.
How much vitamin K do you give when it is needed? I have seen an INR of 9 reduced to less than 2 within 24 hours of giving 2 mg of vitamin K IV. I have also seen a patient with moderate bloody diarrhea and an INR of 7.4 have the diarrhea resolve within 24 hours after an oral dose of 11.25 mg of vitamin K. (He had used all of his sick days and declined to come back to the clinic after the diarrhea resolved, so I do not know what the after-treatment INR was.) I probably would not use this large dose today, but it was advocated a few years ago. I think now that 2.5 to 5 mg of oral vitamin K would have been sufficient.
