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| |  ISTH: Low-Dose Vitamin K Treats Excessive Anticoagulation By Jill Stein Special to DG News
PARIS, FRANCE -- July 9, 2001 -- Intravenous vitamin K may be highly effective for the treatment of patients with excessive anticoagulation. A study presented at the Eighteenth Congress of the International Society on Thrombosis and Haemostasis (ISTH) shows that a dose of 0.5 mg was very effective in patients with a baseline International Normalized Ratio (INR) of 6 to 10 and proved to be predictable and safe. Dr. Aharon Lubetsky and co-workers at the Sheba Medical Center in Tel Hashomer, Israel, tested the efficacy and safety of intravenous (IV) low-dose vitamin K administered by a pre-designed protocol for the correction of excessive anticoagulation. "Excessive anticoagulation is not uncommonly encountered in outpatients receiving long-term anticoagulation," he said. The risk of bleeding in such patients depends in part on the magnitude of INR deviation as well as on the duration of patient exposure to increased INR values. Accordingly, rapid restoration of INR to the therapeutic range is the accepted treatment option, he added. However, no consensus exists regarding the optimal dose or regimen for vitamin K administration. Consecutive patients presenting with an INR of 6.0 or greater while being treated with either warfarin or nicoumalone without major bleeding symptoms were suitable for the study. Patients were hospitalized for 24 hours for vitamin K treatment or for longer time periods, as deemed necessary. All patients received 0.5 mg of vitamin K diluted in 150 mL saline and infused over 30 minutes. The warfarin/nicoumalone dose was withheld for 24 hours. INR values were determined prior to vitamin K infusion and at six, 12 and 24, 48, and 72 hours post-infusion. All patients were reevaluated one week after hospital discharge. Seventy-three consecutive patients with a mean age of 61.5 years were studied during 91 episodes of excessive anticoagulation. Sixty-eight (93 percent) patients were treated with warfarin and five with nicoumalone. The average steady state weekly dose was 34.0 ± 20.1 mg for warfarin-treated patients and 15.6 ± 7.3 mg for nicoumalone-treated patients. The indications for anticoagulation included venous thrombosis in eight patients, atrial fibrillation in 27, prosthetic heart valves in 35, and other heart disease in three patients. Sixty-five (89 percent) patients experienced a single episode of excessive anticoagulation while eight patients had 26 episodes. These eight patients manifested multiple drug interactions as the main reason for recurrence of INR deviation. Overall, 91 episodes of excessive anticoagulation were treated by single or multiple doses of vitamin K. In all patients, INR values declined significantly within 12 to 24 hours of treatment onset to reach the desired therapeutic level in most patients at the 24-hours time point. Stable INR was observed at 72-hour follow-up. Patients with baseline INR 6 to 10 declined more rapidly towards pre-treatment INR levels than patients with baseline INR greater than 10, and significantly fewer patients (eight percent versus 61 percent) needed repeat vitamin K doses. The rate of INR decline depended on the vitamin K dose. Following 0.5 mg of vitamin K administration, INR declined to 2.0 to 4.0 at 24 hours in 98 percent of patients with baseline INR of 6 to 10. These rates were similar in other patient groups, except for patients with a baseline INR greater than 10, who needed repeated vitamin K doses and in whom four of 12 failures were observed at the 24-hour time point. During the study, no major bleeding or thrombosis episodes were observed. Dr. Lubetsky said that the results indicate that IV low-dose vitamin K has a rapid and predictable effect in patients with excessive anticoagulation. He added that a larger dose of vitamin K (possibly 1 mg) should be tested in patients with a baseline INR greater than 10.
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