Reversal of excessive oral anticoagulation with a low oral dose of vitamin K1 compared with acenocoumarine discontinuation.: A prospective, randomized, open study

We performed a prospective, randomized, open study in 109 outpatients under chronic anticoagulation with acenocoumarine, presenting with International Normalized Ratios (INRs) greater than or equal to 6.0 and no or minor bleeding. All the patients withheld one dose of acenocoumarine; in addition, a treated group also received 1 mg oral vitamin K-1. We aimed at a post-intervention INR < 6.0, with a target zone of 2,0-4.0. The INRs were lowered from a mean of 8.1 +/- 1.7 to 4.9 +/- 2.5 in the controls (P= 0.0000) and from 8.4 +/- 2.4 to 3.3 +/- 3 in the treated patients (P = 0.0000). There were no differences in the percentage of patients with postintervention INRs < 6.0 or within the therapeutic zone. One-third of the treated patients and only 2% of the controls reached INRs < 2.0 (P= 0.0003). Oral vitamin K-1 offered no advantageto the simple discontinuation of one dose of acenocoumarine. A substantial number of treated patients were consequently exposed to under-anticoagulation. Blood Coagul Fibrinolysis 12:9-16 (C) 2001 Lippincott Williams & Wilkins.