Influence of body weight on response to subcutaneous vitamin K administration in over-anticoagulated patients

PURPOSE: To determine the influence of body weight on the international nor malized ratio (INR) response to a fixed dose of vitamin K in overanticoagul ated patients. METHODS: Retrospective review of records of patients who received 1 mg of v itamin K subcutaneously to correct excessive INR. Dose of vitamin K in mill igrams per kilograms plotted against change in INR in 24 hours. RESULTS: Fifteen patients were identified who met all inclusion criteria. L inear regression analysis plotted INR response at 24 hours versus dose of v itamin I: adjusted for body weight. Pearson's product moment correlation (R = 0.85) indicated a significant relationship between INR response at 24 ho urs to an adjusted body weight dose of subcutaneous vitamin K (P = 0.000052 3). A strong correlation (r = 0.69) also existed between INR response at 24 hours and the actual body weight dose of subcutaneous vitamin K (P = 0.004 ). CONCLUSIONS: In overanticoagulated patients,variability in response to vita min K may be explained by variability in body weight. Dosing vitamin K acco rding to body weight may result in a more predictable INR response. (C) 200 1 by Excerpta Medica, Inc.