Efficacy and Safety of Intravenous Phytonadione (Vitamin K 1) in Patients on Long-term Oral Anticoagulant Therapy

Abstract

To determine the safety and efficacy of intravenously administered phytonadione (vitamin K1) in patients on routine oral warfarin anticoagulation. This retrospective cohort study comprised adults who were taking warfarin, were not bleeding, and received intravenous phytonadione anticoagulation therapy before a diagnostic or therapeutic procedure between September 1, 1994, and March 31, 1996. The main outcome measures were adverse reactions to intravenously administered phytonadione, prothrombin-international normalized ratio time values, the incidence of bleeding and thrombosis after the procedure, and the time between the procedure and return to anticoagulation after resumption of warfarin treatment. Two (1.9%) of the 105 patients studied had suspected adverse reactions to intravenous phytonadione (dyspnea and chest tightness during infusion in both). For the 82 patients who underwent a procedure, the median time from phytonadione to procedure onset was 27 hours (range, 0.7-147 hours), which was significantly less for patients receiving an initial phytonadione dose of more than 1 mg (P=.009). None had thromboembolism after surgery, although 2 (2.4%) of the 82 patients had procedure-associated major bleeding. For the 60 patients resuming warfarin therapy after a procedure, the median time to return to therapeutic anticoagulation was 4.1 days (range, 0.8-31.7 days) and was unaffected by the phytonadione dosage. Intravenous phytonadione appears to be safe and is effective for semiurgent correction of long-term oral anticoagulation therapy before surgery. In small doses, it does not prolong the patient's time to return to therapeutic anticoagulation.