BRIEF COMMUNICATIONS Potentiation of Vitamin K Antagonists by High-Dose Intravenous Methylprednisolone

Background: Oral anticoagulants and pulse high-dose intravenous methylprednisolone are often administered concomitantly, but no data on potential interactions are available. Objective: To assess possible potentiation of oral anti-coagulation by high-dose intravenous methylpred-nisolone. Design: Prospective cohort study. Setting: University hospital in Paris, France. Patients: 10 consecutive patients concomitantly receiv-ing methylprednisolone and oral anticoagulants (fluindi-one and acenocoumarol) and 5 consecutive controls re-ceiving methylprednisolone alone. Measurements: Serial determinations of the interna-tional normalized ratio (INR) and clotting factors during administration of pulse methylprednisolone. The total plasma fluindione concentration was determined in 3 pa-tients. Results: The mean INR was 2.75 (range, 2.02 to 3.81) at baseline and increased to 8.04 (range, 5.32 to 20.0) after methylprednisolone administration. Plasma fluindione concentrations and the INR increased after methylpred-nisolone administration. Methylprednisolone alone did not increase prothrombin time. Conclusions: The action of oral anticoagulants is poten-tiated by intravenous high-dose methylprednisolone. The INR should be monitored daily during concomitant admin-istration of these medications. Ann Intern Med. 2000;132:631-635