To accomplish these goals, the investigators propose a multinational, double-blind, placebo-controlled trial. The investigators will randomize patients with INR values between 4.5 and 10.0 to receive 1.25 mg of oral vitamin K or placebo and follow them for bleeding and thrombosis. Patients with INR values of more than 10.0 will receive a single 1.25 mg dose of oral vitamin K.