Method of randomization: Randomization will be performed using a computer-generated randomization sequence. This sequence will guide drug packaging. Study drug supply will be packaged and dispensed to each study centre in lots of sequentially numbered appropriately labeled pill bottles. An additional, clearly labeled, supply of capsules containing 1.25 mg of oral vitamin K will be dispensed to each participating centre. Patients will be randomized by allocating the next, sequentially numbered pill bottle.