The more common anticoagulant clinic is one within which patients have their INR determined by an outside laboratory, with the results called to a clinic physician, nurse or pharmacist. Within such a clinic, it is impractical to require patients to present to the hospital for assessment and randomization on the day that their INR is prolonged. For clinics using this model, we propose that when patients are found to have an INR of more than 4.5 they be assessed over the telephone for inclusion and exclusion criteria for the study. Patients meeting inclusion criteria, with no exclusion criteria, will be asked to provide consent over the telephone for the study. Once consent is obtained, and study forms are completed using information obtained over the telephone, the study centre will arrange to have the next numbered study drug allocated to the patient. The study drug will then be shipped to the patient using taxi cabs or a dedicated courier service. Receipt and consumption of the drug will then be confirmed at the time of the mandatory in centre assessment the following day.