Late Phase 2 Study of DU-176b in Patients With Non-Valvular Atrial Fibrillation

Inclusion Criteria: * Patients with non-valvular atrial fibrillation who meet all of the following requirements will be considered for admission to the study: * Age≧20years * Atrial fibrillation confirmed by at least 2 electrocardiographic(ECG) tracings taken at an interval of ≧1week during the year before enrollment * Presence of any (at least )one of the following risk factors for embolism: * Hypertension * Diabetes mellitus * Congestive heart failure * Previous transient ischemic attack (TIA) or cerebral infarction (more than 30 days before giving informed consent ) * Age≧75 years * At time of giving informed consent. * To be confirmed on ECG charts, etc. Exclusion Criteria: * Presence of any of the following conditions with increased risk of hemorrhage: * History of intracranial, intraocular (excluding bleeding beneath the bulbar conjunctiva ), intrathecal, retroperitoneal, or non-traumatic intraarticular hemorrhage * History of gastrointestinal hemorrhage during the year before giving informed consent * History of peptic ulcers during the 90 days before giving informed consent * Surgical treatment or trauma requiring hospitalization during the 30 days before giving informed consent * Hemoglobin level \<10 g/dL platelet count \<10 ×10000 /μL at screening examinations * Active hemorrhage\* present at giving informed consent or at enrollment * Any invasive therapeutic or diagnostic procedure (e.g., surgery, tissue, biopsy, and tooth extraction) scheduled during the period from the time of informed consent until completion of the trial treatment. * Any congenital hemorrhagic disease * History of cerebral infarction or TIA within 30 days before giving informed consent * Current treatment with any anticoagulant(other than warfarin) * Concurrent rheumatic valvular disease * History of valvular surgery * Concurrent infectious endocarditis * Concurrent cardiac myxoma * Confirmed left ventricular or left atrial thrombosis * Any congenital condition with a tendency toward thrombosis * Electrical or pharmacological defibrillation scheduled during the trial treatment * Uncontrolled hypertension (persistently high systolic ［\>160mmHg］or diastolic \[\>100mmHg\] pressure) * Uncontrolled diabetes mellitus * Renal or hepatic dysfunction (as defined below ), confirmed at screening examinations * Serum creatinine\>1.5mg/dL * AST(GOT)or ALT(GPT)≧twice the upper limit of the reference range * Total bilirubin ≧twice the upper limit of the reference range * Current antiplatelet therapy for any concomitant illness that may be aggravated after discontinuation of the therapy. * Any concurrent severe cardiac disease * Known allergy to warfarin or any condition contraindicating its use * Inability to discontinue current treatment with vitamin K * Confirmed or potential pregnancy, wish to become pregnant during the study period, or current breast feeding * Previous treatment with DU-176b * Participation in a trial of any other drug during the 6 month before giving informed consent * Any other condition that disqualifies the patient for the study in the opinion of the investigator/subinvestigator \*This includes ecchymosis identified as at least one hematoma sized ≧5 cm in longer diameter, macroscopic hematuria, and microscopic hematuria defined as a ≧2+test or a 1+ test for occult blood with a urine sediment containing ≧10 red cells per high-power field (except for a 2+ occult blood test persisting for 1 year before giving informed consent).