A Study to Test the Efficacy and Safety of the Beta-3 Agonist Mirabegron (YM178) in Patients With Symptoms of Overactive Bladder

Inclusion Criteria: * Patient is willing and able to complete the micturition diary and questionnaires correctly * Patient has symptoms of overactive bladder (OAB) for ≥ 3 months * Patient must experience frequency of micturition on average ≥ 8 times per 24-hour period during the 3-day micturition diary period * Patient must experience at least 3 episodes of urgency (grade 3 or 4) with or without incontinence during the 3-day micturition diary period Exclusion Criteria: * Patient is breastfeeding, pregnant, intends to become pregnant during the study, or of childbearing potential, sexually active and not practicing a highly reliable method of birth control * Patient has significant stress incontinence or mixed stress/urge incontinence where stress is the predominant factor * Patient is using medications intended to treat OAB * Patient has an indwelling catheter or practices intermittent self-catheterization * Patient has diabetic neuropathy * Patient has evidence of urinary tract infection, chronic inflammation such as interstitial cystitis, bladder stones, previous pelvic radiation therapy or previous or current malignant disease of the pelvic organs * Patient receives non-drug treatment including electro-stimulation therapy * Patient has severe hypertension * Patient has participated in a clinical study within 30 days, or had participated in any previous study with mirabegron * Patient had an average total daily urine volume \> 3000 mL as recorded in the 3-day micturitio…