A Trial Evaluating the Clinical Efficacy and Safety of Hibero SR (Mirabegron) 50 mg and Ditropan (Oxybutynin Chloride) 10 mg in Children Between 5 and 18 Years With Overactive Bladder (OAB)

Inclusion Criteria: * Subject has been diagnosed with overactive bladder (incontinence, frequent urination, enuresis) according to the International Children's Continence Society (ICCS) * Ages between 5 and 18 * Subject has baseline body weight of 11 kg * Subject has symptoms of overactive bladder even after two weeks of wash-out period * Subject is able to follow and record information on 48 hours voiding diary during the trial period * Subject is able to swallow oral pill form of Hibero (Mirabegron) or Ditropan (Oxybutynin Chloride) * Subject has agreed to be followed up for 10 weeks, including the safety monitoring period * Subject, who is sexually active, has agreed to use at least one effective contraceptive method throughout the trial period, including the safety monitoring period. * The baseline hCG urine test should be negative for female subject to be enrolled in the trial. * Subject has normal ECG and vital signs (blood pressure, pulse) at the time of screening Exclusion Criteria: * Subject has been diagnosed with congenital lower urinary tract dysfunction, neurogenic detrusor overactivity, or secondary detrusor overactivity. * Subject is currently in treatment for psychiatric disorder (i.e. depression, attention-deficit/ hyperactivity disorder, bipolar disorder, schizophrenia) * Subject uses clean intermittent catheterization (CIC) for neurogenic detrusor overactivity or due to urologic dysfunction. * At the time of baseline (randomization), the urine test returns positive for urinary tract infection (UTI). * Subject has a history of operation on the lower urinary tract or due to vesicoureteral reflux. * Subject is unable to swallow the pill form of Hibero (Mirabegron) or Ditropan (Oxybutynin Chloride). * Subject is unwilling or unable to follow the directions from the clinical trial team. * Subject has been exposed to either mirabegron or any form of antimuscarinic before the study enrollment (as for antimuscarinic, a subject may be enrolled after two weeks of washout period). * Subject has anaphylactic reactions either to mirabegron or ditropan * Subject has moderate to severe hepatic or renal impairment subjects. * Subject has been prescribed with strong CYP3A4 inhibitors and have moderate-severe hepatic or renal impairment * Subject with the following conditions: lower urinary tract obstruction, urinary retention, glaucoma, narrow tunnel vision, paralytic intestinal obstruction, moderate-severe cardiovascular impaired, ulcerative colitis * As both investigational products contain lactose, the administration of the products is prohibited for those with galactose intolerance, Lapp lactase deficiency, glucose-galactose malabsorption * Subject with uncontrolled hypertension, which is defined as systolic blood pressure greater than or equal to 180 mmHg and/or diastolic blood pressure greater than or equal to 110 mmHg. * Subject has previous history or currently in treatment for any type of cardiovascular disorders.