A Pilot Study of Mirabegron and Behavioral Modification Including Pelvic Floor Exercise for Overactive Bladder in Parkinson's Disease (MAESTRO)

Inclusion Criteria:- * Diagnosis of Parkinsons by United Kingdom brain bank criteria * Age \> 30 years old * No change in Parkinsons medications during the 4 weeks preceding screening, with no dose changes during the study, except that PRN (as needed) doses of carbidopa/levodopa will be allowed to address periodic worsening of parkinsonian symptoms. * Patient willing and able to complete micturition diary * Urinary urgency (≥ 8 entries of bladder urgency score \> 2) in 72hr voiding diary during screening period * Micturition frequency ≥ 8 / 24hr or incontinence ≥ 2 episodes in 72hr voiding diary during screening period * Use of other medication that could influence bladder function, other than those specifically prohibited (see below), will be permitted as long as the dose is stable for 4 weeks preceding screening, with no dose changes during the study. * Patient expects to have valid health insurance for the duration of the study period Exclusion Criteria: * Women who are breast-feeding, pregnant or have potential to become pregnant during the course of the study (fertile and unwilling/unable to use effective contraceptive measures). * Cognitive deficits that in the opinion of the investigator would interfere with the subject's ability to give informed consent or perform study testing. * Screening blood pressure \> 165 systolic or 100 diastolic * Heart rate \> 100 * History of allergy to Mirabegron. * Screening post-void residual \> 200ml * Evidence of urinary tract infection at screening * History of chronic inflammation such as interstitial cystitis, bladder stones, previous pelvic radiation therapy, or previous or current malignant disease of the pelvic organs * Intravesical botulinum toxin treatment within the previous six months of screening. * Presence of Interstim device * Use of indwelling catheter or self-catheterization * Concurrent use of thioridazine, flecainide, propafenone, or Digoxin * Concurrent use of warfarin (Coumadin) * Use of one of the anti-cholinergic bladder medications specified below within 14 days of the screening visit. Subjects who have used one of these medications in the past but discontinued it at least 14 days prior to the screening visit can be enrolled. * Screening estimated glomerular filtration rate (eGFR) \< 60, AST ( aspartate aminotransferase ) or ALT ( alanine aminotransferase ) \> 2x upper limit of normal * Any other serious and/or unstable medical condition * Participation in other drug studies or use of other investigational drugs within 30 days prior to Screening Visit.