Intervention: Mirabegron
Trial phase: Phase 4
ATC code: G04BD12
SMILES: Nc1nc(CC(=O)Nc2ccc(CCNC[C@H](O)c3ccccc3)cc2)cs1
Sex: All
Age groups: Adult | Older Adult
Healthy volunteers: No
Participants at risk: 15
Group description: 1:1 randomization to receive Mirabegron 25 mg daily or placebo at visit 2. At visit 3 all subjects who have tolerated Mirabegron 25 md daily (no adverse events on this dose) will be up-titrated to Mirabegron 50 mg daily. This will be dispensed as two 25mg tablets or , for those in the placebo arm, two placebo tablets.

Mirabegron: 25 mg po daily for 32-40 days. Following up-titration to 50 mg po daily. This is pending no adverse events on the 25 mg dose.

Placebo: Placebo 25 mg po daily. Following up-titration to 50 mg po daily. This is pending no adverse events on the 25 mg dose.
Eligibility criteria:
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.