Outpatient Physical Therapy Intervention in Subjects With Parkinson's Disease Currently Using APOKYN®

To determine if PT intervention will be improved while in the "on" motor state vs. the "end-of-dose-off" motor state during the PT Intervention Visit in subjects with PD.

Multicenter, outpatient trial to evaluate PT outcomes in subjects diagnosed with PD and currently using APOKYN. Those subjects who satisfy all eligibility criteria will be randomized to 2 treatment groups:

1. "APO+" (APOKYN treatment before the PT Intervention Visit) and;
2. "APO-" (APOKYN treatment withheld before the PT Intervention Visit).

The study will have:

* Baseline Assessment Visit(s) - 1 day at Investigator's clinic and PT clinic
* APOKYN Response Verification Visit - 1 day
* PT Intervention Visits - for 6 weeks
* End-of-study Assessment Visit(s) - 1 day at Investigator's clinic and PT clinic All subjects will participate in a standardized PT intervention. In both treatment groups, ALL subjects will arrive for the PT Intervention Visit in an "end-of-dose-off" motor state. The "end-of-dose-off" motor state will be achieved by the subject withholding his/her carbidopa/levodopa dose and APOKYN dose for at least 3 hours before the PT Intervention Visit. It is hypothesized that the outcome of PT will be improved when subjects are in the "on" motor state during PT Intervention visits compared with being in the "end-of-dose-off" motor state during PT Intervention visits.

Eligibility Criteria:
Inclusion Criteria:

* Able to understand and sign an Investigational Review Board (IRB)-approved written informed consent and privacy language (e.g., Health Insurance Portability and Accountability Act (HIPAA) authorization) as per national regulations before any study-related procedures are performed.
* Must have a diagnosis of idiopathic PD.
* Adult male or female 18 to 78 years of age, inclusive.
* Currently using APOKYN, per the Package Insert, for at least 4 weeks before Baseline Assessment Visit(s).
* Currently using carbidopa/levodopa therapy at a steady maintenance dose, representing a stable treatment regimen in the opinion of the Investigator, for at least 4 weeks before Baseline Assessment Visit(s).
* Able to walk 50 feet independently (cane permissible) at the Baseline Assessment Visit.
* Meet all of the following parameters to demonstrate an optimal response to APOKYN at the APOKYN Response Verification Visit: must be "on" in the opinion of the subject and investigator within 20 minutes after the APOKYN injection; and have a motor state improvement of \>25% per the Movement Disorder Society (MDS)-UPDRS Motor Score (Part III), within 20 minutes after the APOKYN injection, as compared to pre-injection.
* Willing and able to comply with scheduled visits, treatment plan, other study-related procedures, and have available caregiver to provide transportation to clinic visits as needed.

Exclusion Criteria:

* Received PT targeting Parkinson's disease within 6 months before Baseline Assessment Visit(s).
* Received any investigational (i.e., unapproved) drug product within the last 30 days (or 5 half-lives, whichever is longer) before the Baseline Assessment Visit(s).
* Currently taking, or likely to need to take at any time during the course of the study, any 5HT3 antagonist (i.e., ondansetron, granisetron, dolasetron, palonosetron, alosetron).
* Currently on or likely to transition to the DUOPA (carbidopa and levodopa enteral suspension) during the course of the study.
* Has orthostatic hypotension (defined as \>30 mmHg decrease in systolic blood pressure or \>15 mmHg decrease in diastolic blood pressure within 2 minutes of standing from a supine position) at the Baseline Assessment Visit(s), or within 20 minutes following APOKYN injection at the APOKYN Verification Visit.
* Has a score of 24 or higher on the Modified Physical Performance Test (M-PPT).
* Has a score of 80% or higher on the Activities-specific Balance Confidence Scale (ABC).
* Has any significant current medical disorder, physical, or mental condition that would, in the Investigator's opinion, represent a hazard to the subject or prevent the subject from completing the study.
* Subjects with dementia, in the Investigator's opinion, or subjects with a Montreal Cognitive Assessment (MoCA) \<18.