Study to Assess Droxidopa in the Treatment of Freezing Of Gait Symptoms in Patients With Parkinson's Disease

Inclusion Criteria:

- Male or female patients, aged at least 30 years;

- Diagnosed with probable levodopa-responsive idiopathic Parkinson's Disease , and
receiving levodopa. Other Parkinson's Disease medications can also be used.

- At least 3 months incidence of typical freezing of gait (FOG) symptoms, occurring
while levodopa is otherwise providing an "on" mobility state (including at least one
of the following FOG patterns: start hesitancy, freezing at making turns or when
passing through a doorway, spontaneous freezing during continued walking, or freezing
of gait related to a simultaneous mental or physical activity).

- Provide written informed consent to participate in the study and understand that they
may withdraw their consent at any time without prejudice to their future medical care

- On a stable dose of carbidopa, alone or with other Parkinson's medication, providing
a range of carbidopa between 100mg and 400mg daily

Exclusion Criteria:

- Taking direct acting vasoconstricting agent (i.e. ephedrine or midodrine). Patients
taking vasoconstrictor agents such as ephedrine or midodrine must stop taking these
drugs at least 2 days or 5 half-lives (whichever is longer) prior to their baseline
visit;

- Taking more than one anti-hypertensive medication for the treatment of high blood
pressure. Short acting anti-hypertensive medication taken at night to prevent supine
hypertension will be allowed.

- Have changed dose or frequency of Parkinson's medication within 2 weeks of baseline

- Known or suspected alcohol or substance abuse within 1 year

- Sustained hypertension (BP greater than 140/90 mmHg in the sitting position)

- Symptomatic coronary artery disease, severe congestive heart failure

- Women who are pregnant, lactating, or plan to become pregnant during the course of
this study;

- Women of child bearing potential (WOCP) who are not using two methods of
contraception (at least one barrier: i.e. condom) with their partner.

- Male patients who are sexually active with a woman of child bearing potential (WOCP)
and not using two methods of contraception (at least one barrier: i.e. condom)

- Untreated closed angle glaucoma, or treated closed angle glaucoma that in the opinion
of an ophthalmologist would cause increased risk to the patient;

- Active (last 6 months) atrial fibrillation or, in the investigator's opinion, any
other significant cardiac arrhythmia that should preclude the patient from this
trial;

- History of myocardial infarction or unstable angina

- Diabetes insipidus, insulin dependent diabetes mellitus, or diabetic neuropathy;

- In the investigator's opinion, any other significant systemic illness;

- Known or suspected malignancy (other than basal cell carcinoma);

- Known gastrointestinal illness or other gastrointestinal disorder that may, in the
investigator's opinion, affect the absorption of study drug;

- Any major surgical procedure within 30 days of the baseline visit;

- Currently receiving any investigational drug or have received an investigational drug
within 30 days of the baseline visit;

- In the investigator's opinion, clinically significant abnormalities on clinical
examination or laboratory testing that should preclude the patient from this trial;

- Patient has only lower body Parkinson's Disease

- In the investigators opinion, freezing of gait is attributable to previous stroke