Study to Assess Droxidopa in Treatment of Neurogenic Orthostatic Hypotension in Patients With Parkinson's Disease (NOH306)

Inclusion criteria:

1. 18 years or over
2. Clinical diagnosis of Parkinson's disease
3. Clinical diagnosis of symptomatic neurogenic orthostatic hypotension

At their baseline visit (Visit 2), patients must demonstrate:

• a score of at least 3 or greater on the OHQ composite
• a score of at least 3 or greater on the clinician CGI-S
• a fall of at least 20 mmHg in their systolic blood pressure, or 10 mmHg in their diastolic blood pressure, within 3 minutes of standing 4. 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

Exclusion Criteria:

1. Score of 23 or lower on the mini-mental state examination (MMSE)

2. Concomitant use of vasoconstricting agents for the purpose of increasing blood pressure;

   - Patients taking vasoconstricting agents such as ephedrine, dihydroergotamine, or midodrine must stop taking these drugs at least 2 days or 5 half-lives (whichever is longer) prior to their baseline visit (Visit 2) and throughout the duration of the study

3. Concomitant use of anti-hypertensive medication for the treatment of essential hypertension

4. Have changed dose, frequency or type of prescribed medication, within two weeks of baseline visit (Visit 2) with the following exceptions:

   • Vasoconstricting agents such a ephedrine, dihydroergotamine, or midodrine
   • Short courses (less than 2 weeks) of medications or treatments that do not interfere with, or exacerbate the patient's condition under study (e.g. antibiotics)
5. Known or suspected alcohol or substance abuse within the past 12 months (DSM-IV definition of alcohol or substance abuse)
6. Women who are pregnant or breastfeeding
7. Women of child bearing potential (WOCP) who are not using at least one method of contraception with their partner
8. Male patients who are sexually active with a woman of child bearing potential (WOCP) and not using at least one method of contraception
9. Untreated closed angle glaucoma, or treated closed angle glaucoma that, in the opinion of an ophthalmologist, might result in an increased risk to the patient
10. Sustained severe hypertension (BP ≥ 180 mmHg systolic or ≥ 110 mmHg diastolic in the seated or supine position which is observed in 3 consecutive measurements over an hour)
11. Any significant uncontrolled cardiac arrhythmia
12. History of myocardial infarction, within the past 2 years
13. Current unstable angina
14. Congestive heart failure (NYHA Class 3 or 4)
15. Diabetic autonomic neuropathy
16. History of cancer within the past 2 years other than a successfully treated, non-metastatic cutaneous squamous cell or basal cell carcinoma or cervical cancer in situ
17. Gastrointestinal condition, which in the Investigator's judgment, may affect the absorption of study drug (e.g. ulcerative colitis, gastric bypass)
18. Any major surgical procedure within 30 days of the baseline visit (Visit 2)
19. Previously treated with droxidopa
20. Currently receiving any investigational drug or have received an investigational drug within 30 days of the baseline visit (Visit 2)
21. Any condition or laboratory test result, which in the Investigator's judgment, might result in an increased risk to the patient, or would affect their participation in the study. Additionally the Investigator has the ability to exclude a patient if for any reason they feel the subject is not a good candidate for the study or will not be able to follow study procedures.