Clinical Study of Droxidopa in Patients With Neurogenic Orthostatic Hypotension (NOH)

PATIENT INCLUSION CRITERIA: * Male or female and aged 18 years or over; * Clinical diagnosis of orthostatic hypotension associated with Primary Autonomic Failure (PD, MSA and PAF), Dopamine Beta Hydroxylase Deficiency or Non-Diabetic Autonomic Neuropathies; * A documented fall in systolic blood pressure of at least 20 mmHg, or in diastolic blood pressure of at least 10 mmHg, within 3 minutes after standing; * 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. MAIN PATIENT EXCLUSION CRITERIA: * Taking ephedrine or midodrine; Patients taking ephedrine or midodrine may enroll after a minimum 7 day washout period; * Taking anti-hypertensive medication; * Have a history of more than moderate alcohol consumption; * Women who are pregnant or lactating; * Have a history of closed angle glaucoma; * Have pre-existing sustained severe hypertension (BP \> 180/110 mmHg in the sitting position); * Have atrial fibrillation or, in the investigator's opinion, have any other significant cardiac arrhythmia; * In the investigator's opinion, have any other significant systemic, hepatic, cardiac or renal illness; * Have diabetes mellitus or insipidus; * Have a known or suspected malignancy; * Have known gastrointestinal illness or other gastrointestinal disorder that may, in the investigator's opinion, affect the absorption of study drug; * In the investigator's opinion, hav…