Treatment of Orthostatic Intolerance in Patients With Parkinson's Disease Using Midodrine

Inclusion Criteria: 1. Patients with a diagnosis of idiopathic Parkinson's Disease 2. Those patients with measured orthostatic hypotension will be included in the positive control group 3. Those patients without measurable orthostatic hypotension who have symptoms of lightheadedness on standing will be included in the study group Exclusion Criteria: 1. Diagnosis of degenerative parkinsonian syndromes other than idiopathic Parkinson's Disease 2. Inability to stand independently and remain standing for 5 minutes 3. Cognitive impairment that is significant enough to affect the ability of the patient to provide informed consent or to reliably report orthostatic symptoms 4. Patients with a pacemaker will also be excluded because the study is measuring heart rate responses which could potentially be altered by a pacemaker 5. Because this study will be using a drug that can affect blood pressure, those patients with a standing BP of \> 139/90 and heart rate \<60 will be excluded 6. Because this study will be using a drug that can affect supine hypertension, those patients with a supine BP of \>139/90 and heart rate \<60 will be excluded 7. Current treatment with other drugs for orthostatic hypotension such as fludrocortisone 8. Patients on phenylephrine, pseudoephedrine, ephedrine, phenylpropanolamine, dihydroergotamine 9. Patients with acute or chronic renal failure (GFR \<60) 10. Patients with a history of pheochromocytoma, urinary retention, severe cardiac disease, history of congestive heart failure, diabetes, narrow-angle glaucoma, arrhythmias, bradycardia, severe hyperthyroidism, severe difficult urination (due to urinary retention or enlarged prostate) 11. Pregnant or breast-feeding women. 12. Women of childbearing potential with no effective contraceptive method of birth control and/or who are unwilling or unable to be tested for pregnancy. 13. Women of childbearing potential must have a confirmed negative pregnancy test at screening and randomization visits. They must use an effective contraceptive method throughout the study, and agree to repeat urine pregnancy test at designated visits. The applied methods of contraception have to meet the criteria for a highly effective method of birth control (condoms, FDA approved oral contraceptives, patches, injections, rings, IUD). 14. Patients with known drug allergy or hypersensitive to midodrine.