The purpose of this study is to learn more about the effects of midodrine and droxidopa, two medications used for the treatment of orthostatic hypotension (low blood pressure on standing), on the veins of the abdomen of patients with autonomic failure. The study will be conducted at Vanderbilt University Medical Center, and consists of 2 parts: a screening and 2 testing days. The total length of the study will be about 5 days. About 34 participants will be screened for the study.
Male and female subjects, age 40-80 years with possible or probable Multiple System Atrophy, Pure Autonomic Failure, or Parkinson disease, as defined by Consensus Criteria.
Neurogenic orthostatic hypotension defined as a ≥30-mmHg decrease in systolic blood pressure within 3 minutes of standing associated with impaired autonomic reflexes determined by autonomic testing in the absence of other identifiable causes.
Subjects able and willing to provide informed consent.
Supine hypertension, defined as systolic blood pressure of ≥ 160 mmHg measured on two separate occasions.
Pregnancy.
Systemic illnesses known to produce autonomic neuropathy, including but not limited to diabetes mellitus, amyloidosis, monoclonal gammopathies, and autoimmune neuropathies.
History of known aortic aneurisms, thoracic, abdominal or pelvic surgery in the past 6 months.