Patients with Parkinson's Disease or Multiple System Atrophy (MSA), and symptoms of orthostatic hypotension, are eligible for the study. Each patient will have three weeks of conservative therapy, three weeks of therapy with fludrocortisone, and three weeks of therapy with domperidone. Autonomic testing, a symptom questionnaire, bedside blood pressure testing, and Unified Parkinson Disease Rating Scale (UPDRS) will be performed after each intervention.

Enrolled patients, ages 40-95, must have Parkinson's or MSA, diagnosed by a neurologist, and symptoms of orthostatic hypotension. Each patient will fill out two validated questionnaires to determine if they are candidates for the study. Baseline patient details, such as their medications and UPDRS, will be recorded. Medications must be held stable during the period of the study.

Each patient will then have three weeks of conservative therapy, three weeks of therapy with fludrocortisone, and three weeks of therapy with domperidone. Autonomic testing, a symptom questionnaire, bedside blood pressure testing, and UPDRS will be performed after each intervention.

Inclusion Criteria:

• Patients residing in Queensland Australia
• Age 40-95
• Parkinson's Disease or MSA diagnosed by a neurologist
• Symptoms of orthostatic hypotension, as defined by 2 validated questionnaires

Exclusion Criteria:

• Patients with acute cardiomyopathy or cardiac condition
• Patients unable to give consent
• Patients not stable on their Parkinsonian medications
• Patients with another cause for autonomic neuropathy