Water and Sudafed in Autonomic Failure

Inclusion Criteria: * Age 18-80 years, with * Neurogenic orthostatic hypotension, ≥30 mmHg drop in SBP within 5 minutes of standing, * Associated with impaired autonomic reflexes, as determined by absence of blood pressure overshoot during phase IV of the valsalva maneuver, * Absence of other identifiable causes of autonomic neuropathy, and * Able and willing to provide informed consent Exclusion Criteria * Pregnancy * Current smoking habit * Systemic illnesses known to produce autonomic neuropathy, including but not limited to diabetes mellitus, amyloidosis, monoclonal gammopathy of unknown significance, and autoimmune neuropathies. * Known intolerance to pseudoephedrine * Pre-existing sustained severe hypertension (BP \> 180/110 mmHg in the sitting position) * Clinically unstable coronary artery disease or major cardiovascular or neurological event in the past 6 months. * Any other significant systemic, hepatic, cardiac or renal illness * Use of MAO-I (i.e. selegiline; rasagiline - Azilect, linezolid and others) within 14 days * Known closed-angle glaucoma * Clinically meaningful arrhythmias * Other factors which in the investigator's opinion would prevent the participant from completing the protocol, including poor compliance during previous studies or an unpredictable schedule