The objective of this study is to find a more objective and accurate way to assess the efficacy of the treatment for neurogenic orthostatic hypotension. For this purpose, the investigators will use an activity monitor to determine the amount of time patients spend in the upright position (standing and walking; upright time) during 1 week of placebo (a pill with no active ingredients) and 1 week of their regular medication for orthostatic hypotension (midodrine or atomoxetine at their usual doses). Total upright time (i.e. tolerance to standing and walking) will be compared between placebo and active treatment to test the hypothesis that it can be used to assess the efficacy of the treatment for orthostatic hypotension and whether this outcome is superior to the assessment of symptoms using validated questionnaires.
Male and female subjects, age 40-80 years.
Possible or probable Multiple Systems Atrophy, Pure Autonomic Failure, or Parkinson's disease with neurogenic orthostatic hypotension.
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.
Patients on treatment for neurogenic orthostatic hypotension with either midodrine or atomoxetine, who have experienced some improvement in their orthostatic symptoms, but still remain symptomatic (Orthostatic hypotension symptom assessment [OHSA] score of 1 to 5 while on medication).
Bedridden, physically disabled, or unable to walk.
Patients with Orthostatic hypotension symptom assessment (OHSA) score ≥ 6, or orthostatic systolic blood pressure drop ≥ 30 mmHg on their regular treatment.
Patients taking more than one medication for the treatment of neurogenic orthostatic hypotension (concomitant use of pyridostigmine or fludrocortisone are accepted).
Pregnancy