Medow, Marvin S, Sood, Shilpa, Messer, Zachary et al. · Journal of applied physiology (Bethesda, Md. : 1985) · 2014 · DOI
Many ME/CFS patients experience dizziness and cognitive problems when standing up because blood flow to the brain decreases. This study tested whether a medication called phenylephrine, which raises blood pressure, could help restore brain blood flow and improve thinking tasks during standing. The researchers found that phenylephrine reduced the brain blood flow drop and helped ME/CFS patients perform better on memory tests while upright.
This research identifies a specific physiological mechanism—hyperventilation-induced reduced brain blood flow—underlying the cognitive dysfunction experienced by many ME/CFS patients with orthostatic intolerance. Understanding that blood pressure support can partially reverse this problem provides a mechanistic rationale for investigating pharmacological interventions and supports the biological basis of orthostatic cognitive symptoms in ME/CFS.
This small, acute study does not prove that phenylephrine is a safe or effective long-term treatment for ME/CFS, nor does it establish that hyperventilation is the sole cause of cognitive symptoms in all ME/CFS patients. The findings also do not demonstrate whether other treatments targeting blood flow or breathing patterns would produce similar benefits. Acute improvements in laboratory conditions may not translate to sustained real-world functional recovery.
About the PEM badge: “PEM required” means post-exertional malaise was an explicit required diagnostic criterion for participant inclusion in this study — not that PEM was studied, observed, or discussed. Studies using criteria that do not require PEM (e.g. Fukuda, Oxford) are tagged “PEM not required”. How the atlas works →
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