Medow, Marvin S, Stewart, Julian M · American journal of physiology. Regulatory, integrative and comparative physiology · 2024 · DOI
People with ME/CFS often experience brain fog and cognitive problems when standing up, possibly because their brain isn't getting enough blood flow and oxygen. This study tested whether a medication called phenylephrine could help restore brain blood flow and improve thinking during standing. The researchers found that phenylephrine was the only treatment tested that significantly improved both cognitive performance and the brain's ability to maintain stable blood flow during head-up tilting.
Orthostatic cognitive dysfunction is a distressing symptom in ME/CFS, and this study identifies a potential pharmacological mechanism to restore both brain blood flow and cognitive performance during standing. Demonstrating that phenylephrine specifically improves cerebral autoregulation offers a mechanistic rationale for a targeted therapeutic approach that might benefit many patients with orthostatic intolerance.
This small study does not prove phenylephrine is a cure or long-term solution for ME/CFS—it shows acute effects during a single tilt test. The findings cannot be generalized to all ME/CFS patients, as all subjects had POTS and the sample was young (mean age ~22 years). Chronic safety and efficacy, optimal dosing, and effects in other patient subgroups remain unknown.
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 →
The first block is for the primary paper and is the citation you should use in research work. The atlas-snapshot line only applies if you are specifically referring to this atlas’s reading of the paper on the date shown.
Primary citation
Medow, Marvin S & Stewart, Julian M (2024). Phenylephrine alters phase synchronization between cerebral blood velocity and blood pressure in ME/CFS with orthostatic intolerance.. American journal of physiology. Regulatory, integrative and comparative physiology. https://doi.org/10.1152/ajpregu.00071.2024
BibTeX
@article{mecfsatlas-medow-2024-phenylephrine-alters,
author = {Medow, Marvin S and Stewart, Julian M},
title = {Phenylephrine alters phase synchronization between cerebral blood velocity and blood pressure in ME/CFS with orthostatic intolerance.},
journal = {American journal of physiology. Regulatory, integrative and comparative physiology},
year = {2024},
doi = {10.1152/ajpregu.00071.2024},
note = {PubMed: 38682242},
url = {https://www.mecfsatlas.com/evidence/medow-2024-phenylephrine-alters},
}Atlas snapshot reference
ME/CFS Atlas. Generator v1 / Scanner v1.4 / policy v0.1. Accessed 2026-05-26. https://www.mecfsatlas.com/evidence/medow-2024-phenylephrine-alters
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