Adults 18 to 80, any sex, with Myalgic Encephalomyelitis/Chronic Fatigue Syndrome or Chronic Fatigue Syndrome. Patients with the condition only — healthy volunteers not accepted.
Results — posted to ClinicalTrials.gov
Per-arm endpoint measurements with 95% confidence intervals where reported. Source: trial results section.
Change in Peak Oxygen Uptake (Peak VO2) Between the First and Second iCPETPrimary· First iCPET up to 30 minutes, 50 minutes rest, second iCPET up to 30 minutes.
Define the response of oxygen uptake to pyridostigmine expressed both as mL/min and mL/min/kg. The difference in peak oxygen uptake from first iCPET to second iCPET. Research has shown that ME/CFS patients have inability to reproduce results on two consecutive cardiopulmonary exercise tests(CPET). Traditionally this is demonstrated with a two-day CPET protocol, but in this study we investigate the acute effects of pyridostigmine administration on the early stages of post exertional malaise(PEM).
Group
Value
95% CI
Study Drug - Pyridostigmine
13.3
± 13.4
Placebo (Female)
-40.3
± 21.3
Placebo (Male)
111.8
± 65.0
Peak-Rest Oxygen Uptake (VO2)Secondary· First iCPET up to 30 minutes, 50 minutes rest, second iCPET up to 30 minutes.
Peak versus rest changes in oxygen uptake between first and second CPETs expressed as mL/min.
Group
Value
95% CI
Study Drug - Pyridostigmine
25.9
± 15.3
Placebo (Female)
-60.8
± 25.6
Placebo (Male)
121.8
± 80.0
Peak Cardiac Output (Qc)Secondary· First iCPET up to 30 minutes, 50 minutes rest, second iCPET up to 30 minutes.
Arterial and mixed-venous blood gases and pH are measured at peak exercise and Qc is calculated using the direct Fick principle Qc=VO2/(Ca-Cv). Change in peak Qc between first and second iCPETs is measured in L/min.
Group
Value
95% CI
Study Drug - Pyridostigmine
0.2
± 0.2
Placebo (Female)
-0.2
± 0.3
Placebo (Male)
1.1
± 0.4
Peak-Rest Cardiac Output (Qc)Secondary· First iCPET up to 30 min, 50 minutes rest, second iCPET up to 30 minutes
Peak versus rest change in cardiac output expressed in L/min between first and second iCPETs. Cardiac output is determined using the direct Fick principle.
Group
Value
95% CI
Study Drug - Pyridostigmine
-0.2
± 0.6
Placebo (Female)
-1.9
± 0.6
Placebo (Male)
0.9
± 0.8
Peak Right Atrial Pressure (RAP)Secondary· First iCPEt up to 30 minutes, 50 minutes rest, second iCPET up to 30 minutes.
Difference in peak RAP between first and second iCPETs measured in mmHg.
Group
Value
95% CI
Study Drug - Pyridostigmine
1.2
± 0.3
Placebo (Female)
0.1
± 0.5
Placebo (Male)
1.7
± 0.7
Peak-Rest Right Atrial Pressure (RAP)Secondary· First iCPEt up to 30 minutes, 50 minutes rest, second iCPET up to 30 minutes.
Peak versus rest changes in RAP between first and second iCPETs measured in mmHg
Group
Value
95% CI
Study Drug - Pyridostigmine
1.0
± 0.5
Placebo (Female)
-0.6
± 0.5
Placebo (Male)
0.0
± 1.0
Peak Pulmonary Arterial Wedge Pressure (PAWP)Secondary· First iCPET up to 30 minutes, 50 minutes rest, second iCPET up to 30 minutes.
Difference in peak PAWP between first and second iCPETs measured in mmHg
Group
Value
95% CI
Study Drug - Pyridostigmine
1.0
± 0.8
Placebo (Female)
1.0
± 0.5
Placebo (Male)
1.5
± 1.4
Peak Stroke Volume (SV)Secondary· First iCPEt up to 30 minutes, 50 minutes rest, second iCPET up to 30 minutes.
Difference in peak SV between first and second iCPETs measured in mL
Group
Value
95% CI
Study Drug - Pyridostigmine
3.0
± 1.4
Placebo (Female)
-1.1
± 1.9
Placebo (Male)
-12.7
± 12.9
Peak (Ca-vO2)/[Hgb]Secondary· First iCPET up to 30 minutes, 50 minutes rest, second iCPET up to 30 minutes.
Difference in peak arterial-venous oxygen content difference normalized to hemoglobin (Ca-vO2)/\[Hgb\] between first and second iCPETs
Group
Value
95% CI
Study Drug - Pyridostigmine
0.0
± 0.0
Placebo (Female)
0.0
± 0.0
Placebo (Male)
0.0
± 0.1
Ventilatory Efficiency (VE/VCO2)Secondary· First iCPET up to 30 minutes, 50 minutes rest, second iCPET up to 30 minutes.
Difference in ventilatory efficiency between first and second iCPETs
Group
Value
95% CI
Study Drug - Pyridostigmine
-0.2
± 0.8
Placebo (Female)
1.0
± 0.6
Placebo (Male)
1.7
± 0.6
Borg Fatigue ScaleSecondary· First iCPET up to 30 minutes, 50 minutes rest, second iCPET up to 30 minutes.
Difference in perception of fatigue at peak exercise between first and second iCPETs. Used Borg Scale 0 (minimal) to 10 (maximal).
Group
Value
95% CI
Study Drug - Pyridostigmine
0.1
± 0.2
Placebo (Female)
-0.6
± 0.3
Placebo (Male)
0.4
± 0.4
Borg Dyspnea ScaleSecondary· First iCPET up to 30 minutes, 50 minutes rest, second iCPET up to 30 minutes.
Difference in perceived dyspnea at peak exercise between first and second iCPETs. Used Borg Scale 0 (minimal) to 10 (maximal).
Group
Value
95% CI
Study Drug - Pyridostigmine
-0.1
± 0.2
Placebo (Female)
-1.0
± 0.5
Placebo (Male)
0.3
± 0.5
Adverse events — posted to ClinicalTrials.gov
Time frame: Adverse events were monitored during the two iCPETs and for the duration of the 50 minutes rest between the two iCPETs. After the second iCPET, the subjects were monitored for an hour in the recovery room. The subjects received a follow up phone call or email up to one week following the day of the procedure to assess if they experienced any adverse events from the study. This was documented for every patient..
Reporting threshold: 0%.
Adverse-event reports describe events observed during the trial — not all are caused by the drug.
Myalgic encephalomyelitis/Chronic fatigue syndrome (ME/CFS), otherwise known as Chronic fatigue syndrome (CFS) or myalgic encephalomyelitis (ME), is an under-recognized disorder whose cause is not yet understood. Suggested theories behind the pathophysiology of this condition include autoimmune causes, an inciting viral illness, and a dysfunctional autonomic nervous system caused by a small fiber polyneuropathy. Symptoms include fatigue, cognitive impairments, gastrointestinal changes, exertional dyspnea, and post-exertional malaise. The latter two symptoms are caused in part by abnormal cardiopulmonary hemodynamics during exercise thought to be due to a small fiber polyneuropathy. This manifests as low biventricular filling pressures throughout exercise seen in patients undergoing an invasive cardiopulmonary exercise test (iCPET) along with small nerve fiber atrophy seen on skin biopsy.
After diagnosis, patients are often treated with pyridostigmine (off-label use of this medication) to enhance cholinergic stimulation of norepinephrine release at the post-ganglionic synapse. This is thought to improve venoconstriction at the site of exercising muscles, leading to improved return of blood to the heart and increasing filling of the heart to more appropriate levels during peak exercise. Retrospective studies have shown that noninvasive measurements of exercise capacity, such as oxygen uptake, end-tidal carbon dioxide, and ventilatory efficiency, improve after treatment with pyridostigmine. To date, there are no studies that assess invasive hemodynamics after pyridostigmine administration.
It is estimated that four million people suffer from ME/CFS worldwide, a number that is thought to be a gross underestimate of disease prevalence. However, despite its potential for debilitating symptoms, loss of productivity, and worldwide burden, the pathophysiology behind ME/CFS remains unknown and its treatment unclear. By evaluating the exercise response to cholinergic stimulation, this study will shed further light on the link between the autonomic nervous system and cardiopulmonary hemodynamics, potentially leading to new therapeutic targets.
Publications & conference data
1 peer-reviewed publication reference this trial (live from Europe PMC):
Publications: Europe PMC API search by NCT ID, retrieved 10 June 2026
Drug + disease cross-links: matched in real time against Drug Landscape's normalised drug + company + condition tables
Sponsor: as reported to ClinicalTrials.gov by Brigham and Women's Hospital
Last refreshed: 8 November 2022
Drug Landscape aggregates and links these public records for informational use only. Always verify against the primary source before clinical or regulatory decisions. Canonical URL: https://druglandscape.com/trial/NCT03674541.