Abstract:
Background: Myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) is a multisystemic disease characterized by exertional intolerance and fatigue which is often accompanied by muscle weakness and fatiguability. A study showed efficacy of the acetylcholinesterase inhibitor pyridostigmine on cardiac output in ME/CFS patients. Pyridostigmine is currently used off-label in ME/CFS and postural orthostatic tachycardia syndrome.
Methods: We evaluated the effect of pyridostigmine on hand grip strength in 20 patients with post-infectious ME/CFS. Hand grip strength testing was performed ten times using an electric dynamometer and was repeated after 1 h. In a second test, 30 mg of pyridostigmine was given immediately after the first measurement. Orthostatic function was assessed using a passive standing test. Neurological examination and autoantibody testing were performed to rule out a diagnosis of myasthenia gravis.
Results: All patients had reduced maximum hand grip strength with a median of 16.45 kg (IQR: 11.45 kg–22.8 kg). Hand grip strength was diminished by a median of 4.65 kg after 1 h. In contrast, 1 h after pyridostigmine administration, patients showed an improvement in maximum hand grip strength with a median increase of 2.6 kg. The maximum hand grip strength after exertion was about 1.5-fold higher with then without pyridostigmine (p = 0.01). The increase in heart rate from lying to standing was median 17 beats per minute without pyridostigmine (IQR: 13 beats per minute – 23 beats per minute) and 13 beats per minute (IQR: 9 beats per minute – 20 beats per minute) (p = 0.017) with pyridostigmine. None of the patients tested positive for myasthenia gravis specific autoantibodies.
Conclusion: Pyridostigmine exerts an immediate effect on muscle strength and orthostatic function. This may be attributed to increased acetylcholine availability at neuromuscular junctions, and its augmentation of parasympathetic tone.
Source: Schlömer Ella , Stein Elisa , Kedor Claudia , Rust Rebekka , Brock Anna , Wittke Kirsten , Scheibenbogen Carmen , Kim Laura. Pyridostigmine improves hand grip strength in patients with myalgic encephalomyelitis/chronic fatigue syndrome. Frontiers in Neuroscience, Volume 19 – 2025. DOI: 10.3389/fnins.2025.1637838 ISSN: 1662-453X https://www.frontiersin.org/journals/neuroscience/articles/10.3389/fnins.2025.1637838/full (Full text)