Asthma therapy may help ease symptoms of MuSK-positive MG

3 patients report reduction in disease severity after taking oral salbutamol

Marisa Wexler, MS avatar

by Marisa Wexler, MS |

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Treatment with an oral version of salbutamol, the active ingredient of medications used for asthma and other respiratory conditions, may help ease symptoms in some people with MuSK-positive myasthenia gravis (MG), a small study reports.

The study was published as a letter to the editor, titled “Oral salbutamol for symptomatic treatment in MuSK antibody-positive myasthenia gravis: a single-centre experience,” in the journal Acta Neurologica Belgica.

MG is caused by antibodies that interfere with the communication between nerve and muscle cells, leading to symptoms such as muscle weakness and fatigue. In about 6% of patients, disease-driving antibodies specifically target a protein called muscle-specific kinase, or MuSK.

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Management of MuSK-positive MG is complex. Mestinon (pyridostigmine), which is a common first-line MG therapy used to improve muscle strength, is often ineffective in this subset of patients.

Also known as albuterol, salbutamol works to activate muscle proteins called beta 2-adrenergic receptors. Inhaled versions of salbutamol are commonly used to help manage lung conditions like asthma, since they can help lung muscles relax, helping to widen and open up the airways.

Data from lab models have suggested salbutamol may help improve muscle strength in MuSK-positive MG, but there’s minimal data on its use in people with the disease.

In this study, researchers at Charing Cross Hospital in the U.K. reported on the outcomes of five MuSK-positive patients who were treated with oral salbutamol on an off-label basis.

One of the five patients stopped taking salbutamol soon after starting treatment due to heart palpitations that arose as a side effect. Another patient experienced weight loss as a side effect and required a dose reduction. No notable safety issues were documented in the other three patients.

“Tolerability due to palpitations and tachycardia [rapid heart beat] [may be] an issue during dose up-titration and requires close monitoring,” the researchers wrote.

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3 of the four patients report improvement in symptoms

Among the four patients who took salbutamol for at least six months — starting at a dose of 2 mg once daily and increased up to a maximal dose of 4 mg twice daily — one patient experienced no change in symptom severity and ended up quitting the medication. However, the other three all reported a notable reduction in disease severity and improvements in the scores of the MG Activities of Daily Living, a standardized scale that measures patients’ ability to function day to day.

These three patients especially reported improvements in ocular (eye-related) symptoms, as well as bulbar (neck- and face-related) symptoms, which can be difficult to manage in patients with
MuSK MG, the researchers noted.

All in all, these findings suggest oral salbutamol could help manage disease symptoms for at least some people with MuSK-positive MG. The researchers stressed, however, that the report covers a handful of patients, so more large-scale studies will be needed to evaluate the efficacy of this therapy in MuSK-positive MG.