Common asthma drug improves strength in children with muscle disease

A common asthma medication improves motor skills and muscle strength in children with congenital myopathies, a group of incurable muscle diseases. In a study, children receiving the drug were able to both walk and stand up more quickly.

Simply the fact that they had more energy, that they could manage a full day at school followed by activities and homework without becoming completely exhausted and bursting into tears, is very important for these children."

Eva Michael, doctoral student in pediatric neurology, University of Gothenburg and specialist physician, Queen Silvia Children's Hospital

Congenital myopathies are a group of rare, inherited muscle diseases that often cause muscle weakness in childhood. This weakness can affect, among other things, the ability to walk, stand up, and use one's arms and hands, and in some cases, it can also affect the respiratory muscles.

Currently, there is no cure or pharmacological treatment for these diseases. Care therefore focuses primarily on alleviating symptoms and preventing complications.

The study investigated whether the substance salbutamol could improve muscle function in children and young people with congenital myopathy. Salbutamol has long been used for asthma, but when administered orally, it also affects skeletal muscle and can, for instance, stimulate the synthesis of muscle protein.

Improved motor function and grip strength

The study included 18 individuals, aged 6–16, with genetically confirmed congenital myopathy. They were randomized to receive either salbutamol in addition to their usual treatment or their usual treatment alone for 24 weeks. They then switched treatments, allowing for a comparison against themselves.

Following the period of salbutamol treatment, the participants' motor function was superior to that observed with standard treatment alone. The difference averaged 3.61 points on a standardized motor function rating scale (MFM-32), a change generally regarded as a clear improvement in the context of neuromuscular diseases.

Muscle strength also improved. Grip strength in the dominant hand increased by the equivalent of approximately 1.5 kilograms during salbutamol treatment compared to standard treatment alone. Increased strength was also observed in other muscle groups examined, though these results were not statistically significant.

In addition, lung function improved. On average, forced vital capacity – a measure of the volume of air exhaled after a maximal inhalation – was approximately 0.2 liters higher during salbutamol treatment than during standard treatment.

Future treatment options

Improvements across several functional tests were observed in the eleven participants who were able to walk. In a six-minute walk test, the children covered an average distance of 435 meters before treatment, whereas with salbutamol, the distance increased to 473 meters. Children of a similar age typically walk about 600 meters in six minutes.

The researchers also assessed how quickly the ambulatory children in the study could rise from the floor to a standing position. On average, it took them 8.29 seconds to stand up, but with salbutamol, that time was reduced to 6.39 seconds. A child with normal strength rises from the floor to a standing position in 1–2 seconds.

The treatment was well tolerated, and no serious side effects were reported.

"The results suggest that oral salbutamol could potentially become a symptom-relieving treatment option for children and adolescents with congenital myopathies in the future, pending the development of other drugs. However, these findings need to be confirmed in larger international studies involving longer treatment periods and follow-up," says Eva Michael.

The study has been published in the Lancet journal eClinicalMedicine.