Background

Asthma attacks are common in adults and children. People having an attack may need to be treated in a hospital emergency department (A&E). Even with the best treatment, some people need to be admitted to hospital or even into the intensive care unit. Some guidelines suggest that giving magnesium sulfate, either by injection or inhaled straight into the lungs, may be beneficial. In this review we focused on inhaled (or ‘nebulised’) magnesium sulfate. We were particularly interested in finding out the effects of magnesium sulfate on lung function (breathing tests), severity scores and hospital admissions. We also wanted to know if it was safe.

Study characteristics

We looked for studies in adults and children attending the emergency department with an asthma attack. We included studies which compared giving inhaled magnesium sulfate, plus standard treatment, with standard treatment alone. We also included studies that compared inhaled magnesium sulfate directly with standard treatment. We included studies carried out anywhere in the world, at any time and written in any language.

Key results

We found 25 studies in total, which included nearly 3000 people with asthma attacks. This latest update of the review includes several large trials that were carried out to a very high standard. We found that adding inhaled magnesium sulfate to standard treatments may result in small benefits in terms of lung function, hospital admission and severity scores, but we are uncertain about these findings. This is because many of the studies were carried out in different ways and measured different outcomes at different times so it was quite hard to combine the results from individual studies. Inhaled magnesium sulfate did not seem to cause any serious side effects in the studies we found. We did not find evidence that using inhaled magnesium sulfate instead of standard treatment is beneficial.

Quality of the evidence

We used a scoring system to rate how confident we are in the findings presented. Our scores ranged from high confidence to very low confidence, but most outcomes we rated as low or very low. This is because we had concerns about the way in which some of the studies were carried out: for example, it was perhaps not clear how people were chosen for the two different treatment groups in the study; or it was unclear whether the patients or people running the trial knew who was getting which treatment. Another factor that reduced our confidence was uncertainty about the combined results: for example in some cases we could not tell whether magnesium sulfate was better, worse or the same.

Key message

There is some limited evidence that inhaled magnesium sulfate may have a small benefit for people having asthma attacks when added to standard treatment. However, the most recent, high-quality trials did not generally show important benefits. Also, we cannot be sure if some groups may benefit more than other, for example those having more severe attacks.