Abstract: Three trials involving 5905 participants were included. In patients with mild asthma who do not need maintenance treatment, no clinically important advantages of budesonide/formoterol as reliever were found in comparison to formoterol as reliever. Two studies enrolled patients with more severe asthma who were not controlled on high doses of inhaled corticosteroids (around 700 mcg/day in adults), and had suffered a clinically important asthma exacerbation in the past year. Hospitalisations related to asthma in the two studies comparing budesonide/formoterol for maintenance and relief with the same dose of budesonide/formoterol for maintenance with terbutaline for relief yielded an odds ratio of 0.68 (95% CI 0.40 to 1.16), which was not a statistically significant reduction. In adults there was a reduction in exacerbations requiring oral corticosteroids compared to terbutaline, odds ratio 0.54 (95% CI 0.44 to 0.65), which translates into a number needed to treat over 12 months of 15 (95% CI 13 to 21). The study in children found less serious adverse events with budesonide/formoterol used for maintenance and relief. There was no significant difference in annual growth in children using budesonide/formoterol reliever in comparison to terbutaline. In mild asthma it is not yet known whether patients who use a budesonide/formoterol inhaler for relief of asthma symptoms derive any clinically important benefits. In more severe asthma, two studies enrolled patients who were not controlled on inhaled corticosteroids, and had suffered an exacerbation in the previous year, and then had their maintenance inhaled corticosteroids reduced in both arms of the study. Under these conditions the studies demonstrated a reduction in the risk of exacerbations that require oral corticosteroids with budesonide/formoterol for maintenance and relief in comparison with budesonide/formoterol for maintenance and terbutaline or formoterol for relief. The incidence of serious adverse events in children was also less using budesonide/formoterol for maintenance and relief in one study, which similarly enrolled children who were not controlled on inhaled corticosteroids, and who had their maintenance inhaled corticosteroids reduced at the start of the study. This study also compared an explorative maintenance dose of budesonide/formoterol that is not approved for treatment.

Plain-language summary: Three trials involving 5905 participants were included. We found very little evidence in relation to the use of formoterol and budesonide for relief of symptoms in people with mild asthma, but in people with more severe asthma who had suffered exacerbations in spite of regular treatment with inhaled corticosteroids, we found that reliever formoterol and budesonide compared favourably with terbutaline in reducing asthma exacerbations that required a course of oral corticosteroids. However only a small proportion of the 'severe asthma exacerbations' as defined in the trials led to hospital admissions, and no significant overall benefit has yet been shown for this outcome. In children with asthma that was not controlled with regular inhaled corticosteroids, there were fewer serious adverse events when formoterol and budesonide were used to relieve symptoms as well as for maintenance treatment.