Two large surveillance studies in adults with asthma have found an increased risk of asthma-related mortality in those who took regular salmeterol as monotherapy in comparison to placebo or regular salbutamol. No similar sized surveillance studies have been carried out in children with asthma, and we remain uncertain about the comparative safety of regular combination therapy with either formoterol or salmeterol in children with asthma.
We have used the paediatric trial results from Cochrane systematic reviews to assess the safety of regular formoterol or salmeterol, either as monotherapy or as combination therapy, in children with asthma.
We included Cochrane reviews relating to the safety of regular formoterol and salmeterol from a search of the Cochrane Database of Systematic Reviews conducted in May 2012, and ran updated searches for each of the reviews. These were independently assessed. All the reviews were assessed for quality using the AMSTAR tool. We extracted the data relating to children from each review and from new trials found in the updated searches (including risks of bias, study characteristics, serious adverse event outcomes, and control arm event rates).
The safety of regular formoterol and salmeterol were assessed directly from the paediatric trials in the Cochrane reviews of monotherapy and combination therapy with each product. Then monotherapy was indirectly compared to combination therapy by looking at the differences between the pooled trial results for monotherapy and the pooled results for combination therapy. The comparative safety of formoterol and salmeterol was assessed using direct evidence from trials that randomised children to each treatment; this was combined with the result of an indirect comparison of the combination therapy trials, which represents the difference between the pooled results of each product when randomised against inhaled corticosteroids alone.
We identified six high quality, up to date Cochrane reviews. Four of these related to the safety of regular formoterol or salmeterol (as monotherapy or combination therapy) and these included 19 studies in children. We added data from two recent studies on salmeterol combination therapy in 689 children which were published after the relevant Cochrane review had been completed, making a total of 21 trials on 7474 children (from four to 17 years of age). The two remaining reviews compared the safety of formoterol with salmeterol from trials randomising participants to one or other treatment, but the reviews only included a single trial in children in which there were 156 participants.
Only one child died across all the trials, so impact on mortality could not be assessed.
We found a statistically significant increase in the odds of suffering a non-fatal serious adverse event of any cause in children on formoterol monotherapy (Peto odds ratio (OR) 2.48; 95% confidence interval (CI) 1.27 to 4.83, I2 = 0%, 5 trials, N = 1335, high quality) and smaller increases in odds which were not statistically significant for salmeterol monotherapy (Peto OR 1.30; 95% CI 0.82 to 2.05, I2 = 17%, 5 trials, N = 1333, moderate quality), formoterol combination therapy (Peto OR 1.60; 95% CI 0.80 to 3.28, I2 = 32%, 7 trials, N = 2788, moderate quality) and salmeterol combination therapy (Peto OR 1.20; 95% CI 0.37 to 2.91, I2 = 0%, 5 trials, N = 1862, moderate quality).
We compared the pooled results of the monotherapy and combination therapy trials. There was no significant difference between the pooled ORs of children with a serious adverse event (SAE) from long-acting beta2-agonist beta agonist (LABA) monotherapy (Peto OR 1.60; 95% CI 1.10 to 2.33, 10 trials, N = 2668) and combination trials (Peto OR 1.50; 95% CI 0.82 to 2.75, 12 trials, N = 4,650). However, there were fewer children with an SAE in the regular inhaled corticosteroid (ICS) control group (0.7%) than in the placebo control group (3.6%). As a result, there was an absolute increase of an additional 21 children (95% CI 4 to 45) suffering such an SAE of any cause for every 1000 children treated over six months with either regular formoterol or salmeterol monotherapy, whilst for combination therapy the increased risk was an additional three children (95% CI 1 fewer to 12 more) per 1000 over three months.
We only found a single trial in 156 children comparing the safety of regular salmeterol to regular formoterol monotherapy, and even with the additional evidence from indirect comparisons between the combination formoterol and salmeterol trials, the CI around the effect on SAEs is too wide to tell whether there is a difference in the comparative safety of formoterol and salmeterol (OR 1.26; 95% CI 0.37 to 4.32).
We do not know if regular combination therapy with formoterol or salmeterol in children alters the risk of dying from asthma.
Regular combination therapy is likely to be less risky than monotherapy in children with asthma, but we cannot say that combination therapy is risk free. There are probably an additional three children per 1000 who suffer a non-fatal serious adverse event on combination therapy in comparison to ICS over three months. This is currently our best estimate of the risk of using LABA combination therapy in children and has to be balanced against the symptomatic benefit obtained for each child. We await the results of large on-going surveillance studies to further clarify the risks of combination therapy in children and adolescents with asthma.
The relative safety of formoterol in comparison to salmeterol remains unclear, even when all currently available direct and indirect trial evidence is combined.