Differential effects of maintenance long-acting β-agonist and inhaled corticosteroid on asthma control and asthma exacerbations

Background: Combination therapy with long-acting beta-agonists (LABAs)/inhaled corticosteroids (ICSs) has become established as effective maintenance treatment for asthma. Objective: To compare and contrast the efficacy and safety of LABAs/ICSs against different maintenance ICS strategies in adults with asthma. Methods: Cochrane systematic reviews of randomized controlled trials (to April 2004) were identified that compared the addition of LABA to ICS against 3 inhaled corticosteroid strategies: (1) a similar dose (n = 4312 subjects), (2) a higher dose (n = 4951), and (3) a similar dose in steroid-naive subjects (n = 968). The outcomes evaluated were asthma exacerbations, asthma control, and adverse effects. Pediatric studies were excluded. Results: The addition of LABA to ICSs significantly reduced the risk of exacerbations compared with a similar ICS dose, number needed to treat = 18. The effects of LABA/ICSs on exacerbations compared with the other maintenance inhaled corticosteroid strategies were not statistically significant. LABA added to inhaled corticosteroids led to significant improvements in asthma control compared with all 3 maintenance ICS strategies. There was an increased risk of tremor with LABA/ICSs that reached significance for initial therapy, number needed to harm = 21, and compared with higher ICS doses, number needed to harm = 74. Conclusion: Maintenance asthma therapy with LABA/ICSs has differential effects on asthma control and asthma exacerbations. Clinical implications: The greatest benefit and least harm of LABAs comes when they are added to a similar ICS dose in adults with symptomatic asthma.