Dose-response relationship of ICS/fast-onset LABA as reliever therapy in asthma

BACKGROUND AND OBJECTIVE: The dose-response relationship of inhaled corticosteroid (ICS)/fast-onset long acting beta agonist (LABA) reliever therapy has not been formally addressed. The objective of this retrospective analysis is to ascertain from the available evidence whether ICS/fast-onset LABA administered as reliever therapy has a different dose-response relationship than maintenance fixed dose ICS/fast-onset LABA therapy in reducing risk of severe exacerbations. METHODS: A systematic literature review was undertaken to identify randomised controlled trials (RCTs) in which randomised treatments included either i) budesonide/formoterol reliever monotherapy versus budesonide/formoterol fixed dose maintenance with short acting beta agonist (SABA) reliever therapy, or ii) budesonide/formoterol reliever therapy in addition to budesonide/formoterol maintenance versus higher fixed dose maintenance budesonide/formoterol with SABA as reliever therapy. Eligible studies were reviewed to allow determination of the relative potency and efficacy of the comparator regimens to reduce the risk of a severe exacerbation. RESULTS: The one RCT of budesonide/formoterol reliever monotherapy showed a 4.6-fold (95% CI 2.9 to 7.3) greater potency than budesonide/formoterol fixed dose maintenance plus SABA reliever therapy in reducing the risk of severe exacerbations. In the one RCT that compared budesonide/formoterol maintenance and reliever therapy with higher fixed dose maintenance budesonide/formoterol plus SABA reliever therapy, there was an additional 26% (95% CI 4 to 42%) reduction in severe exacerbation risk with the addition of budesonide/formoterol reliever therapy to maintenance budesonide/formoterol, despite a 25% lower total budesonide/formoterol dose. CONCLUSION: The limited available evidence suggests that budesonide/formoterol reliever therapy has greater potency and efficacy than budesonide/formoterol fixed dose maintenance plus SABA reliever therapy in reducing the risk of a severe exacerbation. This is an important concept which has the potential to guide clinical practice in asthma, although the small number of studies available highlights the need for further research to better define these pharmacological properties.