Scientific rationale for using a single inhaler for asthma control.

Clinical trials have recently demonstrated that using a budesonide/formoterol combination inhaler as regular maintenance treatment twice daily but also as a rescue therapy for breakthrough symptoms can provide more effective control of asthma, particularly in reducing exacerbations, than using a short-acting beta2-agonist or formoterol as rescue therapy. This suggests that the corticosteroid component of the combination therapy plays an important role in rescue therapy. Formoterol as a rescue therapy is effective in relieving symptoms by relaxing airway smooth muscle but is also likely to have important inhibitory effects on mast cells, plasma exudation and neutrophilic inflammation. Inhaled corticosteroids have much more rapid suppressing effects on airway inflammation than previously recognised and the increased dose used as rescue therapy may prevent the increase in airway inflammation that occurs during the evolution of an exacerbation, thus preventing its development. It is likely that the molecular interactions between beta2-agonists and corticosteroids also enhance the effect of the combination therapy as rescue therapy. There is now a strong scientific rationale for single inhaler therapy in asthma, but more research is now needed to better understand the mechanisms involved.