Defined as a chronic inflammatory airway disorder with bronchial hyper-responsiveness to a variety of stimuli, bronchial asthma is often punctuated with recurrent episodes of exacerbations with classical manifestations such as wheezing, breathlessness, chest tightness, and nocturnal or early morning cough. These episodes are usually associated with widespread but variable airflow obstruction within the lung that is often reversible either spontaneously or with treatment .
Conventionally, a nebulized short-acting β2 agonist (SABA) like salbutamol is often used as the reliever in acute exacerbations of asthma. However, the recent worldwide respiratory outbreaks, such as the H1N1 pandemic flu (in 2009) and the severe acute respiratory syndrome (SARS) outbreak (in 2002-2003), have discouraged routine nebulization because of its apparent association with air-borne infection spread .
Recent studies have shown that the similar bronchodilator delivered via a metered-dose inhaler, combined with a spacer, produces at least an equivalent improvement in lung function as the same dose as delivered via a nebulizer . In fact, a previous study has found that with MDI and a spacer, the dose that reaches the lungs ranges from 15% to 20% of the total dose, whereas jet nebulizers deposit only 8% to 10% of the total dose .
Nonetheless, despite the effectiveness of delivering a bronchodilator via the metered dose route [3, 4], nebulized salbutamol is still very much preferred because of its convenience . Most patients when visiting an emergency department expect to be given "something more" than the metered dose inhalers that they had been taking at home.
Formoterol is a long-acting β2-agonist (LABA) that has a rapid onset bronchodilatory effect within 1-3 min of inhalation . Its rapid bronchodilatory effect is comparable with that of salbutamol, thus making it a suitable alternative for the treatment of acute asthma and to prevent exercise-induced bronchospasm . In fact, formoterol has been shown to produce greater lung improvements than salbutamol up to 4 h after administration .
One of the reasons why formoterol exhibits a rapid onset is because formoterol acts as a full agonist to beta-2 receptors compared to salbutamol that acts as a partial beta-2 agonist . Furthermore, there are additional non-bronchodilatory beneficial effects of formoterol including the effect of reducing plasma exudation by closing the gaps between endothelial cells, stabilizing the mast cells and reducing neutrophilic recruitment, and thus reducing the release of reactive oxygen species through the activated neutrophils .
Combined budesonide/formoterol in a single inhaler (Symbicort®, AstraZeneca) has been shown to be effective as a maintenance and reliever anti-asthmatic medication . In fact, this combination therapy has recently been used in an effective novel approach called Symbicort® as Maintenance and Reliever Therapy (SMART) approach [9, 11]. SMART approach basically means using Symbicort® as a maintenance therapy twice daily with additional puffs of the combination inhaler as needed for symptom relief [9, 11].