Assessment of anti-inflammatory effect from addition of a long-acting beta-2 agonist to inhaled corticosteroid

Background:

Inhaled corticosteroids (ICS) and long-acting beta-2 agonists (LABA) are thought to enhance the pharmacologic action of one another by a synergistic effect.

Objective:

We compared a group of patients who used ICS monotherapy with a group treated with ICS/LABA combination and evaluated the LABAs with regard to the synergistic effect on the anti-inflammatory action of the ICS.

Methods:

This study was conducted with 107 adult patients with mild-to-moderate bronchial asthma. The patients were randomly assigned to either ICS monotherapy (n = 55) or an ICS/LABA combination (n = 52). Both groups were assessed for respiratory function, fractional exhaled nitric oxide, induced sputum, and airway hyperresponsiveness before and after 6 months of treatment.

Results:

The ICS/LABA combination group showed significantly greater improvement than the ICS monotherapy group in the forced expiratory volume in 1 second/forced vital capacity (p < 0.01), forced expiratory volume in 1 second % predicted (p < 0.05), % predicted maximal expiratory flow at 50% (p < 0.01), % predicted maximal expiratory flow at 25% (p < 0.05), and airway hyperresponsiveness (p < 0.01). However, the two groups did not show significant differences in changes in the fractional exhaled nitric oxide (p = 0.47) or the percentage of eosinophils in the central (p = 0.85) or peripheral sputum (p = 0.98).

Conclusion:

The significant improvement in respiratory function in the ICS/LABA combination treatment group compared with the ICS monotherapy group indicated an additive bronchodilator effect of the LABA. However, the two groups did not differ in airway inflammation, which indicated that a synergistic effect of the LABA on enhancing the anti-inflammatory action of the ICS was not clinically apparent.