The airway contains airway smooth muscle and airway vascular smooth muscle. The acute effects of inhaled long-acting β2-adrenergic agonists (LABAs) alone, or in combination with an inhaled glucocorticoid (ICS), on airway smooth muscle tone in asthma are known; however, to the best of our knowledge, their effect on airway vascular smooth muscle tone has not been investigated previously. The objective of this study was to investigate the immediate effects of a LABA and an ICS alone and in combination on airway blood flow (Qaw) as an index of airway vascular smooth muscle tone in patients with stable asthma.
Fourteen subjects with moderate asthma inhaled single doses of salmeterol (50 μg), fluticasone propionate (250 μg), salmeterol/fluticasone propionate (50/250 μg), or placebo; Qaw was measured before and serially for 240 min after drug administration.
Mean Qaw increased after salmeterol and salmeterol/fluticasone propionate, with peaks at 60 min of 34% and 40%, respectively, and returned to baseline by 240 min after inhalation. Fluticasone propionate alone caused a transient decrease in mean Qaw. The maximal changes in Qaw, which occurred at different times, were 60% for salmeterol, 67% for salmeterol/fluticasone propionate, and −19% for fluticasone propionate (P < .05 vs placebo for all).
The LABA salmeterol has an acute vasodilator action on the airway of subjects with stable asthma. The addition of fluticasone propionate, which by itself causes vasoconstriction, does not attenuate the salmeterol-induced vasodilation, suggesting that fluticasone propionate potentiates the vasodilator effect of salmeterol. The vasodilation could be of clinical benefit by promoting the vascular clearance of inflammatory mediators including spasmogens from the airway.
ClinicalTrials.gov; No.: NCT01231230; URL: www.clinicaltrials.gov