The airway contains airway smooth muscle and airway vascular smooth muscle. While 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, their effect on airway vascular smooth muscle tone have not previously been investigated.

OBJECTIVE:To investigate the immediate effect 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.

METHODS:Fourteen subjects with moderate asthma inhaled single doses of salmeterol (50 μg), fluticasone (250 μg), salmeterol/fluticasone (50/250 μg) or placebo; Qaw was measured before and serially for 240 min post drug administration.

Main RESULTS:Mean Qaw increased after salmeterol and salmeterol/fluticasone with a peak at 60 min of 34% and 40 %, respectively; mean Qaw returned toward baseline by 240 min post inhalation. Fluticasone alone caused a transient decrease in mean Qaw. The maximum changes in Qaw, which occurred at different times, were 60% for salmeterol, 67% for salmeterol/fluticasone, and -19 % for fluticasone (p< 0.05 vs. placebo for all).

CONCLUSIONS:The LABA salmeterol has an acute vasodilator action in the airway of subjects with stable asthma. The addition of fluticasone, which by itself causes vasoconstriction, does not attenuate the salmeterol-induced vasodilation, suggesting that fluticasone 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.