Comparative bronchial vasoconstrictive efficacy of inhaled glucocorticosteroids

The vasoconstrictive efficacies of glucocorticosteroids (GS) are usually compared by the McKenzie skin-blanching test and taken as an index of relative potency. The rationale for the present study was to transpose the McKenzie test to the airway and to compare the airway vascular effects of three inhaled GS: beclomethasone dipropionate (BDP), fluticasone propionate (FP) and budesonide (BUD), in healthy subjects and patients with mild stable asthma. A soluble, inert gas-uptake method was used to measure airway blood flow (Qaw). Baseline mean+/-SD Qaw normalised for anatomical dead space was 53.1+/-1.4 microL x min(-1) x mL(-1) in healthy subjects (n=10) and 67.8+/-3 microL x min(-1) x mL(-1) in asthmatics (n=10). All GS caused a transient decrease in Qaw. The magnitude of the vasoconstriction was greater in asthmatics. The relative vasoconstrictive effect of BDP, FP and BUD was 1, 1.9, and 2.7, respectively, in asthmatics and 1, 3.3 and 3.0, respectively, in healthy subjects, as assessed by the dose required to decrease Qaw by 20%, from the baseline, 30-min postdrug inhalation. Therefore, measuring airway blood flow may be a useful, site-specific parameter to assess the tissue bioavailability and vasoconstrictive efficacy of inhaled glucocorticosteroids.