A BIOASSAY FOR TOPICAL AND SYSTEMIC EFFECT OF 3 INHALED CORTICOSTEROIDS

Background: Comparisons of relative potency for the three inhaled cort icosteroids in the United States are limited to assessment of skin bla nching. Objective: Development of a method for comparing relative pote ncies of inhaled corticosteroids for topical effect on human airway an d systemic effect. Methods: With use of partial suppression of immedia te response to inhaled allergen and 24-hour urinary free cortisol outp ut, three-point dose-response curves were constructed for beclomethaso ne dipropionate (50 mu g/puff), triamcinolone acetonide (100 mu g/puff ), and flunisolide (250 mu g/puff). A randomized, parallel, single-bli nd study design was used, Dosing began with one puff four times a day for flunisolide and two puffs four times a day for the others. Doses w ere doubled after 1 week and again after a second week. Results: Twent y-five patients completed the study. Dose-response relationships were shown for each inhaled corticosteroid for both topical and systemic ef fect. Dose-response curves for the three preparations were similar whe n response was plotted against delivered dose in micrograms. Conclusio n: Within the limits of the assays, relative potencies of the three pr eparations appeared to be approximately equivalent for both topical an d systemic effect when dose was expressed in micrograms. Relative pote ncy per puff is therefore approximately proportional to the dose deliv ered. This method has potential for evaluation of relative potency of newer inhaled corticosteroids and the relative advantage of alternativ e delivery systems.