COMPARISON OF INHALED CORTICOSTEROIDS

OBJECTIVE: To review the comparative studies evaluating both efficacy and safety of inhaled corticosteroids in the management of asthma. Spe cifically, comparative clinical trials are evaluated that allow clinic ians to determine relative potencies of the various inhaled corticoste roids. METHODS: A critical review was performed of the published clini cal trials, either as articles or abstracts, comparing the clinical ef ficacy or systemic activity of inhaled corticosteroids. No a priori cr iteria were applied, as this was not a meta-analysis. FINDINGS: In vit ro measures of antiinflammatory activity of corticosteroids consistent ly demonstrate potency differences among the various corticosteroids. Traditionally, these in vitro measures have been used to develop new c orticosteroids with greater topical activity. While no accepted direct measure of antiasthmatic antiinflammatory activity exists, clinical t rials using surrogate measures (e.g., forced expiratory volume in 1 se cond, peak expiratory flow, bronchial hyperresponsiveness, symptom con trol) indicate that in vitro measures provide a relatively accurate as sessment of antiasthmatic potency. The relative antiinflammatory poten cy of the inhaled corticosteroids is in the following rank order: flun isolide = triamcinolone acetonide < beclomethasone dipropionate = bude sonide < fluticasone. Studies of systemic activity appear to confirm t his relative order of potency. Currently, no evidence exists for great er efficacy for any of the inhaled corticosteroids when administered i n their relatively equipotent dosages. The preponderance of current da ta suggests that when administered in equipotent antiinflammatory dose s as a metered-dose inhaler plus spacer or as their respective dry-pow der inhaler, the existing inhaled corticosteroids have similar risks o f producing systemic effects, CONCLUSIONS: Delivery systems can signif icantly affect both topical and systemic activity of inhaled corticost eroids, More direct comparative studies between agents are required to firmly establish comparative topical to systemic activity ratios. Tho preponderance of evidence suggests that the agents are not equipotent on a microgram basis.